Thursday, February 9, 2012

Dialog in C++

While helping out a colleague I recently came across this code where for creating a dialog box first a window was created using CreateWindow method and then for CreateDialog method HWND returned by CreateWindow method was used, also while calling CreateWindow method values for width and height were specified as literals(hard coded).

Now the problem my colleague facing was with different resolutions this dialog was getting displayed differently, and on lower resolutions dialog was cropping the inner content of the dialog. Now the dialog resource template was set with type as Child.
Solution here is that you should not create any parent window for dialog unless its required in some special cases. We can directly pass the dialog resource template id to CreateDialog or DialogBox method and the HWND that we pass to this method specifies the parent window for this dialog. For this type for Dialog in resource has to be overlapped window or popup window. When we call either of this method for creating dialog Windows itself handles the width, height related settings of this dialog, we don't need to handle these things, which reduces non required overhead of managing the resolution related code.

For example when you want to show a modal dialog you can call DialogBox method which displays a modal dialog box.

DialogBox(hInstance, MAKEINTRESOURCE(IDD_DIALOG1), hWndParent, MyDialogProc);

and for creating a non modal dialog box you can call CreateDialog method,

CreateDialog(hInstance, MAKEINTRESOURCE(IDD_DIALOG1), hWndParent, MyDialogProc);

Both methods take same parameters and shows dialog box but one is modal and other is non modal dialog box.

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