Fix T71260: GPencil crash when drawing very long lines

There were two problems:

1) When the buffer was reallocate, the pointer was corrupted.
2) Short variables were too small to hold long lines.

2 files changed, 3 insertions, 3 deletions

diff --git a/source/blender/editors/gpencil/gpencil_paint.c b/source/blender/editors/gpencil/gpencil_paint.c
index f29e782c618..bebdcb34326 100644
--- a/source/blender/editors/gpencil/gpencil_paint.c
+++ b/source/blender/editors/gpencil/gpencil_paint.c
@@ -3660,7 +3660,6 @@ static int gpencil_draw_modal(bContext *C, wmOperator *op, const wmEvent *event)
   tGPsdata *p = op->customdata;
   ToolSettings *ts = CTX_data_tool_settings(C);
   GP_Sculpt_Guide *guide = &p->scene->toolsettings->gp_sculpt.guide;
-  tGPspoint *points = (tGPspoint *)p->gpd->runtime.sbuffer;
 
   /* default exit state - pass through to support MMB view nav, etc. */
   int estate = OPERATOR_PASS_THROUGH;
@@ -3969,6 +3968,7 @@ static int gpencil_draw_modal(bContext *C, wmOperator *op, const wmEvent *event)
       int size_after = p->gpd->runtime.sbuffer_used;
 
       /* Last point of the event is always real (not fake). */
+      tGPspoint *points = (tGPspoint *)p->gpd->runtime.sbuffer;
       tGPspoint *pt = &points[size_after - 1];
       pt->tflag &= ~GP_TPOINT_FAKE;
 
diff --git a/source/blender/editors/gpencil/gpencil_utils.c b/source/blender/editors/gpencil/gpencil_utils.c
index b194d28a8b8..3ca993673d4 100644
--- a/source/blender/editors/gpencil/gpencil_utils.c
+++ b/source/blender/editors/gpencil/gpencil_utils.c
@@ -2530,8 +2530,8 @@ void ED_gpencil_select_toggle_all(bContext *C, int action)
 
 /* 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,
+                                     int *buffer_size,
+                                     int *buffer_used,
                                      const bool clear)
 {
   tGPspoint *p = NULL;