Implement UIElementsForSearchPredicate accessibility APIs for OS X.

content/browser/accessibility/browser_accessibility_cocoa.mm

Index: content/browser/accessibility/browser_accessibility_cocoa.mm
diff --git a/content/browser/accessibility/browser_accessibility_cocoa.mm b/content/browser/accessibility/browser_accessibility_cocoa.mm
index d333ae1d748999b0776c392e4dbca52ce15bf8bc..bd8091511caaf06cc205107d205e8a09f8d8dab7 100644
--- a/content/browser/accessibility/browser_accessibility_cocoa.mm
+++ b/content/browser/accessibility/browser_accessibility_cocoa.mm
@@ -13,6 +13,7 @@
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "content/app/strings/grit/content_strings.h"
+#include "content/browser/accessibility/accessibility_tree_search.h"
 #include "content/browser/accessibility/browser_accessibility_manager.h"
 #include "content/browser/accessibility/browser_accessibility_manager_mac.h"
 #include "content/public/common/content_client.h"
@@ -24,6 +25,8 @@
 extern "C" void NSAccessibilityUnregisterUniqueIdForUIElement(id element);
 
 using ui::AXNodeData;
+using content::AccessibilityMatchPredicate;
+using content::AccessibilityTreeSearch;
 using content::BrowserAccessibility;
 using content::BrowserAccessibilityDelegate;
 using content::BrowserAccessibilityManager;
@@ -50,6 +53,251 @@ bool GetState(BrowserAccessibility* accessibility, ui::AXState state) {
 // A mapping from an accessibility attribute to its method name.
 NSDictionary* attributeToMethodNameMap = nil;
 
+// Given a search key provided to AXUIElementCountForSearchPredicate or
+// AXUIElementsForSearchPredicate, return a predicate that can be added
+// to AccessibilityTreeSearch.
+AccessibilityMatchPredicate PredicateForSearchKey(NSString* searchKey) {
+  if ([searchKey isEqualToString:@"AXAnyTypeSearchKey"]) {

[David Tseng, 2015/05/08 21:58:25]

Is this string defined in NS*? Is this API available only on 10.10?

[dmazzoni, 2015/05/13 04:22:21]

It's not even in 10.10. As far as I can tell the search predicate API is totally
undocumented.

grep Predicate
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/System/Library/Frameworks/AppKit.framework/Headers/NSAccessibility*

If you do a web search for the names in this protocol the only hits are WebKit
code.

+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return true;
+    };
+  } else if ([searchKey isEqualToString:@"AXBlockquoteSameLevelSearchKey"] ||
+             [searchKey isEqualToString:@"AXBlockquoteSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return current->GetRole() == ui::AX_ROLE_BLOCKQUOTE;
+    };
+  } else if ([searchKey isEqualToString:@"AXBoldFontSearchKey"]) {
+    return nullptr;  // TODO(dmazzoni): implement this.

[David Tseng, 2015/05/08 21:58:25]

Can you move the TODO into its own line above?

[dmazzoni, 2015/05/13 04:22:21]

Done throughout.

+  } else if ([searchKey isEqualToString:@"AXButtonSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return (current->GetRole() == ui::AX_ROLE_BUTTON ||

[David Tseng, 2015/05/08 21:58:25]

Not sure if they exist on Mac, but menuButton and switch?

[dmazzoni, 2015/05/13 04:22:21]

Done.

+              current->GetRole() == ui::AX_ROLE_POP_UP_BUTTON ||
+              current->GetRole() == ui::AX_ROLE_TOGGLE_BUTTON);
+    };
+  } else if ([searchKey isEqualToString:@"AXCheckBoxSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return (current->GetRole() == ui::AX_ROLE_CHECK_BOX ||
+              current->GetRole() == ui::AX_ROLE_MENU_ITEM_CHECK_BOX);
+    };
+  } else if ([searchKey isEqualToString:@"AXControlSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return current->HasState(ui::AX_STATE_FOCUSABLE);

[David Tseng, 2015/05/08 21:58:25]

If a button doesn't take focus (like if it were disabled), would the focusable
state still be set?

