test/source/blender/editors/space_sequencer/sequencer_preview_draw.cc

/* SPDX-FileCopyrightText: 2001-2002 NaN Holding BV. All rights reserved.
 *
 * SPDX-License-Identifier: GPL-2.0-or-later */

/** \file
 * \ingroup spseq
 */

#include <cmath>
#include <cstring>

#include "BLI_blenlib.h"
#include "BLI_utildefines.h"

#include "IMB_imbuf_types.h"

#include "DNA_scene_types.h"
#include "DNA_screen_types.h"
#include "DNA_space_types.h"

#include "BKE_context.h"
#include "BKE_global.h"
#include "BKE_scene.h"

#include "IMB_colormanagement.h"
#include "IMB_imbuf.h"

#include "GPU_framebuffer.h"
#include "GPU_immediate.h"
#include "GPU_immediate_util.h"
#include "GPU_matrix.h"
#include "GPU_viewport.h"

#include "ED_gpencil_legacy.hh"
#include "ED_screen.hh"
#include "ED_sequencer.hh"
#include "ED_space_api.hh"
#include "ED_util.hh"

#include "BIF_glutil.hh"

#include "SEQ_channels.h"
#include "SEQ_iterator.h"
#include "SEQ_prefetch.h"
#include "SEQ_proxy.h"
#include "SEQ_render.h"
#include "SEQ_select.h"
#include "SEQ_sequencer.h"
#include "SEQ_time.h"
#include "SEQ_transform.h"

#include "UI_interface.hh"
#include "UI_resources.hh"
#include "UI_view2d.hh"

#include "WM_api.hh"
#include "WM_types.hh"

/* Own include. */
#include "sequencer_intern.hh"

static Sequence *special_seq_update = nullptr;

void sequencer_special_update_set(Sequence *seq)
{
  special_seq_update = seq;
}

Sequence *ED_sequencer_special_preview_get()
{
  return special_seq_update;
}

void ED_sequencer_special_preview_set(bContext *C, const int mval[2])
{
  Scene *scene = CTX_data_scene(C);
  ARegion *region = CTX_wm_region(C);
  int hand;
  Sequence *seq;
  seq = find_nearest_seq(scene, &region->v2d, &hand, mval);
  sequencer_special_update_set(seq);
}

void ED_sequencer_special_preview_clear()
{
  sequencer_special_update_set(nullptr);
}

ImBuf *sequencer_ibuf_get(Main *bmain,
                          ARegion *region,
                          Depsgraph *depsgraph,
                          Scene *scene,
                          SpaceSeq *sseq,
                          int timeline_frame,
                          int frame_ofs,
                          const char *viewname)
{
  SeqRenderData context = {nullptr};
  ImBuf *ibuf;
  int rectx, recty;
  double render_size;
  short is_break = G.is_break;

  if (sseq->render_size == SEQ_RENDER_SIZE_NONE) {
    return nullptr;
  }

  if (sseq->render_size == SEQ_RENDER_SIZE_SCENE) {
    render_size = scene->r.size / 100.0;
  }
  else {
    render_size = SEQ_rendersize_to_scale_factor(sseq->render_size);
  }

  rectx = roundf(render_size * scene->r.xsch);
  recty = roundf(render_size * scene->r.ysch);

  SEQ_render_new_render_data(
      bmain, depsgraph, scene, rectx, recty, sseq->render_size, false, &context);
  context.view_id = BKE_scene_multiview_view_id_get(&scene->r, viewname);
  context.use_proxies = (sseq->flag & SEQ_USE_PROXIES) != 0;

  /* Sequencer could start rendering, in this case we need to be sure it wouldn't be canceled
   * by Escape pressed somewhere in the past. */
  G.is_break = false;

