Dialog manager Chapter 3: create controls

Compared with the previous article on creating frame windows , Creating controls is much easier , Believe it or not .
Each control defined in the dialog template , Its corresponding sub window will be created . The size and position of the control are in the template with DLU Described in units , therefore , Of course , We need to convert them to pixels , The code is as follows ：
int x = XDLU2Pix(ItemTemplate.x);
int y = YDLU2Pix(ItemTemplate.y);
int cx = XDLU2Pix(ItemTemplate.cx);
int cy = YDLU2Pix(ItemTemplate.cy);

The control class name and title also come from the template . There are also some optional extra bytes pExtra No one uses , But it remains in the template definition for historical reasons . Once this information is collected , It's time to make ” Doughnut ” 了 .
HWND hwndChild = CreateWindowEx(
ItemTemplate.dwExStyle | WS_EX_NOPARENTNOTIFY,
pszClass, pwzCaption, ItemTemplate.dwStyle,
x, y, cx, cy, hdlg, ItemTemplate.dwId,
hinst, pExtra);

Please note that , For dialog controls ,WS_EX_NOPARENTNOTIFY Styles are enabled by default .

The next part often makes people stumble . “ When I try to create my dialog , It failed , I don't know why? .” This may be because a control on the dialog cannot be created , Usually because you forget to register the window class for this control . （ for example , You forgot to call InitCommonControlsEx Function or forget LoadLibrary Appropriate version RichEdit Control .）

if (!hwndChild) {
DestroyWindow(hdlg);
return NULL;
}

DS_NOFAILCREATE The style prohibits the above failure check .
however , If you do create a control , You need to initialize it .
SetWindowContextHelpId(hwndChild, ItemTemplate.dwHelpID);
SetWindowFont(hwndChild, hf, FALSE);

After repeating the above steps for each control in the template , You now have a dialog containing all the child controls . Tell the dialog process that it can initialize its child windows , If we delay building the framework WS_VISIBLE position , Is displayed （ Now ready ） Dialog box , And return the dialog box to our caller , The dialog box is now ready .
// The default focus is the first item that is a valid tab-stop.

HWND hwndDefaultFocus = GetNextDlgTabItem(hdlg, NULL, FALSE);
if (SendMessage(hdlg, WM_INITDIALOG, hwndDefaultFocus, lParam)) {
SetDialogFocus(hwndDefaultFocus);
}
if (fWasVisible) ShowWindow(hdlg);
return hdlg;
}

About SetDialogFocus, We talked about that before .

thus , You should understand how the dialog box is created .

（ actually , The reality is much more complicated , Because I skipped all the application compatibility skills ！ for example , There is a program that depends on detailed settings and WS_BORDER The lack of style determines whether the control is a combo box or a list box . I guess GetClassName The workload of functions is too large ？）

I hope this will help you better understand how conversation templates work .

summary

Descriptive language , It is a very friendly way of communication between program developers and operating systems .
like COM In the era of IDL（ Interface description language ）.

Last

Raymond Chen Of 《The Old New Thing》 It's one of my favorite blogs , There's a lot about Windows Little knowledge , For the vast Windows For platform developers , It's really helpful .
This article is from ：《The dialog manager, part 3: Creating the controls》