[dmazzoni, 2015/05/13 04:22:20]

No, good point. I implemented IsControl but decided to also return anything
that's focusable and not a link, because there are some roles like CELL that
could be interactive if focusable, and users probably want anything interactive
that's not a link, right?

+    };
+  } else if ([searchKey isEqualToString:@"AXDifferentTypeSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return current->GetRole() != start->GetRole();
+    };
+  } else if ([searchKey isEqualToString:@"AXFontChangeSearchKey"]) {
+    return nullptr;  // TODO(dmazzoni): implement this.

[David Tseng, 2015/05/08 21:58:25]

Ditto

+  } else if ([searchKey isEqualToString:@"AXFontColorChangeSearchKey"]) {
+    return nullptr;  // TODO(dmazzoni): implement this.

[David Tseng, 2015/05/08 21:58:25]

Ditto

+  } else if ([searchKey isEqualToString:@"AXFrameSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      if (current->IsWebAreaForPresentationalIframe())
+        return false;
+      return (current->GetRole() == ui::AX_ROLE_WEB_AREA ||
+              current->GetRole() == ui::AX_ROLE_ROOT_WEB_AREA);
+    };
+  } else if ([searchKey isEqualToString:@"AXGraphicSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return current->GetRole() == ui::AX_ROLE_IMAGE;
+    };
+  } else if ([searchKey isEqualToString:@"AXHeadingLevel1SearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return (current->GetRole() == ui::AX_ROLE_HEADING &&
+              current->GetIntAttribute(ui::AX_ATTR_HIERARCHICAL_LEVEL) == 1);
+    };
+  } else if ([searchKey isEqualToString:@"AXHeadingLevel2SearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return (current->GetRole() == ui::AX_ROLE_HEADING &&
+              current->GetIntAttribute(ui::AX_ATTR_HIERARCHICAL_LEVEL) == 2);
+    };
+  } else if ([searchKey isEqualToString:@"AXHeadingLevel3SearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return (current->GetRole() == ui::AX_ROLE_HEADING &&
+              current->GetIntAttribute(ui::AX_ATTR_HIERARCHICAL_LEVEL) == 3);
+    };
+  } else if ([searchKey isEqualToString:@"AXHeadingLevel4SearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return (current->GetRole() == ui::AX_ROLE_HEADING &&
+              current->GetIntAttribute(ui::AX_ATTR_HIERARCHICAL_LEVEL) == 4);
+    };
+  } else if ([searchKey isEqualToString:@"AXHeadingLevel5SearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return (current->GetRole() == ui::AX_ROLE_HEADING &&
+              current->GetIntAttribute(ui::AX_ATTR_HIERARCHICAL_LEVEL) == 5);

[David Tseng, 2015/05/08 21:58:25]

Maybe worth writing a helper returning a predicate given a heading level.

[dmazzoni, 2015/05/13 04:22:21]

It's only 6 heading levels and they're 2 lines each and I don't anticipate
needing to change this code again, so I'd prefer to keep it here.

+    };
+  } else if ([searchKey isEqualToString:@"AXHeadingLevel6SearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return (current->GetRole() == ui::AX_ROLE_HEADING &&
+              current->GetIntAttribute(ui::AX_ATTR_HIERARCHICAL_LEVEL) == 6);
+    };
+  } else if ([searchKey isEqualToString:@"AXHeadingSameLevelSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return (current->GetRole() == ui::AX_ROLE_HEADING &&
+              current->GetIntAttribute(ui::AX_ATTR_HIERARCHICAL_LEVEL) ==
+              start->GetIntAttribute(ui::AX_ATTR_HIERARCHICAL_LEVEL));

[David Tseng, 2015/05/08 21:58:25]

Need to check start is a heading too?

[dmazzoni, 2015/05/13 04:22:20]

Done.

