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<HTML><LINK HREF="style.css" REL="STYLESHEET" TYPE="text/css"><HEAD><TITLE>Tutorial: Modeless Dialogs</TITLE></HEAD><BODY><FONT SIZE="-1">[ <A HREF="./index.html">contents</A>| <A HREF="http://www.winprog.org/">#winprog</A>]</FONT><HR><H1>Modeless Dialogs</H1><P>Example: dlg_two</P><IMG SRC="images/dlg_two.gif" ALT="[images/dlg_two.gif]" ALIGN="right"><P>Now we take a look at <CODE>CreateDialog()</CODE>, <CODE>DialogBox()</CODE>'s sister function. The difference is that while <CODE>DialogBox()</CODE> implementsit's own message loop and does not return untill the dialog is closed, <CODE>CreateDialog()</CODE> acts more like a window created with <CODE>CreateWindowEx()</CODE> in that it returns immediately and depends on yourmessage loop to pump the messages as it does for your main window. This is termed<I>Modeless</I>, whereas <CODE>DialogBox()</CODE> creates <I>Modal</I> dialogs.<P>You can create the dialog resource just like you did for the last dialog example, youmight also want to set the "Tool window" extended style to give it's title bar thetypical smaller caption of toolbars. The dialog resource I created follows:<PRE CLASS="SNIP">IDD_TOOLBAR DIALOGEX 0, 0, 98, 52STYLE DS_MODALFRAME | WS_POPUP | WS_CAPTIONEXSTYLE WS_EX_TOOLWINDOWCAPTION "My Dialog Toolbar"FONT 8, "MS Sans Serif"BEGIN PUSHBUTTON "&Press This Button",IDC_PRESS,7,7,84,14 PUSHBUTTON "&Or This One",IDC_OTHER,7,31,84,14END</PRE><P>You may notice that the resource editor has replaced <CODE>DIALOG</CODE> with <CODE>DIALOGEX</CODE> indicating we want to set an EXSTYLE on our dialog.<P>Next we want to create the dialog when our program runs, I want the dialog visible right away so we do this in <CODE>WM_CREATE</CODE>. We also want to declare a global variable to hold the window handle returned from <CODE>CreateDialog()</CODE> so that we can use it later. <CODE>DialogBox()</CODE> didn't return a handle to us since when <CODE>DialogBox()</CODE> returns the window has been destroyed.<PRE CLASS="SNIP">HWND g_hToolbar = NULL;</PRE><PRE CLASS="SNIP"> case WM_CREATE: g_hToolbar = CreateDialog(GetModuleHandle(NULL), MAKEINTRESOURCE(IDD_TOOLBAR), hwnd, ToolDlgProc); if(g_hToolbar != NULL) { ShowWindow(g_hToolbar, SW_SHOW); } else { MessageBox(hwnd, "CreateDialog returned NULL", "Warning!", MB_OK | MB_ICONINFORMATION); } break;</PRE><P>We check the return value, which is ALWAYS a good idea, and if it's valid (not <CODE>NULL</CODE>) we show the window with <CODE>ShowWindow()</CODE>, with <CODE>DialogBox()</CODE> this isn'tnecessary since the system calls <CODE>ShowWindow()</CODE> for us.<P>Now we need a dialog procedure for our toolbar.<PRE CLASS="SNIP">BOOL CALLBACK ToolDlgProc(HWND hwnd, UINT Message, WPARAM wParam, LPARAM lParam){ switch(Message) { case WM_COMMAND: switch(LOWORD(wParam)) { case IDC_PRESS: MessageBox(hwnd, "Hi!", "This is a message", MB_OK | MB_ICONEXCLAMATION); break; case IDC_OTHER: MessageBox(hwnd, "Bye!", "This is also a message", MB_OK | MB_ICONEXCLAMATION); break; } break; default: return FALSE; } return TRUE;}</PRE><P>Most of the same message handling rules apply to dialogs created with <CODE>CreateDialog()</CODE> as with <CODE>DialogBox()</CODE>, don't call <CODE>DefWindowProc()</CODE>, return <CODE>FALSE</CODE> for messages you don't handleand <CODE>TRUE</CODE> for those you do.<P>One change is that we don't call <CODE>EndDialog()</CODE> for modeless dialogs, we can use <CODE>DestroyWindow()</CODE> just like for regular windows. In this case I destroy thedialog when the main window is destroyed. In the main window's <CODE>WndProc()</CODE>...<PRE CLASS="SNIP"> case WM_DESTROY: DestroyWindow(g_hToolbar); PostQuitMessage(0); break;</PRE><P>Last but not least, we want to be able to display and hide our toolbar whenever we chooseso I've added two commands to my menu to do this, and handled them so:<PRE CLASS="SNIP"> case WM_COMMAND: switch(LOWORD(wParam)) { case ID_DIALOG_SHOW: ShowWindow(g_hToolbar, SW_SHOW); break; case ID_DIALOG_HIDE: ShowWindow(g_hToolbar, SW_HIDE); break; //... other command handlers } break;</PRE><P>You should be able to create your own menu using the resource editor or manually, but ifnot (as always) take a look at the example project dlg_two provided with the tutorial.<P>Now when you run the program, you should be able to access both the dialog window, andmain window at the same time.<P>If you've run the program at this point and tried tabbing between the two buttons, you have probablynoticed it doesn't work, neither does hitting Alt-P or Alt-O to activate the buttons. Why not? Whereas <CODE>DialogBox()</CODE> implements it'sown message loop and handles these events by default, <CODE>CreateDialog()</CODE> does not.We can do it ourselves though, by calling <CODE>IsDialogMessage()</CODE> in our message loopwhich will do the default processing for us.<PRE CLASS="SNIP"> while(GetMessage(&Msg, NULL, 0, 0)) { if(!IsDialogMessage(g_hToolbar, &Msg)) { TranslateMessage(&Msg); DispatchMessage(&Msg); } }</PRE><P>Here we first pass the message to <CODE>IsDialogMessage()</CODE>, if the message isdestined for our toolbar (indicated by the window handle we pass in) the system willperform the default processing and return <CODE>TRUE</CODE>. Is this case the messagehas already been handled so we don't want to call <CODE>TranslateMessage()</CODE> or <CODE>DispatchMessage()</CODE>.If the message is for another window we process as usual.<P>It's also worth noting that <CODE>IsDialogMessage()</CODE> can also be used with windows that aren't dialogsin order to to give them dialog-like behaviour. Remember, a dialog is a window, and most (if not all)dialog APIs will work on any window.<P>And that is pretty much all there is to modeless dialogs! One issue that may arise is ifyou have more than one toolbar... what do you do? Well one possible solution is to havea list (either an array, an STL <CODE>std::list</CODE>, or similar) and loop through it in your messageloop passing each handle to <CODE>IsDialogMessage()</CODE> until the right one is found, andif none, do the regular processing. This is a generic programming problem, not one that isWin32 related, and is left as an excersize to the reader.<HR><FONT SIZE="-1">Copyright © 1998-2003, Brook Miles (<A HREF="mailto:forger(nospam)winprog.org">theForger</A>). All rights reserved.</FONT><SCRIPT language="JavaScript"><!-- var re = /\(nospam\)/ig; var str; for(i = 0;i < document.links.length;i++) { str = "" + document.links(i).href; if(str.search(re) != -1) document.links(i).href = str.replace(re, "@"); str = "" + document.links(i).innerHTML; if(str.search(re) != -1) document.links(i).innerHTML = str.replace(re, "@"); }--></SCRIPT></BODY></HTML>⌨️ 快捷键说明
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