\nLet’s say that we did want to support Move in our\ndrag\/drop program, for whatever reason.\nLet’s do it with some scratch file instead\nof \nOh wait, there are people out there who think I’m advocating hard-coded\npaths, so let me change the program to operate on a path passed on the\ncommand line.\nThis is code that is purely a distraction from the point of this\narticle, which is why I avoided it originally.\nPersonally I dislike it when somebody hands me a sample program\nthat is 90% unrelated to the technology the program is trying to demonstrate.\nI have to go\ndigging through the code hunting for the 10% of stuff that matters.\n<\/P>\n LPWSTR *g_argv;\nLPCWSTR g_pszTarget;<\/FONT><\/p>\n void OnLButtonDown(HWND hwnd, BOOL fDoubleClick,\n int x, int y, UINT keyFlags)\n{\n IDataObject *pdto;\n if (SUCCEEDED(GetUIObjectOfFile(hwnd,\n g_pszTarget<\/FONT>,\n IID_IDataObject, (void**)&pdto))) {\n …\n DeleteFileW(g_pszTarget<\/FONT>);\n …\n}<\/p>\n BOOL\nInitApp(void)\n{\n int argc;\n g_argv = CommandLineToArgvW(GetCommandLineW(), &argc);\n if (!g_argv || argc != 2) return FALSE;\n g_pszTarget = g_argv[1];\n if (PathIsRelative(g_pszTarget)) return FALSE;<\/FONT>\n …\n}\n<\/PRE>\n \nWoo-hoo, eight distracting lines of code that have nothing to do\nwith the subject of dragging shell objects around. I hope you’re\nhappy.\n<\/P>\n \nWhere was I? Oh right, explaining the first batch of blue code\nthat by now has scrolled off your screen thanks to the intervening\nmeaningless drivel.\n<\/P>\n \nNow that we allow move, we need to check whether the resulting effect\nwas \nNotice that \n(One case where \nIf the data object represents a file, then the shell is pretty\ngood at figuring out how to move the file to the destination\ninstead of copying it and asking you to delete the original.\nYou will typically get \nBut what if you want to know whether the operation was a move,\nregardless of whether the operation was optimized by the drop\ntarget?\nWe’ll look at that next time.\n<\/P>\n \n(By the way, if you execute a Move of the throwaway file,\ndon’t forget to move it back so you can run the scratch\nprogram again!)\n<\/P><\/p>\n","protected":false},"excerpt":{"rendered":" Let’s say that we did want to support Move in our drag\/drop program, for whatever reason. Let’s do it with some scratch file instead of clock.avi, though. Create a file somewhere that you don’t mind losing; let’s say it’s C:\\throwaway.txt. Change the function OnLButtonDown as follows: void OnLButtonDown(HWND hwnd, BOOL fDoubleClick, int x, int y, […]<\/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-37123","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-code"],"acf":[],"blog_post_summary":" Let’s say that we did want to support Move in our drag\/drop program, for whatever reason. Let’s do it with some scratch file instead of clock.avi, though. Create a file somewhere that you don’t mind losing; let’s say it’s C:\\throwaway.txt. Change the function OnLButtonDown as follows: void OnLButtonDown(HWND hwnd, BOOL fDoubleClick, int x, int y, […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/37123","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=37123"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/37123\/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=37123"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=37123"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=37123"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}clock.avi<\/CODE>, though. Create a file somewhere\nthat you don’t mind losing; let’s say it’s C:\\throwaway.txt<\/CODE>.\nChange the function OnLButtonDown<\/CODE> as follows:\n<\/P>\n\nvoid OnLButtonDown(HWND hwnd, BOOL fDoubleClick,\n int x, int y, UINT keyFlags)\n{\n IDataObject *pdto;\n if (SUCCEEDED(GetUIObjectOfFile(hwnd,\n L”C:\\\\throwaway.txt”<\/FONT>,\n IID_IDataObject, (void**)&pdto))) {\n IDropSource *pds = new CDropSource();\n if (pds) {\n DWORD dwEffect;\n if (DoDragDrop(pdto, pds,\n DROPEFFECT_COPY | DROPEFFECT_LINK | DROPEFFECT_MOVE,\n &dwEffect) == DRAGDROP_S_DROP) {\n if (dwEffect & DROPEFFECT_MOVE) {\n DeleteFile(TEXT(“C:\\\\throwaway.txt”));\n }\n }<\/FONT>\n pds->Release();\n }\n pdto->Release();\n }\n}\n<\/PRE>\n\n#include <shellapi.h><\/p>\n
DROPEFFECT_MOVE<\/CODE>, which tells us,\n“The drop target wanted to perform a move operation, but it only\ngot as far as copying the object; please finish the move operation\nby deleting the original.”\n<\/P>\nDROPEFFECT_MOVE<\/CODE> does not<\/STRONG>\nmean, “The drop target performed a move.”\nRather, it tells you that the drop target wants you to delete\nthe original.\nIf the drop target was able to delete the original (or move it\ndirectly), then you will not get\nDROPEFFECT_MOVE<\/CODE> back.\n<\/P>\nDROPEFFECT_MOVE<\/CODE> doesn’t even mean\nthat a Move operation occurred at all is if the user dragged\nthe object to an “Incinerator” icon, the purpose of which is\nto destroy whatever is dropped onto it. In this case the\nIncinerator would return DROPEFFECT_MOVE<\/CODE> without\neven making a copy. Result: The object is deleted.\nA better name for DROPEFFECT_MOVE<\/CODE> would have been\nDROPEFFECT_DELETEORIGINAL<\/CODE>.)\n<\/P>\nDROPEFFECT_MOVE<\/CODE> back only\nif the data object represents a non-file, since in that case\nthe shell doesn’t know how to delete the original.\n<\/P>\n