+    };
+  } else if ([searchKey isEqualToString:@"AXHeadingSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return current->GetRole() == ui::AX_ROLE_HEADING;
+    };
+  } else if ([searchKey isEqualToString:@"AXHighlightedSearchKey"]) {
+    return nullptr;  // TODO(dmazzoni): implement this.
+  } else if ([searchKey isEqualToString:@"AXItalicFontSearchKey"]) {
+    return nullptr;  // TODO(dmazzoni): implement this.
+  } else if ([searchKey isEqualToString:@"AXLandmarkSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return (current->GetRole() == ui::AX_ROLE_APPLICATION ||
+              current->GetRole() == ui::AX_ROLE_BANNER ||
+              current->GetRole() == ui::AX_ROLE_COMPLEMENTARY ||
+              current->GetRole() == ui::AX_ROLE_CONTENT_INFO ||
+              current->GetRole() == ui::AX_ROLE_FORM ||
+              current->GetRole() == ui::AX_ROLE_MAIN ||
+              current->GetRole() == ui::AX_ROLE_NAVIGATION ||
+              current->GetRole() == ui::AX_ROLE_SEARCH);
+    };
+  } else if ([searchKey isEqualToString:@"AXLinkSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return current->GetRole() == ui::AX_ROLE_LINK;
+    };
+  } else if ([searchKey isEqualToString:@"AXListSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return current->GetRole() == ui::AX_ROLE_LIST;
+    };
+  } else if ([searchKey isEqualToString:@"AXLiveRegionSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return current->HasStringAttribute(ui::AX_ATTR_LIVE_STATUS);
+    };
+  } else if ([searchKey isEqualToString:@"AXMisspelledWordSearchKey"]) {
+    return nullptr;  // TODO(dmazzoni): implement this.
+  } else if ([searchKey isEqualToString:@"AXOutlineSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return current->GetRole() == ui::AX_ROLE_TREE;
+    };
+  } else if ([searchKey isEqualToString:@"AXPlainTextSearchKey"]) {
+    return nullptr;  // TODO(dmazzoni): implement this.
+  } else if ([searchKey isEqualToString:@"AXRadioGroupSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return current->GetRole() == ui::AX_ROLE_RADIO_GROUP;
+    };
+  } else if ([searchKey isEqualToString:@"AXSameTypeSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return current->GetRole() == start->GetRole();
+    };
+  } else if ([searchKey isEqualToString:@"AXStaticTextSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return current->GetRole() == ui::AX_ROLE_STATIC_TEXT;
+    };
+  } else if ([searchKey isEqualToString:@"AXStyleChangeSearchKey"]) {
+    return nullptr;  // TODO(dmazzoni): implement this.
+  } else if ([searchKey isEqualToString:@"AXTableSameLevelSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return current->GetRole() == ui::AX_ROLE_TABLE;

[David Tseng, 2015/05/08 21:58:25]

What about grid? I think this means you need to check you don't descend into a
nested table.

[dmazzoni, 2015/05/13 04:22:21]

Done.

Added TODO for nested, I wasn't planning on implementing that unless users
request it.

