UI: Follow HIG for view item selecting/activating

Makes selecting/activating view items (tree and grid view items) behave
as wanted by the guidelines, consistent with many other editors:
https://developer.blender.org/docs/features/interface/human_interface_guidelines/selection/#select-tweaking

Noteworthy:
- View items activate on press again, not on release
- Pose library still only activates poses on click (releasing mouse
  before moving cursor), so dragging can be used to blend poses
- New: Clicking on empty space in a view deselects all
- Redundant activation in interface handlers code is removed

Pull Request: https://projects.blender.org/blender/blender/pulls/146569

scripts/presets/keyconfig/keymap_data/blender_default.py

@@ -1042,7 +1042,7 @@ def km_user_interface(_params):
         ("ui.view_scroll", {"type": 'WHEELUPMOUSE', "value": 'ANY'}, None),
         ("ui.view_scroll", {"type": 'WHEELDOWNMOUSE', "value": 'ANY'}, None),
         ("ui.view_scroll", {"type": 'TRACKPADPAN', "value": 'ANY'}, None),
-        ("ui.view_item_select", {"type": 'LEFTMOUSE', "value": 'CLICK'}, None),
+        ("ui.view_item_select", {"type": 'LEFTMOUSE', "value": 'PRESS'}, None),
         ("ui.view_item_select", {"type": 'LEFTMOUSE', "value": 'PRESS', "ctrl": True},
          {"properties": [("extend", True)]}),
         ("ui.view_item_select", {"type": 'LEFTMOUSE', "value": 'PRESS', "shift": True},

scripts/presets/keyconfig/keymap_data/industry_compatible_data.py

@@ -420,7 +420,7 @@ def km_user_interface(params):
         ("anim.driver_button_remove", {"type": 'D', "value": 'PRESS', "alt": True}, None),
         ("anim.keyingset_button_add", {"type": 'K', "value": 'PRESS'}, None),
         ("anim.keyingset_button_remove", {"type": 'K', "value": 'PRESS', "alt": True}, None),
-        ("ui.view_item_select", {"type": 'LEFTMOUSE', "value": 'CLICK'}, None),
+        ("ui.view_item_select", {"type": 'LEFTMOUSE', "value": 'PRESS'}, None),
     ])
 
     return keymap

source/blender/editors/asset/intern/asset_shelf_asset_view.cc

@@ -124,6 +124,12 @@ void AssetView::build_items()
     if (shelf_.type->flag & ASSET_SHELF_TYPE_FLAG_NO_ASSET_DRAG) {
       item.disable_asset_drag();
     }
+    if (!shelf_.type->drag_operator.empty()) {
+      /* For now always select/activate items on click instead of press when there's a drag
+       * operator set. Important for pose library blending. Maybe we want to make this an explicit
+       * option of the asset shelf instead. */
+      item.select_on_click_set();
+    }
     /* Make sure every click calls the #bl_activate_operator. We might want to add a flag to
      * enable/disable this. Or we only call #bl_activate_operator when an item becomes active, and
      * add a #bl_click_operator for repeated execution on every click. So far it seems like every

source/blender/editors/include/UI_abstract_view.hh

@@ -216,6 +216,8 @@ class AbstractViewItem {
    * children currently.
    */
   bool is_always_collapsible_ = false;
+  /** See #select_on_click_set(). */
+  bool select_on_click_ = false;
   /** See #always_reactivate_on_click(). */
   bool reactivate_on_click_ = false;
   /** See #activate_for_context_menu_set(). */
@@ -312,6 +314,13 @@ class AbstractViewItem {
   bool is_interactive() const;
 
   void disable_activatable();
+  /**
+   * Configure this view item to only select/activate on mouse-click (i.e. when the mouse is
+   * pressed and released without much movement in-between); the default is to select/activate on
+   * mouse-press.
+   */
+  void select_on_click_set();
+  bool is_select_on_click() const;
   /** Call #on_activate() on every click on the item, even when the item was active before. */
   void always_reactivate_on_click();
   /** Call #on_activate() when spawning a context menu. Otherwise the item will only be highlighted

source/blender/editors/interface/interface.cc

@@ -264,6 +264,13 @@ void ui_region_to_window(const ARegion *region, int *x, int *y)
   *y += region->winrct.ymin;
 }
 
+void ui_region_to_window(
+    const ARegion *region, int region_x, int region_y, int *r_window_x, int *r_window_y)
+{
+  *r_window_x = region_x + region->winrct.xmin;
+  *r_window_y = region_y + region->winrct.ymin;
+}
+
 int uiBlock::but_index(const uiBut *but) const
 {
   BLI_assert(!buttons.is_empty() && but);

source/blender/editors/interface/interface_handlers.cc

@@ -5142,7 +5142,7 @@ static int ui_do_but_VIEW_ITEM(bContext *C,
   BLI_assert(view_item_but->type == ButType::ViewItem);
 
   if (data->state == BUTTON_STATE_HIGHLIGHT) {
-    if ((event->type == LEFTMOUSE) && (event->modifier == 0)) {
+    if (event->type == LEFTMOUSE) {
       switch (event->val) {
         case KM_PRESS:
           /* Extra icons have priority, don't mess with them. */
@@ -5155,9 +5155,6 @@ static int ui_do_but_VIEW_ITEM(bContext *C,
             data->dragstartx = event->xy[0];
             data->dragstarty = event->xy[1];
           }
-          else {
-            force_activate_view_item_but(C, data->region, view_item_but);
-          }
 
