base/base_drop_target.cc

   1 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "base/base_drop_target.h"
   6
   7 #include <shlobj.h>
   8
   9 #include "base/logging.h"
  10
  11 ///////////////////////////////////////////////////////////////////////////////
  12
  13 IDropTargetHelper* BaseDropTarget::cached_drop_target_helper_ = NULL;
  14 int32 BaseDropTarget::drag_identity_ = 0;
  15
  16 BaseDropTarget::BaseDropTarget(HWND hwnd)
  17     : hwnd_(hwnd),
  18       suspended_(false),
  19       ref_count_(0) {
  20   DCHECK(hwnd);
  21   HRESULT result = RegisterDragDrop(hwnd, this);
  22   DCHECK(SUCCEEDED(result));
  23 }
  24
  25 BaseDropTarget::~BaseDropTarget() {
  26 }
  27
  28 // static
  29 IDropTargetHelper* BaseDropTarget::DropHelper() {
  30   if (!cached_drop_target_helper_) {
  31     CoCreateInstance(CLSID_DragDropHelper, 0, CLSCTX_INPROC_SERVER,
  32                      IID_IDropTargetHelper,
  33                      reinterpret_cast<void**>(&cached_drop_target_helper_));
  34   }
  35   return cached_drop_target_helper_;
  36 }
  37
  38 ///////////////////////////////////////////////////////////////////////////////
  39 // BaseDropTarget, IDropTarget implementation:
  40
  41 HRESULT BaseDropTarget::DragEnter(IDataObject* data_object,
  42                                   DWORD key_state,
  43                                   POINTL cursor_position,
  44                                   DWORD* effect) {
  45   // Tell the helper that we entered so it can update the drag image.
  46   IDropTargetHelper* drop_helper = DropHelper();
  47   if (drop_helper) {
  48     drop_helper->DragEnter(GetHWND(), data_object,
  49                            reinterpret_cast<POINT*>(&cursor_position), *effect);
  50   }
  51
  52   // You can't drag and drop within the same HWND.
  53   if (suspended_) {
  54     *effect = DROPEFFECT_NONE;
  55     return S_OK;
  56   }
  57
  58   // Update the drag identity, skipping 0.
  59   if (++drag_identity_ == 0)
  60     ++drag_identity_;
  61
  62   current_data_object_ = data_object;
  63   POINT screen_pt = { cursor_position.x, cursor_position.y };
  64   *effect = OnDragEnter(current_data_object_, key_state, screen_pt, *effect);
  65   return S_OK;
  66 }
  67
  68 HRESULT BaseDropTarget::DragOver(DWORD key_state,
  69                                  POINTL cursor_position,
  70                                  DWORD* effect) {
  71   // Tell the helper that we moved over it so it can update the drag image.
  72   IDropTargetHelper* drop_helper = DropHelper();
  73   if (drop_helper)
  74     drop_helper->DragOver(reinterpret_cast<POINT*>(&cursor_position), *effect);
  75
  76   if (suspended_) {
  77     *effect = DROPEFFECT_NONE;
  78     return S_OK;
  79   }
  80
  81   POINT screen_pt = { cursor_position.x, cursor_position.y };
  82   *effect = OnDragOver(current_data_object_, key_state, screen_pt, *effect);
  83   return S_OK;
  84 }
  85
  86 HRESULT BaseDropTarget::DragLeave() {
  87   // Tell the helper that we moved out of it so it can update the drag image.
  88   IDropTargetHelper* drop_helper = DropHelper();
  89   if (drop_helper)
  90     drop_helper->DragLeave();
  91
  92   if (suspended_)
  93     return S_OK;
  94
  95   OnDragLeave(current_data_object_);
  96
  97   current_data_object_ = NULL;
  98   return S_OK;
  99 }
 100
 101 HRESULT BaseDropTarget::Drop(IDataObject* data_object,
 102                              DWORD key_state,
 103                              POINTL cursor_position,
 104                              DWORD* effect) {
 105   // Tell the helper that we dropped onto it so it can update the drag image.
 106   IDropTargetHelper* drop_helper = DropHelper();
 107   if (drop_helper) {
 108     drop_helper->Drop(current_data_object_,
 109                       reinterpret_cast<POINT*>(&cursor_position), *effect);
 110   }
 111
 112   if (suspended_) {
 113     *effect = DROPEFFECT_NONE;
 114     return S_OK;
 115   }
 116
 117   POINT screen_pt = { cursor_position.x, cursor_position.y };
 118   *effect = OnDrop(current_data_object_, key_state, screen_pt, *effect);
 119   return S_OK;
 120 }
 121
 122 ///////////////////////////////////////////////////////////////////////////////
 123 // BaseDropTarget, IUnknown implementation:
 124
 125 HRESULT BaseDropTarget::QueryInterface(const IID& iid, void** object) {
 126   *object = NULL;
 127   if (IsEqualIID(iid, IID_IUnknown) || IsEqualIID(iid, IID_IDropTarget)) {
 128     *object = this;
 129   } else {
 130     return E_NOINTERFACE;
 131   }
 132   AddRef();
 133   return S_OK;
 134 }
 135
 136 ULONG BaseDropTarget::AddRef() {
 137   return ++ref_count_;
 138 }
 139
 140 ULONG BaseDropTarget::Release() {
 141   if (--ref_count_ == 0) {
 142     delete this;
 143     return 0U;
 144   }
 145   return ref_count_;
 146 }
 147
 148 DWORD BaseDropTarget::OnDragEnter(IDataObject* data_object,
 149                                   DWORD key_state,
 150                                   POINT cursor_position,
 151                                   DWORD effect) {
 152   return DROPEFFECT_NONE;
 153 }
 154
 155 DWORD BaseDropTarget::OnDragOver(IDataObject* data_object,
 156                                  DWORD key_state,
 157                                  POINT cursor_position,
 158                                  DWORD effect) {
 159   return DROPEFFECT_NONE;
 160 }
 161
 162 void BaseDropTarget::OnDragLeave(IDataObject* data_object) {
 163 }
 164
 165 DWORD BaseDropTarget::OnDrop(IDataObject* data_object,
 166                              DWORD key_state,
 167                              POINT cursor_position,
 168                              DWORD effect) {
 169   return DROPEFFECT_NONE;
 170 }