  GPUViewport *viewport = WM_draw_region_get_bound_viewport(region);
  GPUFrameBuffer *fb = GPU_framebuffer_active_get();
  if (viewport) {
    /* Unbind viewport to release the DRW context. */
    GPU_viewport_unbind(viewport);
  }
  else {
    /* Rendering can change OGL context. Save & Restore frame-buffer. */
    GPU_framebuffer_restore();
  }

  if (special_seq_update) {
    ibuf = SEQ_render_give_ibuf_direct(&context, timeline_frame + frame_ofs, special_seq_update);
  }
  else {
    ibuf = SEQ_render_give_ibuf(&context, timeline_frame + frame_ofs, sseq->chanshown);
  }

  if (viewport) {
    /* Follows same logic as wm_draw_window_offscreen to make sure to restore the same
     * viewport. */
    int view = (sseq->multiview_eye == STEREO_RIGHT_ID) ? 1 : 0;
    GPU_viewport_bind(viewport, view, &region->winrct);
  }
  else if (fb) {
    GPU_framebuffer_bind(fb);
  }

  /* Restore state so real rendering would be canceled if needed. */
  G.is_break = is_break;

  return ibuf;
}

static void sequencer_check_scopes(SequencerScopes *scopes, ImBuf *ibuf)
{
  if (scopes->reference_ibuf != ibuf) {
    if (scopes->zebra_ibuf) {
      IMB_freeImBuf(scopes->zebra_ibuf);
      scopes->zebra_ibuf = nullptr;
    }

    if (scopes->waveform_ibuf) {
      IMB_freeImBuf(scopes->waveform_ibuf);
      scopes->waveform_ibuf = nullptr;
    }

    if (scopes->sep_waveform_ibuf) {
      IMB_freeImBuf(scopes->sep_waveform_ibuf);
      scopes->sep_waveform_ibuf = nullptr;
    }

    if (scopes->vector_ibuf) {
      IMB_freeImBuf(scopes->vector_ibuf);
      scopes->vector_ibuf = nullptr;
    }

    if (scopes->histogram_ibuf) {
      IMB_freeImBuf(scopes->histogram_ibuf);
      scopes->histogram_ibuf = nullptr;
    }
  }
}

static ImBuf *sequencer_make_scope(Scene *scene, ImBuf *ibuf, ImBuf *(*make_scope_fn)(ImBuf *ibuf))
{
  ImBuf *display_ibuf = IMB_dupImBuf(ibuf);
  ImBuf *scope;

  IMB_colormanagement_imbuf_make_display_space(
      display_ibuf, &scene->view_settings, &scene->display_settings);

  scope = make_scope_fn(display_ibuf);
  IMB_rectfill_alpha(scope, 1.0f);

  IMB_freeImBuf(display_ibuf);

  return scope;
}

static void sequencer_display_size(Scene *scene, float r_viewrect[2])
{
  r_viewrect[0] = float(scene->r.xsch);
  r_viewrect[1] = float(scene->r.ysch);

  r_viewrect[0] *= scene->r.xasp / scene->r.yasp;
}

static void sequencer_draw_gpencil_overlay(const bContext *C)
{
  /* Draw grease-pencil (image aligned). */
  ED_annotation_draw_2dimage(C);

  /* Orthographic at pixel level. */
  UI_view2d_view_restore(C);

  /* Draw grease-pencil (screen aligned). */
  ED_annotation_draw_view2d(C, false);
}

/**
 * Draw content and safety borders.
 */
static void sequencer_draw_borders_overlay(const SpaceSeq *sseq,
                                           const View2D *v2d,
                                           const Scene *scene)
{
  float x1 = v2d->tot.xmin;
  float y1 = v2d->tot.ymin;
  float x2 = v2d->tot.xmax;
  float y2 = v2d->tot.ymax;

  GPU_line_width(1.0f);

