VSE strip thumbnails

Draw thumbnails as strip overlay. This works for movie and image strips.
To draw thumbnails, this overlay has to be enabled and strips must be
tall enough.

The thumbnails are loaded from source file using separate thread and
stored in cache.

Drawing code uses only images stored in cache, and if any is missing,
background rendering job is started. If job can not render thumbnail,
to prevent endless loop of creating job for missing image it sets
`SEQ_FLAG_SKIP_THUMBNAILS` bit of `Sequence` flag.

To prevent visual glitches during timeline panning and zooming, `View2D`
flag `V2D_IS_NAVIGATING` is implemented. If bit is set, drawing code
will look for set of evenly distributed thumbnails that should be
guaranteed to exist and also set of previously displayed thumbnails.
Due to volatile nature of cache these thumbnails can be missing anyway,
in which case no new thumbnails will be drawn for particular strip.

Cache capacity is limited to 5000 thumbnails and performs cleanup of
non visible images when limit is reached.

ref T89143

Reviewed By: ISS

Differential Revision: https://developer.blender.org/D12266

1 files changed, 13 insertions, 1 deletions

diff --git a/source/blender/editors/space_sequencer/space_sequencer.c b/source/blender/editors/space_sequencer/space_sequencer.c
index cb5fe6f0ef3..0f23c61a2ca 100644
--- a/source/blender/editors/space_sequencer/space_sequencer.c
+++ b/source/blender/editors/space_sequencer/space_sequencer.c
@@ -32,6 +32,7 @@
 #include "MEM_guardedalloc.h"
 
 #include "BLI_blenlib.h"
+#include "BLI_ghash.h"
 #include "BLI_utildefines.h"
 
 #include "BKE_context.h"
@@ -105,6 +106,9 @@ static SpaceLink *sequencer_create(const ScrArea *UNUSED(area), const Scene *sce
                                 SEQ_TIMELINE_SHOW_STRIP_DURATION | SEQ_TIMELINE_SHOW_GRID |
                                 SEQ_TIMELINE_SHOW_FCURVES;
 
+  BLI_rctf_init(&sseq->runtime.last_thumbnail_area, 0.0f, 0.0f, 0.0f, 0.0f);
+  sseq->runtime.last_displayed_thumbnails = NULL;
+
   /* Tool header. */
   region = MEM_callocN(sizeof(ARegion), "tool header for sequencer");
 
@@ -174,7 +178,7 @@ static SpaceLink *sequencer_create(const ScrArea *UNUSED(area), const Scene *sce
   region->v2d.cur = region->v2d.tot;
 
   region->v2d.min[0] = 10.0f;
-  region->v2d.min[1] = 0.5f;
+  region->v2d.min[1] = 4.0f;
 
   region->v2d.max[0] = MAXFRAMEF;
   region->v2d.max[1] = MAXSEQ;
@@ -188,6 +192,8 @@ static SpaceLink *sequencer_create(const ScrArea *UNUSED(area), const Scene *sce
   region->v2d.keeptot = 0;
   region->v2d.align = V2D_ALIGN_NO_NEG_Y;
 
+  sseq->runtime.last_displayed_thumbnails = NULL;
+
   return (SpaceLink *)sseq;
 }
 
@@ -218,6 +224,12 @@ static void sequencer_free(SpaceLink *sl)
   if (scopes->histogram_ibuf) {
     IMB_freeImBuf(scopes->histogram_ibuf);
   }
+
+  if (sseq->runtime.last_displayed_thumbnails) {
+    BLI_ghash_free(
+        sseq->runtime.last_displayed_thumbnails, NULL, last_displayed_thumbnails_list_free);
+    sseq->runtime.last_displayed_thumbnails = NULL;
+  }
 }
 
 /* Spacetype init callback. */