render_preview.cc

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/* SPDX-FileCopyrightText: Blender Authors
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

 
/* global includes */
 
#include <algorithm>
#include <atomic>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <list>
 
#ifndef WIN32
#  include <unistd.h>
#else
#  include <io.h>
#endif
#include "MEM_guardedalloc.h"
 
#include "BLI_math_matrix.h"
#include "BLI_math_rotation.h"
#include "BLI_path_utils.hh"
#include "BLI_rect.h"
#include "BLI_string.h"
#include "BLI_string_utf8.h"
#include "BLI_utildefines.h"
 
#include "BLT_translation.hh"
 
#include "BLO_readfile.hh"
 
#include "DNA_camera_types.h"
#include "DNA_collection_types.h"
#include "DNA_light_types.h"
#include "DNA_material_types.h"
#include "DNA_mesh_types.h"
#include "DNA_node_types.h"
#include "DNA_object_types.h"
#include "DNA_scene_types.h"
#include "DNA_screen_types.h"
#include "DNA_space_types.h"
#include "DNA_world_types.h"
 
#include "BKE_animsys.h"
#include "BKE_armature.hh"
#include "BKE_brush.hh"
#include "BKE_collection.hh"
#include "BKE_colortools.hh"
#include "BKE_context.hh"
#include "BKE_global.hh"
#include "BKE_icons.h"
#include "BKE_idprop.hh"
#include "BKE_image.hh"
#include "BKE_layer.hh"
#include "BKE_lib_id.hh"
#include "BKE_library.hh"
#include "BKE_light.h"
#include "BKE_main.hh"
#include "BKE_material.hh"
#include "BKE_node.hh"
#include "BKE_object.hh"
#include "BKE_pose_backup.h"
#include "BKE_preview_image.hh"
#include "BKE_report.hh"
#include "BKE_scene.hh"
#include "BKE_screen.hh"
#include "BKE_texture.h"
#include "BKE_world.h"
 
#include "BLI_math_vector.h"
 
#include "DEG_depsgraph.hh"
#include "DEG_depsgraph_build.hh"
#include "DEG_depsgraph_query.hh"
 
#include "IMB_imbuf.hh"
#include "IMB_imbuf_types.hh"
#include "IMB_thumbs.hh"
 
#include "BIF_glutil.hh"
 
#include "RE_engine.h"
#include "RE_pipeline.h"
#include "RE_texture.h"
 
#include "WM_api.hh"
#include "WM_types.hh"
 
#include "ED_datafiles.h"
#include "ED_render.hh"
#include "ED_screen.hh"
#include "ED_view3d.hh"
#include "ED_view3d_offscreen.hh"
 
#include "UI_interface_icons.hh"
 
#include "ANIM_action.hh"
#include "ANIM_pose.hh"
 
#ifndef NDEBUG
/* Used for database init assert(). */
#  include "BLI_threads.h"
#endif
 
static void icon_copy_rect(const ImBuf *ibuf, uint w, uint h, uint *rect);
 
/* -------------------------------------------------------------------- */
 
struct ShaderPreview {
  /* from wmJob */
  const void *owner;
  bool *stop, *do_update;
 
  Scene *scene;
  ID *id, *id_copy;
  ID *parent;
  MTex *slot;
 
  /* Data-blocks with nodes need full copy during preview render, GLSL uses it too. */
  Material *matcopy;
  Tex *texcopy;
  Light *lampcopy;
  World *worldcopy;

  float color[4];
 
  int sizex, sizey;
  uint *pr_rect;
  ePreviewRenderMethod pr_method;
  bool own_id_copy;
 
  Main *bmain;
  Main *pr_main;
};
 
struct IconPreviewSize {
  IconPreviewSize *next, *prev;
  int sizex, sizey;
  uint *rect;
};
 
struct IconPreview {
  Main *bmain;
  Depsgraph *depsgraph; /* May be nullptr (see #WM_OT_previews_ensure). */
  Scene *scene;
  void *owner;
  ID *id;
  ID *id_copy;
  ListBase sizes;
 
  /* May be nullptr, is used for rendering IDs that require some other object for it to be applied
   * on before the ID can be represented as an image, for example when rendering an Action. */
  Object *active_object;
};

 
/* -------------------------------------------------------------------- */
 
static Main *G_pr_main_grease_pencil = nullptr;
 
#ifndef WITH_HEADLESS
static Main *load_main_from_memory(const void *blend, int blend_size)
{
  const int fileflags = G.fileflags;
  Main *bmain = nullptr;
  BlendFileData *bfd;
 
  G.fileflags |= G_FILE_NO_UI;
  bfd = BLO_read_from_memory(blend, blend_size, BLO_READ_SKIP_NONE, nullptr);
  if (bfd) {
    bmain = bfd->main;
    MEM_delete(bfd);
  }
  G.fileflags = fileflags;
 
  return bmain;
}
#endif
 
void ED_preview_ensure_dbase(const bool with_gpencil)
{
#ifndef WITH_HEADLESS
  static bool base_initialized = false;
  static bool base_initialized_gpencil = false;
  BLI_assert(BLI_thread_is_main());
  if (!base_initialized) {
    G.pr_main = load_main_from_memory(datatoc_preview_blend, datatoc_preview_blend_size);
    base_initialized = true;
  }
  if (!base_initialized_gpencil && with_gpencil) {
    G_pr_main_grease_pencil = load_main_from_memory(datatoc_preview_grease_pencil_blend,
                                                    datatoc_preview_grease_pencil_blend_size);
    base_initialized_gpencil = true;
  }
#else
  UNUSED_VARS(with_gpencil);
#endif
}
 
bool ED_check_engine_supports_preview(const Scene *scene)
{
  RenderEngineType *type = RE_engines_find(scene->r.engine);
  return (type->flag & RE_USE_PREVIEW) != 0;
}
 
static bool preview_method_is_render(const ePreviewRenderMethod pr_method)
{
  return ELEM(pr_method, PR_ICON_RENDER, PR_BUTS_RENDER);
}
 
void ED_preview_free_dbase()
{
  if (G.pr_main) {
    BKE_main_free(G.pr_main);
  }
 
  if (G_pr_main_grease_pencil) {
    BKE_main_free(G_pr_main_grease_pencil);
  }
}
 
static Scene *preview_get_scene(Main *pr_main)
{
  if (pr_main == nullptr) {
    return nullptr;
  }
 
  return static_cast<Scene *>(pr_main->scenes.first);
}
 
const char *ED_preview_collection_name(const ePreviewType pr_type)
{
  switch (pr_type) {
    case MA_FLAT:
      return "Flat";
    case MA_SPHERE:
      return "Sphere";
    case MA_CUBE:
      return "Cube";
    case MA_SHADERBALL:
      return "Shader Ball";
    case MA_CLOTH:
      return "Cloth";
    case MA_FLUID:
      return "Fluid";
    case MA_SPHERE_A:
      return "World Sphere";
    case MA_LAMP:
      return "Lamp";
    case MA_SKY:
      return "Sky";
    case MA_HAIR:
      return "Hair";
    case MA_ATMOS:
      return "Atmosphere";
    default:
      BLI_assert_msg(0, "Unknown preview type");
      return "";
  }
}
 
static bool render_engine_supports_ray_visibility(const Scene *sce)
{
  return !STREQ(sce->r.engine, RE_engine_id_BLENDER_EEVEE);
}
 
static void switch_preview_collection_visibility(ViewLayer *view_layer, const ePreviewType pr_type)
{
  /* Set appropriate layer as visible. */
  LayerCollection *lc = static_cast<LayerCollection *>(view_layer->layer_collections.first);
  const char *collection_name = ED_preview_collection_name(pr_type);
 
  for (lc = static_cast<LayerCollection *>(lc->layer_collections.first); lc; lc = lc->next) {
    if (STREQ(lc->collection->id.name + 2, collection_name)) {
      lc->collection->flag &= ~COLLECTION_HIDE_RENDER;
    }
    else {
      lc->collection->flag |= COLLECTION_HIDE_RENDER;
    }
  }
}
 
static const char *preview_floor_material_name(const Scene *scene,
                                               const ePreviewRenderMethod pr_method)
{
  if (pr_method == PR_ICON_RENDER && render_engine_supports_ray_visibility(scene)) {
    return "FloorHidden";
  }
  return "Floor";
}
 
static void switch_preview_floor_material(Main *pr_main,
                                          Mesh *mesh,
                                          const Scene *scene,
                                          const ePreviewRenderMethod pr_method)
{
  if (mesh->totcol == 0) {
    return;
  }
 
  const char *material_name = preview_floor_material_name(scene, pr_method);
  Material *mat = static_cast<Material *>(
      BLI_findstring(&pr_main->materials, material_name, offsetof(ID, name) + 2));
  if (mat) {
    mesh->mat[0] = mat;
  }
}
 
static void switch_preview_floor_visibility(Main *pr_main,
                                            const Scene *scene,
                                            ViewLayer *view_layer,
                                            const ePreviewRenderMethod pr_method)
{
  /* Hide floor for icon renders. */
  BKE_view_layer_synced_ensure(scene, view_layer);
  LISTBASE_FOREACH (Base *, base, BKE_view_layer_object_bases_get(view_layer)) {
    if (STREQ(base->object->id.name + 2, "Floor")) {
      base->object->visibility_flag &= ~OB_HIDE_RENDER;
      if (pr_method == PR_ICON_RENDER) {
        if (!render_engine_supports_ray_visibility(scene)) {
          base->object->visibility_flag |= OB_HIDE_RENDER;
        }
      }
      if (base->object->type == OB_MESH) {
        switch_preview_floor_material(
            pr_main, static_cast<Mesh *>(base->object->data), scene, pr_method);
      }
    }
  }
}
 
void ED_preview_set_visibility(Main *pr_main,
                               Scene *scene,
                               ViewLayer *view_layer,
                               const ePreviewType pr_type,
                               const ePreviewRenderMethod pr_method)
{
  switch_preview_collection_visibility(view_layer, pr_type);
  switch_preview_floor_visibility(pr_main, scene, view_layer, pr_method);
  BKE_layer_collection_sync(scene, view_layer);
}
 
static World *preview_get_localized_world(ShaderPreview *sp, World *world)
{
  if (world == nullptr) {
    return nullptr;
  }
  if (sp->worldcopy != nullptr) {
    return sp->worldcopy;
  }
 