  /* Draw border. */
  const uint shdr_pos = GPU_vertformat_attr_add(
      immVertexFormat(), "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);

  immBindBuiltinProgram(GPU_SHADER_3D_LINE_DASHED_UNIFORM_COLOR);

  float viewport_size[4];
  GPU_viewport_size_get_f(viewport_size);
  immUniform2f("viewport_size", viewport_size[2] / UI_SCALE_FAC, viewport_size[3] / UI_SCALE_FAC);

  immUniformThemeColor(TH_BACK);
  immUniform1i("colors_len", 0); /* Simple dashes. */
  immUniform1f("dash_width", 6.0f);
  immUniform1f("udash_factor", 0.5f);

  imm_draw_box_wire_2d(shdr_pos, x1 - 0.5f, y1 - 0.5f, x2 + 0.5f, y2 + 0.5f);

  /* Draw safety border. */
  if (sseq->preview_overlay.flag & SEQ_PREVIEW_SHOW_SAFE_MARGINS) {
    immUniformThemeColorBlend(TH_VIEW_OVERLAY, TH_BACK, 0.25f);
    rctf rect;
    rect.xmin = x1;
    rect.xmax = x2;
    rect.ymin = y1;
    rect.ymax = y2;
    UI_draw_safe_areas(shdr_pos, &rect, scene->safe_areas.title, scene->safe_areas.action);

    if (sseq->preview_overlay.flag & SEQ_PREVIEW_SHOW_SAFE_CENTER) {

      UI_draw_safe_areas(
          shdr_pos, &rect, scene->safe_areas.title_center, scene->safe_areas.action_center);
    }
  }

  immUnbindProgram();
}

#if 0
void sequencer_draw_maskedit(const bContext *C, Scene *scene, ARegion *region, SpaceSeq *sseq)
{
  /* NOTE: sequencer mask editing isn't finished, the draw code is working but editing not.
   * For now just disable drawing since the strip frame will likely be offset. */

  // if (sc->mode == SC_MODE_MASKEDIT)
  if (0 && sseq->mainb == SEQ_DRAW_IMG_IMBUF) {
    Mask *mask = SEQ_active_mask_get(scene);

    if (mask) {
      int width, height;
      float aspx = 1.0f, aspy = 1.0f;
      // ED_mask_get_size(C, &width, &height);

      // Scene *scene = CTX_data_scene(C);
      BKE_render_resolution(&scene->r, false, &width, &height);

      ED_mask_draw_region(mask,
                          region,
                          0,
                          0,
                          0, /* TODO */
                          width,
                          height,
                          aspx,
                          aspy,
                          false,
                          true,
                          nullptr,
                          C);
    }
  }
}
#endif

/* Force redraw, when prefetching and using cache view. */
static void seq_prefetch_wm_notify(const bContext *C, Scene *scene)
{
  if (SEQ_prefetch_need_redraw(CTX_data_main(C), scene)) {
    WM_event_add_notifier(C, NC_SCENE | ND_SEQUENCER, nullptr);
  }
}

static void *sequencer_OCIO_transform_ibuf(const bContext *C,
                                           ImBuf *ibuf,
                                           bool *r_glsl_used,
                                           eGPUTextureFormat *r_format,
                                           eGPUDataFormat *r_data,
                                           void **r_buffer_cache_handle)
{
  void *display_buffer;
  bool force_fallback = false;
  *r_glsl_used = false;
  force_fallback |= (ED_draw_imbuf_method(ibuf) != IMAGE_DRAW_METHOD_GLSL);
  force_fallback |= (ibuf->dither != 0.0f);

  /* Default */
  *r_format = GPU_RGBA8;
  *r_data = GPU_DATA_UBYTE;

  /* Fallback to CPU based color space conversion. */
  if (force_fallback) {
    *r_glsl_used = false;
    display_buffer = nullptr;
  }
  else if (ibuf->float_buffer.data) {
    display_buffer = ibuf->float_buffer.data;

