Do not post hint descriptors back to the frame itself.

When distributing hint descriptors, do not post a frame's own hint
descriptors back to the frame itself.  It already has them.

With regard to the message-passing cost only, this represents a speedup
of approximately 3/2 for link-busy sites like reddit -- several tens of
milliseconds for me.  There are other costs too (such as processing the
hint descriptors) bu these are not affected.

3 files changed, 32 insertions, 16 deletions

diff --git a/background_scripts/main.coffee b/background_scripts/main.coffee
index 829b0abb..cac35100 100644
--- a/background_scripts/main.coffee
+++ b/background_scripts/main.coffee
@@ -355,35 +355,45 @@ HintCoordinator =
       # If there's no handler here, then the message is forwarded to all frames in the sender's tab.
       @sendMessage request.messageType, tabId, request
 
+  # Post a link-hints message to a particular frame's port. We catch errors in case the frame has gone away.
+  postMessage: (tabId, frameId, messageType, port, request = {}) ->
+    try
+      port.postMessage extend request, {handler: "linkHintsMessage", messageType}
+    catch
+      @unregisterFrame tabId, frameId
+
+  # Post a link-hints message to all participating frames.
   sendMessage: (messageType, tabId, request = {}) ->
-    extend request, {handler: "linkHintsMessage", messageType}
     for own frameId, port of @tabState[tabId].ports
-      try
-        port.postMessage request
-      catch
-        @unregisterFrame tabId, parseInt frameId
+      @postMessage tabId, parseInt(frameId), messageType, port, request
 
   prepareToActivateMode: (tabId, originatingFrameId, {modeIndex}) ->
-    @tabState[tabId] = {frameIds: frameIdsForTab[tabId][..], hintDescriptors: [], originatingFrameId, modeIndex}
+    @tabState[tabId] = {frameIds: frameIdsForTab[tabId][..], hintDescriptors: {}, originatingFrameId, modeIndex}
     @tabState[tabId].ports = extend {}, portsForTab[tabId]
     @sendMessage "getHintDescriptors", tabId, {modeIndex}
 
   # Receive hint descriptors from all frames and activate link-hints mode when we have them all.
   postHintDescriptors: (tabId, frameId, {hintDescriptors}) ->
     if frameId in @tabState[tabId].frameIds
-      @tabState[tabId].hintDescriptors.push hintDescriptors...
+      @tabState[tabId].hintDescriptors[frameId] = hintDescriptors
       @tabState[tabId].frameIds = @tabState[tabId].frameIds.filter (fId) -> fId != frameId
       if @tabState[tabId].frameIds.length == 0
-        @sendMessage "activateMode", tabId,
-          originatingFrameId: @tabState[tabId].originatingFrameId
-          hintDescriptors: @tabState[tabId].hintDescriptors
-          modeIndex: @tabState[tabId].modeIndex
+        for own frameId, port of @tabState[tabId].ports
+          if frameId of @tabState[tabId].hintDescriptors
+            hintDescriptors = extend {}, @tabState[tabId].hintDescriptors
+            # We do not send back the frame's own hint descriptors.  This is faster (approx. speedup 3/2) for
+            # link-busy sites like reddit.
+            delete hintDescriptors[frameId]
+            @postMessage tabId, parseInt(frameId), "activateMode", port,
+              originatingFrameId: @tabState[tabId].originatingFrameId
+              hintDescriptors: hintDescriptors
+              modeIndex: @tabState[tabId].modeIndex
 
   # If an unregistering frame is participating in link-hints mode, then we need to tidy up after it.
   unregisterFrame: (tabId, frameId) ->
     delete @tabState[tabId]?.ports?[frameId]
-    # We fake "postHintDescriptors" for an unregistering frame, if necessary.
-    @postHintDescriptors tabId, frameId, hintDescriptors: [] if @tabState[tabId]?.frameIds
+    # We fake "postHintDescriptors" for an unregistering frame.
+    @postHintDescriptors tabId, frameId, hintDescriptors: []
 
 # Port handler mapping
 portHandlers =
diff --git a/content_scripts/link_hints.coffee b/content_scripts/link_hints.coffee
index 56cea78d..70c51eac 100644
--- a/content_scripts/link_hints.coffee
+++ b/content_scripts/link_hints.coffee
@@ -82,13 +82,17 @@ HintCoordinator =
     DomUtils.documentReady => Settings.onLoaded =>
       requireHref = availableModes[modeIndex] in [COPY_LINK_URL, OPEN_INCOGNITO]
       @localHints = LocalHints.getLocalHints requireHref
-      @sendMessage "postHintDescriptors", hintDescriptors:
-        @localHints.map ({linkText}, localIndex) -> {frameId, localIndex, linkText}
+      @localHintDescriptors = @localHints.map ({linkText}, localIndex) -> {frameId, localIndex, linkText}
+      @sendMessage "postHintDescriptors", hintDescriptors: @localHintDescriptors
 
   # We activate LinkHintsMode() in every frame and provide every frame with exactly the same hint descriptors.
   # We also propagate the key state between frames.  Therefore, the hint-selection process proceeds in lock
   # step in every frame, and @linkHintsMode is in the same state in every frame.
   activateMode: ({hintDescriptors, modeIndex, originatingFrameId}) ->
+    # We do not receive the frame's own hint descritors back from the background page.  Instead, we merge them
+    # with the hint descriptors from other frames here.
+    [hintDescriptors[frameId], @localHintDescriptors] = [@localHintDescriptors, null]
+    hintDescriptors = [].concat (hintDescriptors[fId] for fId in (fId for own fId of hintDescriptors).sort())...
     # Ensure that the document is ready and that the settings are loaded.
     DomUtils.documentReady => Settings.onLoaded =>
       @suppressKeyboardEvents.exit() if @suppressKeyboardEvents?.modeIsActive
diff --git a/tests/dom_tests/dom_tests.coffee b/tests/dom_tests/dom_tests.coffee
index 3977d046..76c09f13 100644
--- a/tests/dom_tests/dom_tests.coffee
+++ b/tests/dom_tests/dom_tests.coffee
@@ -64,7 +64,9 @@ getHintMarkers = ->
 stubSettings = (key, value) -> stub Settings.cache, key, JSON.stringify value
 
 HintCoordinator.sendMessage = (name, request = {}) -> HintCoordinator[name]? request; request
-activateLinkHintsMode = -> HintCoordinator.activateMode HintCoordinator.getHintDescriptors {modeIndex: 0}
+activateLinkHintsMode = ->
+  HintCoordinator.getHintDescriptors modeIndex: 0
+  HintCoordinator.activateMode hintDescriptors: {}, modeIndex: 0, originatingFrameId: frameId,
 
 #
 # Generate tests that are common to both default and filtered