{"id":4323,"date":"2013-05-17T07:00:00","date_gmt":"2013-05-17T07:00:00","guid":{"rendered":"https:\/\/blogs.msdn.microsoft.com\/oldnewthing\/2013\/05\/17\/who-sends-the-initial-wm_updateuistate-message\/"},"modified":"2013-05-17T07:00:00","modified_gmt":"2013-05-17T07:00:00","slug":"who-sends-the-initial-wm_updateuistate-message","status":"publish","type":"post","link":"https:\/\/devblogs.microsoft.com\/oldnewthing\/20130517-00\/?p=4323","title":{"rendered":"Who sends the initial WM_UPDATEUISTATE message?"},"content":{"rendered":"

\n\nLast time<\/A>,\nwe looked at the\nconfusingly-named\nWM_UPDATE­UI­STATE<\/CODE>\nand\nWM_CHANGE­UI­STATE<\/CODE>\nmessages.\nBut how does the whole indicator thingie get off the ground?\n<\/P>\n

\nThe default state for a window is to show all indicators.\nBut as a special trick,\nthe dialog manager will send a\nWM_UPDATE­UI­STATE<\/CODE> message\nwith UIS_INITIALIZE<\/CODE> after the dialog\nhas been initialized,\nwhich turns off the indicators if the last input event\nwas a mouse event.\nThis is its way of inferring whether the dialog box was\ntriggered by a mouse or keyboard action\nand setting the initial indicators accordingly.\n(Note that if the user checked\nUnderline keyboard shortcuts and access keys<\/I>,\nthen the dialog manager leaves the indicators enabled\nregardless of the last input event.)\n<\/P>\n

\nThat special\nWM_UPDATE­UI­STATE<\/CODE> message\nis what gives dialog boxes the extra special feature\nof hiding the keyboard accelerators until you use the keyboard.\n<\/P>\n

\nBut notice that only the dialog manager does this.\nIf you want this behavior in your own non-dialog windows,\nyou will need to send the message yourself.\n<\/P>\n

\nBOOL MyWindow::OnCreate(…)\n{\n … create and initialize any child windows …<\/p>\n
 \/\/ initialize indicators\n BOOL fAlwaysUnderline = FALSE;\n SystemParametersInfo(SPI_GETKEYBOARDCUES, 0,\n                      &fAlwaysUnderline, 0);\n if (!fAlwaysUnderline) {\n  SendMessage(this->m_hwnd, WM_UPDATEUISTATE,\n              MAKEWPARAM(UIS_INITIALIZE, 0), 0);\n }<\/FONT>\n}\n<\/PRE>\n
\nExercise<\/B>:\nWhy is it important to create and initialize the child windows\nbefore sending the\nWM_UPDATE­UI­STATE<\/CODE> message?\n<\/P>\n
\nExercise<\/B>:\nWhy can’t the window manager do this automatically\nafter WM_CREATE<\/CODE> returns?\n<\/P>\n
\nExercise<\/B>:\nExplain the behavior this customer observes.\n<\/P>\n
\nWe have a dialog box with three buttons.\nSometimes the dialog displays underlines for the hotkeys,\nand sometimes it doesn’t.\nI know about the feature which hides keyboard accelerators\nby default, but that doesn’t explain why the setting gets\nignored sometimes.\nThe first time I show the dialog in my program,\nI get the underlines, but the second and subsequent times,\nI do not.\n<\/BLOCKQUOTE><\/p>\n","protected":false},"excerpt":{"rendered":"
Last time, we looked at the confusingly-named WM_UPDATE­UI­STATE and WM_CHANGE­UI­STATE messages. But how does the whole indicator thingie get off the ground? The default state for a window is to show all indicators. But as a special trick, the dialog manager will send a WM_UPDATE­UI­STATE message with UIS_INITIALIZE after the dialog has been initialized, which […]<\/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-4323","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-oldnewthing","tag-code"],"acf":[],"blog_post_summary":"
Last time, we looked at the confusingly-named WM_UPDATE­UI­STATE and WM_CHANGE­UI­STATE messages. But how does the whole indicator thingie get off the ground? The default state for a window is to show all indicators. But as a special trick, the dialog manager will send a WM_UPDATE­UI­STATE message with UIS_INITIALIZE after the dialog has been initialized, which […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/4323","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=4323"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/posts\/4323\/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=4323"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/categories?post=4323"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/oldnewthing\/wp-json\/wp\/v2\/tags?post=4323"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}