\nYou may have noticed that the drag feedback is rather sad-looking.\nJust a box, maybe with a plus sign or an arrow; you don’t\neven know what it is you’re dragging.\n<\/P>\n
\nLet’s fix that. We’ll drag the icon of the file around.\nWe’ll need to add the drag image to the data object.\n<\/P>\n
\nvoid OnLButtonDown(HWND hwnd, BOOL fDoubleClick, int x, int y, UINT keyFlags)\n{\n IDataObject *pdto;\n if (SUCCEEDED(GetDataObjectOfFileWithCuteIcon(\n hwnd, g_pszTarget, &pdto))<\/FONT>) {\n IDropSource *pds = new CDropSource();\n …\n<\/PRE>\n\nThis new function GetDataObjectOfFileWithCuteIcon<\/CODE>\ncreates the data object and then attaches the cute icon to it.\n<\/P>\n\nHRESULT GetDataObjectOfFileWithCuteIcon(HWND hwnd,\n LPCWSTR pszPath, IDataObject **ppdto)\n{\n HRESULT hr = GetUIObjectOfFile(hwnd, pszPath,\n IID_IDataObject, (void**)ppdto);\n if (SUCCEEDED(hr)) {\n IDragSourceHelper *pdsh;\n if (SUCCEEDED(CoCreateInstance(CLSID_DragDropHelper, NULL, CLSCTX_ALL,\n IID_IDragSourceHelper, (void**)&pdsh))) {\n SHDRAGIMAGE sdi;\n if (CreateDragImage(pszPath, &sdi)) {\n pdsh->InitializeFromBitmap(&sdi, *ppdto);\n DeleteObject(sdi.hbmpDragImage);\n }\n pdsh->Release();\n }\n }\n return hr;\n}\n<\/PRE>\n\nWe use the\n\nshell drag\/drop helper object<\/A>\nto attach the bitmap to the data object.\nThe shell drag\/drop helper object requires that the data object\nbe able to accept arbitrary blobs, but fortunately, the standard\nshell data object does this.\n<\/P>\n\nThe nasty part is generating the drag image.\nThis is not the fun part, and you’re not going to learn anything\nfrom this function. It just has to be written.\n<\/P>\n
\nBOOL CreateDragImage(LPCWSTR pszPath, SHDRAGIMAGE *psdi)\n{\n psdi->hbmpDragImage = NULL;\n SHFILEINFOW sfi;\n HIMAGELIST himl = (HIMAGELIST)\n SHGetFileInfoW(pszPath, 0, &sfi, sizeof(sfi), SHGFI_SYSICONINDEX);\n if (himl) {\n int cx, cy;\n ImageList_GetIconSize(himl, &cx, &cy);\n psdi->sizeDragImage.cx = cx;\n psdi->sizeDragImage.cy = cy;\n psdi->ptOffset.x = cx;\n psdi->ptOffset.y = cy;\n psdi->crColorKey = CLR_NONE;\n HDC hdc = CreateCompatibleDC(NULL);\n if (hdc) {\n psdi->hbmpDragImage = CreateBitmap(cx, cy, 1, 32, NULL);\n if (psdi->hbmpDragImage) {\n HBITMAP hbmPrev = SelectBitmap(hdc, psdi->hbmpDragImage);\n ImageList_Draw(himl, sfi.iIcon, hdc, 0, 0, ILD_NORMAL);\n SelectBitmap(hdc, hbmPrev);\n }\n DeleteDC(hdc);\n }\n }\n return psdi->hbmpDragImage != NULL;\n}\n<\/PRE>\n\nTo create the drag image, we ask\n\nthe SHGetFileInfo<\/CODE> function<\/A>\nto give us the imagelist handle and icon index\nfor the icon that represents the file.\nThe icon size in the imagelist goes into\n\nthe SHDRAGIMAGE<\/CODE> structure<\/A>\nas the bitmap dimensions and as the cursor point.\n(We put the cursor at the bottom right corner of the image.)\nSince we are creating an alpha-blended bitmap, we don’t need\na color-key.\nFinally, we create a memory DC to house an ARGB bitmap into which\nwe draw the icon.\n<\/P>\n\nIf you run this program, you should see the icon for a text file\nbeing dragged around as you drag your throwaway file around\nthe screen.\n<\/P>\n
\nNext time, a way to make somebody else do the heavy lifting for you.\n<\/P><\/p>\n","protected":false},"excerpt":{"rendered":"
You may have noticed that the drag feedback is rather sad-looking. Just a box, maybe with a plus sign or an arrow; you don’t even know what it is you’re dragging. Let’s fix that. We’ll drag the icon of the file around. We’ll need to add the drag image to the data object. void OnLButtonDown(HWND […]<\/p>\n","protected":false},"author":1069,"featured_media":111744,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[25],"class_list":["post-37083","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-code"],"acf":[],"blog_post_summary":"
You may have noticed that the drag feedback is rather sad-looking. Just a box, maybe with a plus sign or an arrow; you don’t even know what it is you’re dragging. Let’s fix that. We’ll drag the icon of the file around. We’ll need to add the drag image to the data object. void OnLButtonDown(HWND […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/37083","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/users\/1069"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/comments?post=37083"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/37083\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media\/111744"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/media?parent=37083"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=37083"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=37083"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}