WinAPI - dialogs: how does disabled main window flash dialog on mouseclick? - c

Question

Using WinAPI in C, there are two ways to create a dialog with WinAPI: the more common one is to create a dialog resource in the project's .rc file and then use it with DialogBox(), which automates the creation of a standart dialog. The other way is to use CreateWindowEx with specific parameters so that the created window acts like a dialog.
An example of dialog creation with DialogBox can be seen at winprog.org: http://www.winprog.org/tutorial/dialogs.html
Out of pure interest, I've tried to recreate the dialog created with DialogBox(), using CreateWindowEx. To do this, I simply disabled the main window and then CreateWindowEx'ed the dialog. However, what I got still had one difference from the dialog created with DialogBox: when I click on the disabled main window, a DialogBox-created dialog flashes (most probably with the FlashWindowEx function).
Here's my code for creating a dialog box with CreateWindowEx:
HWND hwndParent;
HINSTANCE ghInstance;
LPCWSTR g_szDialogClassName = L"DialogClass";
void populateDialog(HWND hwnd){
/* Create various dialog controls */
}
LRESULT CALLBACK aboutDlgProc(HWND hwnd, UINT Message, WPARAM wParam, LPARAM lParam){
switch(Message){
case WM_CREATE:
populateDialog(hwnd);
return DefWindowProc(hwnd, Message, wParam, lParam);
case WM_COMMAND:
switch(LOWORD(wParam)){
case IDC_CLOSEDLG:
EnableWindow(hwndParent, TRUE);
DestroyWindow(hwnd);
UnregisterClass(g_szDialogClassName, ghInstance);
break;
}
break;
case WM_CLOSE:
EnableWindow(hwndParent, TRUE);
DestroyWindow(hwnd);
UnregisterClass(g_szDialogClassName, ghInstance);
break;
default:
return DefWindowProc(hwnd, Message, wParam, lParam);
}
return DefWindowProc(hwnd, Message, wParam, lParam);
}
int createDialogBox(HWND hwnd, HINSTANCE hInstance){
if (registerClass(hInstance, g_szDialogClassName, (WNDPROC)aboutDlgProc) == 0){
MessageBoxA(NULL, "Dialog Registration Failed!", "Error!", MB_ICONEXCLAMATION | MB_OK);
return 0;
}
EnableWindow(hwnd, FALSE);
CreateWindowEx(WS_EX_DLGMODALFRAME | WS_EX_TOPMOST | WS_EX_TOOLWINDOW, g_szDialogClassName, L"About", WS_VISIBLE | WS_CAPTION | WS_POPUP | WS_SYSMENU, 100, 100, 450, 150, NULL, NULL, hInstance, NULL);
hwndParent = hwnd;
}
Now I am very interested in how is this done inside DialogBox()? How can a disabled window recieve mouse input? Or maybe it wasn't disabled by standart means (by something different than EnableWindow(hwnd, FALSE))? Or is it impossible to reproduce this effect with normal WinAPI calls?

Answer 1

The problem with your code is that you created the window un-owned. Specify the main window as the owner when you call CreateWindowEx.