Allow middle-click scrolling to work for PDFs and print preview

pdf/out_of_process_instance.cc

 // Copyright (c) 2012 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 "pdf/out_of_process_instance.h"
 
 #include <algorithm>  // for min/max()
 #define _USE_MATH_DEFINES  // for M_PI
 #include <cmath>      // for log() and pow()
 #include <math.h>
@@ skipping 532 matching lines @@
           mouse_event.GetClickCount(),
           mouse_event.GetMovement());
       break;
     }
     default:
       break;
   }
   if (engine_->HandleEvent(offset_event))
     return true;
 
-  // TODO(raymes): Implement this scroll behavior in JS:
-  // When click+dragging, scroll the document correctly.
+  // Middle click is used for scrolling and is handled by the container page.
+  pp::MouseInputEvent mouse_event(event_device_res);
+  if (!mouse_event.is_null() &&
+      mouse_event.GetButton() == PP_INPUTEVENT_MOUSEBUTTON_MIDDLE) {
+    return false;
+  }
 
   // Return true for unhandled clicks so the plugin takes focus.
   return (event.GetType() == PP_INPUTEVENT_TYPE_MOUSEDOWN);
 }
 
 void OutOfProcessInstance::DidChangeView(const pp::View& view) {
   pp::Rect view_rect(view.GetRect());
   float old_device_scale = device_scale_;
   float device_scale = view.GetDeviceScale();
   pp::Size view_device_size(view_rect.width() * device_scale,
@@ skipping 842 matching lines @@
 pp::FloatPoint OutOfProcessInstance::BoundScrollOffsetToDocument(
     const pp::FloatPoint& scroll_offset) {
   float max_x = document_size_.width() * zoom_ - plugin_dip_size_.width();
   float x = std::max(std::min(scroll_offset.x(), max_x), 0.0f);
   float max_y = document_size_.height() * zoom_ - plugin_dip_size_.height();
   float y = std::max(std::min(scroll_offset.y(), max_y), 0.0f);
   return pp::FloatPoint(x, y);
 }
 
 }  // namespace chrome_pdf