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, 34 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_gpencil.h b/source/blender/blenkernel/BKE_gpencil.h
index 885d0c2fd90..fd8996993c0 100644
--- a/source/blender/blenkernel/BKE_gpencil.h
+++ b/source/blender/blenkernel/BKE_gpencil.h
@@ -48,6 +48,7 @@ struct bGPDlayer;
 struct bGPDlayer_Mask;
 struct bGPDstroke;
 struct bGPdata;
+struct GPencilUpdateCache;
 
 #define GPENCIL_SIMPLIFY(scene) (scene->r.simplify_gpencil & SIMPLIFY_GPENCIL_ENABLE)
 #define GPENCIL_SIMPLIFY_ONPLAY(playing) \
@@ -175,10 +176,28 @@ struct bGPDframe *BKE_gpencil_frame_duplicate(const struct bGPDframe *gpf_src, b
 struct bGPDlayer *BKE_gpencil_layer_duplicate(const struct bGPDlayer *gpl_src,
                                               bool dup_frames,
                                               bool dup_strokes);
+
+/**
+ * Make a copy of a given gpencil data settings.
+ */
+void BKE_gpencil_data_copy_settings(const struct bGPdata *gpd_src, struct bGPdata *gpd_dst);
+
 /**
  * Make a copy of a given gpencil layer settings.
  */
 void BKE_gpencil_layer_copy_settings(const struct bGPDlayer *gpl_src, struct bGPDlayer *gpl_dst);
+
+/**
+ * Make a copy of a given gpencil frame settings.
+ */
+void BKE_gpencil_frame_copy_settings(const struct bGPDframe *gpf_src, struct bGPDframe *gpf_dst);
+
+/**
+ * Make a copy of a given gpencil stroke settings.
+ */
+void BKE_gpencil_stroke_copy_settings(const struct bGPDstroke *gpf_src,
+                                      struct bGPDstroke *gpf_dst);
+
 /**
  * Make a copy of strokes between gpencil frames.
  * \param gpf_src: Source grease pencil frame
@@ -675,6 +694,9 @@ extern void (*BKE_gpencil_batch_cache_free_cb)(struct bGPdata *gpd);
  */
 void BKE_gpencil_frame_original_pointers_update(const struct bGPDframe *gpf_orig,
                                                 const struct bGPDframe *gpf_eval);
+
+void BKE_gpencil_layer_original_pointers_update(const struct bGPDlayer *gpl_orig,
+                                                const struct bGPDlayer *gpl_eval);
 /**
  * Update pointers of eval data to original data to keep references.
  * \param ob_orig: Original grease pencil object
@@ -683,6 +705,14 @@ void BKE_gpencil_frame_original_pointers_update(const struct bGPDframe *gpf_orig
 void BKE_gpencil_update_orig_pointers(const struct Object *ob_orig, const struct Object *ob_eval);
 
 /**
+ * Update pointers of eval data to original data to keep references.
+ * \param gpd_orig: Original grease pencil data
+ * \param gpd_eval: Evaluated grease pencil data
+ */
+void BKE_gpencil_data_update_orig_pointers(const struct bGPdata *gpd_orig,
+                                           const struct bGPdata *gpd_eval);
+
+/**
  * Get parent matrix, including layer parenting.
  * \param depsgraph: Depsgraph
  * \param obact: Grease pencil object
@@ -711,6 +741,10 @@ int BKE_gpencil_material_find_index_by_name_prefix(struct Object *ob, const char
 
 void BKE_gpencil_blend_read_data(struct BlendDataReader *reader, struct bGPdata *gpd);
 
+bool BKE_gpencil_can_avoid_full_copy_on_write(const struct Depsgraph *depsgraph, struct bGPdata *gpd);
+
+void BKE_gpencil_update_on_write(struct bGPdata *gpd_orig, struct bGPdata *gpd_eval);
+
 #ifdef __cplusplus
 }
 #endif