Search code examples
winapidialogwindows-xphook

using hook on OPENFILEW dialog disables resize control

Using this code the resulting dialog box is drawn without ability to be able to be resized by mouse:

#include <windows.h>

static UINT_PTR CALLBACK OFNHookProc (HWND hdlg, UINT uiMsg, WPARAM wParam, LPARAM lParam) {
  return 0;
}

int main() {
  OPENFILENAMEW ofn;
  ZeroMemory(&ofn, sizeof(ofn));
  ofn.lStructSize = sizeof(OPENFILENAMEW);
  ofn.nMaxFile = MAX_PATH;
  ofn.Flags = OFN_EXPLORER | OFN_FILEMUSTEXIST | OFN_ENABLEHOOK;
  ofn.lpfnHook = OFNHookProc;
  GetOpenFileNameW(&ofn);
  return 0;
}

Removing OFN_ENABLEHOOK shows correct dialog window with resize indicator at bottom right corner. How to make dialog that is user-resizeable and with hook procedure ?

(of course that hook is mock here, only to illustrate the error, no matter what I put inside, of course if it is correct on other matters, result is the same)

Solution

  • You need to include the OFN_ENABLESIZING flag when using OFN_ENABLEHOOK. This is documented behavior:

    OPENFILENAME structure

    OFN_ENABLESIZING
    0x00800000
    Enables the Explorer-style dialog box to be resized using either the mouse or the keyboard. By default, the Explorer-style Open and Save As dialog boxes allow the dialog box to be resized regardless of whether this flag is set. This flag is necessary only if you provide a hook procedure or custom template. The old-style dialog box does not permit resizing.