  ID *id_copy = BKE_id_copy_ex(nullptr,
                               &world->id,
                               nullptr,
                               LIB_ID_CREATE_LOCAL | LIB_ID_COPY_LOCALIZE |
                                   LIB_ID_COPY_NO_ANIMDATA);
  sp->worldcopy = (World *)id_copy;
  BLI_addtail(&sp->pr_main->worlds, sp->worldcopy);
  return sp->worldcopy;
}
 
World *ED_preview_prepare_world_simple(Main *pr_main)
{
  using namespace blender::bke;
 
  World *world = BKE_world_add(pr_main, "SimpleWorld");
  bNodeTree *ntree = world->nodetree;
  ntree = blender::bke::node_tree_add_tree_embedded(
      nullptr, &world->id, "World Nodetree", "ShaderNodeTree");
 
  bNode *background = node_add_node(nullptr, *ntree, "ShaderNodeBackground");
  bNode *output = node_add_node(nullptr, *ntree, "ShaderNodeOutputWorld");
  node_add_link(*world->nodetree,
                *background,
                *node_find_socket(*background, SOCK_OUT, "Background"),
                *output,
                *node_find_socket(*output, SOCK_IN, "Surface"));
  node_set_active(*ntree, *output);
 
  world->nodetree = ntree;
  return world;
}
 
void ED_preview_world_simple_set_rgb(World *world, const float color[4])
{
  BLI_assert(world != nullptr);
 
  bNode *background = blender::bke::node_find_node_by_name(*world->nodetree, "Background");
  BLI_assert(background != nullptr);
 
  auto color_socket = static_cast<bNodeSocketValueRGBA *>(
      blender::bke::node_find_socket(*background, SOCK_IN, "Color")->default_value);
  copy_v4_v4(color_socket->value, color);
}
 
static ID *duplicate_ids(ID *id, const bool allow_failure)
{
  if (id == nullptr) {
    /* Non-ID preview render. */
    return nullptr;
  }
 
  switch (GS(id->name)) {
    case ID_OB:
    case ID_MA:
    case ID_TE:
    case ID_LA:
    case ID_WO: {
      BLI_assert(BKE_previewimg_id_supports_jobs(id));
      ID *id_copy = BKE_id_copy_ex(nullptr,
                                   id,
                                   nullptr,
                                   LIB_ID_CREATE_LOCAL | LIB_ID_COPY_LOCALIZE |
                                       LIB_ID_COPY_NO_ANIMDATA);
      return id_copy;
    }
    case ID_GR: {
      /* Doesn't really duplicate the collection. Just creates a collection instance empty. */
      BLI_assert(BKE_previewimg_id_supports_jobs(id));
      Object *instance_empty = BKE_object_add_only_object(nullptr, OB_EMPTY, nullptr);
      instance_empty->instance_collection = (Collection *)id;
      instance_empty->transflag |= OB_DUPLICOLLECTION;
      return &instance_empty->id;
    }
    /* These support threading, but don't need duplicating. */
    case ID_IM:
      BLI_assert(BKE_previewimg_id_supports_jobs(id));
      return nullptr;
    default:
      if (!allow_failure) {
        BLI_assert_msg(0, "ID type preview not supported.");
      }
      return nullptr;
  }
}
 
static const char *preview_world_name(const Scene *sce,
                                      const ID_Type id_type,
                                      const ePreviewRenderMethod pr_method)
{
  /* When rendering material icons the floor will not be shown in the output. Cycles will use a
   * material trick to show the floor in the reflections, but hide the floor for camera rays. For
   * Eevee we use a transparent world that has a projected grid.
   *
   * In the future when Eevee supports VULKAN ray-tracing we can re-evaluate and perhaps remove
   * this approximation.
   */
  if (id_type == ID_MA && pr_method == PR_ICON_RENDER &&
      !render_engine_supports_ray_visibility(sce))
  {
    return "WorldFloor";
  }
  return "World";
}
 
static World *preview_get_world(Main *pr_main,
                                const Scene *sce,
                                const ID_Type id_type,
                                const ePreviewRenderMethod pr_method)
{
  World *result = nullptr;
  const char *world_name = preview_world_name(sce, id_type, pr_method);
  result = static_cast<World *>(
      BLI_findstring(&pr_main->worlds, world_name, offsetof(ID, name) + 2));
 
  /* No world found return first world. */
  if (result == nullptr) {
    result = static_cast<World *>(pr_main->worlds.first);
  }
 
  BLI_assert_msg(result, "Preview file has no world.");
  return result;
}
 
static void preview_sync_exposure(World *dst, const World *src)
{
  BLI_assert(dst);
  BLI_assert(src);
  dst->exp = src->exp;
  dst->range = src->range;
}
 
World *ED_preview_prepare_world(Main *pr_main,
                                const Scene *scene,
                                const World *world,
                                const ID_Type id_type,
                                const ePreviewRenderMethod pr_method)
{
  World *result = preview_get_world(pr_main, scene, id_type, pr_method);
  if (world) {
    preview_sync_exposure(result, world);
  }
  return result;
}
 
/* call this with a pointer to initialize preview scene */
/* call this with nullptr to restore assigned ID pointers in preview scene */
static Scene *preview_prepare_scene(
    Main *bmain, Scene *scene, ID *id, int id_type, ShaderPreview *sp)
{
  Scene *sce;
  Main *pr_main = sp->pr_main;
 
  memcpy(pr_main->filepath, BKE_main_blendfile_path(bmain), sizeof(pr_main->filepath));
 
  sce = preview_get_scene(pr_main);
  if (sce) {
    ViewLayer *view_layer = static_cast<ViewLayer *>(sce->view_layers.first);
 
    /* Only enable the combined render-pass. */
    view_layer->passflag = SCE_PASS_COMBINED;
    view_layer->eevee.render_passes = 0;
 
    /* This flag tells render to not execute depsgraph or F-Curves etc. */
    sce->r.scemode |= R_BUTS_PREVIEW;
    STRNCPY_UTF8(sce->r.engine, scene->r.engine);
 
    sce->r.color_mgt_flag = scene->r.color_mgt_flag;
    BKE_color_managed_display_settings_copy(&sce->display_settings, &scene->display_settings);
 
    BKE_color_managed_view_settings_free(&sce->view_settings);
    BKE_color_managed_view_settings_copy(&sce->view_settings, &scene->view_settings);
 
    if ((id && sp->pr_method == PR_ICON_RENDER) && id_type != ID_WO) {
      sce->r.alphamode = R_ALPHAPREMUL;
    }
    else {
      sce->r.alphamode = R_ADDSKY;
    }
 
    sce->r.cfra = scene->r.cfra;
 
    /* Setup the world. */
    sce->world = ED_preview_prepare_world(
        pr_main, sce, scene->world, static_cast<ID_Type>(id_type), sp->pr_method);
 
    if (id_type == ID_TE) {
      /* Texture is not actually rendered with engine, just set dummy value. */
      STRNCPY_UTF8(sce->r.engine, RE_engine_id_BLENDER_EEVEE);
    }
 
    if (id_type == ID_MA) {
      Material *mat = nullptr, *origmat = (Material *)id;
 
      if (origmat) {
        /* work on a copy */
        BLI_assert(sp->id_copy != nullptr);
        mat = sp->matcopy = (Material *)sp->id_copy;
        sp->id_copy = nullptr;
        BLI_addtail(&pr_main->materials, mat);
 
        /* Use current scene world for lighting. */
        if (mat->pr_flag == MA_PREVIEW_WORLD && sp->pr_method == PR_BUTS_RENDER) {
          /* Use current scene world to light sphere. */
          sce->world = preview_get_localized_world(sp, scene->world);
        }
        else if (sce->world && sp->pr_method != PR_ICON_RENDER) {
          /* Use a default world color. Using the current
           * scene world can be slow if it has big textures. */
          sce->world = ED_preview_prepare_world_simple(sp->bmain);
 
