text: // 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 "content/browser/tab_contents/web_drag_source_win.h"
  
  #include "base/bind.h"
  #include "content/browser/renderer_host/render_view_host_impl.h"
  #include "content/browser/tab_contents/web_drag_utils_win.h"
  #include "content/public/browser/browser_thread.h"
  #include "content/public/browser/notification_source.h"
  #include "content/public/browser/notification_types.h"
  #include "content/public/browser/web_contents.h"
  
  using WebKit::WebDragOperationNone;
  using content::BrowserThread;
  using content::WebContents;
  
  namespace {
  
  static void GetCursorPositions(gfx::NativeWindow wnd, gfx::Point* client,
                                 gfx::Point* screen) {
    POINT cursor_pos;
    GetCursorPos(&cursor_pos);
    screen->SetPoint(cursor_pos.x, cursor_pos.y);
    ScreenToClient(wnd, &cursor_pos);
    client->SetPoint(cursor_pos.x, cursor_pos.y);
  }
  
  }  // namespace
  
  ///////////////////////////////////////////////////////////////////////////////
  // WebDragSource, public:
  
  WebDragSource::WebDragSource(gfx::NativeWindow source_wnd,
                               WebContents* web_contents)
      : ui::DragSource(),
        source_wnd_(source_wnd),
        render_view_host_(web_contents->GetRenderViewHost()),
        effect_(DROPEFFECT_NONE) {
    registrar_.Add(this, content::NOTIFICATION_WEB_CONTENTS_SWAPPED,
                   content::Source<WebContents>(web_contents));
    registrar_.Add(this, content::NOTIFICATION_WEB_CONTENTS_DISCONNECTED,
                   content::Source<WebContents>(web_contents));
  }
  
  WebDragSource::~WebDragSource() {
  }
  
  void WebDragSource::OnDragSourceCancel() {
    // Delegate to the UI thread if we do drag-and-drop in the background thread.
    if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
      BrowserThread::PostTask(
          BrowserThread::UI, FROM_HERE,
          base::Bind(&WebDragSource::OnDragSourceCancel, this));
      return;
    }
  
    if (!render_view_host_)
      return;
  
    gfx::Point client;
    gfx::Point screen;
    GetCursorPositions(source_wnd_, &client, &screen);
    render_view_host_->DragSourceEndedAt(client.x(), client.y(),
                                         screen.x(), screen.y(),
                                         WebDragOperationNone);
  }
  
  void WebDragSource::OnDragSourceDrop() {
    // On Windows, we check for drag end in IDropSource::QueryContinueDrag which
    // happens before IDropTarget::Drop is called. HTML5 requires the "dragend"
    // event to happen after the "drop" event. Since  Windows calls these two
    // directly after each other we can just post a task to handle the
    // OnDragSourceDrop after the current task.
    BrowserThread::PostTask(
        BrowserThread::UI, FROM_HERE,
        base::Bind(&WebDragSource::DelayedOnDragSourceDrop, this));
  }
  
  void WebDragSource::DelayedOnDragSourceDrop() {
    if (!render_view_host_)
      return;
  
    gfx::Point client;
    gfx::Point screen;
    GetCursorPositions(source_wnd_, &client, &screen);
    render_view_host_->DragSourceEndedAt(
        client.x(), client.y(), screen.x(), screen.y(),
        web_drag_utils_win::WinDragOpToWebDragOp(effect_));
  }
  
  void WebDragSource::OnDragSourceMove() {
    // Delegate to the UI thread if we do drag-and-drop in the background thread.
    if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
      BrowserThread::PostTask(
          BrowserThread::UI, FROM_HERE,
          base::Bind(&WebDragSource::OnDragSourceMove, this));
      return;
    }
  
    if (!render_view_host_)
      return;
  
    gfx::Point client;
    gfx::Point screen;
    GetCursorPositions(source_wnd_, &client, &screen);
    render_view_host_->DragSourceMovedTo(client.x(), client.y(),
                                         screen.x(), screen.y());
  }
  
  void WebDragSource::Observe(int type,
      const content::NotificationSource& source,
      const content::NotificationDetails& details) {
    if (content::NOTIFICATION_WEB_CONTENTS_SWAPPED == type) {
      // When the tab contents get swapped, our render view host goes away.
      // That's OK, we can continue the drag, we just can't send messages back to
      // our drag source.
      render_view_host_ = NULL;
    } else if (content::NOTIFICATION_WEB_CONTENTS_DISCONNECTED == type) {
      // This could be possible when we close the tab and the source is still
      // being used in DoDragDrop at the time that the virtual file is being
      // downloaded.
      render_view_host_ = NULL;
    }
  }
  