DrawManager: Engine Instance Data.

In the original design draw engines had to copy with a limitation that
they were not allowed to reuse complex data structures between drawing
calls. Data that could be reused were limited to:
- GPUFramebuffers
- GPUTextures
- Memory that could be removed calling MEM_freeN (storage list)
- DRWPass

This is fine when the storage list contains arrays or structs but when
more complex data types (vectors, maps) etc wasn't possible.

This patch adds instance_data that can be reused between drawing calls.
The instance_data is controlled by the draw engine and doesn't need to
be limited as described above.

When an engines stores instance_data it must implement the
`DrawEngineType.instance_free` callback to free the data.

The patch originates from eevee rewrite. But was added to master as the
image engine rewrite also has a need for it.

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D13425

1 files changed, 2 insertions, 0 deletions

diff --git a/source/blender/draw/intern/DRW_render.h b/source/blender/draw/intern/DRW_render.h
index c1cab931f6a..6491f5ca411 100644
--- a/source/blender/draw/intern/DRW_render.h
+++ b/source/blender/draw/intern/DRW_render.h
@@ -121,6 +121,8 @@ typedef struct DrawEngineType {
   void (*engine_init)(void *vedata);
   void (*engine_free)(void);
 
+  void (*instance_free)(void *instance_data);
+
   void (*cache_init)(void *vedata);
   void (*cache_populate)(void *vedata, struct Object *ob);
   void (*cache_finish)(void *vedata);