          /* Use brighter world color for grease pencil. */
          if (sp->pr_main == G_pr_main_grease_pencil) {
            const float white[4] = {1.0f, 1.0f, 1.0f, 1.0f};
            ED_preview_world_simple_set_rgb(sce->world, white);
          }
          else {
            const float dark[4] = {0.05f, 0.05f, 0.05f, 0.05f};
            ED_preview_world_simple_set_rgb(sce->world, dark);
          }
        }
 
        const ePreviewType preview_type = static_cast<ePreviewType>(mat->pr_type);
        ED_preview_set_visibility(pr_main, sce, view_layer, preview_type, sp->pr_method);
      }
      else {
        sce->display.render_aa = SCE_DISPLAY_AA_OFF;
      }
      BKE_view_layer_synced_ensure(sce, view_layer);
      LISTBASE_FOREACH (Base *, base, BKE_view_layer_object_bases_get(view_layer)) {
        if (base->object->id.name[2] == 'p') {
          /* copy over object color, in case material uses it */
          copy_v4_v4(base->object->color, sp->color);
 
          if (OB_TYPE_SUPPORT_MATERIAL(base->object->type)) {
            /* don't use BKE_object_material_assign, it changed mat->id.us, which shows in the UI
             */
            Material ***matar = BKE_object_material_array_p(base->object);
            int actcol = max_ii(base->object->actcol - 1, 0);
 
            if (matar && actcol < base->object->totcol) {
              (*matar)[actcol] = mat;
            }
          }
          else if (base->object->type == OB_LAMP) {
            base->flag |= BASE_ENABLED_AND_MAYBE_VISIBLE_IN_VIEWPORT;
          }
        }
      }
    }
    else if (id_type == ID_TE) {
      Tex *tex = nullptr, *origtex = (Tex *)id;
 
      if (origtex) {
        BLI_assert(sp->id_copy != nullptr);
        tex = sp->texcopy = (Tex *)sp->id_copy;
        sp->id_copy = nullptr;
        BLI_addtail(&pr_main->textures, tex);
      }
    }
    else if (id_type == ID_LA) {
      Light *la = nullptr, *origla = (Light *)id;
 
      /* work on a copy */
      if (origla) {
        BLI_assert(sp->id_copy != nullptr);
        la = sp->lampcopy = (Light *)sp->id_copy;
        sp->id_copy = nullptr;
        BLI_addtail(&pr_main->lights, la);
      }
 
      ED_preview_set_visibility(pr_main, sce, view_layer, MA_LAMP, sp->pr_method);
 
      if (sce->world) {
        /* Only use lighting from the light. */
        sce->world = ED_preview_prepare_world_simple(pr_main);
        const float black[4] = {0.0f, 0.0f, 0.0f, 0.0f};
        ED_preview_world_simple_set_rgb(sce->world, black);
      }
 
      BKE_view_layer_synced_ensure(sce, view_layer);
      LISTBASE_FOREACH (Base *, base, BKE_view_layer_object_bases_get(view_layer)) {
        if (base->object->id.name[2] == 'p') {
          if (base->object->type == OB_LAMP) {
            base->object->data = la;
          }
        }
      }
    }
    else if (id_type == ID_WO) {
      World *wrld = nullptr, *origwrld = (World *)id;
 
      if (origwrld) {
        BLI_assert(sp->id_copy != nullptr);
        wrld = sp->worldcopy = (World *)sp->id_copy;
        sp->id_copy = nullptr;
        BLI_addtail(&pr_main->worlds, wrld);
      }
 
      ED_preview_set_visibility(pr_main, sce, view_layer, MA_SKY, sp->pr_method);
      sce->world = wrld;
    }
 
    return sce;
  }
 
  return nullptr;
}
 
/* new UI convention: draw is in pixel space already. */
/* uses ButType::Roundbox button in block to get the rect */
static bool ed_preview_draw_rect(
    Scene *scene, const void *owner, int split, int first, const rcti *rect, rcti *newrect)
{
  Render *re;
  RenderView *rv;
  RenderResult rres;
  int offx = 0;
  int newx = BLI_rcti_size_x(rect);
  int newy = BLI_rcti_size_y(rect);
  const void *split_owner = (!split || first) ? owner : (char *)owner + 1;
  bool ok = false;
 
  if (split) {
    if (first) {
      offx = 0;
      newx = newx / 2;
    }
    else {
      offx = newx / 2;
      newx = newx - newx / 2;
    }
  }
 
  /* test if something rendered ok */
  re = RE_GetRender(split_owner);
 
  if (re == nullptr) {
    return false;
  }
 
  RE_AcquireResultImageViews(re, &rres);
 
  if (!BLI_listbase_is_empty(&rres.views)) {
    /* material preview only needs monoscopy (view 0) */
    rv = RE_RenderViewGetById(&rres, 0);
  }
  else {
    /* possible the job clears the views but we're still drawing #45496 */
    rv = nullptr;
  }
 
  if (rv && rv->ibuf) {
    if (abs(rres.rectx - newx) < 2 && abs(rres.recty - newy) < 2) {
      newrect->xmax = max_ii(newrect->xmax, rect->xmin + rres.rectx + offx);
      newrect->ymax = max_ii(newrect->ymax, rect->ymin + rres.recty);
 
      if (rres.rectx && rres.recty) {
        float fx = rect->xmin + offx;
        float fy = rect->ymin;
 
        ED_draw_imbuf(
            rv->ibuf, fx, fy, false, &scene->view_settings, &scene->display_settings, 1.0f, 1.0f);
 
        ok = true;
      }
    }
  }
 
  RE_ReleaseResultImageViews(re, &rres);
 
  return ok;
}
 
void ED_preview_draw(
    const bContext *C, void *idp, void *parentp, void *slotp, uiPreview *ui_preview, rcti *rect)
{
  if (idp) {
    Scene *scene = CTX_data_scene(C);
    wmWindowManager *wm = CTX_wm_manager(C);
    ID *id = (ID *)idp;
    ID *parent = (ID *)parentp;
    MTex *slot = (MTex *)slotp;
    SpaceProperties *sbuts = CTX_wm_space_properties(C);
    const void *owner = CTX_wm_area(C);
    ShaderPreview *sp = static_cast<ShaderPreview *>(
        WM_jobs_customdata_from_type(wm, owner, WM_JOB_TYPE_RENDER_PREVIEW));
    rcti newrect;
    bool ok;
    int newx = BLI_rcti_size_x(rect);
    int newy = BLI_rcti_size_y(rect);
 
    newrect.xmin = rect->xmin;
    newrect.xmax = rect->xmin;
    newrect.ymin = rect->ymin;
    newrect.ymax = rect->ymin;
 
    if (parent) {
      ok = ed_preview_draw_rect(scene, owner, 1, 1, rect, &newrect);
      ok &= ed_preview_draw_rect(scene, owner, 1, 0, rect, &newrect);
    }
    else {
      ok = ed_preview_draw_rect(scene, owner, 0, 0, rect, &newrect);
    }
 
    if (ok) {
      *rect = newrect;
    }
 
    /* start a new preview render job if signaled through sbuts->preview,
     * if no render result was found and no preview render job is running,
     * or if the job is running and the size of preview changed */
    if ((sbuts != nullptr && sbuts->preview) || (ui_preview->tag & UI_PREVIEW_TAG_DIRTY) ||
        (!ok && !WM_jobs_test(wm, owner, WM_JOB_TYPE_RENDER_PREVIEW)) ||
        (sp && (abs(sp->sizex - newx) >= 2 || abs(sp->sizey - newy) > 2)))
    {
      if (sbuts != nullptr) {
        sbuts->preview = 0;
      }
      ED_preview_shader_job(C, owner, id, parent, slot, newx, newy, PR_BUTS_RENDER);
      ui_preview->tag &= ~UI_PREVIEW_TAG_DIRTY;
    }
  }
}
 
void ED_previews_tag_dirty_by_id(const Main &bmain, const ID &id)
{
  LISTBASE_FOREACH (const bScreen *, screen, &bmain.screens) {
    LISTBASE_FOREACH (const ScrArea *, area, &screen->areabase) {
      LISTBASE_FOREACH (const ARegion *, region, &area->regionbase) {
        LISTBASE_FOREACH (uiPreview *, preview, &region->ui_previews) {
          if (preview->id_session_uid == id.session_uid) {
            preview->tag |= UI_PREVIEW_TAG_DIRTY;
          }
        }
      }
    }
  }
}

 
/* -------------------------------------------------------------------- */
 
struct ObjectPreviewData {
  /* The main for the preview, not of the current file. */
  Main *pr_main;
  /* Copy of the object to create the preview for. The copy is for thread safety (and to insert
   * it into its own main). */
  Object *object;
  /* Current frame. */
  int cfra;
  int sizex;
  int sizey;
};
 
static bool object_preview_is_type_supported(const Object *ob)
{
  return OB_TYPE_IS_GEOMETRY(ob->type);
}
 
static Object *object_preview_camera_create(Main *preview_main,
                                            Scene *scene,
                                            ViewLayer *view_layer,
                                            Object *preview_object)
{
  Object *camera = BKE_object_add(preview_main, scene, view_layer, OB_CAMERA, "Preview Camera");
 
  float rotmat[3][3];
  float dummy_scale[3];
  mat4_to_loc_rot_size(camera->loc, rotmat, dummy_scale, preview_object->object_to_world().ptr());
 
  /* Camera is Y up, so needs additional rotations to obliquely face the front. */
  float drotmat[3][3];
  const float eul[3] = {M_PI * 0.4f, 0.0f, M_PI * 0.1f};
  eul_to_mat3(drotmat, eul);
  mul_m3_m3_post(rotmat, drotmat);
 
  camera->rotmode = ROT_MODE_QUAT;
  mat3_to_quat(camera->quat, rotmat);
 
  /* Nice focal length for close portraiture. */
  ((Camera *)camera->data)->lens = 85;
 
  return camera;
}
 
static Scene *object_preview_scene_create(const ObjectPreviewData *preview_data,
                                          Depsgraph **r_depsgraph)
{
  Scene *scene = BKE_scene_add(preview_data->pr_main, "Object preview scene");
  /* Preview need to be in the current frame to get a thumbnail similar of what
   * viewport displays. */
  scene->r.cfra = preview_data->cfra;
 
  ViewLayer *view_layer = static_cast<ViewLayer *>(scene->view_layers.first);
  Depsgraph *depsgraph = DEG_graph_new(
      preview_data->pr_main, scene, view_layer, DAG_EVAL_VIEWPORT);
 
