Fix T74662: Prefetching causes random crashes

Caused by 18b693bdbd6b, due to lack of thread safety.
Beteween calling BKE_sequencer_cache_get_num_items and BKE_sequencer_cache_iterate
New items could be inserted in the cache.

BKE_sequencer_cache_iterate() now use 2 callbcack functions for initial setup
during which buffers with correct length can be initialized and finally iterating.

Additionally drawing of unselected items was fixed again introduced in 18b693bdbd6b.

T74662 is reporting quite different symptoms, than I get on my machine, so I am not
entirely sure this is complete fix.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D7220

1 files changed, 85 insertions, 77 deletions

diff --git a/source/blender/editors/space_sequencer/sequencer_draw.c b/source/blender/editors/space_sequencer/sequencer_draw.c
index 058d41ab294..06158e6f1f4 100644
--- a/source/blender/editors/space_sequencer/sequencer_draw.c
+++ b/source/blender/editors/space_sequencer/sequencer_draw.c
@@ -1968,6 +1968,7 @@ typedef struct CacheDrawData {
   struct View2D *v2d;
   float stripe_offs;
   float stripe_ht;
+  int cache_flag;
   GPUVertBuf *raw_vbo;
   GPUVertBuf *preprocessed_vbo;
   GPUVertBuf *composite_vbo;
@@ -1979,7 +1980,25 @@ typedef struct CacheDrawData {
 } CacheDrawData;
 
 /* Called as a callback */
-static bool draw_cache_view_cb(
+static bool draw_cache_view_init_cb(void *userdata, size_t item_count)
+{
+  if (item_count == 0) {
+    return true;
+  }
+
+  CacheDrawData *drawdata = userdata;
+  /* We can not get item count per cache type, so using total item count is safe. */
+  size_t max_vert_count = item_count * 6;
+  GPU_vertbuf_data_alloc(drawdata->raw_vbo, max_vert_count);
+  GPU_vertbuf_data_alloc(drawdata->preprocessed_vbo, max_vert_count);
+  GPU_vertbuf_data_alloc(drawdata->composite_vbo, max_vert_count);
+  GPU_vertbuf_data_alloc(drawdata->final_out_vbo, max_vert_count);
+
+  return false;
+}
+
+/* Called as a callback */
+static bool draw_cache_view_iter_cb(
     void *userdata, struct Sequence *seq, int nfra, int cache_type, float UNUSED(cost))
 {
   CacheDrawData *drawdata = userdata;
@@ -1987,44 +2006,43 @@ static bool draw_cache_view_cb(
   float stripe_bot, stripe_top, stripe_offs, stripe_ht;
   GPUVertBuf *vbo;
   size_t *vert_count;
-  switch (cache_type) {
-    case SEQ_CACHE_STORE_FINAL_OUT:
-      stripe_ht = UI_view2d_region_to_view_y(v2d, 4.0f * UI_DPI_FAC * U.pixelsize) - v2d->cur.ymin;
-      stripe_bot = UI_view2d_region_to_view_y(v2d, V2D_SCROLL_HANDLE_HEIGHT);
-      stripe_top = stripe_bot + stripe_ht;
-      vbo = drawdata->final_out_vbo;
-      vert_count = &drawdata->final_out_vert_count;
-      break;
-
-    case SEQ_CACHE_STORE_RAW:
-      stripe_offs = drawdata->stripe_offs;
-      stripe_ht = drawdata->stripe_ht;
-      stripe_bot = seq->machine + SEQ_STRIP_OFSBOTTOM + stripe_offs;
-      stripe_top = stripe_bot + stripe_ht;
-      vbo = drawdata->raw_vbo;
-      vert_count = &drawdata->raw_vert_count;
-      break;
 