    *r_data = GPU_DATA_FLOAT;
    if (ibuf->channels == 4) {
      *r_format = GPU_RGBA16F;
    }
    else if (ibuf->channels == 3) {
      /* Alpha is implicitly 1. */
      *r_format = GPU_RGB16F;
    }
    else {
      BLI_assert_msg(0, "Incompatible number of channels for float buffer in sequencer");
      *r_format = GPU_RGBA16F;
      display_buffer = nullptr;
    }

    if (ibuf->float_buffer.colorspace) {
      *r_glsl_used = IMB_colormanagement_setup_glsl_draw_from_space_ctx(
          C, ibuf->float_buffer.colorspace, ibuf->dither, true);
    }
    else {
      *r_glsl_used = IMB_colormanagement_setup_glsl_draw_ctx(C, ibuf->dither, true);
    }
  }
  else if (ibuf->byte_buffer.data) {
    display_buffer = ibuf->byte_buffer.data;

    *r_glsl_used = IMB_colormanagement_setup_glsl_draw_from_space_ctx(
        C, ibuf->byte_buffer.colorspace, ibuf->dither, false);
  }
  else {
    display_buffer = nullptr;
  }

  /* There is data to be displayed, but GLSL is not initialized
   * properly, in this case we fallback to CPU-based display transform. */
  if ((ibuf->byte_buffer.data || ibuf->float_buffer.data) && !*r_glsl_used) {
    display_buffer = IMB_display_buffer_acquire_ctx(C, ibuf, r_buffer_cache_handle);
    *r_format = GPU_RGBA8;
    *r_data = GPU_DATA_UBYTE;
  }

  return display_buffer;
}

static void sequencer_stop_running_jobs(const bContext *C, Scene *scene)
{
  if (G.is_rendering == false && (scene->r.seq_prev_type) == OB_RENDER) {
    /* Stop all running jobs, except screen one. Currently previews frustrate Render.
     * Need to make so sequencers rendering doesn't conflict with compositor. */
    WM_jobs_kill_type(CTX_wm_manager(C), nullptr, WM_JOB_TYPE_COMPOSITE);

    /* In case of final rendering used for preview, kill all previews,
     * otherwise threading conflict will happen in rendering module. */
    WM_jobs_kill_type(CTX_wm_manager(C), nullptr, WM_JOB_TYPE_RENDER_PREVIEW);
  }
}

static void sequencer_preview_clear()
{
  UI_ThemeClearColor(TH_SEQ_PREVIEW);
}

static void sequencer_preview_get_rect(rctf *preview,
                                       Scene *scene,
                                       ARegion *region,
                                       SpaceSeq *sseq,
                                       bool draw_overlay,
                                       bool draw_backdrop)
{
  View2D *v2d = &region->v2d;
  float viewrect[2];

  sequencer_display_size(scene, viewrect);
  BLI_rctf_init(preview, -1.0f, 1.0f, -1.0f, 1.0f);

  if (draw_overlay && (sseq->overlay_frame_type == SEQ_OVERLAY_FRAME_TYPE_RECT)) {
    preview->xmax = v2d->tot.xmin +
                    (fabsf(BLI_rctf_size_x(&v2d->tot)) * scene->ed->overlay_frame_rect.xmax);
    preview->xmin = v2d->tot.xmin +
                    (fabsf(BLI_rctf_size_x(&v2d->tot)) * scene->ed->overlay_frame_rect.xmin);
    preview->ymax = v2d->tot.ymin +
                    (fabsf(BLI_rctf_size_y(&v2d->tot)) * scene->ed->overlay_frame_rect.ymax);
    preview->ymin = v2d->tot.ymin +
                    (fabsf(BLI_rctf_size_y(&v2d->tot)) * scene->ed->overlay_frame_rect.ymin);
  }
  else if (draw_backdrop) {
    float aspect = BLI_rcti_size_x(&region->winrct) / float(BLI_rcti_size_y(&region->winrct));
    float image_aspect = viewrect[0] / viewrect[1];

    if (aspect >= image_aspect) {
      preview->xmax = image_aspect / aspect;
      preview->xmin = -preview->xmax;
    }
    else {
      preview->ymax = aspect / image_aspect;
      preview->ymin = -preview->ymax;
    }
  }
  else {
    *preview = v2d->tot;
  }
}

static void sequencer_draw_display_buffer(const bContext *C,
                                          Scene *scene,
                                          ARegion *region,
                                          SpaceSeq *sseq,
                                          ImBuf *ibuf,
                                          ImBuf *scope,
                                          bool draw_overlay,
                                          bool draw_backdrop)
{
  void *display_buffer;
  void *buffer_cache_handle = nullptr;

  if (sseq->mainb == SEQ_DRAW_IMG_IMBUF && sseq->flag & SEQ_USE_ALPHA) {
    GPU_blend(GPU_BLEND_ALPHA);
  }

