{"id":24863,"date":"2007-10-08T10:00:00","date_gmt":"2007-10-08T10:00:00","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/oldnewthing\/2007\/10\/08\/which-windows-appear-in-the-alttab-list\/"},"modified":"2007-10-08T10:00:00","modified_gmt":"2007-10-08T10:00:00","slug":"which-windows-appear-in-the-alttab-list","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20071008-00\/?p=24863","title":{"rendered":"Which windows appear in the Alt+Tab list?"},"content":{"rendered":"

\nCommenter Phil Quirk\n\nwants to know what the rules are for determining which windows\nappear in the Alt+Tab list<\/a>.\nIt’s actually pretty simple although hardly anything you’d be able to guess\non your own.\nNote<\/b>: The details of this algorithm are an implementation detail.\nIt can change at any time, so don’t rely on it.\nIn fact, it already changed with Flip and Flip3D;\nI’m just talking about the Classic Alt+Tab window here.\n<\/p>\n

\nFor each visible window,\nwalk up its owner chain until you find the root owner.\nThen walk back down the visible last active popup chain until you find\na visible window.\nIf you’re back to where you’re started, then put the window in the\nAlt+Tab list.\nIn pseudo-code:\n<\/p>\n

\nBOOL IsAltTabWindow(HWND hwnd)\n{\n \/\/ Start at the root owner\n HWND hwndWalk = GetAncestor(hwnd, GA_ROOTOWNER);\n \/\/ See if we are the last active visible popup\n HWND hwndTry;\n while ((hwndTry = GetLastActivePopup(hwndWalk)) != hwndTry) {\n  if (IsWindowVisible(hwndTry)) break;\n  hwndWalk = hwndTry;\n }\n return hwndWalk == hwnd;\n}\n<\/pre>\n
\nThe purpose of this algorithm is to assign the most meaningful\nrepresentative winow from each cluster of windows\nrelated by ownership.\n(Notice that the algorithm doesn’t care whether the owned window is\nmodal or non-modal.)\n<\/p>\n
\nAt least that’s the simple rule if you’re not playing crazy window\nstyle games.\nThe WS_EX_TOOLWINDOW<\/code> and WS_EX_APPWINDOW<\/code>\nextended styles were created so people can play games and put their\nwindow in the Alt+Tab list or take it out even if the simple rule\nwould normally have decided otherwise.\nThis is one of those\n“Okay, if you think you’re smarter than Windows, here’s your chance\nto prove it” options.\nPersonally, I would avoid them since it makes your window behave\ndifferently from the rest of the windows in the system.\n<\/p>\n
\nA window with the\nWS_EX_TOOLWINDOW<\/code> extended style is treated as if it\nweren’t visible, even if it is.\nA window with the\nWS_EX_APPWINDOW<\/code> extended style is treated as if it\nhas no owner, even if it does.\n<\/p>\n
\nOnce you start adding these extended styles, you enter the world\nof “I’m trying to work around the rules” and the result is typically\neven worse confusion than what you had without them.\n<\/p>\n
\nI’m not sure what the original commenter is getting at.\nThe window hierarchy described in the suggestion\n(which doesn’t make it so much a suggestion as it is a request\nfor me to debug their problem) says that window C is\nmodal on both windows A and B, which doesn’t make\nsense to me, since a window has only one owner.\n<\/p>\n
\nThe algorithm for choosing the Alt+Tab representative from each\ncluster of windows may not be the best, but it’s what we have.\nI wouldn’t be surprised if the details are tweaked from time to time.\nNo, wait, let me rephrase that.\nI know<\/i> that the details are tweaked from time to time.\nThe spirit of the operation is preserved\n(to show the windows the user can switch to, using the most “natural”\ncandidate for each cluster of windows),\nbut the specific details may be fined-tuned as the concept of “naturalness”\nis refined.<\/p>\n","protected":false},"excerpt":{"rendered":"
Commenter Phil Quirk wants to know what the rules are for determining which windows appear in the Alt+Tab list. It’s actually pretty simple although hardly anything you’d be able to guess on your own. Note: The details of this algorithm are an implementation detail. It can change at any time, so don’t rely on it. […]<\/p>\n","protected":false},"author":1069,"featured_media":111744,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[25],"class_list":["post-24863","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-code"],"acf":[],"blog_post_summary":"
Commenter Phil Quirk wants to know what the rules are for determining which windows appear in the Alt+Tab list. It’s actually pretty simple although hardly anything you’d be able to guess on your own. Note: The details of this algorithm are an implementation detail. It can change at any time, so don’t rely on it. […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/24863","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=24863"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/24863\/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=24863"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=24863"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=24863"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}