-    case SEQ_CACHE_STORE_PREPROCESSED:
-      stripe_offs = drawdata->stripe_offs;
-      stripe_ht = drawdata->stripe_ht;
-      stripe_bot = seq->machine + SEQ_STRIP_OFSBOTTOM + (stripe_offs + stripe_ht) + stripe_offs;
-      stripe_top = stripe_bot + stripe_ht;
-      vbo = drawdata->preprocessed_vbo;
-      vert_count = &drawdata->preprocessed_vert_count;
-      break;
-
-    case SEQ_CACHE_STORE_COMPOSITE:
-      stripe_offs = drawdata->stripe_offs;
-      stripe_ht = drawdata->stripe_ht;
-      stripe_top = seq->machine + SEQ_STRIP_OFSTOP - stripe_offs;
-      stripe_bot = stripe_top - stripe_ht;
-      vbo = drawdata->composite_vbo;
-      vert_count = &drawdata->composite_vert_count;
-      break;
-
-    default:
-      return true;
+  if ((cache_type & SEQ_CACHE_STORE_FINAL_OUT) &&
+      (drawdata->cache_flag & SEQ_CACHE_VIEW_FINAL_OUT)) {
+    stripe_ht = UI_view2d_region_to_view_y(v2d, 4.0f * UI_DPI_FAC * U.pixelsize) - v2d->cur.ymin;
+    stripe_bot = UI_view2d_region_to_view_y(v2d, V2D_SCROLL_HANDLE_HEIGHT);
+    stripe_top = stripe_bot + stripe_ht;
+    vbo = drawdata->final_out_vbo;
+    vert_count = &drawdata->final_out_vert_count;
+  }
+  else if ((cache_type & SEQ_CACHE_STORE_RAW) && (drawdata->cache_flag & SEQ_CACHE_VIEW_RAW)) {
+    stripe_offs = drawdata->stripe_offs;
+    stripe_ht = drawdata->stripe_ht;
+    stripe_bot = seq->machine + SEQ_STRIP_OFSBOTTOM + stripe_offs;
+    stripe_top = stripe_bot + stripe_ht;
+    vbo = drawdata->raw_vbo;
+    vert_count = &drawdata->raw_vert_count;
+  }
+  else if ((cache_type & SEQ_CACHE_STORE_PREPROCESSED) &&
+           (drawdata->cache_flag & SEQ_CACHE_VIEW_PREPROCESSED)) {
+    stripe_offs = drawdata->stripe_offs;
+    stripe_ht = drawdata->stripe_ht;
+    stripe_bot = seq->machine + SEQ_STRIP_OFSBOTTOM + (stripe_offs + stripe_ht) + stripe_offs;
+    stripe_top = stripe_bot + stripe_ht;
+    vbo = drawdata->preprocessed_vbo;
+    vert_count = &drawdata->preprocessed_vert_count;
+  }
+  else if ((cache_type & SEQ_CACHE_STORE_COMPOSITE) &&
+           (drawdata->cache_flag & SEQ_CACHE_VIEW_COMPOSITE)) {
+    stripe_offs = drawdata->stripe_offs;
+    stripe_ht = drawdata->stripe_ht;
+    stripe_top = seq->machine + SEQ_STRIP_OFSTOP - stripe_offs;
+    stripe_bot = stripe_top - stripe_ht;
+    vbo = drawdata->composite_vbo;
+    vert_count = &drawdata->composite_vert_count;
+  }
+  else {
+    return false;
   }
 
   int cfra = seq->start + nfra;
@@ -2048,10 +2066,10 @@ static void draw_cache_view_batch(
     GPUVertBuf *vbo, size_t vert_count, float col_r, float col_g, float col_b, float col_a)
 {
   GPUBatch *batch = GPU_batch_create_ex(GPU_PRIM_TRIS, vbo, NULL, GPU_BATCH_OWNS_VBO);
-  GPU_vertbuf_data_len_set(vbo, vert_count);
-  GPU_batch_program_set_builtin(batch, GPU_SHADER_2D_UNIFORM_COLOR);
-  GPU_batch_uniform_4f(batch, "color", col_r, col_g, col_b, col_a);
   if (vert_count > 0) {
+    GPU_vertbuf_data_len_set(vbo, vert_count);
+    GPU_batch_program_set_builtin(batch, GPU_SHADER_2D_UNIFORM_COLOR);
+    GPU_batch_uniform_4f(batch, "color", col_r, col_g, col_b, col_a);
     GPU_batch_draw(batch);
   }
   GPU_batch_discard(batch);
@@ -2127,42 +2145,32 @@ static void draw_cache_view(const bContext *C)
 
   immUnbindProgram();
 