  /* Format needs to be created prior to any #immBindShader call.
   * Do it here because OCIO binds its own shader. */
  eGPUTextureFormat format;
  eGPUDataFormat data;
  bool glsl_used = false;
  GPUVertFormat *imm_format = immVertexFormat();
  uint pos = GPU_vertformat_attr_add(imm_format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
  uint texCoord = GPU_vertformat_attr_add(
      imm_format, "texCoord", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);

  if (scope) {
    ibuf = scope;

    if (ibuf->float_buffer.data && ibuf->byte_buffer.data == nullptr) {
      IMB_rect_from_float(ibuf);
    }

    display_buffer = ibuf->byte_buffer.data;
    format = GPU_RGBA8;
    data = GPU_DATA_UBYTE;
  }
  else {
    display_buffer = sequencer_OCIO_transform_ibuf(
        C, ibuf, &glsl_used, &format, &data, &buffer_cache_handle);
  }

  if (draw_backdrop) {
    GPU_matrix_push();
    GPU_matrix_identity_set();
    GPU_matrix_push_projection();
    GPU_matrix_identity_projection_set();
  }
  eGPUTextureUsage usage = GPU_TEXTURE_USAGE_SHADER_READ | GPU_TEXTURE_USAGE_ATTACHMENT;
  GPUTexture *texture = GPU_texture_create_2d(
      "seq_display_buf", ibuf->x, ibuf->y, 1, format, usage, nullptr);
  GPU_texture_update(texture, data, display_buffer);
  GPU_texture_filter_mode(texture, false);

  GPU_texture_bind(texture, 0);

  if (!glsl_used) {
    immBindBuiltinProgram(GPU_SHADER_3D_IMAGE_COLOR);
    immUniformColor3f(1.0f, 1.0f, 1.0f);
  }

  immBegin(GPU_PRIM_TRI_FAN, 4);

  rctf preview;
  rctf canvas;
  sequencer_preview_get_rect(&preview, scene, region, sseq, draw_overlay, draw_backdrop);

  if (draw_overlay && (sseq->overlay_frame_type == SEQ_OVERLAY_FRAME_TYPE_RECT)) {
    canvas = scene->ed->overlay_frame_rect;
  }
  else {
    BLI_rctf_init(&canvas, 0.0f, 1.0f, 0.0f, 1.0f);
  }

  immAttr2f(texCoord, canvas.xmin, canvas.ymin);
  immVertex2f(pos, preview.xmin, preview.ymin);

  immAttr2f(texCoord, canvas.xmin, canvas.ymax);
  immVertex2f(pos, preview.xmin, preview.ymax);

  immAttr2f(texCoord, canvas.xmax, canvas.ymax);
  immVertex2f(pos, preview.xmax, preview.ymax);

  immAttr2f(texCoord, canvas.xmax, canvas.ymin);
  immVertex2f(pos, preview.xmax, preview.ymin);

  immEnd();