           /* Always continue for drag and drop handling. Also for cases where keymap items are
            * registered to add custom activate or drag operators (the pose library does this for

source/blender/editors/interface/interface_intern.hh

@@ -756,6 +756,8 @@ void ui_window_to_region(const ARegion *region, int *x, int *y);
 void ui_window_to_region_rcti(const ARegion *region, rcti *rect_dst, const rcti *rct_src);
 void ui_window_to_region_rctf(const ARegion *region, rctf *rect_dst, const rctf *rct_src);
 void ui_region_to_window(const ARegion *region, int *x, int *y);
+void ui_region_to_window(
+    const ARegion *region, int region_x, int region_y, int *r_window_x, int *r_window_y);
 /**
  * Popups will add a margin to #ARegion.winrct for shadow,
  * for interactivity (point-inside tests for eg), we want the winrct without the margin added.

source/blender/editors/interface/interface_ops.cc

@@ -2771,27 +2771,32 @@ static void UI_OT_view_item_rename(wmOperatorType *ot)
   ot->flag = OPTYPE_INTERNAL;
 }
 
-static wmOperatorStatus ui_view_item_select_invoke(bContext *C,
-                                                   wmOperator *op,
-                                                   const wmEvent *event)
+static wmOperatorStatus view_item_click_select(bContext &C,
+                                               AbstractViewItem *clicked_item,
+                                               const AbstractView &view,
+                                               const bool extend,
+                                               const bool range_select,
+                                               bool wait_to_deselect_others)
 {
-  ARegion &region = *CTX_wm_region(C);
+  const bool already_selected = clicked_item && clicked_item->is_selected();
 
-  AbstractViewItem *clicked_item = UI_region_views_find_item_at(region, event->xy);
-  if (clicked_item == nullptr) {
-    return OPERATOR_CANCELLED;
+  if (extend || range_select) {
+    wait_to_deselect_others = false;
   }
 
-  AbstractView &view = clicked_item->get_view();
-  const bool is_multiselect = view.is_multiselect_supported();
-  const bool extend = RNA_boolean_get(op->ptr, "extend") && is_multiselect;
-  const bool range_select = RNA_boolean_get(op->ptr, "range_select") && is_multiselect;
+  if (clicked_item && already_selected && wait_to_deselect_others) {
+    return OPERATOR_RUNNING_MODAL;
+  }
 
   if (!extend) {
-    /* Keep previous selection for extend selection, see: !138979. */
     view.foreach_view_item([](AbstractViewItem &item) { item.set_selected(false); });
   }
 
+  if (clicked_item == nullptr) {
+    /* Only clear selection (if needed). */
+    return OPERATOR_FINISHED;
+  }
+
   if (range_select) {
     bool is_inside_range = false;
     view.foreach_view_item([&](AbstractViewItem &item) {
@@ -2805,26 +2810,85 @@ static wmOperatorStatus ui_view_item_select_invoke(bContext *C,
         item.set_selected(true);
       }
     });
-    ED_region_tag_redraw(&region);
     return OPERATOR_FINISHED;
   }
 
-  clicked_item->activate(*C);
+  clicked_item->activate(C);
 
   return OPERATOR_FINISHED;
 }
 
+static std::pair<AbstractView *, AbstractViewItem *> select_operator_view_and_item_find_xy(
+    const ARegion &region, const wmOperator &op)
+{
+  /* Mouse coordinates in window space. */
+  int window_xy[2];
+  {
+    /* Mouse coordinates in region space. */
+    int region_xy[2];
+    region_xy[0] = RNA_int_get(op.ptr, "mouse_x");
+    region_xy[1] = RNA_int_get(op.ptr, "mouse_y");
+    ui_region_to_window(&region, region_xy[0], region_xy[1], &window_xy[0], &window_xy[1]);
+  }
+
+  AbstractView *view = UI_region_view_find_at(&region, window_xy, 0);
+  AbstractViewItem *item = UI_region_views_find_item_at(region, window_xy);
+  BLI_assert(!item || &item->get_view() == view);
+
+  return std::make_pair(view, item);
+}
+
+static wmOperatorStatus ui_view_item_select_exec(bContext *C, wmOperator *op)
+{
+  ARegion &region = *CTX_wm_region(C);
+  auto [view, clicked_item] = select_operator_view_and_item_find_xy(region, *op);
+
+  if (!view) {
+    return OPERATOR_CANCELLED;
+  }
+
+  const bool is_multiselect = view->is_multiselect_supported();
+  const bool extend = RNA_boolean_get(op->ptr, "extend") && is_multiselect;
+  const bool range_select = RNA_boolean_get(op->ptr, "range_select") && is_multiselect;
+  const bool wait_to_deselect_others = RNA_boolean_get(op->ptr, "wait_to_deselect_others");
+
+  const wmOperatorStatus status = view_item_click_select(
+      *C, clicked_item, *view, extend, range_select, wait_to_deselect_others);
+
+  ED_region_tag_redraw(&region);
+
+  return status;
+}
+
+static wmOperatorStatus ui_view_item_select_invoke(bContext *C,
+                                                   wmOperator *op,
+                                                   const wmEvent *event)
+{
+  const ARegion &region = *CTX_wm_region(C);
+  const AbstractViewItem *clicked_item = UI_region_views_find_item_at(region, event->xy);
+
+  /* Wait with selecting to see if there's a click or drag event, if requested by the view item. */
+  if (clicked_item && clicked_item->is_select_on_click()) {
+    RNA_boolean_set(op->ptr, "use_select_on_click", true);
+  }
+
+  return WM_generic_select_invoke(C, op, event);
+}
+
 static void UI_OT_view_item_select(wmOperatorType *ot)
 {
   ot->name = "Select View Item";
   ot->idname = "UI_OT_view_item_select";
   ot->description = "Activate selected view item";
 
