client-side wheel mouse support

remoting/host/event_executor_linux.cc

 // Copyright (c) 2011 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.
 
 #include "remoting/host/event_executor.h"
 
 #include <X11/Xlib.h>
 #include <X11/XF86keysym.h>
 #include <X11/keysym.h>
 #include <X11/extensions/XTest.h>
@@ skipping 18 matching lines @@
  public:
   EventExecutorLinux(MessageLoop* message_loop, Capturer* capturer);
   virtual ~EventExecutorLinux() {};
 
   bool Init();
 
   virtual void InjectKeyEvent(const KeyEvent& event) OVERRIDE;
   virtual void InjectMouseEvent(const MouseEvent& event) OVERRIDE;
 
  private:
+  void InjectScrollWheelClicks(int button, int count);
+
   MessageLoop* message_loop_;
   Capturer* capturer_;
 
   // X11 graphics context.
   Display* display_;
   Window root_window_;
   int width_;
   int height_;
 
   int test_event_base_;
@@ skipping 12 matching lines @@
 
     case MouseEvent::BUTTON_MIDDLE:
       return 2;
 
     case MouseEvent::BUTTON_UNDEFINED:
     default:
       return -1;
   }
 }
 
+int ScrollWheelToX11ButtonNumber(int dx, int dy) {

[Wez, 2011/10/14 21:42:54]

Split this into two separate functions for clarity, since it never makes sense
to call it for arbitrary dx & dy.

+  // Horizontal scroll wheel.
+  if (dx != 0)
+    return (dx > 0 ? 6 : 7);
+
+  // Positive y-values are wheel scroll-up events (button 4), negative y-values
+  // are wheel scroll-down events (button 5).
+  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.
 // Because we're passing VK codes on the wire, with no Scancode,
 // "extended" flag, etc, things like distinguishing left & right
 // Shift keys doesn't work.
 //
 // TODO(wez): Replace this with something more closely tied to what
 // WebInputEventFactory does on Linux/GTK, and which respects the
 // host's keyboard layout (see http://crbug.com/74550 ).
@@ skipping 221 matching lines @@
     return;
   }
 
   VLOG(3) << "Got pepper key: " << event.keycode()
           << " sending keysym: " << keysym
           << " to keycode: " << keycode;
   XTestFakeKeyEvent(display_, keycode, event.pressed(), CurrentTime);
   XFlush(display_);
 }
 
+void EventExecutorLinux::InjectScrollWheelClicks(int button, int count) {
+  for (int i = 0; i < count; i++) {
+    // Generate a button-down and a button-up to simulate a wheel click.
+    XTestFakeButtonEvent(display_, button, true, CurrentTime);
+    XTestFakeButtonEvent(display_, button, false, CurrentTime);
+  }
+  XFlush(display_);
+}
+
 void EventExecutorLinux::InjectMouseEvent(const MouseEvent& event) {
   if (MessageLoop::current() != message_loop_) {
     message_loop_->PostTask(
         FROM_HERE,
         base::Bind(&EventExecutorLinux::InjectMouseEvent,
                    base::Unretained(this), event));
     return;
   }
 
   if (event.has_x() && event.has_y()) {
@@ skipping 10 matching lines @@
     XTestFakeMotionEvent(display_, DefaultScreen(display_),
                          event.x(), event.y(),
                          CurrentTime);
     XFlush(display_);
   }
 
   if (event.has_button() && event.has_button_down()) {
     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;
     }
 
     VLOG(3) << "Button " << event.button()
             << " received, sending "
             << (event.button_down() ? "down " : "up ")
             << button_number;
     XTestFakeButtonEvent(display_, button_number, event.button_down(),
                          CurrentTime);
     XFlush(display_);
   }
 
-  if (event.has_wheel_offset_x() && event.has_wheel_offset_y()) {
-    NOTIMPLEMENTED() << "No scroll wheel support yet.";
+  if (event.has_wheel_offset_y() && event.wheel_offset_y() != 0) {
+    int dy = event.wheel_offset_y();
+    InjectScrollWheelClicks(ScrollWheelToX11ButtonNumber(0, dy),
+                            (dy > 0) ? dy : -dy);

[Lambros, 2011/10/14 21:00:25]

Optional nit: Maybe use abs() from <stdlib.h> or <cstdlib>?  From the man-page:
  GCC handles abs() and labs() as built-in functions.
so there shouldn't be any performance penalty at least on Linux.

+  }
+  if (event.has_wheel_offset_x() && event.wheel_offset_x() != 0) {
+    int dx = event.wheel_offset_x();
+    InjectScrollWheelClicks(ScrollWheelToX11ButtonNumber(dx, 0),
+                            (dx > 0) ? dx : -dx);
   }
 }
 
 }  // namespace
 
 EventExecutor* EventExecutor::Create(MessageLoop* message_loop,
                                      Capturer* capturer) {
   EventExecutorLinux* executor = new EventExecutorLinux(message_loop, capturer);
   if (!executor->Init()) {
     delete executor;
     executor = NULL;
   }
   return executor;
 }
 
 }  // namespace remoting