WM: de-duplicate cursor motion checks for selection picking

Replace local static mouse coordinate storage with a single function.
also resolve inconsistencies.

- Edit-mesh selection used equality check (ignoring `U.move_threshold`).
- Motion to clear tooltips checked the value without scaling by the DPI.

Also prevent the unlikely case of the previous motion check matching
a different area by resetting the value when the active region changes.

source/blender/editors/armature/armature_select.c

@@ -673,11 +673,7 @@ static EditBone *get_nearest_editbonepoint(
   }
 
   if (use_cycle) {
-    static int last_mval[2] = {-100, -100};
-    if ((len_manhattan_v2v2_int(vc->mval, last_mval) <= WM_EVENT_CURSOR_MOTION_THRESHOLD) == 0) {
-      use_cycle = false;
-    }
-    copy_v2_v2_int(last_mval, vc->mval);
+    use_cycle = !WM_cursor_test_motion_and_update(vc->mval);
   }
 
   const bool do_nearest = !(XRAY_ACTIVE(vc->v3d) || use_cycle);

source/blender/editors/mesh/editmesh_select.c

@@ -884,9 +884,8 @@ static bool unified_findnearest(ViewContext *vc,
                                 BMFace **r_efa)
 {
   BMEditMesh *em = vc->em;
-  static short mval_prev[2] = {-1, -1};
-  /* only cycle while the mouse remains still */
-  const bool use_cycle = ((mval_prev[0] == vc->mval[0]) && (mval_prev[1] == vc->mval[1]));
+
+  const bool use_cycle = !WM_cursor_test_motion_and_update(vc->mval);
   const float dist_init = ED_view3d_select_dist_px();
   /* since edges select lines, we give dots advantage of ~20 pix */
   const float dist_margin = (dist_init / 2);
@@ -988,9 +987,6 @@ static bool unified_findnearest(ViewContext *vc,
     }
   }
 
-  mval_prev[0] = vc->mval[0];
-  mval_prev[1] = vc->mval[1];
-
   /* Only one element type will be non-null. */
   BLI_assert(((hit.v.ele != NULL) + (hit.e.ele != NULL) + (hit.f.ele != NULL)) <= 1);
 

source/blender/editors/screen/screen_edit.c

@@ -935,6 +935,10 @@ void ED_screen_set_active_region(bContext *C, wmWindow *win, const int xy[2])
         }
       }
     }
+
+    /* Ensure test-motion values are never shared between regions. */
+    const bool use_cycle = !WM_cursor_test_motion_and_update((const int[2]){-1, -1});
+    UNUSED_VARS(use_cycle);
   }
 
   /* Cursors, for time being set always on edges,

source/blender/editors/space_view3d/view3d_select.c

@@ -2047,19 +2047,16 @@ static int mixed_bones_object_selectbuffer_extended(ViewContext *vc,
                                                     bool enumerate,
                                                     bool *r_do_nearest)
 {
-  static int last_mval[2] = {-100, -100};
   bool do_nearest = false;
   View3D *v3d = vc->v3d;
 
   /* define if we use solid nearest select or not */
   if (use_cycle) {
+    /* Update the coordinates (even if the return value isn't used). */
+    const bool has_motion = WM_cursor_test_motion_and_update(mval);
     if (!XRAY_ACTIVE(v3d)) {
-      do_nearest = true;
-      if (len_manhattan_v2v2_int(mval, last_mval) <= WM_EVENT_CURSOR_MOTION_THRESHOLD) {
-        do_nearest = false;
-      }
+      do_nearest = has_motion;
     }
-    copy_v2_v2_int(last_mval, mval);
   }
   else {
     if (!XRAY_ACTIVE(v3d)) {

source/blender/windowmanager/WM_api.h

@@ -937,6 +937,7 @@ bool WM_event_is_modal_tweak_exit(const struct wmEvent *event, int tweak_event);
 bool WM_event_is_last_mousemove(const struct wmEvent *event);
 bool WM_event_is_mouse_drag(const struct wmEvent *event);
 bool WM_event_is_mouse_drag_or_press(const wmEvent *event);
+bool WM_cursor_test_motion_and_update(const int mval[2]) ATTR_NONNULL(1) ATTR_WARN_UNUSED_RESULT;
 
 int WM_event_drag_threshold(const struct wmEvent *event);
 bool WM_event_drag_test(const struct wmEvent *event, const int prev_xy[2]);

source/blender/windowmanager/intern/wm_event_query.c

@@ -276,6 +276,28 @@ bool WM_event_is_mouse_drag_or_press(const wmEvent *event)
          (ISMOUSE_BUTTON(event->type) && (event->val == KM_PRESS));
 }
 
+/**
+ * Detect motion between selection (callers should only use this for selection picking),
+ * typically mouse press/click events.
+ *
+ * \param mval: Region relative coordinates, call with (-1, -1) resets the last cursor location.
+ * \returns True when there was motion since last called.
+ *
+ * NOTE(@campbellbarton): The logic used here isn't foolproof.
+ * It's possible that users move the cursor past #WM_EVENT_CURSOR_MOTION_THRESHOLD then back to
+ * a position within the threshold (between mouse clicks).
+ * In practice users never reported this since the threshold is very small (a few pixels).
+ * To prevent the unlikely case of values matching from another region,
+ * changing regions resets this value to (-1, -1).
+ */
+bool WM_cursor_test_motion_and_update(const int mval[2])
+{
+  static int mval_prev[2] = {-1, -1};
+  bool use_cycle = (len_manhattan_v2v2_int(mval, mval_prev) <= WM_EVENT_CURSOR_MOTION_THRESHOLD);
+  copy_v2_v2_int(mval_prev, mval);
+  return !use_cycle;
+}
+
 /** \} */
 
 /* -------------------------------------------------------------------- */

source/blender/windowmanager/intern/wm_event_system.c

@@ -3628,7 +3628,8 @@ void wm_event_do_handlers(bContext *C)
       /* Clear tool-tip on mouse move. */
       if (screen->tool_tip && screen->tool_tip->exit_on_event) {
         if (ELEM(event->type, MOUSEMOVE, INBETWEEN_MOUSEMOVE)) {
-          if (len_manhattan_v2v2_int(screen->tool_tip->event_xy, event->xy) > U.move_threshold) {
+          if (len_manhattan_v2v2_int(screen->tool_tip->event_xy, event->xy) >
+              WM_EVENT_CURSOR_MOTION_THRESHOLD) {
             WM_tooltip_clear(C, win);
           }
         }