+  ot->exec = ui_view_item_select_exec;
   ot->invoke = ui_view_item_select_invoke;
+  ot->modal = WM_generic_select_modal;
   ot->poll = ui_view_focused_poll;
 
   ot->flag = OPTYPE_INTERNAL;
 
+  WM_operator_properties_generic_select(ot);
   PropertyRNA *prop = RNA_def_boolean(ot->srna, "extend", false, "extend", "Extend Selection");
   RNA_def_property_flag(prop, PROP_SKIP_SAVE);
   prop = RNA_def_boolean(ot->srna,

source/blender/editors/interface/views/abstract_view_item.cc

@@ -340,6 +340,16 @@ void AbstractViewItem::disable_activatable()
   is_activatable_ = false;
 }
 
+void AbstractViewItem::select_on_click_set()
+{
+  select_on_click_ = true;
+}
+
+bool AbstractViewItem::is_select_on_click() const
+{
+  return select_on_click_;
+}
+
 void AbstractViewItem::always_reactivate_on_click()
 {
   reactivate_on_click_ = true;

source/blender/windowmanager/intern/wm_operator_props.cc

@@ -512,6 +512,16 @@ void WM_operator_properties_generic_select(wmOperatorType *ot)
       ot->srna, "wait_to_deselect_others", false, "Wait to Deselect Others", "");
   RNA_def_property_flag(prop, PROP_HIDDEN | PROP_SKIP_SAVE);
 
+  /* Force the selection to act on mouse click, not press. Necessary for some cases, but isn't used
+   * much.  */
+  prop = RNA_def_boolean(ot->srna,
+                         "use_select_on_click",
+                         false,
+                         "Act on Click",
+                         "Instead of selecting on mouse press, wait to see if there's drag event. "
+                         "Otherwise select on mouse release");
+  RNA_def_property_flag(prop, PROP_HIDDEN | PROP_SKIP_SAVE);
+
   RNA_def_int(ot->srna, "mouse_x", 0, INT_MIN, INT_MAX, "Mouse X", "", INT_MIN, INT_MAX);
   RNA_def_int(ot->srna, "mouse_y", 0, INT_MIN, INT_MAX, "Mouse Y", "", INT_MIN, INT_MAX);
 }

source/blender/windowmanager/intern/wm_operators.cc

@@ -982,19 +982,27 @@ wmOperatorStatus WM_generic_select_modal(bContext *C, wmOperator *op, const wmEv
 {
   PropertyRNA *wait_to_deselect_prop = RNA_struct_find_property(op->ptr,
                                                                 "wait_to_deselect_others");
+  const bool use_select_on_click = RNA_struct_property_is_set(op->ptr, "use_select_on_click");
   const short init_event_type = short(POINTER_AS_INT(op->customdata));
 
   /* Get settings from RNA properties for operator. */
   const int mval[2] = {RNA_int_get(op->ptr, "mouse_x"), RNA_int_get(op->ptr, "mouse_y")};
 
   if (init_event_type == 0) {
+    op->customdata = POINTER_FROM_INT(int(event->type));
+
+    if (use_select_on_click) {
+      /* Don't do any selection yet. Wait to see if there's a drag or click (release) event. */
+      WM_event_add_modal_handler(C, op);
+      return OPERATOR_RUNNING_MODAL | OPERATOR_PASS_THROUGH;
+    }
+
     if (event->val == KM_PRESS) {
       RNA_property_boolean_set(op->ptr, wait_to_deselect_prop, true);
 
       wmOperatorStatus retval = op->type->exec(C, op);
       OPERATOR_RETVAL_CHECK(retval);
 
-      op->customdata = POINTER_FROM_INT(int(event->type));
       if (retval & OPERATOR_RUNNING_MODAL) {
         WM_event_add_modal_handler(C, op);
       }