Performance: Draw play head as an overlay

When playing back animations a playhead is updated in all the animation editors.
The drawing of the playhead is part of the drawing of the main region
`RGN_TYPE_WINDOW` that redraws the whole region.

This change will draw the play head and window scrollers when updating the
screen. This affects the Action editor, Timeline, Graph editor, NLA editor and
Sequence editor. There is noticeable speedup when using complex animation files.

Spring 02_020_A.anim.blend fps went from 11.8 to 12.5 when showing a timeline
and a action editor on a Ryzen 1700.

* When playing back animation the markers don't jump up/down when near the
  frame. This could be added back.

Reviewed By: Brecht van Lommel

Differential Revision: https://developer.blender.org/D8066

1 files changed, 42 insertions, 3 deletions

diff --git a/source/blender/editors/animation/time_scrub_ui.c b/source/blender/editors/animation/time_scrub_ui.c
index 863f433c778..f4ed2add624 100644
--- a/source/blender/editors/animation/time_scrub_ui.c
+++ b/source/blender/editors/animation/time_scrub_ui.c
@@ -92,7 +92,9 @@ static void draw_current_frame(const Scene *scene,
                                bool display_seconds,
                                const View2D *v2d,
                                const rcti *scrub_region_rect,
-                               int current_frame)
+                               int current_frame,
+                               float sub_frame,
+                               bool draw_line)
 {
   const uiFontStyle *fstyle = UI_FSTYLE_WIDGET;
   int frame_x = UI_view2d_view_to_region_x(v2d, current_frame);
@@ -106,6 +108,23 @@ static void draw_current_frame(const Scene *scene,
   float bg_color[4];
   UI_GetThemeColorShade4fv(TH_CFRAME, -5, bg_color);
 
+  if (draw_line) {
+    /* Draw vertical line to from the bottom of the current frame box to the bottom of the screen.
+     */
+    const float subframe_x = UI_view2d_view_to_region_x(v2d, current_frame + sub_frame);
+    GPU_line_width(2.0f);
+    GPUVertFormat *format = immVertexFormat();
+    uint pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
+    immBindBuiltinProgram(GPU_SHADER_2D_UNIFORM_COLOR);
+    immUniformThemeColor(TH_CFRAME);
+    immBegin(GPU_PRIM_LINES, 2);
+
+    immVertex2f(pos, subframe_x, scrub_region_rect->ymax - box_padding);
+    immVertex2f(pos, subframe_x, 0.0f);
+    immEnd();
+    immUnbindProgram();
+  }
+
   UI_draw_roundbox_corner_set(UI_CNR_ALL);
 
   UI_draw_roundbox_3fv_alpha(true,
@@ -135,6 +154,28 @@ static void draw_current_frame(const Scene *scene,
                            text_color);
 }
 
+void ED_time_scrub_draw_current_frame(const ARegion *region,
+                                      const Scene *scene,
+                                      bool display_seconds,
+                                      bool draw_line)
+{
+  const View2D *v2d = &region->v2d;
+  GPU_matrix_push_projection();
+  wmOrtho2_region_pixelspace(region);
+
+  rcti scrub_region_rect;
+  get_time_scrub_region_rect(region, &scrub_region_rect);
+
+  draw_current_frame(scene,
+                     display_seconds,
+                     v2d,
+                     &scrub_region_rect,
+                     scene->r.cfra,
+                     scene->r.subframe,
+                     draw_line);
+  GPU_matrix_pop_projection();
+}
+
 void ED_time_scrub_draw(const ARegion *region,
                         const Scene *scene,
                         bool display_seconds,
@@ -161,8 +202,6 @@ void ED_time_scrub_draw(const ARegion *region,
         region, v2d, &numbers_rect, scene, display_seconds, TH_TEXT);
   }
 
-  draw_current_frame(scene, display_seconds, v2d, &scrub_region_rect, scene->r.cfra);
-
   GPU_matrix_pop_projection();
 }