+    };
+  } else if ([searchKey isEqualToString:@"AXTableSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return current->GetRole() == ui::AX_ROLE_TABLE;
+    };
+  } else if ([searchKey isEqualToString:@"AXTextFieldSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return current->GetRole() == ui::AX_ROLE_TEXT_FIELD;
+    };
+  } else if ([searchKey isEqualToString:@"AXUnderlineSearchKey"]) {
+    return nullptr;  // TODO(dmazzoni): implement this.
+  } else if ([searchKey isEqualToString:@"AXUnvisitedLinkSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return (current->GetRole() == ui::AX_ROLE_LINK &&
+              !current->HasState(ui::AX_STATE_VISITED));
+    };
+  } else if ([searchKey isEqualToString:@"AXVisitedLinkSearchKey"]) {
+    return [](BrowserAccessibility* start, BrowserAccessibility* current) {
+      return (current->GetRole() == ui::AX_ROLE_LINK &&
+              current->HasState(ui::AX_STATE_VISITED));
+    };
+  }
+
+  return nullptr;
+}
+
+// Initialize an AccessibilityTreeSearch object given the parameters
+// passed to AXUIElementCountForSearchPredicate or
+// AXUIElementsForSearchPredicate. Return true on success.
+bool InitializeAccessibilityTreeSearch(
+    AccessibilityTreeSearch* search,
+    id parameter) {
+  if (![parameter isKindOfClass:[NSDictionary class]])
+    return false;
+  NSDictionary* dictionary = parameter;
+
+  id startElementParameter = [dictionary objectForKey:@"AXStartElement"];
+  BrowserAccessibility* startNode = nullptr;
+  if ([startElementParameter isKindOfClass:[BrowserAccessibilityCocoa class]]) {
+    BrowserAccessibilityCocoa* startNodeCocoa =
+        (BrowserAccessibilityCocoa*)startElementParameter;
+    startNode = [startNodeCocoa browserAccessibility];
+  }
+
+  bool immediateDescendantsOnly = false;
+  NSNumber *immediateDescendantsOnlyParameter =
+      [dictionary objectForKey:@"AXImmediateDescendantsOnly"];
+  if ([immediateDescendantsOnlyParameter isKindOfClass:[NSNumber class]])
+    immediateDescendantsOnly = [immediateDescendantsOnlyParameter boolValue];
+
+  bool visibleOnly = false;
+  NSNumber *visibleOnlyParameter = [dictionary objectForKey:@"AXVisibleOnly"];
+  if ([visibleOnlyParameter isKindOfClass:[NSNumber class]])
+    visibleOnly = [visibleOnlyParameter boolValue];
+
+  content::AccessibilityTreeSearch::Direction direction =
+      content::AccessibilityTreeSearch::FORWARDS;
+  NSString* directionParameter = [dictionary objectForKey:@"AXDirection"];
+  if ([directionParameter isKindOfClass:[NSString class]]) {
+    if ([directionParameter isEqualToString:@"AXDirectionNext"])
+      direction = content::AccessibilityTreeSearch::FORWARDS;
+    else if ([directionParameter isEqualToString:@"AXDirectionPrevious"])
+      direction = content::AccessibilityTreeSearch::BACKWARDS;
+  }
+
+  int resultsLimit = 0;
+  NSNumber* resultsLimitParameter = [dictionary objectForKey:@"AXResultsLimit"];
+  if ([resultsLimitParameter isKindOfClass:[NSNumber class]])
+    resultsLimit = [resultsLimitParameter intValue];
+
+  std::string searchText;
+  NSString* searchTextParameter = [dictionary objectForKey:@"AXSearchText"];
+  if ([searchTextParameter isKindOfClass:[NSString class]])
+    searchText = base::SysNSStringToUTF8(searchTextParameter);
+
+  search->SetStartNode(startNode);
+  search->SetDirection(direction);
+  search->SetResultLimit(resultsLimit);
+  search->SetImmediateDescendantsOnly(immediateDescendantsOnly);
+  search->SetVisibleOnly(visibleOnly);
+  search->SetSearchText(searchText);

[David Tseng, 2015/05/08 21:58:25]

Looks like you do have all args available here; could just make
AccessibilityTreeSearch take all arguments on construction and eliminate all the
setters.

[dmazzoni, 2015/05/13 04:22:20]

Two reasons not to:
* I think this is more readable than a bunch of positional arguments - it's easy
to get the order wrong by accident
* We may reuse AccessibilityTreeSearch for Android and we wouldn't need all of
these, so I think it'd be cleaner to keep them separate

+
+  id searchKey = [dictionary objectForKey:@"AXSearchKey"];
+  if ([searchKey isKindOfClass:[NSString class]]) {
+    AccessibilityMatchPredicate predicate =
+        PredicateForSearchKey((NSString*)searchKey);
+    if (predicate)
+      search->AddPredicate(predicate);
+  } else if ([searchKey isKindOfClass:[NSArray class]]) {
+    size_t searchKeyCount = static_cast<size_t>([searchKey count]);
+    for (size_t i = 0; i < searchKeyCount; ++i) {
+      id key = [searchKey objectAtIndex:i];
+      if ([key isKindOfClass:[NSString class]]) {
+        AccessibilityMatchPredicate predicate =
+            PredicateForSearchKey((NSString*)key);
+        if (predicate)
+          search->AddPredicate(predicate);
+      }
+    }
+  }
+
+  return true;
+}
+
 } // namespace
 
