{"id":11873,"date":"2010-12-30T07:00:00","date_gmt":"2010-12-30T07:00:00","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/oldnewthing\/2010\/12\/30\/windowfrompoint-childwindowfrompoint-realchildwindowfrompoint-when-will-it-all-end\/"},"modified":"2010-12-30T07:00:00","modified_gmt":"2010-12-30T07:00:00","slug":"windowfrompoint-childwindowfrompoint-realchildwindowfrompoint-when-will-it-all-end","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20101230-00\/?p=11873","title":{"rendered":"WindowFromPoint, ChildWindowFromPoint, RealChildWindowFromPoint, when will it all end?"},"content":{"rendered":"

Oh wait, there’s also ChildWindowFromPointEx<\/code>.\n There are many ways of identifying the window that appears beneath a point. The documentation for each one describes how they work, but I figured I’d do a little compare\/contrast to help you decide which one you want for your particular programming problem.\n The oldest functions are WindowFromPoint<\/code> and ChildWindowFromPoint<\/code>. The primary difference between them is that WindowFromPoint<\/code> returns the deepest window beneath the point, whereas ChildWindowFromPoint<\/code> returns the shallowest.\n What do I mean by deep and shallow?\n Suppose you have a top-level window P and a child window C. And suppose you ask one of the above functions, “What window is beneath this point?” when the point is squarely over window C. The WindowFromPoint<\/code> function looks for the most heavily nested window that contains the point, which is window C. On the other hand ChildWindowFromPoint<\/code> function looks for the least nested window that contains the point, which is window P, assuming you passed GetDesktopWindow<\/code> as the starting point.\n That’s the most important difference between the two functions, but there are others, primarily with how the functions treat hidden, disabled, and transparent windows. Some functions will pay attention to hidden, disabled, and\/or transparent windows; others will skip them. Note that when a window is skipped, the entire window hierarchy starting from that window is skipped. For example, if you call a function that skips disabled windows, then all children of disabled windows will also be skipped (even if the children are enabled).\n Here we go in tabular form.<\/p>\n\n\n\n\n\n\n\n
Function<\/th>\nSearch<\/th>\nHidden?<\/th>\nDisabled?<\/th>\nTransparent?¹<\/th>\n<\/tr>\n
WindowFromPoint<\/code><\/td>\nDeep<\/td>\nSkip<\/td>\nSkip<\/td>\nIt’s Complicated<\/a>²<\/td>\n<\/tr>\n
ChildWindowFromPoint<\/code><\/td>\nShallow<\/td>\nInclude<\/td>\nInclude<\/td>\nInclude<\/td>\n<\/tr>\n
ChildWindowFromPointEx<\/code><\/td>\nShallow<\/td>\nOptional<\/td>\nOptional<\/td>\nOptional<\/td>\n<\/tr>\n
RealChildWindowFromPoint<\/code><\/td>\nShallow<\/td>\nSkip<\/td>\nInclude<\/td>\nInclude³<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The return values for the various ...FromPoint...<\/code> functions are the same:<\/p>\n