Image: support storing full image buffers for each undo step

Update image undo to store buffers for each step:

- Undo buffers share tiles to avoid using too much memory.
- Undo support for different sized buffers
  allowing operations such as crop or resize.
- Paint tiles have been split into separate API/storage.
- Painting speed wont be impacted significantly
  since storing the extra tiles is done after the stroke & only
  for the first undo step.

Resolves T61263, see D5939 for details.

2 files changed, 41 insertions, 0 deletions

diff --git a/source/blender/imbuf/IMB_imbuf.h b/source/blender/imbuf/IMB_imbuf.h
index 6e49630dc46..9e9c47194e1 100644
--- a/source/blender/imbuf/IMB_imbuf.h
+++ b/source/blender/imbuf/IMB_imbuf.h
@@ -228,6 +228,8 @@ void IMB_blend_color_float(float dst[4],
 
 void IMB_rect_crop(struct ImBuf *ibuf, const struct rcti *crop);
 
+void IMB_rect_size_set(struct ImBuf *ibuf, const uint size[2]);
+
 void IMB_rectclip(struct ImBuf *dbuf,
                   const struct ImBuf *sbuf,
                   int *destx,
diff --git a/source/blender/imbuf/intern/rectop.c b/source/blender/imbuf/intern/rectop.c
index b8ea6c2ea03..3163a960892 100644
--- a/source/blender/imbuf/intern/rectop.c
+++ b/source/blender/imbuf/intern/rectop.c
@@ -279,6 +279,45 @@ void IMB_rect_crop(ImBuf *ibuf, const rcti *crop)
   ibuf->y = size_dst[1];
 }
 
+/** Re-alloc buffers at a new size */
+
+static void rect_realloc_4bytes(void **buf_p, const uint size[2])
+{
+  if (*buf_p == NULL) {
+    return;
+  }
+  MEM_freeN(*buf_p);
+  *buf_p = MEM_mallocN(sizeof(uint) * size[0] * size[1], __func__);
+}
+
+static void rect_realloc_16bytes(void **buf_p, const uint size[2])
+{
+  if (*buf_p == NULL) {
+    return;
+  }
+  MEM_freeN(*buf_p);
+  *buf_p = MEM_mallocN(sizeof(uint[4]) * size[0] * size[1], __func__);
+}
+
+/**
+ * In-place size setting (caller must fill in buffer contents).
+ */
+void IMB_rect_size_set(ImBuf *ibuf, const uint size[2])
+{
+  BLI_assert(size[0] > 0 && size[0] > 0);
+  if ((size[0] == ibuf->x) && (size[1] == ibuf->y)) {
+    return;
+  }
+
+  rect_realloc_4bytes((void **)&ibuf->rect, size);
+  rect_realloc_4bytes((void **)&ibuf->zbuf, size);
+  rect_realloc_4bytes((void **)&ibuf->zbuf_float, size);
+  rect_realloc_16bytes((void **)&ibuf->rect_float, size);
+
+  ibuf->x = size[0];
+  ibuf->y = size[1];
+}
+
 /* clipping */
 
 void IMB_rectclip(ImBuf *dbuf,