Fix T95591: Crash on drawing with measure tool with tweak fallback tool

Using press to activate the Tweak tool doesn't work well when used a
fallback tool as the drag event is often used by the current tool -
making it impossible not to select when dragging (unless the fallback
tool is disabled entirely).
Resolve this by using CLICK events when the Tweak tool is used as a
fallback.

Even though this avoids the crash, check for null-pointer de-reference
since changes to the key-map shouldn't cause operators to crash.

Note that the ability for operators to access a gizmo before it's fully
initialized is a more general problem that should be addressed, but out
of scope for a bug-fix.

Reviewed By: zeddb, JulienKaspar, Severin

Maniphest Tasks: T95591

Ref D14231

2 files changed, 34 insertions, 9 deletions

diff --git a/release/scripts/presets/keyconfig/keymap_data/blender_default.py b/release/scripts/presets/keyconfig/keymap_data/blender_default.py
index eab97b30fff..3694f275d35 100644
--- a/release/scripts/presets/keyconfig/keymap_data/blender_default.py
+++ b/release/scripts/presets/keyconfig/keymap_data/blender_default.py
@@ -442,13 +442,18 @@ def _template_items_change_frame(params):
 
 # Tool System Templates
 
-def _template_items_tool_select(params, operator, cursor_operator, *, extend):
+def _template_items_tool_select(params, operator, cursor_operator, fallback, *, extend):
     if params.select_mouse == 'LEFTMOUSE':
-        # Immediate select without quick delay.
+        # By default use 'PRESS' for immediate select without quick delay.
+        # Fallback key-maps 'CLICK' since 'PRESS' events passes through (allowing either click or drag).
+        #
+        # NOTE: When the active (non-fallback) tool uses a key-map that activates it's primary tool on drag,
+        # it's important that this key-map uses click and not press. Otherwise it becomes impossible to use
+        # the tool without selecting elements under the cursor.
         return [
-            (operator, {"type": 'LEFTMOUSE', "value": 'PRESS'},
+            (operator, {"type": 'LEFTMOUSE', "value": 'CLICK' if fallback else 'PRESS'},
              {"properties": [("deselect_all", True)]}),
-            (operator, {"type": 'LEFTMOUSE', "value": 'PRESS', "shift": True},
+            (operator, {"type": 'LEFTMOUSE', "value": 'CLICK' if fallback else 'PRESS', "shift": True},
              {"properties": [(extend, True)]}),
         ]
     else:
@@ -6283,7 +6288,7 @@ def km_image_editor_tool_uv_select(params, *, fallback):
         {"space_type": 'IMAGE_EDITOR', "region_type": 'WINDOW'},
         {"items": [
             *([] if (fallback and (params.select_mouse == 'RIGHTMOUSE')) else _template_items_tool_select(
-                params, "uv.select", "uv.cursor_set", extend="extend")),
+                params, "uv.select", "uv.cursor_set", fallback, extend="extend")),
             *([] if (not params.use_fallback_tool_rmb) else _template_uv_select(
                 type=params.select_mouse, value=params.select_mouse_value, legacy=params.legacy)),
         ]},
@@ -6490,7 +6495,7 @@ def km_3d_view_tool_select(params, *, fallback):
         {"space_type": 'VIEW_3D', "region_type": 'WINDOW'},
         {"items": [
             *([] if (fallback and (params.select_mouse == 'RIGHTMOUSE')) else _template_items_tool_select(
-                params, "view3d.select", "view3d.cursor3d", extend="toggle")),
+                params, "view3d.select", "view3d.cursor3d", fallback, extend="toggle")),
             *([] if (not params.use_fallback_tool_rmb) else _template_view3d_select(
                 type=params.select_mouse, value=params.select_mouse_value, legacy=params.legacy, exclude_mod="ctrl")),
         ]},
@@ -7402,7 +7407,7 @@ def km_3d_view_tool_edit_gpencil_select(params, *, fallback):
         {"space_type": 'VIEW_3D', "region_type": 'WINDOW'},
         {"items": [
             *([] if (fallback and (params.select_mouse == 'RIGHTMOUSE')) else _template_items_tool_select(
-                params, "gpencil.select", "view3d.cursor3d", extend="toggle")),
+                params, "gpencil.select", "view3d.cursor3d", fallback, extend="toggle")),
             *([] if (not params.use_fallback_tool_rmb) else _template_view3d_gpencil_select(
                 type=params.select_mouse, value=params.select_mouse_value, legacy=params.legacy)),
         ]},
@@ -7540,7 +7545,7 @@ def km_3d_view_tool_sculpt_gpencil_select(params):
     return (
         "3D View Tool: Sculpt Gpencil, Tweak",
         {"space_type": 'VIEW_3D', "region_type": 'WINDOW'},
-        {"items": _template_items_tool_select(params, "gpencil.select", "view3d.cursor3d", extend="toggle")},
+        {"items": _template_items_tool_select(params, "gpencil.select", "view3d.cursor3d", False, extend="toggle")},
     )
 
