MacViews a11y: Support the "Show menu" action in Textfield and Combobox.

ui/views/controls/combobox/combobox.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/controls/combobox/combobox.h"
 
 #include <stddef.h>
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "build/build_config.h"
+#include "ui/accessibility/ax_action_data.h"
 #include "ui/accessibility/ax_node_data.h"
 #include "ui/base/default_style.h"
 #include "ui/base/ime/input_method.h"
 #include "ui/base/material_design/material_design_controller.h"
 #include "ui/base/models/combobox_model_observer.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/events/event.h"
 #include "ui/gfx/animation/throb_animation.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/color_palette.h"
@@ skipping 730 matching lines @@
   // AX_ROLE_COMBO_BOX is for UI elements with a dropdown and an editable text
   // field, which views::Combobox does not have. Use AX_ROLE_POP_UP_BUTTON to
   // match an HTML <select> element.
   node_data->role = ui::AX_ROLE_POP_UP_BUTTON;
 
   node_data->SetName(accessible_name_);
   node_data->SetValue(model_->GetItemAt(selected_index_));
   if (enabled()) {
     node_data->AddIntAttribute(ui::AX_ATTR_DEFAULT_ACTION_VERB,
                                ui::AX_DEFAULT_ACTION_VERB_OPEN);
+    node_data->AddAction(ui::AX_ACTION_SHOW_CONTEXT_MENU);
   }
   node_data->AddIntAttribute(ui::AX_ATTR_POS_IN_SET, selected_index_);
   node_data->AddIntAttribute(ui::AX_ATTR_SET_SIZE, model_->GetItemCount());
 }
 
+bool Combobox::HandleAccessibleAction(const ui::AXActionData& action_data) {
+  // The action handling in View would generate a mouse event, but mouse events
+  // for Combobox are handled by |arrow_button_|. Handle the action explicitly.
+  // Also handle AX_SHOW_CONTEXT_MENU so that a "show menu" action is exposed to
+  // native accessibility tools.
+  if (enabled() && (action_data.action == ui::AX_ACTION_DO_DEFAULT ||
+                    action_data.action == ui::AX_ACTION_SHOW_CONTEXT_MENU)) {

[dmazzoni, 2017/06/21 06:09:35]

Wait, so the SHOW_CONTEXT_MENU action also drops down the menu for a
combo box? That doesn't sound right. It should do the same thing as
right-clicking, which is probably nothing.

(For a text field, it should open a menu with things like Cut, Copy, Paste.)

[tapted, 2017/06/21 06:52:55]

Cocoa offers both "press" and "show menu" actions for combox/popup menus. press
is the default. "show menu" also shows the menu (although positioned
differently).

Cocoa doesn't use the word "context" menu, but there isn't a separate AX enum
for a non-context menu. I'm not sure what approach is. Renaming
AX_SHOW_CONTEXT_MENU to AX_SHOW_MENU might be bad (e.g. menu-like items in the
bookmarks toolbar can expand into submenus and also expose a right-click menu).

I could just leave off SHOW_CONTEXT_MENU for now, and explore in a follow-up. Or
only handle add it above between #if mac.
yup - this CL achieves this for text field.

+    ShowDropDownMenu(ui::MENU_SOURCE_KEYBOARD);
+    return true;
+  }
+  return View::HandleAccessibleAction(action_data);
+}
+
 void Combobox::ButtonPressed(Button* sender, const ui::Event& event) {
   if (!enabled())
     return;
 
   if (!UseMd())
     RequestFocus();
 
   if (sender == text_button_) {
     OnPerformAction();
   } else {
@@ skipping 235 matching lines @@
   constexpr int kMdPaddingWidth = 8;
   constexpr int kNormalPaddingWidth = 7;
   int arrow_pad = UseMd() ? kMdPaddingWidth : kNormalPaddingWidth;
   int padding = style_ == STYLE_NORMAL
                     ? arrow_pad * 2
                     : kActionLeftPadding + kActionRightPadding;
   return ArrowSize().width() + padding;
 }
 
 }  // namespace views