-  size_t cache_num_items = BKE_sequencer_cache_get_num_items(scene);
-
-  if (cache_num_items > 0) {
-    GPUVertFormat format = {0};
-    GPU_vertformat_attr_add(&format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
-
-    CacheDrawData userdata;
-    userdata.v2d = v2d;
-    userdata.stripe_offs = stripe_offs;
-    userdata.stripe_ht = stripe_ht;
-    userdata.raw_vert_count = 0;
-    userdata.preprocessed_vert_count = 0;
-    userdata.composite_vert_count = 0;
-    userdata.final_out_vert_count = 0;
-    userdata.raw_vbo = GPU_vertbuf_create_with_format(&format);
-    userdata.preprocessed_vbo = GPU_vertbuf_create_with_format(&format);
-    userdata.composite_vbo = GPU_vertbuf_create_with_format(&format);
-    userdata.final_out_vbo = GPU_vertbuf_create_with_format(&format);
-
-    /* We can not get item count per cache type, so using total item count is safe. */
-    size_t max_vert_count = cache_num_items * 6;
-    GPU_vertbuf_data_alloc(userdata.raw_vbo, max_vert_count);
-    GPU_vertbuf_data_alloc(userdata.preprocessed_vbo, max_vert_count);
-    GPU_vertbuf_data_alloc(userdata.composite_vbo, max_vert_count);
-    GPU_vertbuf_data_alloc(userdata.final_out_vbo, max_vert_count);
-
-    BKE_sequencer_cache_iterate(scene, &userdata, draw_cache_view_cb);
-
-    draw_cache_view_batch(userdata.raw_vbo, userdata.raw_vert_count, 1.0f, 0.1f, 0.02f, 0.4f);
-    draw_cache_view_batch(
-        userdata.preprocessed_vbo, userdata.preprocessed_vert_count, 0.1f, 0.1f, 0.75f, 0.4f);
-    draw_cache_view_batch(
-        userdata.composite_vbo, userdata.composite_vert_count, 1.0f, 0.6f, 0.0f, 0.4f);
-    draw_cache_view_batch(
-        userdata.final_out_vbo, userdata.final_out_vert_count, 1.0f, 0.4f, 0.2f, 0.4f);
-  }
+  GPUVertFormat format = {0};
+  GPU_vertformat_attr_add(&format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
+
+  CacheDrawData userdata;
+  userdata.v2d = v2d;
+  userdata.stripe_offs = stripe_offs;
+  userdata.stripe_ht = stripe_ht;
+  userdata.cache_flag = scene->ed->cache_flag;
+  userdata.raw_vert_count = 0;
+  userdata.preprocessed_vert_count = 0;
+  userdata.composite_vert_count = 0;
+  userdata.final_out_vert_count = 0;
+  userdata.raw_vbo = GPU_vertbuf_create_with_format(&format);
+  userdata.preprocessed_vbo = GPU_vertbuf_create_with_format(&format);
+  userdata.composite_vbo = GPU_vertbuf_create_with_format(&format);
+  userdata.final_out_vbo = GPU_vertbuf_create_with_format(&format);
+
+  BKE_sequencer_cache_iterate(scene, &userdata, draw_cache_view_init_cb, draw_cache_view_iter_cb);
+
+  draw_cache_view_batch(userdata.raw_vbo, userdata.raw_vert_count, 1.0f, 0.1f, 0.02f, 0.4f);
+  draw_cache_view_batch(
+      userdata.preprocessed_vbo, userdata.preprocessed_vert_count, 0.1f, 0.1f, 0.75f, 0.4f);
+  draw_cache_view_batch(
+      userdata.composite_vbo, userdata.composite_vert_count, 1.0f, 0.6f, 0.0f, 0.4f);
+  draw_cache_view_batch(
+      userdata.final_out_vbo, userdata.final_out_vert_count, 1.0f, 0.4f, 0.2f, 0.4f);
 
   GPU_blend(false);
 }