client-side wheel mouse support

remoting/host/event_executor_linux.cc

Index: remoting/host/event_executor_linux.cc
diff --git a/remoting/host/event_executor_linux.cc b/remoting/host/event_executor_linux.cc
index 2321c5c0ec3dd2d059f237e47c7f5d1456a773e7..9e2701ebf84c26156d665ecf98440358d36e1703 100644
--- a/remoting/host/event_executor_linux.cc
+++ b/remoting/host/event_executor_linux.cc
@@ -68,6 +68,12 @@ int MouseButtonToX11ButtonNumber(MouseEvent::MouseButton button) {
   }
 }
 
+int VerticalScrollWheelToX11ButtonNumber(int dy) {

[Lambros, 2011/10/13 00:56:06]

Personally, I like "dy", but it might fall foul of the Chrome Style Police!  You
should use something long and convoluted, like "vertical_offset_y" instead :)

[garykac, 2011/10/13 21:18:53]

^_^

+  // Positive y-values are wheel down events (button 4), negative y-values are
+  // wheel up (button 5).

[Lambros, 2011/10/13 00:41:13]

Is this comment the wrong way round?  If I touch my wheel and slide my finger
towards me, I think of that as "wheel down".  That generates a button 5 event,
not button 4.

[garykac, 2011/10/13 21:18:53]

Fixed.

+  return (dy > 0 ? 4 : 5);
+}
+
 // Hard-coded mapping from Virtual Key codes to X11 KeySyms.
 // This mapping is only valid if both client and host are using a
 // US English keyboard layout.
@@ -339,8 +345,7 @@ void EventExecutorLinux::InjectMouseEvent(const MouseEvent& event) {
     int button_number = MouseButtonToX11ButtonNumber(event.button());
 
     if (button_number < 0) {
-      LOG(WARNING) << "Ignoring unknown button type: "
-                   << event.button();
+      LOG(WARNING) << "Ignoring unknown button type: " << event.button();
       return;
     }
 
@@ -353,8 +358,21 @@ void EventExecutorLinux::InjectMouseEvent(const MouseEvent& event) {
     XFlush(display_);
   }
 
-  if (event.has_wheel_offset_x() && event.has_wheel_offset_y()) {
-    NOTIMPLEMENTED() << "No scroll wheel support yet.";
+  if (event.has_wheel_offset_x() && event.wheel_offset_x() != 0) {
+    NOTIMPLEMENTED() << "No horizontal scroll wheel support yet.";
+  }
+  if (event.has_wheel_offset_y()) {
+    int dy = event.wheel_offset_y();
+    int button_number = VerticalScrollWheelToX11ButtonNumber(dy);
+    if (dy < 0)
+      dy = -dy;
+
+    for (int i = 0; i < dy; i++) {
+      // Generate a button-down and a button-up to simulate a wheel click.
+      XTestFakeButtonEvent(display_, button_number, true, CurrentTime);
+      XTestFakeButtonEvent(display_, button_number, false, CurrentTime);
+    }
+    XFlush(display_);
   }
 }