Improve switch between gestures and touch mode when kEnableTouchEvents

content/browser/renderer_host/render_widget_host_view_win.cc

Index: content/browser/renderer_host/render_widget_host_view_win.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_win.cc b/content/browser/renderer_host/render_widget_host_view_win.cc
index 344e11bc533aeb3ab9bd3bd8b0c6de256c27c009..6c879554275de3284988130525c3bec4b32fcbdb 100644
--- a/content/browser/renderer_host/render_widget_host_view_win.cc
+++ b/content/browser/renderer_host/render_widget_host_view_win.cc
@@ -329,7 +329,8 @@ RenderWidgetHostViewWin::RenderWidgetHostViewWin(RenderWidgetHost* widget)
       pointer_down_context_(false),
       focus_on_editable_field_(false),
       received_focus_change_after_pointer_down_(false),
-      transparent_region_(0) {
+      transparent_region_(0),
+      touch_events_enabled_(false) {
   render_widget_host_ = static_cast<RenderWidgetHostImpl*>(widget);
   render_widget_host_->SetView(this);
   registrar_.Add(this,
@@ -910,7 +911,47 @@ void RenderWidgetHostViewWin::UnhandledWheelEvent(
     const WebKit::WebMouseWheelEvent& event) {
 }
 
-void RenderWidgetHostViewWin::ProcessTouchAck(bool processed) {
+void RenderWidgetHostViewWin::ProcessTouchAck(int type, bool processed) {
+  if (type == WebKit::WebInputEvent::TouchStart)
+    EnableDesiredTouchMode(processed);
+}
+
+void RenderWidgetHostViewWin::EnableDesiredTouchMode(bool touch_mode) {
+  // Make sure that touch events even make sense.
+  bool touch_mode_valid = base::win::GetVersion() >= base::win::VERSION_WIN7 &&
+      CommandLine::ForCurrentProcess()->HasSwitch(switches::kEnableTouchEvents);
+  touch_mode = touch_mode && touch_mode_valid;
+
+  // Already in correct mode, nothing to do.
+  if ((touch_mode && touch_events_enabled_) ||
+      (!touch_mode && !touch_events_enabled_))
+    return;
+
+  // Now we know that the window's current state doesn't match the desired
+  // state. If we want touch mode, then we attempt to register for touch
+  // events, and otherwise to unregister.
+  if (touch_mode) {
+    touch_mode = !!RegisterTouchWindow(m_hWnd, TWF_WANTPALM);
+  }
+  if (!touch_mode) {
+    UnregisterTouchWindow(m_hWnd);
+    // Single finger panning is consistent with other windows applications.
+    const DWORD gesture_allow = GC_PAN_WITH_SINGLE_FINGER_VERTICALLY |
+                                GC_PAN_WITH_SINGLE_FINGER_HORIZONTALLY;
+    const DWORD gesture_block = GC_PAN_WITH_GUTTER;
+    GESTURECONFIG gc[] = {
+        { GID_ZOOM, GC_ZOOM, 0 },
+        { GID_PAN, gesture_allow , gesture_block},
+        { GID_TWOFINGERTAP, GC_TWOFINGERTAP , 0},
+        { GID_PRESSANDTAP, GC_PRESSANDTAP , 0}
+    };
+    if (!SetGestureConfig(m_hWnd, 0, arraysize(gc), gc,
+        sizeof(GESTURECONFIG))) {
+      NOTREACHED();
+    }
+  }
+
+  touch_events_enabled_ = touch_mode;
 }
 
 void RenderWidgetHostViewWin::SetHasHorizontalScrollbar(
@@ -932,27 +973,8 @@ LRESULT RenderWidgetHostViewWin::OnCreate(CREATESTRUCT* create_struct) {
   // scrolled when under the mouse pointer even if inactive.
   props_.push_back(ui::SetWindowSupportsRerouteMouseWheel(m_hWnd));
 
-  if (base::win::GetVersion() >= base::win::VERSION_WIN7) {
-    // Use gestures if touch event switch isn't present or registration fails.
-    if (!CommandLine::ForCurrentProcess()->HasSwitch(
-            switches::kEnableTouchEvents) ||
-        !RegisterTouchWindow(m_hWnd, TWF_WANTPALM)) {
-      // Single finger panning is consistent with other windows applications.
-      const DWORD gesture_allow = GC_PAN_WITH_SINGLE_FINGER_VERTICALLY |
-                                  GC_PAN_WITH_SINGLE_FINGER_HORIZONTALLY;
-      const DWORD gesture_block = GC_PAN_WITH_GUTTER;
-      GESTURECONFIG gc[] = {
-          { GID_ZOOM, GC_ZOOM, 0 },
-          { GID_PAN, gesture_allow , gesture_block},
-          { GID_TWOFINGERTAP, GC_TWOFINGERTAP , 0},
-          { GID_PRESSANDTAP, GC_PRESSANDTAP , 0}
-      };
-      if (!SetGestureConfig(m_hWnd, 0, arraysize(gc), gc,
-          sizeof(GESTURECONFIG))) {
-        NOTREACHED();
-      }
-    }
-  }
+  EnableDesiredTouchMode(true);
+
   return 0;
 }
 
@@ -1906,7 +1928,24 @@ LRESULT RenderWidgetHostViewWin::OnGestureEvent(
       handled = TRUE;
       render_widget_host_->ForwardWheelEvent(
           MakeFakeScrollWheelEvent(m_hWnd, start, delta));
+
+      // Send a touch event at this location; if the touch start is handled
+      // then we switch to touch mode, rather than gesture mode (in the ACK).
+      TOUCHINPUT fake_touch;
+      fake_touch.x = gi.ptsLocation.x * 100;
+      fake_touch.y = gi.ptsLocation.y * 100;
+      fake_touch.cxContact = 100;
+      fake_touch.cyContact = 100;
+      fake_touch.dwMask = 0;
+      fake_touch.dwFlags = TOUCHEVENTF_DOWN | TOUCHEVENTF_PRIMARY;
+      fake_touch.dwID = gi.dwInstanceID;
+      touch_state_.UpdateTouchPoints(&fake_touch, 1);
+      if (touch_state_.is_changed())
+        render_widget_host_->ForwardTouchEvent(touch_state_.touch_event());
     }
+  } else if (gi.dwID == GID_END) {
+    if (touch_state_.ReleaseTouchPoints())
+      render_widget_host_->ForwardTouchEvent(touch_state_.touch_event());
   }
   ::CloseGestureInfoHandle(gi_handle);
   return 0;