  GPU_texture_unbind(texture);
  GPU_texture_free(texture);

  if (!glsl_used) {
    immUnbindProgram();
  }
  else {
    IMB_colormanagement_finish_glsl_draw();
  }

  if (buffer_cache_handle) {
    IMB_display_buffer_release(buffer_cache_handle);
  }

  if (sseq->mainb == SEQ_DRAW_IMG_IMBUF && sseq->flag & SEQ_USE_ALPHA) {
    GPU_blend(GPU_BLEND_NONE);
  }

  if (draw_backdrop) {
    GPU_matrix_pop();
    GPU_matrix_pop_projection();
  }
}

static ImBuf *sequencer_get_scope(Scene *scene, SpaceSeq *sseq, ImBuf *ibuf, bool draw_backdrop)
{
  ImBuf *scope = nullptr;
  SequencerScopes *scopes = &sseq->scopes;

  if (!draw_backdrop && (sseq->mainb != SEQ_DRAW_IMG_IMBUF || sseq->zebra != 0)) {
    sequencer_check_scopes(scopes, ibuf);

    switch (sseq->mainb) {
      case SEQ_DRAW_IMG_IMBUF:
        if (!scopes->zebra_ibuf) {
          ImBuf *display_ibuf = IMB_dupImBuf(ibuf);

          if (display_ibuf->float_buffer.data) {
            IMB_colormanagement_imbuf_make_display_space(
                display_ibuf, &scene->view_settings, &scene->display_settings);
          }
          scopes->zebra_ibuf = make_zebra_view_from_ibuf(display_ibuf, sseq->zebra);
          IMB_freeImBuf(display_ibuf);
        }
        scope = scopes->zebra_ibuf;
        break;
      case SEQ_DRAW_IMG_WAVEFORM:
        if ((sseq->flag & SEQ_DRAW_COLOR_SEPARATED) != 0) {
          if (!scopes->sep_waveform_ibuf) {
            scopes->sep_waveform_ibuf = sequencer_make_scope(
                scene, ibuf, make_sep_waveform_view_from_ibuf);
          }
          scope = scopes->sep_waveform_ibuf;
        }
        else {
          if (!scopes->waveform_ibuf) {
            scopes->waveform_ibuf = sequencer_make_scope(
                scene, ibuf, make_waveform_view_from_ibuf);
          }
          scope = scopes->waveform_ibuf;
        }
        break;
      case SEQ_DRAW_IMG_VECTORSCOPE:
        if (!scopes->vector_ibuf) {
          scopes->vector_ibuf = sequencer_make_scope(scene, ibuf, make_vectorscope_view_from_ibuf);
        }
        scope = scopes->vector_ibuf;
        break;
      case SEQ_DRAW_IMG_HISTOGRAM:
        if (!scopes->histogram_ibuf) {
          scopes->histogram_ibuf = sequencer_make_scope(
              scene, ibuf, make_histogram_view_from_ibuf);
        }
        scope = scopes->histogram_ibuf;
        break;
    }

    /* Future files may have new scopes we don't catch above. */
    if (scope) {
      scopes->reference_ibuf = ibuf;
    }
  }
  return scope;
}

bool sequencer_draw_get_transform_preview(SpaceSeq *sseq, Scene *scene)
{
  Sequence *last_seq = SEQ_select_active_get(scene);
  if (last_seq == nullptr) {
    return false;
  }

  return (G.moving & G_TRANSFORM_SEQ) && (last_seq->flag & SELECT) &&
         ((last_seq->flag & SEQ_LEFTSEL) || (last_seq->flag & SEQ_RIGHTSEL)) &&
         (sseq->draw_flag & SEQ_DRAW_TRANSFORM_PREVIEW);
}

int sequencer_draw_get_transform_preview_frame(Scene *scene)
{
  Sequence *last_seq = SEQ_select_active_get(scene);
  /* #sequencer_draw_get_transform_preview must already have been called. */
  BLI_assert(last_seq != nullptr);
  int preview_frame;

  if (last_seq->flag & SEQ_RIGHTSEL) {
    preview_frame = SEQ_time_right_handle_frame_get(scene, last_seq) - 1;
  }
  else {
    preview_frame = SEQ_time_left_handle_frame_get(scene, last_seq);
  }