  BLI_assert(preview_data->object != nullptr);
  BLI_addtail(&preview_data->pr_main->objects, preview_data->object);
 
  BKE_collection_object_add(preview_data->pr_main, scene->master_collection, preview_data->object);
 
  Object *camera_object = object_preview_camera_create(
      preview_data->pr_main, scene, view_layer, preview_data->object);
 
  scene->camera = camera_object;
  scene->r.xsch = preview_data->sizex;
  scene->r.ysch = preview_data->sizey;
  scene->r.size = 100;
 
  BKE_view_layer_synced_ensure(scene, view_layer);
  Base *preview_base = BKE_view_layer_base_find(view_layer, preview_data->object);
  /* For 'view selected' below. */
  preview_base->flag |= BASE_SELECTED;
 
  DEG_graph_build_from_view_layer(depsgraph);
  DEG_evaluate_on_refresh(depsgraph);
 
  ED_view3d_camera_to_view_selected_with_set_clipping(
      preview_data->pr_main, depsgraph, scene, camera_object);
 
  BKE_scene_graph_update_tagged(depsgraph, preview_data->pr_main);
 
  *r_depsgraph = depsgraph;
  return scene;
}
 
static void object_preview_render(IconPreview *preview, IconPreviewSize *preview_sized)
{
  Main *preview_main = BKE_main_new();
  char err_out[256] = "unknown";
 
  BLI_assert(preview->id_copy && (preview->id_copy != preview->id));
 
  ObjectPreviewData preview_data = {};
  preview_data.pr_main = preview_main;
  /* Act on a copy. */
  preview_data.object = (Object *)preview->id_copy;
  preview_data.cfra = preview->scene->r.cfra;
  preview_data.sizex = preview_sized->sizex;
  preview_data.sizey = preview_sized->sizey;
 
  Depsgraph *depsgraph;
  Scene *scene = object_preview_scene_create(&preview_data, &depsgraph);
 
  /* Ownership is now ours. */
  preview->id_copy = nullptr;
 
  View3DShading shading;
  BKE_screen_view3d_shading_init(&shading);
  /* Enable shadows, makes it a bit easier to see the shape. */
  shading.flag |= V3D_SHADING_SHADOW;
 
  ImBuf *ibuf = ED_view3d_draw_offscreen_imbuf_simple(depsgraph,
                                                      DEG_get_evaluated_scene(depsgraph),
                                                      &shading,
                                                      OB_TEXTURE,
                                                      DEG_get_evaluated(depsgraph, scene->camera),
                                                      preview_sized->sizex,
                                                      preview_sized->sizey,
                                                      IB_byte_data,
                                                      V3D_OFSDRAW_OVERRIDE_SCENE_SETTINGS,
                                                      R_ALPHAPREMUL,
                                                      nullptr,
                                                      nullptr,
                                                      nullptr,
                                                      err_out);
  /* TODO: color-management? */
 
  if (ibuf) {
    icon_copy_rect(ibuf, preview_sized->sizex, preview_sized->sizey, preview_sized->rect);
    IMB_freeImBuf(ibuf);
  }
 
  DEG_graph_free(depsgraph);
  BKE_main_free(preview_main);
}

 
/* -------------------------------------------------------------------- */

 
/* -------------------------------------------------------------------- */
 
static PoseBackup *action_preview_render_prepare(IconPreview *preview)
{
  Object *object = preview->active_object;
  if (object == nullptr) {
    WM_global_report(RPT_WARNING, "No active object, unable to apply the Action before rendering");
    return nullptr;
  }
  if (object->pose == nullptr) {
    WM_global_reportf(RPT_WARNING,
                      "Object %s has no pose, unable to apply the Action before rendering",
                      object->id.name + 2);
    return nullptr;
  }
 
  /* Create a backup of the current pose. */
  blender::animrig::Action &pose_action = reinterpret_cast<bAction *>(preview->id)->wrap();
 
  if (pose_action.slot_array_num == 0) {
    WM_global_report(RPT_WARNING, "Action has no data, cannot render preview");
    return nullptr;
  }
 
  blender::animrig::Slot &slot = blender::animrig::get_best_pose_slot_for_id(object->id,
                                                                             pose_action);
  PoseBackup *pose_backup = BKE_pose_backup_create_all_bones({object}, &pose_action);
 
  /* Apply the Action as pose, so that it can be rendered. This assumes the Action represents a
   * single pose, and that thus the evaluation time doesn't matter. */
  AnimationEvalContext anim_eval_context = {preview->depsgraph, 0.0f};
  blender::animrig::pose_apply_action_all_bones(
      object, &pose_action, slot.handle, &anim_eval_context);
 
  /* Force evaluation of the new pose, before the preview is rendered. */
  DEG_id_tag_update(&object->id, ID_RECALC_GEOMETRY);
  DEG_evaluate_on_refresh(preview->depsgraph);
 
  return pose_backup;
}
 
static void action_preview_render_cleanup(IconPreview *preview, PoseBackup *pose_backup)
{
  if (pose_backup == nullptr) {
    return;
  }
  BKE_pose_backup_restore(pose_backup);
  BKE_pose_backup_free(pose_backup);
 
  DEG_id_tag_update(&preview->active_object->id, ID_RECALC_GEOMETRY);
}
 
/* Render a pose from the scene camera. It is assumed that the scene camera is
 * capturing the pose. The pose is applied temporarily to the current object
 * before rendering. */
static void action_preview_render(IconPreview *preview, IconPreviewSize *preview_sized)
{
  char err_out[256] = "";
 
  Depsgraph *depsgraph = preview->depsgraph;
  /* Not all code paths that lead to this function actually provide a depsgraph.
   * The "Refresh Asset Preview" button (#ED_OT_lib_id_generate_preview) does,
   * but #WM_OT_previews_ensure does not. */
  BLI_assert(depsgraph != nullptr);
  BLI_assert(preview->scene == DEG_get_input_scene(depsgraph));
 
  /* Apply the pose before getting the evaluated scene, so that the new pose is evaluated. */
  PoseBackup *pose_backup = action_preview_render_prepare(preview);
 
  Scene *scene_eval = DEG_get_evaluated_scene(depsgraph);
  Object *camera_eval = scene_eval->camera;
  if (camera_eval == nullptr) {
    printf("Scene has no camera, unable to render preview of %s without it.\n",
           preview->id->name + 2);
    action_preview_render_cleanup(preview, pose_backup);
    return;
  }
 
  /* This renders with the Workbench engine settings stored on the Scene. */
  ImBuf *ibuf = ED_view3d_draw_offscreen_imbuf_simple(depsgraph,
                                                      scene_eval,
                                                      nullptr,
                                                      OB_SOLID,
                                                      camera_eval,
                                                      preview_sized->sizex,
                                                      preview_sized->sizey,
                                                      IB_byte_data,
                                                      V3D_OFSDRAW_NONE,
                                                      R_ADDSKY,
                                                      nullptr,
                                                      nullptr,
                                                      nullptr,
                                                      err_out);
 
  action_preview_render_cleanup(preview, pose_backup);
 
  if (err_out[0] != '\0') {
    printf("Error rendering Action %s preview: %s\n", preview->id->name + 2, err_out);
  }
 
  if (ibuf) {
    icon_copy_rect(ibuf, preview_sized->sizex, preview_sized->sizey, preview_sized->rect);
    IMB_freeImBuf(ibuf);
  }
}

 
/* -------------------------------------------------------------------- */
 
static bool scene_preview_is_supported(const Scene *scene)
{
  return scene->camera != nullptr;
}
 
static void scene_preview_render(IconPreview *preview,
                                 IconPreviewSize *preview_sized,
                                 ReportList *reports)
{
  Depsgraph *depsgraph = preview->depsgraph;
  /* Not all code paths that lead to this function actually provide a depsgraph.
   * The "Refresh Asset Preview" button (#ED_OT_lib_id_generate_preview) does,
   * but #WM_OT_previews_ensure does not. */
  BLI_assert(depsgraph != nullptr);
  BLI_assert(preview->id != nullptr);
 
  Scene *scene_eval = DEG_get_evaluated_scene(depsgraph);
  Object *camera_eval = scene_eval->camera;
  if (camera_eval == nullptr) {
    BKE_reportf(reports,
                RPT_ERROR,
                "Scene has no camera, unable to render preview of %s without it.",
                BKE_id_name(*preview->id));
    return;
  }
 
  char err_out[256] = "";
  /* This renders with the Workbench engine settings stored on the Scene. */
  ImBuf *ibuf = ED_view3d_draw_offscreen_imbuf_simple(depsgraph,
                                                      scene_eval,
                                                      nullptr,
                                                      OB_SOLID,
                                                      camera_eval,
                                                      preview_sized->sizex,
                                                      preview_sized->sizey,
                                                      IB_byte_data,
                                                      V3D_OFSDRAW_NONE,
                                                      R_ADDSKY,
                                                      nullptr,
                                                      nullptr,
                                                      nullptr,
                                                      err_out);
 
  if (err_out[0] != '\0') {
    BKE_reportf(reports,
                RPT_ERROR,
                "Error rendering Scene %s preview: %s.",
                BKE_id_name(*preview->id),
                err_out);
  }
 
  if (ibuf) {
    icon_copy_rect(ibuf, preview_sized->sizex, preview_sized->sizey, preview_sized->rect);
    IMB_freeImBuf(ibuf);
  }
}

