GPencil: Update-on-write using update cache

This implements the update cache described in T95401.

The cache is currently only used for drawing strokes and
sculpting (using the push brush).
**Note: Making use of the cache throughout grease pencil will
have to be done incrementally in other patches. **

The update cache stores what elements have changed in the
original data-block since the last time the eval object
was updated. Additionally, the update cache can store multiple
updates to the data and minimizes the number of elements
that need to be copied.

Elements can be tagged using `BKE_gpencil_tag_full_update` and
`BKE_gpencil_tag_light_update`. A full update means that the element
itself will be copied but also all of the content inside. E.g. when a
layer is tagged for a full update, the layer, all the frames inside the
layer and all the strokes inside the frames will be copied.
A light update means that only the properties of the element are copied
without any of the content. E.g. if a layer is tagged with a light
update, it will copy the layer name, opacity, transform, etc.

When the update cache is in use (e.g. elements have been tagged) then
the depsgraph will not trigger a copy-on-write, but an update-on-write.
This means that the update cache will be used to determine what elements
have changed and then only those elements will be copied over to the
eval object.

If the update cache is empty or the data block was tagged with a full
update, we always fall back to a copy-on-write.

Currently, the update cache is only used by the active depsgraph. This
is because we need to free the update cache after an update-on-write so
it's reset and we need to make sure it is not freed or read by other
depsgraphs.

Co-authored-by: @yann-lty
This patch was contributed by The SPA Studios.

Reviewed By: sergey, antoniov, #dependency_graph, pepeland, mendio

Maniphest Tasks: T95401

Differential Revision: https://developer.blender.org/D13984

1 files changed, 11 insertions, 0 deletions

diff --git a/source/blender/makesdna/DNA_gpencil_types.h b/source/blender/makesdna/DNA_gpencil_types.h
index 0f570f8603d..3340782d64a 100644
--- a/source/blender/makesdna/DNA_gpencil_types.h
+++ b/source/blender/makesdna/DNA_gpencil_types.h
@@ -35,6 +35,7 @@ struct AnimData;
 struct Curve;
 struct Curve;
 struct MDeformVert;
+struct GPencilUpdateCache;
 
 #define GP_DEFAULT_PIX_FACTOR 1.0f
 #define GP_DEFAULT_GRID_LINES 4
@@ -325,6 +326,8 @@ typedef struct bGPDstroke {
   /** Curve used to edit the stroke using Bezier handlers. */
   struct bGPDcurve *editcurve;
 
+  /* NOTE: When adding new members, make sure to add them to BKE_gpencil_stroke_copy_settings as well! */
+
   bGPDstroke_Runtime runtime;
   void *_pad5;
 } bGPDstroke;
@@ -409,6 +412,8 @@ typedef struct bGPDframe {
   /** Keyframe type (eBezTriple_KeyframeType). */
   short key_type;
 
+  /* NOTE: When adding new members, make sure to add them to BKE_gpencil_frame_copy_settings as well! */
+
   bGPDframe_Runtime runtime;
 } bGPDframe;
 
@@ -532,6 +537,8 @@ typedef struct bGPDlayer {
   float layer_mat[4][4], layer_invmat[4][4];
   char _pad3[4];
 
+  /* NOTE: When adding new members, make sure to add them to BKE_gpencil_layer_copy_settings as well! */
+
   bGPDlayer_Runtime runtime;
 } bGPDlayer;
 
@@ -633,6 +640,8 @@ typedef struct bGPdata_Runtime {
   Brush *sbuffer_brush;
   struct GpencilBatchCache *gpencil_cache;
   struct LineartCache *lineart_cache;
+
+  struct GPencilUpdateCache *update_cache;
 } bGPdata_Runtime;
 
 /* grid configuration */
@@ -726,6 +735,8 @@ typedef struct bGPdata {
 
   bGPgrid grid;
 
+  /* NOTE: When adding new members, make sure to add them to BKE_gpencil_data_copy_settings as well! */
+
   bGPdata_Runtime runtime;
 } bGPdata;