Fix T65691: GPencil Drawing long strokes turn invisible

There was a fixed limit to the number of points available in a buffer stroke.

Now, the array is expanded as needed using a predefined number of points for each expansion, instead to add one by one. This is done to reduce the number of times the memory allocation is required.

As part of the fix, some variables have been renamed to reflect better their use.

1 files changed, 35 insertions, 1 deletions

diff --git a/source/blender/editors/gpencil/gpencil_utils.c b/source/blender/editors/gpencil/gpencil_utils.c
index 065c133bf97..ac8196f5ed0 100644
--- a/source/blender/editors/gpencil/gpencil_utils.c
+++ b/source/blender/editors/gpencil/gpencil_utils.c
@@ -1740,7 +1740,7 @@ static void gp_brush_cursor_draw(bContext *C, int x, int y, void *customdata)
     }
 
     /* while drawing hide */
-    if ((gpd->runtime.sbuffer_size > 0) &&
+    if ((gpd->runtime.sbuffer_used > 0) &&
         ((brush->gpencil_settings->flag & GP_BRUSH_STABILIZE_MOUSE) == 0) &&
         ((brush->gpencil_settings->flag & GP_BRUSH_STABILIZE_MOUSE_TEMP) == 0)) {
       return;
@@ -2525,3 +2525,37 @@ void ED_gpencil_select_toggle_all(bContext *C, int action)
     CTX_DATA_END;
   }
 }
+
+/* Ensure the SBuffer (while drawing stroke) size is enough to save all points of the stroke */
+tGPspoint *ED_gpencil_sbuffer_ensure(tGPspoint *buffer_array,
+                                     short *buffer_size,
+                                     short *buffer_used,
+                                     const bool clear)
+{
+  tGPspoint *p = NULL;
+
+  /* By default a buffer is created with one block with a predefined number of free points,
+   * if the size is not enough, the cache is reallocated adding a new block of free points.
+   * This is done in order to keep cache small and improve speed. */
+  if (*buffer_used + 1 > *buffer_size) {
+    if ((*buffer_size == 0) || (buffer_array == NULL)) {
+      p = MEM_callocN(sizeof(struct tGPspoint) * GP_STROKE_BUFFER_CHUNK, "GPencil Sbuffer");
+      *buffer_size = GP_STROKE_BUFFER_CHUNK;
+    }
+    else {
+      *buffer_size += GP_STROKE_BUFFER_CHUNK;
+      p = MEM_recallocN(buffer_array, sizeof(struct tGPspoint) * *buffer_size);
+    }
+    buffer_array = p;
+  }
+
+  /* clear old data */
+  if (clear) {
+    *buffer_used = 0;
+    if (buffer_array != NULL) {
+      memset(buffer_array, 0, sizeof(tGPspoint) * *buffer_size);
+    }
+  }
+
+  return buffer_array;
+}