{"id":97025,"date":"2017-09-14T07:00:00","date_gmt":"2017-09-14T21:00:00","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/oldnewthing\/?p=97025"},"modified":"2019-03-13T01:16:49","modified_gmt":"2019-03-13T08:16:49","slug":"20170914-00","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20170914-00\/?p=97025","title":{"rendered":"Why is my window unexpectedly becoming topmost?"},"content":{"rendered":"

A customer had a problem where one of their program’s windows was somehow receiving the WS_<\/code>EX_<\/code>TOP­MOST<\/code> extended window style, thereby becoming topmost. The scenario was that they created a popup window with the WS_<\/code>EX_<\/code>TOP­MOST<\/code> extended style, and subsequently opened a document window. If they destroyed the popup window before creating the document window, then everything was fine. But if they created the document window before destroying the popup window, then their main app magically gained the WS_<\/code>EX_<\/code>TOP­MOST<\/code> extended style. Their investigation revealed that nobody was calling Set­Window­Long<\/code> with GWL_<\/code>EXSTYLE<\/code> and WS_<\/code>EX_<\/code>TOP­MOST<\/code>.¹ Are there other ways that a window can become topmost? <\/p>\n

One way that a window can become topmost is if it is created with the WS_<\/code>EX_<\/code>TOP­MOST<\/code> extended style. <\/p>\n

Another way that a window can become topmost is if you call Set­Window­Pos<\/code> and pass HWND_<\/code>TOP­MOST<\/code> as the hwnd­Insert­After<\/code>. <\/p>\n

Yet another way that a window can become topmost is if you pass a topmost window as the hwnd­Insert­After<\/code>. <\/p>\n

Armed with this information, the customer did some more investigation and reported back: They found a call to Set­Window­Pos<\/code> that was making the window topmost. <\/p>\n

Mystery solved! <\/p>\n

¹ Not that anybody should be doing that anyway. The documentation for the WS_<\/code>EX_<\/code>TOP­MOST<\/code> extended style<\/a> says that you shouldn’t be manipulating the extended style bit directly. “To add or remove this style, use the Set­Window­Pos<\/code> function.” <\/p>\n","protected":false},"excerpt":{"rendered":"

There are a few places where the system will auto-topmost a window.<\/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-97025","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-code"],"acf":[],"blog_post_summary":"

There are a few places where the system will auto-topmost a window.<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/97025","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=97025"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/97025\/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=97025"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=97025"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=97025"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}