Initial support for native accessibility in ARC

chrome/browser/chromeos/arc/accessibility/ax_tree_source_arc.h

+// Copyright 2017 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.
+
+#ifndef CHROME_BROWSER_CHROMEOS_ARC_ACCESSIBILITY_AX_TREE_SOURCE_ARC_H_
+#define CHROME_BROWSER_CHROMEOS_ARC_ACCESSIBILITY_AX_TREE_SOURCE_ARC_H_
+
+#include "components/arc/common/accessibility_helper.mojom.h"
+#include "ui/accessibility/ax_node.h"
+#include "ui/accessibility/ax_node_data.h"
+#include "ui/accessibility/ax_tree_data.h"
+#include "ui/accessibility/ax_tree_serializer.h"
+#include "ui/accessibility/ax_tree_source.h"
+#include "ui/views/view.h"
+
+namespace arc {
+
+using AXTreeArcSerializer =
+    ui::AXTreeSerializer<mojom::AccessibilityNodeInfoData*,
+                         ui::AXNodeData,
+                         ui::AXTreeData>;
+
+// This class represents the accessibility tree from the focused ARC window.
+class AXTreeSourceArc
+    : public ui::AXTreeSource<mojom::AccessibilityNodeInfoData*,
+                              ui::AXNodeData,
+                              ui::AXTreeData>,
+      public views::View {

[dmazzoni, 2017/02/09 01:18:09]

Seems like a bit of a hack to make this a View and attach it as a child. I'm
worried that could
cause side effects or it could be a poorly-tested configuration.

How about making the content view for the ExoShell window into a specific View
subclass,
and adding the GetAccessibilityNodeData override directly?

It'd be essentially the same. The difference is that now everybody using ARC++
would be
using that View so accessibility is less likely to break.

Ping me if that isn't clear.

[David Tseng, 2017/02/09 03:10:09]

No, its clear because I did that in the first patchsets of this change (please
see).

Ping again @reveman. The advantage of this approach is it makes it so we're not
as tightly coupled with the exo component and don't have to introduce more
dependencies for exo. There's also the need to plumb through access to
ShellSurface from Surface; ShellSurface is the content view for a
ShellSurfaceWidget.

The downside is as you pointed out, side effects. I made the view owned by
client (so we're explicitly responsible for managing it) and we're making it
focusable.  I'm not sure if we can do the same for the exo shell surface?

I think we can mitigate the downside by writing good tests.

+ public:
+  AXTreeSourceArc();
+  ~AXTreeSourceArc() override;
+
+  // Notify automation of an accessibility event.
+  void NotifyAccessibilityEvent(mojom::AccessibilityEventData* event_data);
+
+ private:
+  // AXTreeSource overrides.
+  bool GetTreeData(ui::AXTreeData* data) const override;
+  mojom::AccessibilityNodeInfoData* GetRoot() const override;
+  mojom::AccessibilityNodeInfoData* GetFromId(int32_t id) const override;
+  int32_t GetId(mojom::AccessibilityNodeInfoData* node) const override;
+  void GetChildren(mojom::AccessibilityNodeInfoData* node,
+                   std::vector<mojom::AccessibilityNodeInfoData*>* out_children)
+      const override;
+  mojom::AccessibilityNodeInfoData* GetParent(
+      mojom::AccessibilityNodeInfoData* node) const override;
+  bool IsValid(mojom::AccessibilityNodeInfoData* node) const override;
+  bool IsEqual(mojom::AccessibilityNodeInfoData* node1,
+               mojom::AccessibilityNodeInfoData* node2) const override;
+  mojom::AccessibilityNodeInfoData* GetNull() const override;
+  void SerializeNode(mojom::AccessibilityNodeInfoData* node,
+                     ui::AXNodeData* out_data) const override;
+
+  // views::View overrides.
+  void GetAccessibleNodeData(ui::AXNodeData* node_data) override;
+
+  // Resets tree state.
+  void Reset();
+
+  // The id of this tree.
+  int32_t id_;

[dmazzoni, 2017/02/09 01:18:09]

tree_id_?

+
+  // Maps an AccessibilityNodeInfo to its tree data.
+  std::map<int32_t, mojom::AccessibilityNodeInfoData*> tree_map_;
+  std::map<int32_t, int32_t> parent_map_;
+  std::unique_ptr<AXTreeArcSerializer> current_tree_serializer_;
+  int32_t root_id_;
+  int32_t focused_node_id_;
+
+  DISALLOW_COPY_AND_ASSIGN(AXTreeSourceArc);
+};
+
+}  // namespace arc
+
+#endif  // CHROME_BROWSER_CHROMEOS_ARC_ACCESSIBILITY_AX_TREE_SOURCE_ARC_H_