DS_CONTROL | WS_CHILD combination causes infinite loop - c

Question

Hello.I'm trying to create a "dialog in dialog" example using the WinAPI and C. This example consists in a child dialog with an autocheckbox, and a main dialog containing a static black rectangle which is the parent for the child dialog and a push button that shows in a message box a text with the checkbox status.When I set the flags DS_CONTROL | WS_CHILD for the child dialog, whenever I try to change the checkbox status the application enters into an infinite loop and I have to force close it. When I remove the DS_CONTROL flag, works as intended but I cannot cycle between the controls using the tab key.What can I do in order to make it work as intended using the DS_CONTROL flag?Here's the content of my main.c file:
#include <windows.h>
#pragma comment (lib, "user32")
HINSTANCE hInst;
BOOL isChecked;
const unsigned char checkedStr[] = "Checkbox is checked";
const unsigned char notCheckedStr[] = "Checkbox is not checked";
BOOL CALLBACK ChildDlgProc(HWND hwndDlg, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
switch (uMsg)
{
case WM_COMMAND:
switch (LOWORD(wParam))
{
case 21:
isChecked = IsDlgButtonChecked(hwndDlg, 21);
return TRUE;
}
return FALSE;
}
return FALSE;
}
BOOL CALLBACK DialogProc(HWND hwndDlg, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
switch (uMsg)
{
case WM_INITDIALOG:
{
HWND hContainer, hChilddDlg;
hContainer = GetDlgItem(hwndDlg, 11);
hChilddDlg = CreateDialogParam(hInst, MAKEINTRESOURCE(20), hContainer, ChildDlgProc, 0);
ShowWindow(hChilddDlg, SW_SHOW);
return TRUE;
}
case WM_COMMAND:
switch (LOWORD(wParam))
{
case 12:
{
const unsigned char *ptr;
if (isChecked)
{
ptr = checkedStr;
}
else
{
ptr = notCheckedStr;
}
MessageBox(hwndDlg, ptr, TEXT("Checkbox status"), MB_OK | MB_ICONINFORMATION);
return TRUE;
}
}
return FALSE;
case WM_CLOSE:
EndDialog(hwndDlg, 0);
return TRUE;
}
return FALSE;
}
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)
{
hInst = hInstance;
isChecked = FALSE;
return DialogBoxParam(hInstance, MAKEINTRESOURCE(10), NULL, DialogProc, 0);
}
And here's the content of my rsrc.rcfile:
#include <windows.h>
10 DIALOGEX 0, 0, 130, 47
STYLE DS_CENTER | DS_SETFONT | WS_CAPTION | WS_MINIMIZEBOX | WS_SYSMENU
CAPTION "Checkbox status"
LANGUAGE LANG_ENGLISH, SUBLANG_ENGLISH_US
FONT 9, "Segoe UI"
{
CONTROL "", 11, STATIC, SS_BLACKRECT | WS_CHILD | WS_VISIBLE, 5, 5, 120, 20
CONTROL "&Status", 12, BUTTON, BS_DEFPUSHBUTTON | WS_CHILD | WS_VISIBLE | WS_TABSTOP, 75, 30, 50, 12
}
20 DIALOGEX 0, 0, 120, 20
STYLE DS_SETFONT | DS_CONTROL | WS_CHILD
LANGUAGE LANG_ENGLISH, SUBLANG_ENGLISH_US
FONT 9, "Segoe UI"
{
CONTROL "Checkbox", 21, BUTTON, BS_AUTOCHECKBOX | WS_CHILD | WS_VISIBLE | WS_TABSTOP, 0, 5, 50, 10
}
I compile it in the Visual C++ command prompt with: cl /c main.c && rc rsrc.rc && link /SUBSYSTEM:WINDOWS /OUT:test.exe main.obj rsrc.res.Thanks in advance for your help.

Answer 1

Found the solution in the NSIS source code. The problem was that I was putting the child dialog as a child of the blackrect so it was out of the event loop of the main dialog, causing the hang. In order to solve this I had to put it as a child of the main dialog and move it over the blackrect.Here's the updated code of the WM_INITDIALOG case in the main dialog proc:
// ...
case WM_INITDIALOG:
{
HWND hChilddDlg;
hChilddDlg = CreateDialogParam(hInst, MAKEINTRESOURCE(20), hwndDlg, ChildDlgProc, 0);
if (hChilddDlg)
{
RECT rect;
GetWindowRect(GetDlgItem(hwndDlg, 11), &rect);
ScreenToClient(hwndDlg, (LPPOINT)&rect);
SetWindowPos(hChilddDlg, 0, rect.left, rect.top, 0, 0, SWP_NOACTIVATE | SWP_NOSIZE | SWP_NOZORDER);
ShowWindow(hChilddDlg, SW_SHOWNA);
}
return TRUE;
}
// ...
With this I was able to use the DS_CONTROL flag and tab cycle between controls.