 
/* -------------------------------------------------------------------- */
 
/* inside thread, called by renderer, sets job update value */
static void shader_preview_update(void *spv, RenderResult * /*rr*/, rcti * /*rect*/)
{
  ShaderPreview *sp = static_cast<ShaderPreview *>(spv);
 
  *(sp->do_update) = true;
}
 
/* called by renderer, checks job value */
static bool shader_preview_break(void *spv)
{
  ShaderPreview *sp = static_cast<ShaderPreview *>(spv);
 
  return *(sp->stop);
}
 
static void shader_preview_updatejob(void * /*spv*/) {}
 
/* Renders texture directly to render buffer. */
static void shader_preview_texture(ShaderPreview *sp, Tex *tex, Scene *sce, Render *re)
{
  /* Setup output buffer. */
  int width = sp->sizex;
  int height = sp->sizey;
 
  /* This is needed otherwise no RenderResult is created. */
  sce->r.scemode &= ~R_BUTS_PREVIEW;
  RE_InitState(re, nullptr, &sce->r, &sce->view_layers, nullptr, width, height, nullptr);
  RE_SetScene(re, sce);
 
  /* Create buffer in empty RenderView created in the init step. */
  RenderResult *rr = RE_AcquireResultWrite(re);
  RenderView *rv = (RenderView *)rr->views.first;
  ImBuf *rv_ibuf = RE_RenderViewEnsureImBuf(rr, rv);
  IMB_assign_float_buffer(rv_ibuf,
                          MEM_calloc_arrayN<float>(4 * width * height, "texture render result"),
                          IB_TAKE_OWNERSHIP);
  RE_ReleaseResult(re);
 
  /* Get texture image pool (if any) */
  ImagePool *img_pool = BKE_image_pool_new();
  BKE_texture_fetch_images_for_pool(tex, img_pool);
 
  /* Fill in image buffer. */
  float *rect_float = rv_ibuf->float_buffer.data;
  float tex_coord[3] = {0.0f, 0.0f, 0.0f};
 
  for (int y = 0; y < height; y++) {
    /* Tex coords between -1.0f and 1.0f. */
    tex_coord[1] = (float(y) / float(height)) * 2.0f - 1.0f;
 
    for (int x = 0; x < width; x++) {
      tex_coord[0] = (float(x) / float(height)) * 2.0f - 1.0f;
 
      /* Evaluate texture at tex_coord. */
      TexResult texres = {0};
      BKE_texture_get_value_ex(tex, tex_coord, &texres, img_pool, true);
      copy_v4_fl4(rect_float,
                  texres.trgba[0],
                  texres.trgba[1],
                  texres.trgba[2],
                  texres.talpha ? texres.trgba[3] : 1.0f);
 
      rect_float += 4;
    }
 
    /* Check if we should cancel texture preview. */
    if (shader_preview_break(sp)) {
      break;
    }
  }
 
  BKE_image_pool_free(img_pool);
}
 
static void shader_preview_render(ShaderPreview *sp, ID *id, int split, int first)
{
  Render *re;
  Scene *sce;
  float oldlens;
  short idtype = GS(id->name);
  int sizex;
  Main *pr_main = sp->pr_main;
 
  /* in case of split preview, use border render */
  if (split) {
    if (first) {
      sizex = sp->sizex / 2;
    }
    else {
      sizex = sp->sizex - sp->sizex / 2;
    }
  }
  else {
    sizex = sp->sizex;
  }
 
  /* we have to set preview variables first */
  sce = preview_get_scene(pr_main);
  if (sce) {
    sce->r.xsch = sizex;
    sce->r.ysch = sp->sizey;
    sce->r.size = 100;
  }
 
  /* get the stuff from the builtin preview dbase */
  sce = preview_prepare_scene(sp->bmain, sp->scene, id, idtype, sp);
  if (sce == nullptr) {
    return;
  }
 
  const void *split_owner = (!split || first) ? sp->owner : (char *)sp->owner + 1;
  re = RE_GetRender(split_owner);
 
  /* full refreshed render from first tile */
  if (re == nullptr) {
    re = RE_NewRender(split_owner);
  }
 
  /* sce->r gets copied in RE_InitState! */
  sce->r.scemode &= ~(R_MATNODE_PREVIEW | R_TEXNODE_PREVIEW);
  sce->r.scemode &= ~R_NO_IMAGE_LOAD;
 
  if (sp->pr_method == PR_ICON_RENDER) {
    sce->r.scemode |= R_NO_IMAGE_LOAD;
    sce->display.render_aa = SCE_DISPLAY_AA_SAMPLES_8;
  }
  else { /* PR_BUTS_RENDER */
    sce->display.render_aa = SCE_DISPLAY_AA_SAMPLES_8;
  }
 
  /* Callbacks are cleared on GetRender(). */
  if (sp->pr_method == PR_BUTS_RENDER) {
    RE_display_update_cb(re, sp, shader_preview_update);
  }
  /* set this for all previews, default is react to G.is_break still */
  RE_test_break_cb(re, sp, shader_preview_break);
 
  /* lens adjust */
  oldlens = ((Camera *)sce->camera->data)->lens;
  if (sizex > sp->sizey) {
    ((Camera *)sce->camera->data)->lens *= float(sp->sizey) / float(sizex);
  }
 
  /* entire cycle for render engine */
  if (idtype == ID_TE) {
    shader_preview_texture(sp, (Tex *)id, sce, re);
  }
  else {
    /* Render preview scene */
    RE_PreviewRender(re, pr_main, sce);
  }
 
  ((Camera *)sce->camera->data)->lens = oldlens;
 
  /* handle results */
  if (sp->pr_method == PR_ICON_RENDER) {
    // char *rct = (char *)(sp->pr_rect + 32 * 16 + 16);
 
    if (sp->pr_rect) {
      RE_ResultGet32(re, sp->pr_rect);
    }
  }
 
  /* unassign the pointers, reset vars */
  preview_prepare_scene(sp->bmain, sp->scene, nullptr, GS(id->name), sp);
 
  /* XXX bad exception, end-exec is not being called in render, because it uses local main. */
#if 0
  if (idtype == ID_TE) {
    Tex *tex = (Tex *)id;
    if (tex->use_nodes && tex->nodetree) {
      ntreeEndExecTree(tex->nodetree);
    }
  }
#endif
}
 
/* runs inside thread for material and icons */
static void shader_preview_startjob(void *customdata, bool *stop, bool *do_update)
{
  ShaderPreview *sp = static_cast<ShaderPreview *>(customdata);
 
  sp->stop = stop;
  sp->do_update = do_update;
 
  if (sp->parent) {
    shader_preview_render(sp, sp->id, 1, 1);
    shader_preview_render(sp, sp->parent, 1, 0);
  }
  else {
    shader_preview_render(sp, sp->id, 0, 0);
  }
 
  *do_update = true;
}
 
static void preview_id_copy_free(ID *id)
{
  BKE_libblock_free_datablock(id, 0);
  BKE_libblock_free_data(id, false);
  MEM_freeN(id);
}
 
static void shader_preview_free(void *customdata)
{
  ShaderPreview *sp = static_cast<ShaderPreview *>(customdata);
  Main *pr_main = sp->pr_main;
  ID *main_id_copy = nullptr;
  ID *sub_id_copy = nullptr;
 
  if (sp->matcopy) {
    main_id_copy = (ID *)sp->matcopy;
    BLI_remlink(&pr_main->materials, sp->matcopy);
  }
  if (sp->texcopy) {
    BLI_assert(main_id_copy == nullptr);
    main_id_copy = (ID *)sp->texcopy;
    BLI_remlink(&pr_main->textures, sp->texcopy);
  }
  if (sp->worldcopy) {
    /* worldcopy is also created for material with `Preview World` enabled */
    if (main_id_copy) {
      sub_id_copy = (ID *)sp->worldcopy;
    }
    else {
      main_id_copy = (ID *)sp->worldcopy;
    }
    BLI_remlink(&pr_main->worlds, sp->worldcopy);
  }
  if (sp->lampcopy) {
    BLI_assert(main_id_copy == nullptr);
    main_id_copy = (ID *)sp->lampcopy;
    BLI_remlink(&pr_main->lights, sp->lampcopy);
  }
  if (sp->own_id_copy) {
    if (sp->id_copy) {
      preview_id_copy_free(sp->id_copy);
    }
    if (main_id_copy) {
      preview_id_copy_free(main_id_copy);
    }
    if (sub_id_copy) {
      preview_id_copy_free(sub_id_copy);
    }
  }
 
  MEM_freeN(sp);
}

 
/* -------------------------------------------------------------------- */
 
static void icon_copy_rect(const ImBuf *ibuf, uint w, uint h, uint *rect)
{
  if (ibuf == nullptr ||
      (ibuf->byte_buffer.data == nullptr && ibuf->float_buffer.data == nullptr) || rect == nullptr)
  {
    return;
  }
 
  float scaledx, scaledy;
  if (ibuf->x > ibuf->y) {
    scaledx = float(w);
    scaledy = (float(ibuf->y) / float(ibuf->x)) * float(w);
  }
  else {
    scaledx = (float(ibuf->x) / float(ibuf->y)) * float(h);
    scaledy = float(h);
  }
 
  /* Scaling down must never assign zero width/height, see: #89868. */
  int ex = std::max<int>(1, scaledx);
  int ey = std::max<int>(1, scaledy);
 
  int dx = (w - ex) / 2;
  int dy = (h - ey) / 2;
 
  ImBuf *ima = IMB_scale_into_new(ibuf, ex, ey, IMBScaleFilter::Nearest, false);
  if (ima == nullptr) {
    return;
  }
 
