Drag-and-drop: DragEnter, DragOver, DragLeave, DragDrop

third_party/WebKit/Source/web/WebFrameWidgetBase.cpp

+// Copyright 2016 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 "web/WebFrameWidgetBase.h"
+
+#include "core/frame/FrameHost.h"
+#include "core/frame/VisualViewport.h"
+#include "core/page/DragActions.h"
+#include "core/page/DragController.h"
+#include "core/page/DragData.h"
+#include "core/page/DragSession.h"
+#include "core/page/Page.h"
+#include "public/web/WebAutofillClient.h"
+#include "public/web/WebDocument.h"
+#include "web/WebLocalFrameImpl.h"
+#include "web/WebViewImpl.h"
+
+namespace blink {
+
+WebDragOperation WebFrameWidgetBase::dragTargetDragEnter(
+    const WebDragData& webDragData,
+    const WebPoint& pointInViewport,
+    const WebPoint& screenPoint,
+    WebDragOperationsMask operationsAllowed,
+    int modifiers) {
+  DCHECK(!m_currentDragData);
+
+  m_currentDragData = DataObject::create(webDragData);
+  m_operationsAllowed = operationsAllowed;
+
+  return dragTargetDragEnterOrOver(pointInViewport, screenPoint, DragEnter,
+                                   modifiers);
+}
+
+WebDragOperation WebFrameWidgetBase::dragTargetDragOver(
+    const WebPoint& pointInViewport,
+    const WebPoint& screenPoint,
+    WebDragOperationsMask operationsAllowed,
+    int modifiers) {
+  m_operationsAllowed = operationsAllowed;
+
+  return dragTargetDragEnterOrOver(pointInViewport, screenPoint, DragOver,
+                                   modifiers);
+}
+
+void WebFrameWidgetBase::dragTargetDragLeave() {
+  DCHECK(m_currentDragData);
+
+  DragData dragData(m_currentDragData.get(), IntPoint(), IntPoint(),
+                    static_cast<DragOperation>(m_operationsAllowed));
+
+  page()->dragController().dragExited(&dragData);
+
+  // FIXME: why is the drag scroll timer not stopped here?
+
+  m_dragOperation = WebDragOperationNone;
+  m_currentDragData = nullptr;
+}
+
+void WebFrameWidgetBase::dragTargetDrop(const WebDragData& webDragData,
+                                        const WebPoint& pointInViewport,
+                                        const WebPoint& screenPoint,
+                                        int modifiers) {
+  WebPoint pointInRootFrame(viewportToRootFrame(pointInViewport));
+
+  DCHECK(m_currentDragData);
+  m_currentDragData = DataObject::create(webDragData);
+  WebViewImpl::UserGestureNotifier notifier(view());
+
+  // If this webview transitions from the "drop accepting" state to the "not
+  // accepting" state, then our IPC message reply indicating that may be in-
+  // flight, or else delayed by javascript processing in this webview.  If a
+  // drop happens before our IPC reply has reached the browser process, then
+  // the browser forwards the drop to this webview.  So only allow a drop to
+  // proceed if our webview m_dragOperation state is not DragOperationNone.
+
+  if (m_dragOperation ==
+      WebDragOperationNone) {  // IPC RACE CONDITION: do not allow this drop.

[dcheng, 2016/11/09 20:23:17]

Nit: let's put this comment on the previous line, to avoid the funny wrapping.

[paulmeyer, 2016/11/09 23:19:11]

Done.

+    dragTargetDragLeave();
+    return;
+  }
+
+  m_currentDragData->setModifiers(modifiers);
+  DragData dragData(m_currentDragData.get(), pointInRootFrame, screenPoint,
+                    static_cast<DragOperation>(m_operationsAllowed));
+
+  page()->dragController().performDrag(&dragData);
+
+  m_dragOperation = WebDragOperationNone;
+  m_currentDragData = nullptr;
+}
+
+WebDragOperation WebFrameWidgetBase::dragTargetDragEnterOrOver(
+    const WebPoint& pointInViewport,
+    const WebPoint& screenPoint,
+    DragAction dragAction,
+    int modifiers) {
+  DCHECK(m_currentDragData);
+
+  WebPoint pointInRootFrame(viewportToRootFrame(pointInViewport));
+
+  m_currentDragData->setModifiers(modifiers);
+  DragData dragData(m_currentDragData.get(), pointInRootFrame, screenPoint,
+                    static_cast<DragOperation>(m_operationsAllowed));
+
+  DragSession dragSession;
+  dragSession = page()->dragController().dragEnteredOrUpdated(&dragData);
+
+  DragOperation dropEffect = dragSession.operation;
+
+  // Mask the drop effect operation against the drag source's allowed
+  // operations.
+  if (!(dropEffect & dragData.draggingSourceOperationMask()))
+    dropEffect = DragOperationNone;
+
+  m_dragOperation = static_cast<WebDragOperation>(dropEffect);
+
+  return m_dragOperation;
+}
+
+WebPoint WebFrameWidgetBase::viewportToRootFrame(
+    const WebPoint& pointInViewport) const {
+  return page()->frameHost().visualViewport().viewportToRootFrame(
+      pointInViewport);
+}
+
+WebViewImpl* WebFrameWidgetBase::view() const {
+  return static_cast<WebLocalFrameImpl*>(localRoot())->viewImpl();
+}
+
+Page* WebFrameWidgetBase::page() const {
+  return view()->page();
+}
+
+}  // namespace blink