Add more fine-grained accessibility modes.

content/common/accessibility_mode_enums.h

 // Copyright 2014 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 CONTENT_COMMON_ACCESSIBILITY_MODE_ENUMS_H_
 #define CONTENT_COMMON_ACCESSIBILITY_MODE_ENUMS_H_
 
 // Note: keep enums in content/browser/resources/accessibility/accessibility.js
 // in sync with these two enums.
 enum AccessibilityModeFlag {
-  // Accessibility updates are processed to create platform trees and events are
-  // passed to platform APIs in the browser.
-  AccessibilityModeFlagPlatform = 1 << 0,
+  // Native accessibility APIs, specific to each platform, are enabled.
+  // When this flag is set that indicates the presence of a third-party
+  // client accessing Chrome via accessibility APIs. However, unless one
+  // of the flags below is set, the contents of web pages will not be
+  // accessible.
+  AccessibilityModeFlagNativeAPIs = 1 << 0,
 
-  // Accessibility is on, and the full tree is computed. If this flag is off,
-  // only limited information about editable text nodes is sent to the browser
-  // process. Useful for implementing limited UIA on tablets.
-  AccessibilityModeFlagFullTree = 1 << 1,

[aboxhall, 2016/12/12 20:18:29]

Did this comment become inaccurate?

[dmazzoni, 2016/12/12 22:15:36]

Yeah, a while back we had an "EditableTextOnly"
mode, and "FullTree" made sense when juxtaposed with
that. But now that we don't have an EditableTextOnly
mode, FullTree doesn't really make sense.

What this mode *actually* does is make the web contents
get an accessibility tree, but doesn't necessarily
expose that tree to content/browser unless the first
flag is set.

In the context of supporting lots of accessibility modes,
this is going to be the minimal mode that has to be enabled
for the web to be accessible, but it won't imply
necessarily exposing ALL accessibility attributes anymore,
just the minimal ones.

+  // The renderer process will generate an accessibility tree containing
+  // basic information about all nodes, including role, name, value,
+  // state, and location. This is the minimum flag required in order for
+  // web contents to be accessible, and the remaining flags are meaningless
+  // unless this one is set.
+  //
+  // Note that sometimes this flag will be set when
+  // AccessibilityModeFlagNativeAPIs is not, when the content layer embedder
+  // is providing accessibility support via some other mechanism other than
+  // what's implemented in content/browser.
+  AccessibilityModeFlagWebContents = 1 << 1,
+
+  // The accessibility tree will contain inline text boxes, which are
+  // necessary to expose information about line breaks and word boundaries.
+  // Without this flag, you can retrieve the plaintext value of a text field
+  // but not the information about how it's broken down into lines.
+  //
+  // Note that when this flag is off it's still possible to request inline
+  // text boxes for a specific node on-demand, asynchronously.
+  AccessibilityModeFlagInlineTextBoxes = 1 << 2,
+
+  // The accessibility tree will contain extra accessibility
+  // attributes typically only needed by screen readers and other
+  // assistive technology for blind users. Examples include text style
+  // attributes, table cell information, live region properties, range
+  // values, and relationship attributes.
+  AccessibilityModeFlagScreenReader = 1 << 3,
+
+  // The accessibility tree will contain the HTML tag name and HTML attributes
+  // for all accessibility nodes that come from web content.
+  AccessibilityModeFlagHTML = 1 << 4,
 };
 
-enum AccessibilityMode {
-  // All accessibility is off.
-  AccessibilityModeOff = 0,
+typedef int AccessibilityMode;
 
-  // Renderer accessibility is on, and platform APIs are called.
-  AccessibilityModeComplete =
-      AccessibilityModeFlagPlatform | AccessibilityModeFlagFullTree,
+const AccessibilityMode AccessibilityModeOff = 0;
 
-  // Renderer accessibility is on, and events are passed to any extensions
-  // requesting automation, but not to platform accessibility.
-  AccessibilityModeTreeOnly = AccessibilityModeFlagFullTree,
-};
+const AccessibilityMode kAccessibilityModeComplete =
+    AccessibilityModeFlagNativeAPIs |
+    AccessibilityModeFlagWebContents |
+    AccessibilityModeFlagInlineTextBoxes |
+    AccessibilityModeFlagScreenReader |
+    AccessibilityModeFlagHTML;
+
+const AccessibilityMode kAccessibilityModeWebContentsOnly =
+    AccessibilityModeFlagWebContents |
+    AccessibilityModeFlagInlineTextBoxes |
+    AccessibilityModeFlagScreenReader |
+    AccessibilityModeFlagHTML;
 
 #endif  // CONTENT_COMMON_ACCESSIBILITY_MODE_ENUMS_H_