  /* if needed, convert to 32 bits */
  if (ima->byte_buffer.data == nullptr) {
    IMB_byte_from_float(ima);
  }
 
  const uint *srect = reinterpret_cast<const uint *>(ima->byte_buffer.data);
  uint *drect = rect;
 
  drect += dy * w + dx;
  for (; ey > 0; ey--) {
    memcpy(drect, srect, ex * sizeof(int));
    drect += w;
    srect += ima->x;
  }
 
  IMB_freeImBuf(ima);
}
 
static void set_alpha(char *cp, int sizex, int sizey, char alpha)
{
  int a, size = sizex * sizey;
 
  for (a = 0; a < size; a++, cp += 4) {
    cp[3] = alpha;
  }
}
 
static void icon_preview_startjob(void *customdata, bool *stop, bool *do_update)
{
  ShaderPreview *sp = static_cast<ShaderPreview *>(customdata);
 
  if (sp->pr_method == PR_ICON_DEFERRED) {
    BLI_assert_unreachable();
    return;
  }
 
  ID *id = sp->id;
  short idtype = GS(id->name);
 
  BLI_assert(id != nullptr);
 
  if (idtype == ID_IM) {
    Image *ima = (Image *)id;
    ImBuf *ibuf = nullptr;
    ImageUser iuser;
    BKE_imageuser_default(&iuser);
 
    if (ima == nullptr) {
      return;
    }
 
    /* setup dummy image user */
    iuser.framenr = 1;
    iuser.scene = sp->scene;
 
    /* NOTE(@elubie): this needs to be changed: here image is always loaded if not
     * already there. Very expensive for large images. Need to find a way to
     * only get existing `ibuf`. */
    ibuf = BKE_image_acquire_ibuf(ima, &iuser, nullptr);
    if (ibuf == nullptr ||
        (ibuf->byte_buffer.data == nullptr && ibuf->float_buffer.data == nullptr))
    {
      BKE_image_release_ibuf(ima, ibuf, nullptr);
      return;
    }
 
    icon_copy_rect(ibuf, sp->sizex, sp->sizey, sp->pr_rect);
 
    *do_update = true;
 
    BKE_image_release_ibuf(ima, ibuf, nullptr);
  }
  else {
    /* re-use shader job */
    shader_preview_startjob(customdata, stop, do_update);
 
    /* world is rendered with alpha=0, so it wasn't displayed
     * this could be render option for sky to, for later */
    if (idtype == ID_WO) {
      set_alpha((char *)sp->pr_rect, sp->sizex, sp->sizey, 255);
    }
  }
}
 
/* use same function for icon & shader, so the job manager
 * does not run two of them at the same time. */
 
static void common_preview_startjob(void *customdata, wmJobWorkerStatus *worker_status)
{
  ShaderPreview *sp = static_cast<ShaderPreview *>(customdata);
 
  if (ELEM(sp->pr_method, PR_ICON_RENDER, PR_ICON_DEFERRED)) {
    icon_preview_startjob(customdata, &worker_status->stop, &worker_status->do_update);
  }
  else {
    shader_preview_startjob(customdata, &worker_status->stop, &worker_status->do_update);
  }
}

static void other_id_types_preview_render(IconPreview *ip,
                                          IconPreviewSize *cur_size,
                                          const ePreviewRenderMethod pr_method,
                                          wmJobWorkerStatus *worker_status)
{
  ShaderPreview *sp = MEM_callocN<ShaderPreview>("Icon ShaderPreview");
 
  /* These types don't use the ShaderPreview mess, they have their own types and functions. */
  BLI_assert(!ip->id || !ELEM(GS(ip->id->name), ID_OB));
 
  /* Construct shader preview from image size and preview custom-data. */
  sp->scene = ip->scene;
  sp->owner = ip->owner;
  sp->sizex = cur_size->sizex;
  sp->sizey = cur_size->sizey;
  sp->pr_method = pr_method;
  sp->pr_rect = cur_size->rect;
  sp->id = ip->id;
  sp->id_copy = ip->id_copy;
  sp->bmain = ip->bmain;
  sp->own_id_copy = false;
  Material *ma = nullptr;
 
  if (sp->pr_method == PR_ICON_RENDER) {
    BLI_assert(ip->id);
 
    /* grease pencil use its own preview file */
    if (GS(ip->id->name) == ID_MA) {
      ma = (Material *)ip->id;
    }
 
    if ((ma == nullptr) || (ma->gp_style == nullptr)) {
      sp->pr_main = G.pr_main;
    }
    else {
      sp->pr_main = G_pr_main_grease_pencil;
    }
  }
 
  common_preview_startjob(sp, worker_status);
  shader_preview_free(sp);
}
 
/* exported functions */

static int icon_previewimg_size_index_get(const IconPreviewSize *icon_size,
                                          const PreviewImage *preview_image)
{
  for (int i = 0; i < NUM_ICON_SIZES; i++) {
    if ((preview_image->w[i] == icon_size->sizex) && (preview_image->h[i] == icon_size->sizey)) {
      return i;
    }
  }
 
  BLI_assert_msg(0, "The searched icon size does not match any in the preview image");
  return -1;
}
 
static void icon_preview_startjob_all_sizes(void *customdata, wmJobWorkerStatus *worker_status)
{
  IconPreview *ip = (IconPreview *)customdata;
 
  LISTBASE_FOREACH (IconPreviewSize *, cur_size, &ip->sizes) {
    PreviewImage *prv = static_cast<PreviewImage *>(ip->owner);
    /* Is this a render job or a deferred loading job? */
    const ePreviewRenderMethod pr_method = (prv->runtime->deferred_loading_data) ?
                                               PR_ICON_DEFERRED :
                                               PR_ICON_RENDER;
 
    if (worker_status->stop) {
      break;
    }
 
    if (prv->runtime->tag & PRV_TAG_DEFFERED_DELETE) {
      /* Non-thread-protected reading is not an issue here. */
      continue;
    }
 
    /* check_engine_supports_preview() checks whether the engine supports "preview mode" (think:
     * Material Preview). This check is only relevant when the render function called below is
     * going to use such a mode. Group, Object and Action render functions use Solid mode, though,
     * so they can skip this test. Same is true for Images and Brushes, they can also skip this
     * test since their preview is just pulled from ImBuf which is not dependent on the render
     * engine. */
    /* TODO: Decouple the ID-type-specific render functions from this function, so that it's not
     * necessary to know here what happens inside lower-level functions. */
    const bool use_solid_render_mode = (ip->id != nullptr) &&
                                       ELEM(GS(ip->id->name), ID_OB, ID_AC, ID_IM, ID_GR, ID_SCE);
    if (!use_solid_render_mode && preview_method_is_render(pr_method) &&
        !ED_check_engine_supports_preview(ip->scene))
    {
      continue;
    }
 
    /* Workaround: Skip preview renders for linked IDs. Preview rendering can be slow and even
     * freeze the UI (e.g. on Eevee shader compilation). And since the result will never be stored
     * in a file, it's done every time the file is reloaded, so this becomes a frequent annoyance.
     */
    if (!use_solid_render_mode && ip->id && !ID_IS_EDITABLE(ip->id)) {
      continue;
    }
 
#ifndef NDEBUG
    {
      int size_index = icon_previewimg_size_index_get(cur_size, prv);
      BLI_assert(!BKE_previewimg_is_finished(prv, size_index));
    }
#endif
 
    if (ip->id != nullptr) {
      switch (GS(ip->id->name)) {
        case ID_OB:
          if (object_preview_is_type_supported((Object *)ip->id)) {
            /* Much simpler than the ShaderPreview mess used for other ID types. */
            object_preview_render(ip, cur_size);
          }
          continue;
        case ID_GR:
          BLI_assert(BKE_collection_contains_geometry_recursive(
              reinterpret_cast<const Collection *>(ip->id)));
          /* A collection instance empty was created, so this can just reuse the object preview
           * rendering. */
          object_preview_render(ip, cur_size);
          continue;
        case ID_AC:
          action_preview_render(ip, cur_size);
          continue;
        case ID_SCE:
          scene_preview_render(ip, cur_size, worker_status->reports);
          continue;
        default:
          /* Fall through to the same code as the `ip->id == nullptr` case. */
          break;
      }
    }
    other_id_types_preview_render(ip, cur_size, pr_method, worker_status);
  }
}
 
static void icon_preview_add_size(IconPreview *ip, uint *rect, int sizex, int sizey)
{
  IconPreviewSize *cur_size = static_cast<IconPreviewSize *>(ip->sizes.first);
 
  while (cur_size) {
    if (cur_size->sizex == sizex && cur_size->sizey == sizey) {
      /* requested size is already in list, no need to add it again */
      return;
    }
 
    cur_size = cur_size->next;
  }
 
  IconPreviewSize *new_size = MEM_callocN<IconPreviewSize>("IconPreviewSize");
  new_size->sizex = sizex;
  new_size->sizey = sizey;
  new_size->rect = rect;
 
  BLI_addtail(&ip->sizes, new_size);
}
 
static void icon_preview_endjob(void *customdata)
{
  IconPreview *ip = static_cast<IconPreview *>(customdata);
 
  if (ip->id) {
 
#if 0
    if (GS(ip->id->name) == ID_MA) {
      Material *ma = (Material *)ip->id;
      PreviewImage *prv_img = ma->preview;
      int i;
 
