GPUVertBuf: Add handle refcount

A handle refcount is here to avoid freeing of the GPUVertBuf datablock
if it is still referenced somewhere else.

This does not prevent deleting the actual data. This is to avoid too
much zombie data usage.

This is in order to avoid most hacks inside `draw_instance_data.c`.

1 files changed, 18 insertions, 1 deletions

diff --git a/source/blender/gpu/intern/gpu_vertex_buffer.cc b/source/blender/gpu/intern/gpu_vertex_buffer.cc
index 67ad8835b6a..debf9835c90 100644
--- a/source/blender/gpu/intern/gpu_vertex_buffer.cc
+++ b/source/blender/gpu/intern/gpu_vertex_buffer.cc
@@ -77,6 +77,7 @@ void GPU_vertbuf_init(GPUVertBuf *verts, GPUUsageType usage)
   memset(verts, 0, sizeof(GPUVertBuf));
   verts->usage = usage;
   verts->dirty = true;
+  verts->handle_refcount = 1;
 }
 
 void GPU_vertbuf_init_with_format_ex(GPUVertBuf *verts,
@@ -137,7 +138,23 @@ void GPU_vertbuf_clear(GPUVertBuf *verts)
 void GPU_vertbuf_discard(GPUVertBuf *verts)
 {
   GPU_vertbuf_clear(verts);
-  MEM_freeN(verts);
+  GPU_vertbuf_handle_ref_remove(verts);
+}
+
+void GPU_vertbuf_handle_ref_add(GPUVertBuf *verts)
+{
+  verts->handle_refcount++;
+}
+
+void GPU_vertbuf_handle_ref_remove(GPUVertBuf *verts)
+{
+  BLI_assert(verts->handle_refcount > 0);
+  verts->handle_refcount--;
+  if (verts->handle_refcount == 0) {
+    /* Should already have been cleared. */
+    BLI_assert(verts->vbo_id == 0 && verts->data == NULL);
+    MEM_freeN(verts);
+  }
 }
 
 uint GPU_vertbuf_size_get(const GPUVertBuf *verts)