  return preview_frame;
}

static void seq_draw_image_origin_and_outline(const bContext *C, Sequence *seq, bool is_active_seq)
{
  SpaceSeq *sseq = CTX_wm_space_seq(C);
  const ARegion *region = CTX_wm_region(C);
  if (region->regiontype == RGN_TYPE_PREVIEW && !sequencer_view_preview_only_poll(C)) {
    return;
  }
  if ((seq->flag & SELECT) == 0) {
    return;
  }
  if (ED_screen_animation_no_scrub(CTX_wm_manager(C))) {
    return;
  }
  if ((sseq->flag & SEQ_SHOW_OVERLAY) == 0 ||
      (sseq->preview_overlay.flag & SEQ_PREVIEW_SHOW_OUTLINE_SELECTED) == 0)
  {
    return;
  }
  if (ELEM(sseq->mainb, SEQ_DRAW_IMG_WAVEFORM, SEQ_DRAW_IMG_VECTORSCOPE, SEQ_DRAW_IMG_HISTOGRAM)) {
    return;
  }

  float origin[2];
  SEQ_image_transform_origin_offset_pixelspace_get(CTX_data_scene(C), seq, origin);

  /* Origin. */
  GPUVertFormat *format = immVertexFormat();
  uint pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
  immBindBuiltinProgram(GPU_SHADER_2D_POINT_UNIFORM_SIZE_UNIFORM_COLOR_OUTLINE_AA);
  immUniform1f("outlineWidth", 1.5f);
  immUniformColor3f(1.0f, 1.0f, 1.0f);
  immUniform4f("outlineColor", 0.0f, 0.0f, 0.0f, 1.0f);
  immUniform1f("size", 15.0f * U.pixelsize);
  immBegin(GPU_PRIM_POINTS, 1);
  immVertex2f(pos, origin[0], origin[1]);
  immEnd();
  immUnbindProgram();

  /* Outline. */
  float seq_image_quad[4][2];
  SEQ_image_transform_final_quad_get(CTX_data_scene(C), seq, seq_image_quad);

  GPU_line_smooth(true);
  GPU_blend(GPU_BLEND_ALPHA);
  GPU_line_width(2);
  immBindBuiltinProgram(GPU_SHADER_3D_UNIFORM_COLOR);

  float col[3];
  if (is_active_seq) {
    UI_GetThemeColor3fv(TH_SEQ_ACTIVE, col);
  }
  else {
    UI_GetThemeColor3fv(TH_SEQ_SELECTED, col);
  }
  immUniformColor3fv(col);
  immUniform1f("lineWidth", U.pixelsize);
  immBegin(GPU_PRIM_LINE_LOOP, 4);
  immVertex2f(pos, seq_image_quad[0][0], seq_image_quad[0][1]);
  immVertex2f(pos, seq_image_quad[1][0], seq_image_quad[1][1]);
  immVertex2f(pos, seq_image_quad[2][0], seq_image_quad[2][1]);
  immVertex2f(pos, seq_image_quad[3][0], seq_image_quad[3][1]);
  immEnd();
  immUnbindProgram();
  GPU_line_width(1);
  GPU_blend(GPU_BLEND_NONE);
  GPU_line_smooth(false);
}

void sequencer_draw_preview(const bContext *C,
                            Scene *scene,
                            ARegion *region,
                            SpaceSeq *sseq,
                            int timeline_frame,
                            int offset,
                            bool draw_overlay,
                            bool draw_backdrop)
{
  Main *bmain = CTX_data_main(C);
  Depsgraph *depsgraph = CTX_data_expect_evaluated_depsgraph(C);
  View2D *v2d = &region->v2d;
  ImBuf *ibuf = nullptr;
  ImBuf *scope = nullptr;
  float viewrect[2];
  const bool show_imbuf = ED_space_sequencer_check_show_imbuf(sseq);
  const bool draw_gpencil = ((sseq->preview_overlay.flag & SEQ_PREVIEW_SHOW_GPENCIL) && sseq->gpd);
  const char *names[2] = {STEREO_LEFT_NAME, STEREO_RIGHT_NAME};

  sequencer_stop_running_jobs(C, scene);
  if (G.is_rendering) {
    return;
  }

  int preview_frame = timeline_frame;
  if (sequencer_draw_get_transform_preview(sseq, scene)) {
    preview_frame = sequencer_draw_get_transform_preview_frame(scene);
  }