      /* signal to gpu texture */
      for (i = 0; i < NUM_ICON_SIZES; i++) {
        if (prv_img->gputexture[i]) {
          GPU_texture_free(prv_img->gputexture[i]);
          prv_img->gputexture[i] = nullptr;
          WM_main_add_notifier(NC_MATERIAL | ND_SHADING_DRAW, ip->id);
        }
      }
    }
#endif
  }
 
  if (ip->owner) {
    PreviewImage *prv_img = static_cast<PreviewImage *>(ip->owner);
    prv_img->runtime->tag &= ~PRV_TAG_DEFFERED_RENDERING;
 
    LISTBASE_FOREACH (IconPreviewSize *, icon_size, &ip->sizes) {
      int size_index = icon_previewimg_size_index_get(icon_size, prv_img);
      BKE_previewimg_finish(prv_img, size_index);
    }
 
    if (prv_img->runtime->tag & PRV_TAG_DEFFERED_DELETE) {
      BLI_assert(prv_img->runtime->deferred_loading_data);
      BKE_previewimg_deferred_release(prv_img);
    }
  }
}

class PreviewLoadJob {
  struct RequestedPreview {
    PreviewImage *preview;
    eIconSizes icon_size;
    std::atomic<bool> done = false;
    std::atomic<bool> failure = false;
 
    RequestedPreview(PreviewImage *preview, eIconSizes icon_size)
        : preview(preview), icon_size(icon_size)
    {
    }
  };

  ThreadQueue *todo_queue_; /* RequestedPreview * */
  std::list<RequestedPreview> requested_previews_;
 
 public:
  PreviewLoadJob();
  ~PreviewLoadJob();
 
  static PreviewLoadJob &ensure_job(wmWindowManager *wm, wmWindow *win);
  static void load_jobless(PreviewImage *preview, eIconSizes icon_size);
 
  void push_load_request(PreviewImage *preview, eIconSizes icon_size);
 
 private:
  static void run_fn(void *customdata, wmJobWorkerStatus *worker_status);
  static void update_fn(void *customdata);
  static void end_fn(void *customdata);
  static void free_fn(void *customdata);

  static void finish_request(RequestedPreview &request);
};
 
PreviewLoadJob::PreviewLoadJob() : todo_queue_(BLI_thread_queue_init()) {}
 
PreviewLoadJob::~PreviewLoadJob()
{
  BLI_thread_queue_free(todo_queue_);
}
 
PreviewLoadJob &PreviewLoadJob::ensure_job(wmWindowManager *wm, wmWindow *win)
{
  wmJob *wm_job = WM_jobs_get(
      wm, win, nullptr, "Loading previews...", eWM_JobFlag(0), WM_JOB_TYPE_LOAD_PREVIEW);
 
  if (!WM_jobs_is_running(wm_job)) {
    PreviewLoadJob *job_data = MEM_new<PreviewLoadJob>("PreviewLoadJobData");
 
    WM_jobs_customdata_set(wm_job, job_data, free_fn);
    WM_jobs_timer(wm_job, 0.1, NC_WINDOW, NC_WINDOW);
    WM_jobs_callbacks(wm_job, run_fn, nullptr, update_fn, end_fn);
 
    WM_jobs_start(wm, wm_job);
  }
 
  return *static_cast<PreviewLoadJob *>(WM_jobs_customdata_get(wm_job));
}
 
void PreviewLoadJob::load_jobless(PreviewImage *preview, const eIconSizes icon_size)
{
  PreviewLoadJob job_data{};
 
  job_data.push_load_request(preview, icon_size);
 
  wmJobWorkerStatus worker_status = {};
  run_fn(&job_data, &worker_status);
  update_fn(&job_data);
  end_fn(&job_data);
}
 
void PreviewLoadJob::push_load_request(PreviewImage *preview, const eIconSizes icon_size)
{
  BLI_assert(preview->runtime->deferred_loading_data);
 
  preview->flag[icon_size] |= PRV_RENDERING;
  /* Warn main thread code that this preview is being rendered and cannot be freed. */
  preview->runtime->tag |= PRV_TAG_DEFFERED_RENDERING;
 
  requested_previews_.emplace_back(preview, icon_size);
  BLI_thread_queue_push(
      todo_queue_, &requested_previews_.back(), BLI_THREAD_QUEUE_WORK_PRIORITY_NORMAL);
}
 
void PreviewLoadJob::run_fn(void *customdata, wmJobWorkerStatus *worker_status)
{
  PreviewLoadJob *job_data = static_cast<PreviewLoadJob *>(customdata);
 
  IMB_thumb_locks_acquire();
 
  while (RequestedPreview *request = static_cast<RequestedPreview *>(
             BLI_thread_queue_pop_timeout(job_data->todo_queue_, 100)))
  {
    if (worker_status->stop) {
      break;
    }
 
    PreviewImage *preview = request->preview;
 
    const std::optional<int> source = BKE_previewimg_deferred_thumb_source_get(preview);
    const char *filepath = BKE_previewimg_deferred_filepath_get(preview);
 
    if (!source || !filepath) {
      continue;
    }
 
    // printf("loading deferred %dx%d preview for %s\n", request->sizex, request->sizey, filepath);
 
    IMB_thumb_path_lock(filepath);
    ImBuf *thumb = IMB_thumb_manage(filepath, THB_LARGE, ThumbSource(*source));
    IMB_thumb_path_unlock(filepath);
 
    if (thumb) {
      /* PreviewImage assumes premultiplied alpha. */
      IMB_premultiply_alpha(thumb);
 
      if (ED_preview_use_image_size(preview, request->icon_size)) {
        preview->w[request->icon_size] = thumb->x;
        preview->h[request->icon_size] = thumb->y;
        BLI_assert(preview->rect[request->icon_size] == nullptr);
        preview->rect[request->icon_size] = (uint *)MEM_dupallocN(thumb->byte_buffer.data);
      }
      else {
        icon_copy_rect(thumb,
                       preview->w[request->icon_size],
                       preview->h[request->icon_size],
                       preview->rect[request->icon_size]);
      }
      IMB_freeImBuf(thumb);
    }
    else {
      request->failure = true;
    }
 
    request->done = true;
    worker_status->do_update = true;
  }
 
  IMB_thumb_locks_release();
}
 
/* Only execute on the main thread! */
void PreviewLoadJob::finish_request(RequestedPreview &request)
{
  PreviewImage *preview = request.preview;
 
  preview->runtime->tag &= ~PRV_TAG_DEFFERED_RENDERING;
  if (request.failure) {
    preview->runtime->tag |= PRV_TAG_DEFFERED_INVALID;
  }
  BKE_previewimg_finish(preview, request.icon_size);
 
  BLI_assert_msg(BLI_thread_is_main(),
                 "Deferred releasing of preview images should only run on the main thread");
  if (preview->runtime->tag & PRV_TAG_DEFFERED_DELETE) {
    BLI_assert(preview->runtime->deferred_loading_data);
    BKE_previewimg_deferred_release(preview);
  }
}
 
void PreviewLoadJob::update_fn(void *customdata)
{
  PreviewLoadJob *job_data = static_cast<PreviewLoadJob *>(customdata);
 
  for (auto request_it = job_data->requested_previews_.begin();
       request_it != job_data->requested_previews_.end();)
  {
    RequestedPreview &requested = *request_it;
    /* Skip items that are not done loading yet. */
    if (!requested.done) {
      ++request_it;
      continue;
    }
    finish_request(requested);
 
    /* Remove properly finished previews from the job data. */
    auto next_it = job_data->requested_previews_.erase(request_it);
    request_it = next_it;
  }
}
 
void PreviewLoadJob::end_fn(void *customdata)
{
  PreviewLoadJob *job_data = static_cast<PreviewLoadJob *>(customdata);
 
  /* Finish any possibly remaining queued previews. */
  for (RequestedPreview &request : job_data->requested_previews_) {
    finish_request(request);
  }
  job_data->requested_previews_.clear();
}
 
void PreviewLoadJob::free_fn(void *customdata)
{
  MEM_delete(static_cast<PreviewLoadJob *>(customdata));
}
 
static void icon_preview_free(void *customdata)
{
  IconPreview *ip = (IconPreview *)customdata;
 
  if (ip->id_copy) {
    preview_id_copy_free(ip->id_copy);
  }
 
  BLI_freelistN(&ip->sizes);
  MEM_freeN(ip);
}
 
bool ED_preview_use_image_size(const PreviewImage *preview, eIconSizes size)
{
  return size == ICON_SIZE_PREVIEW && preview->runtime->deferred_loading_data;
}
 
bool ED_preview_id_is_supported(const ID *id, const char **r_disabled_hint)
{
  if (id == nullptr) {
    return false;
  }
 
  /* Get both the result and the "potential" disabled hint. After that we can decide if the
   * disabled hint needs to be returned to the caller. */
  const auto [result, disabled_hint] = [id]() -> std::pair<bool, const char *> {
    switch (GS(id->name)) {
      case ID_NT:
        return {false, RPT_("Node groups do not support automatic previews")};
      case ID_OB:
        return {object_preview_is_type_supported((const Object *)id),
                RPT_("Object type does not support automatic previews")};
      case ID_GR:
        return {
            BKE_collection_contains_geometry_recursive(reinterpret_cast<const Collection *>(id)),
            RPT_("Collection does not contain object types that can be rendered for the automatic "
                 "preview")};
      case ID_SCE:
        return {scene_preview_is_supported((const Scene *)id),
                RPT_("Scenes without a camera do not support previews")};
      default:
        return {BKE_previewimg_id_get_p(id) != nullptr,
                RPT_("Data-block type does not support automatic previews")};
    }
  }();
 
  if (result == false && disabled_hint && r_disabled_hint) {
    *r_disabled_hint = disabled_hint;
  }
 
  return result;
}
 
void ED_preview_icon_render(
    const bContext *C, Scene *scene, PreviewImage *prv_img, ID *id, eIconSizes icon_size)
{
  /* Deferred loading of previews from the file system. */
  if (prv_img->runtime->deferred_loading_data) {
    if (prv_img->flag[icon_size] & PRV_RENDERING) {
      /* Already in the queue, don't add it again. */
      return;
    }
 
