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Diffstat (limited to 'base/base_drop_target.h')
| -rw-r--r-- | base/base_drop_target.h | 142 |
1 files changed, 142 insertions, 0 deletions
diff --git a/base/base_drop_target.h b/base/base_drop_target.h new file mode 100644 index 0000000..24e8ee5 --- /dev/null +++ b/base/base_drop_target.h @@ -0,0 +1,142 @@ +// Copyright 2008, Google Inc. +// All rights reserved. +// +// Redistribution and use in source and binary forms, with or without +// modification, are permitted provided that the following conditions are +// met: +// +// * Redistributions of source code must retain the above copyright +// notice, this list of conditions and the following disclaimer. +// * Redistributions in binary form must reproduce the above +// copyright notice, this list of conditions and the following disclaimer +// in the documentation and/or other materials provided with the +// distribution. +// * Neither the name of Google Inc. nor the names of its +// contributors may be used to endorse or promote products derived from +// this software without specific prior written permission. +// +// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS +// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR +// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT +// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, +// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT +// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE +// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +#ifndef BASE_BASE_DROP_TARGET_H__ +#define BASE_BASE_DROP_TARGET_H__ + +#include <atlbase.h> +#include <objidl.h> +#include <shobjidl.h> + +#include "base/basictypes.h" + +// A DropTarget implementation that takes care of the nitty gritty +// of dnd. While this class is concrete, subclasses will most likely +// want to override various OnXXX methods. +// +// Because BaseDropTarget is ref counted you shouldn't delete it directly, +// rather wrap it in a scoped_refptr. Be sure and invoke RevokeDragDrop(m_hWnd) +// before the HWND is deleted too. +class BaseDropTarget : public IDropTarget { + public: + // Create a new BaseDropTarget associating it with the given HWND. + explicit BaseDropTarget(HWND hwnd); + virtual ~BaseDropTarget(); + + // When suspend is set to |true|, the drop target does not receive drops from + // drags initiated within the owning HWND. + // TODO(beng): (http://b/1085385) figure out how we will handle legitimate + // drag-drop operations within the same HWND, such as dragging + // selected text to an edit field. + void set_suspend(bool suspend) { suspend_ = suspend; } + + // IDropTarget implementation: + HRESULT __stdcall DragEnter(IDataObject* data_object, + DWORD key_state, + POINTL cursor_position, + DWORD* effect); + HRESULT __stdcall DragOver(DWORD key_state, + POINTL cursor_position, + DWORD* effect); + HRESULT __stdcall DragLeave(); + HRESULT __stdcall Drop(IDataObject* data_object, + DWORD key_state, + POINTL cursor_position, + DWORD* effect); + + // IUnknown implementation: + HRESULT __stdcall QueryInterface(const IID& iid, void** object); + ULONG __stdcall AddRef(); + ULONG __stdcall Release(); + + protected: + // Returns the hosting HWND. + HWND GetHWND() { return hwnd_; } + + // Invoked when the cursor first moves over the hwnd during a dnd session. + // This should return a bitmask of the supported drop operations: + // DROPEFFECT_NONE, DROPEFFECT_COPY, DROPEFFECT_LINK and/or + // DROPEFFECT_MOVE. + virtual DWORD OnDragEnter(IDataObject* data_object, + DWORD key_state, + POINT cursor_position, + DWORD effect); + + // Invoked when the cursor moves over the window during a dnd session. + // This should return a bitmask of the supported drop operations: + // DROPEFFECT_NONE, DROPEFFECT_COPY, DROPEFFECT_LINK and/or + // DROPEFFECT_MOVE. + virtual DWORD OnDragOver(IDataObject* data_object, + DWORD key_state, + POINT cursor_position, + DWORD effect); + + // Invoked when the cursor moves outside the bounds of the hwnd during a + // dnd session. + virtual void OnDragLeave(IDataObject* data_object); + + // Invoked when the drop ends on the window. This should return the operation + // that was taken. + virtual DWORD OnDrop(IDataObject* data_object, + DWORD key_state, + POINT cursor_position, + DWORD effect); + + private: + // Returns the cached drop helper, creating one if necessary. The returned + // object is not addrefed. May return NULL if the object couldn't be created. + static IDropTargetHelper* DropHelper(); + + // The data object currently being dragged over this drop target. + CComPtr<IDataObject> current_data_object_; + + // A helper object that is used to provide drag image support while the mouse + // is dragging over the content area. + // + // DO NOT ACCESS DIRECTLY! Use DropHelper() instead, which will lazily create + // this if it doesn't exist yet. This object can take tens of milliseconds to + // create, and we don't want to block any window opening for this, especially + // since often, DnD will never be used. Instead, we force this penalty to the + // first time it is actually used. + static IDropTargetHelper* cached_drop_target_helper_; + + // The HWND of the source. This HWND is used to determine coordinates for + // mouse events that are sent to the renderer notifying various drag states. + HWND hwnd_; + + // Whether or not we are currently processing drag notifications for drags + // initiated in this window. + bool suspend_; + + LONG ref_count_; + + DISALLOW_EVIL_CONSTRUCTORS(BaseDropTarget); +}; + +#endif // BASE_BASE_DROP_TARGET_H__ |