 @implementation BrowserAccessibilityCocoa
@@ -557,6 +805,10 @@ NSDictionary* attributeToMethodNameMap = nil;
       nil;
 }
 
+- (content::BrowserAccessibility*)browserAccessibility {
+  return browserAccessibility_;
+}
+
 - (NSPoint)pointInScreen:(NSPoint)origin
                     size:(NSSize)size {
   if (!browserAccessibility_)
@@ -1213,6 +1465,26 @@ NSDictionary* attributeToMethodNameMap = nil;
         pointInScreen.x, pointInScreen.y, rect.width(), rect.height());
     return [NSValue valueWithRect:nsrect];
   }
+  if ([attribute isEqualToString:@"AXUIElementCountForSearchPredicate"]) {
+    AccessibilityTreeSearch search(browserAccessibility_->manager());
+    if (InitializeAccessibilityTreeSearch(&search, parameter))
+      return [NSNumber numberWithInt:search.CountMatches()];
+    return nil;
+  }
+
+  if ([attribute isEqualToString:@"AXUIElementsForSearchPredicate"]) {
+    AccessibilityTreeSearch search(browserAccessibility_->manager());
+    if (InitializeAccessibilityTreeSearch(&search, parameter)) {
+      size_t count = search.CountMatches();
+      NSMutableArray* result = [NSMutableArray arrayWithCapacity:count];
+      for (size_t i = 0; i < count; i++) {
+        BrowserAccessibility* match = search.GetMatchAtIndex(i);
+        [result addObject:match->ToBrowserAccessibilityCocoa()];
+      }
+      return result;
+    }
+    return nil;
+  }
 
   // TODO(dtseng): support the following attributes.
   if ([attribute isEqualTo:
@@ -1233,14 +1505,20 @@ NSDictionary* attributeToMethodNameMap = nil;
   if (!browserAccessibility_)
     return nil;
 
+  // General attributes.
+  NSMutableArray* ret = [NSMutableArray arrayWithObjects:
+      @"AXUIElementCountForSearchPredicate",
+      @"AXUIElementsForSearchPredicate",
+      nil];
+
   if ([[self role] isEqualToString:NSAccessibilityTableRole] ||
       [[self role] isEqualToString:NSAccessibilityGridRole]) {
-    return [NSArray arrayWithObjects:
+    [ret addObjectsFromArray:[NSArray arrayWithObjects:
         NSAccessibilityCellForColumnAndRowParameterizedAttribute,
-        nil];
+        nil]];
   }
   if ([[self role] isEqualToString:NSAccessibilityTextFieldRole]) {
-    return [NSArray arrayWithObjects:
+    [ret addObjectsFromArray:[NSArray arrayWithObjects:
         NSAccessibilityLineForIndexParameterizedAttribute,
         NSAccessibilityRangeForLineParameterizedAttribute,
         NSAccessibilityStringForRangeParameterizedAttribute,
@@ -1250,14 +1528,14 @@ NSDictionary* attributeToMethodNameMap = nil;
         NSAccessibilityRTFForRangeParameterizedAttribute,
         NSAccessibilityAttributedStringForRangeParameterizedAttribute,
         NSAccessibilityStyleRangeForIndexParameterizedAttribute,
-        nil];
+        nil]];
   }
   if ([self internalRole] == ui::AX_ROLE_STATIC_TEXT) {
-    return [NSArray arrayWithObjects:
+    [ret addObjectsFromArray:[NSArray arrayWithObjects:
         NSAccessibilityBoundsForRangeParameterizedAttribute,
-        nil];
+        nil]];
   }
-  return nil;
+  return ret;
 }
 
 // Returns an array of action names that this object will respond to.