    PreviewLoadJob::load_jobless(prv_img, icon_size);
    return;
  }
 
  IconPreview ip = {nullptr};
 
  ED_preview_ensure_dbase(true);
 
  ip.bmain = CTX_data_main(C);
  if (GS(id->name) == ID_SCE) {
    Scene *icon_scene = reinterpret_cast<Scene *>(id);
    ip.scene = icon_scene;
    ip.depsgraph = BKE_scene_ensure_depsgraph(
        ip.bmain, ip.scene, BKE_view_layer_default_render(ip.scene));
    ip.active_object = nullptr;
  }
  else {
    ip.scene = scene;
    ip.depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
    /* Control isn't given back to the caller until the preview is done. So we don't need to copy
     * the ID to avoid thread races. */
    ip.id_copy = duplicate_ids(id, true);
    ip.active_object = CTX_data_active_object(C);
  }
  ip.owner = BKE_previewimg_id_ensure(id);
  ip.id = id;
 
  prv_img->flag[icon_size] |= PRV_RENDERING;
 
  icon_preview_add_size(
      &ip, prv_img->rect[icon_size], prv_img->w[icon_size], prv_img->h[icon_size]);
 
  wmJobWorkerStatus worker_status = {};
  icon_preview_startjob_all_sizes(&ip, &worker_status);
 
  icon_preview_endjob(&ip);
 
  BLI_freelistN(&ip.sizes);
  if (ip.id_copy != nullptr) {
    preview_id_copy_free(ip.id_copy);
  }
}
 
void ED_preview_icon_job(
    const bContext *C, PreviewImage *prv_img, ID *id, eIconSizes icon_size, const bool delay)
{
  /* Deferred loading of previews from the file system. */
  if (prv_img->runtime->deferred_loading_data) {
    if (prv_img->flag[icon_size] & PRV_RENDERING) {
      /* Already in the queue, don't add it again. */
      return;
    }
    PreviewLoadJob &load_job = PreviewLoadJob::ensure_job(CTX_wm_manager(C), CTX_wm_window(C));
    load_job.push_load_request(prv_img, icon_size);
 
    return;
  }
 
  IconPreview *ip, *old_ip;
 
  ED_preview_ensure_dbase(true);
 
  /* suspended start means it starts after 1 timer step, see WM_jobs_timer below */
  wmJob *wm_job = WM_jobs_get(CTX_wm_manager(C),
                              CTX_wm_window(C),
                              prv_img,
                              "Generating icon preview...",
                              WM_JOB_EXCL_RENDER,
                              WM_JOB_TYPE_RENDER_PREVIEW);
 
  ip = MEM_callocN<IconPreview>("icon preview");
 
  /* render all resolutions from suspended job too */
  old_ip = static_cast<IconPreview *>(WM_jobs_customdata_get(wm_job));
  if (old_ip) {
    BLI_movelisttolist(&ip->sizes, &old_ip->sizes);
  }
 
  /* customdata for preview thread */
  ip->bmain = CTX_data_main(C);
  if (GS(id->name) == ID_SCE) {
    Scene *icon_scene = reinterpret_cast<Scene *>(id);
    ip->scene = icon_scene;
    ip->depsgraph = BKE_scene_ensure_depsgraph(
        ip->bmain, ip->scene, BKE_view_layer_default_render(ip->scene));
    ip->active_object = nullptr;
  }
  else {
    ip->depsgraph = CTX_data_ensure_evaluated_depsgraph(C);
    ip->scene = DEG_get_input_scene(ip->depsgraph);
    ip->id_copy = duplicate_ids(id, false);
    ip->active_object = CTX_data_active_object(C);
  }
  ip->owner = prv_img;
  ip->id = id;
 
  prv_img->flag[icon_size] |= PRV_RENDERING;
 
  icon_preview_add_size(
      ip, prv_img->rect[icon_size], prv_img->w[icon_size], prv_img->h[icon_size]);
 
  /* setup job */
  WM_jobs_customdata_set(wm_job, ip, icon_preview_free);
  WM_jobs_timer(wm_job, 0.1, NC_WINDOW, NC_WINDOW);
  /* Wait 2s to start rendering icon previews, to not bog down user interaction.
   * Particularly important for heavy scenes and Eevee using OpenGL that blocks
   * the user interface drawing. */
  WM_jobs_delay_start(wm_job, (delay) ? 2.0 : 0.0);
  WM_jobs_callbacks(
      wm_job, icon_preview_startjob_all_sizes, nullptr, nullptr, icon_preview_endjob);
 
  WM_jobs_start(CTX_wm_manager(C), wm_job);
}
 
void ED_preview_shader_job(const bContext *C,
                           const void *owner,
                           ID *id,
                           ID *parent,
                           MTex *slot,
                           int sizex,
                           int sizey,
                           ePreviewRenderMethod method)
{
  Object *ob = CTX_data_active_object(C);
  wmJob *wm_job;
  ShaderPreview *sp;
  Scene *scene = CTX_data_scene(C);
  const ID_Type id_type = GS(id->name);
 
  BLI_assert(BKE_previewimg_id_supports_jobs(id));
 
  /* Use workspace render only for buttons Window,
   * since the other previews are related to the datablock. */
 
  if (preview_method_is_render(method) && !ED_check_engine_supports_preview(scene)) {
    return;
  }
 
  ED_preview_ensure_dbase(true);
 
  wm_job = WM_jobs_get(CTX_wm_manager(C),
                       CTX_wm_window(C),
                       owner,
                       "Generating shader preview...",
                       WM_JOB_EXCL_RENDER,
                       WM_JOB_TYPE_RENDER_PREVIEW);
  sp = MEM_callocN<ShaderPreview>("shader preview");
 
  /* customdata for preview thread */
  sp->scene = scene;
  sp->owner = owner;
  sp->sizex = sizex;
  sp->sizey = sizey;
  sp->pr_method = method;
  sp->id = id;
  sp->id_copy = duplicate_ids(id, false);
  sp->own_id_copy = true;
  sp->parent = parent;
  sp->slot = slot;
  sp->bmain = CTX_data_main(C);
  Material *ma = nullptr;
 
  /* hardcoded preview .blend for Eevee + Cycles, this should be solved
   * once with custom preview .blend path for external engines */
 
  /* grease pencil use its own preview file */
  if (id_type == ID_MA) {
    ma = (Material *)id;
  }
 
  if ((ma == nullptr) || (ma->gp_style == nullptr)) {
    sp->pr_main = G.pr_main;
  }
  else {
    sp->pr_main = G_pr_main_grease_pencil;
  }
 
  if (ob && ob->totcol) {
    copy_v4_v4(sp->color, ob->color);
  }
  else {
    ARRAY_SET_ITEMS(sp->color, 0.0f, 0.0f, 0.0f, 1.0f);
  }
 
  /* setup job */
  WM_jobs_customdata_set(wm_job, sp, shader_preview_free);
  WM_jobs_timer(wm_job, 0.1, NC_MATERIAL, NC_MATERIAL);
  WM_jobs_callbacks(wm_job, common_preview_startjob, nullptr, shader_preview_updatejob, nullptr);
 
  WM_jobs_start(CTX_wm_manager(C), wm_job);
}
 
void ED_preview_kill_jobs(wmWindowManager *wm, Main * /*bmain*/)
{
  if (wm) {
    /* This is called to stop all preview jobs before scene data changes, to
     * avoid invalid memory access. */
    WM_jobs_kill_type(wm, nullptr, WM_JOB_TYPE_RENDER_PREVIEW);
  }
}
 
void ED_preview_kill_jobs_for_id(wmWindowManager *wm, const ID *id)
{
  const PreviewImage *preview = BKE_previewimg_id_get(id);
  if (wm && preview) {
    WM_jobs_kill_type(wm, preview, WM_JOB_TYPE_RENDER_PREVIEW);
  }
}
 
struct PreviewRestartQueueEntry {
  PreviewRestartQueueEntry *next, *prev;
 
  enum eIconSizes size;
  ID *id;
};
 
static ListBase /* #PreviewRestartQueueEntry */ G_restart_previews_queue;
 
void ED_preview_restart_queue_free()
{
  BLI_freelistN(&G_restart_previews_queue);
}
 
void ED_preview_restart_queue_add(ID *id, enum eIconSizes size)
{
  PreviewRestartQueueEntry *queue_entry = MEM_callocN<PreviewRestartQueueEntry>(__func__);
  queue_entry->size = size;
  queue_entry->id = id;
  BLI_addtail(&G_restart_previews_queue, queue_entry);
}
 
void ED_preview_restart_queue_work(const bContext *C)
{
  LISTBASE_FOREACH_MUTABLE (PreviewRestartQueueEntry *, queue_entry, &G_restart_previews_queue) {
    PreviewImage *preview = BKE_previewimg_id_get(queue_entry->id);
    if (!preview) {
      continue;
    }
    if (preview->flag[queue_entry->size] & PRV_USER_EDITED) {
      /* Don't touch custom previews. */
      continue;
    }
 
    BKE_previewimg_clear_single(preview, queue_entry->size);
    UI_icon_render_id(C, nullptr, queue_entry->id, queue_entry->size, true);
 
    BLI_freelinkN(&G_restart_previews_queue, queue_entry);
  }
}