  /* Get image. */
  ibuf = sequencer_ibuf_get(
      bmain, region, depsgraph, scene, sseq, preview_frame, offset, names[sseq->multiview_eye]);

  /* Setup off-screen buffers. */
  GPUViewport *viewport = WM_draw_region_get_viewport(region);
  GPUFrameBuffer *framebuffer_overlay = GPU_viewport_framebuffer_overlay_get(viewport);
  GPU_framebuffer_bind_no_srgb(framebuffer_overlay);
  GPU_depth_test(GPU_DEPTH_NONE);

  if (sseq->render_size == SEQ_RENDER_SIZE_NONE) {
    sequencer_preview_clear();
    return;
  }

  /* Setup view. */
  sequencer_display_size(scene, viewrect);
  UI_view2d_totRect_set(v2d, roundf(viewrect[0] + 0.5f), roundf(viewrect[1] + 0.5f));
  UI_view2d_curRect_validate(v2d);
  UI_view2d_view_ortho(v2d);

  /* Draw background. */
  if (!draw_backdrop &&
      (!draw_overlay || (sseq->overlay_frame_type == SEQ_OVERLAY_FRAME_TYPE_REFERENCE)))
  {
    sequencer_preview_clear();

    if (sseq->flag & SEQ_USE_ALPHA) {
      imm_draw_box_checker_2d(v2d->tot.xmin, v2d->tot.ymin, v2d->tot.xmax, v2d->tot.ymax);
    }
  }

  if (ibuf) {
    scope = sequencer_get_scope(scene, sseq, ibuf, draw_backdrop);

    /* Draw image. */
    sequencer_draw_display_buffer(
        C, scene, region, sseq, ibuf, scope, draw_overlay, draw_backdrop);

    /* Draw over image. */
    if (sseq->preview_overlay.flag & SEQ_PREVIEW_SHOW_METADATA && sseq->flag & SEQ_SHOW_OVERLAY) {
      ED_region_image_metadata_draw(0.0, 0.0, ibuf, &v2d->tot, 1.0, 1.0);
    }
  }

  if (show_imbuf && (sseq->flag & SEQ_SHOW_OVERLAY)) {
    sequencer_draw_borders_overlay(sseq, v2d, scene);
  }

  if (!draw_backdrop && scene->ed != nullptr) {
    Editing *ed = SEQ_editing_get(scene);
    ListBase *channels = SEQ_channels_displayed_get(ed);
    SeqCollection *collection = SEQ_query_rendered_strips(
        scene, channels, ed->seqbasep, timeline_frame, 0);
    Sequence *seq;
    Sequence *active_seq = SEQ_select_active_get(scene);
    SEQ_ITERATOR_FOREACH (seq, collection) {
      seq_draw_image_origin_and_outline(C, seq, seq == active_seq);
    }
    SEQ_collection_free(collection);
  }

  if (draw_gpencil && show_imbuf && (sseq->flag & SEQ_SHOW_OVERLAY)) {
    sequencer_draw_gpencil_overlay(C);
  }

#if 0
  sequencer_draw_maskedit(C, scene, region, sseq);
#endif

  /* Draw registered callbacks. */
  GPU_framebuffer_bind(framebuffer_overlay);
  ED_region_draw_cb_draw(C, region, REGION_DRAW_POST_VIEW);
  GPU_framebuffer_bind_no_srgb(framebuffer_overlay);

  /* Scope is freed in sequencer_check_scopes when `ibuf` changes and redraw is needed. */
  if (ibuf) {
    IMB_freeImBuf(ibuf);
  }

  UI_view2d_view_restore(C);
  seq_prefetch_wm_notify(C, scene);
}