DRW: New function to retry stencil_mask value

This function is a workaround to use the stencil in grease pencil and reduce the number of clears.

Reviewed by @fclem.

Note: This function will be removed when draw manager supports stencil clearing by group.

source/blender/draw/intern/DRW_render.h

@@ -531,7 +531,11 @@ void DRW_shgroup_uniform_float_copy(DRWShadingGroup *shgroup, const char *name,
 void DRW_shgroup_uniform_vec2_copy(DRWShadingGroup *shgroup, const char *name, const float *value);
 
 bool DRW_shgroup_is_empty(DRWShadingGroup *shgroup);
+
+/* TODO: workaround functions waiting for the clearing operation to be available inside the
+ * shgroups. */
 DRWShadingGroup *DRW_shgroup_get_next(DRWShadingGroup *shgroup);
+uint DRW_shgroup_stencil_mask_get(DRWShadingGroup *shgroup);
 
 /* Passes */
 DRWPass *DRW_pass_create(const char *name, DRWState state);

source/blender/draw/intern/draw_manager_data.c

@@ -1003,6 +1003,13 @@ DRWShadingGroup *DRW_shgroup_get_next(DRWShadingGroup *shgroup)
   return shgroup->next;
 }
 
+/* This is a workaround function waiting for the clearing operation to be available inside the
+ * shgroups. */
+uint DRW_shgroup_stencil_mask_get(DRWShadingGroup *shgroup)
+{
+  return shgroup->stencil_mask;
+}
+
 DRWShadingGroup *DRW_shgroup_create_sub(DRWShadingGroup *shgroup)
 {
   DRWShadingGroup *shgroup_new = BLI_memblock_alloc(DST.vmempool->shgroups);