 
@@ -7580,7 +7585,7 @@ def km_sequencer_editor_tool_generic_select(params, *, fallback):
         {"space_type": 'SEQUENCE_EDITOR', "region_type": 'WINDOW'},
         {"items": [
             *([] if (fallback and (params.select_mouse == 'RIGHTMOUSE')) else _template_items_tool_select(
-                params, "sequencer.select", "sequencer.cursor_set", extend="toggle")),
+                params, "sequencer.select", "sequencer.cursor_set", fallback, extend="toggle")),
 
             *([] if (not params.use_fallback_tool_rmb) else _template_sequencer_preview_select(
                 type=params.select_mouse, value=params.select_mouse_value, legacy=params.legacy)),
diff --git a/source/blender/editors/space_view3d/view3d_gizmo_ruler.c b/source/blender/editors/space_view3d/view3d_gizmo_ruler.c
index 1082483dcd7..adcb101bca9 100644
--- a/source/blender/editors/space_view3d/view3d_gizmo_ruler.c
+++ b/source/blender/editors/space_view3d/view3d_gizmo_ruler.c
@@ -469,6 +469,19 @@ static bool view3d_ruler_item_mousemove(const bContext *C,
   return false;
 }
 
+/**
+ * When the gizmo-group has been created immediately before running an operator
+ * to manipulate rulers, it's possible the new gizmo-group has not yet been initialized.
+ * in 3.0 this happened because left-click drag would both select and add a new ruler,
+ * significantly increasing the likelihood of this happening.
+ * Workaround this crash by checking the gizmo's custom-data has not been cleared.
+ * The key-map has also been modified not to trigger this bug, see T95591.
+ */
+static bool gizmo_ruler_check_for_operator(const wmGizmoGroup *gzgroup)
+{
+  return gzgroup->customdata != NULL;
+}
+
 /** \} */
 
 /* -------------------------------------------------------------------- */
@@ -1308,6 +1321,10 @@ static int view3d_ruler_add_invoke(bContext *C, wmOperator *op, const wmEvent *e
   wmGizmoGroup *gzgroup = WM_gizmomap_group_find(gzmap, view3d_gzgt_ruler_id);
   const bool use_depth = (v3d->shading.type >= OB_SOLID);
 
+  if (!gizmo_ruler_check_for_operator(gzgroup)) {
+    return OPERATOR_CANCELLED;
+  }
+
   /* Create new line */
   RulerItem *ruler_item;
   ruler_item = ruler_item_add(gzgroup);
@@ -1383,6 +1400,9 @@ static int view3d_ruler_remove_invoke(bContext *C, wmOperator *op, const wmEvent
   wmGizmoMap *gzmap = region->gizmo_map;
   wmGizmoGroup *gzgroup = WM_gizmomap_group_find(gzmap, view3d_gzgt_ruler_id);
   if (gzgroup) {
+    if (!gizmo_ruler_check_for_operator(gzgroup)) {
+      return OPERATOR_CANCELLED;
+    }
     RulerInfo *ruler_info = gzgroup->customdata;
     if (ruler_info->item_active) {
       RulerItem *ruler_item = ruler_info->item_active;