Callback not firing on edit control - c

Question

I'm trying to attach a callback event handler to a windows control. My code is below:
URLInput.c
#include <windows.h>
#define ID_EDITCHILD 100
LRESULT CALLBACK URLInputWndProc(
HWND hwnd,
UINT uMsg,
WPARAM wParam,
LPARAM lParam)
{
switch (uMsg) // Breakpoint set here never fires
{
...
default:
return DefWindowProc(hwnd, uMsg, wParam, lParam);
}
}
HWND URLInput(HWND hwnd)
{
HINSTANCE hInstance = GetModuleHandle(NULL);
WNDCLASSW wc = { 0 };
wc.lpszClassName = L"Edit Control";
wc.lpfnWndProc = URLInputWndProc;
wc.hInstance = hInstance;
RegisterClassW(&wc);
hwnd = CreateWindowExW(
0,
L"EDIT",
NULL,
WS_CHILD | WS_VISIBLE | ES_LEFT | ES_AUTOVSCROLL,
0,
0,
100,
100,
hwnd,
(HMENU) ID_EDITCHILD,
(HINSTANCE) GetWindowLong(hwnd, GWL_HINSTANCE),
NULL
);
if (hwnd == NULL) {
return 0;
}
return hwnd;
}
In main.c I call like so:
INT WINAPI WinMain(
HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nShowCmd)
{
...
URLInputHwnd = URLInput(hwnd);
...
It renders fine. But, if I set a breakpoint on line 11 switch(uMsg) it never breaks. I'm expecting it to break when the window is created for example. Or, when entering text into the input. But this doesn't happen.
I've checked the MSDN documentation, although I can't find anything on using WNDCLASS with controls.
Any ideas where I'm going wrong?

Answer 1

Thanks to #Thomas for help in the comments. I solved my problem subclassing the created component.
URLInput.c
#include <windows.h>
#define ID_EDITCHILD 100
static WNDPROC oldURLInputProc = 0;
LRESULT CALLBACK URLInputWndProc(
HWND hwnd,
UINT uMsg,
WPARAM wParam,
LPARAM lParam)
{
switch (uMsg)
{
/* Do something with messages */
}
return CallWindowProc(oldURLInputProc, hwnd, uMsg, wParam, lParam);
}
HWND URLInput(HWND hwnd)
{
return CreateWindowExW(
0,
L"EDIT",
NULL,
WS_CHILD | WS_VISIBLE | ES_LEFT | ES_AUTOVSCROLL,
0,
0,
100,
100,
hwnd,
(HMENU) ID_EDITCHILD,
(HINSTANCE) GetWindowLong(hwnd, GWL_HINSTANCE),
NULL
);
}
void setOldURLInputProc(WNDPROC wndProc)
{
oldURLInputProc = wndProc;
}
And in main.c:
URLInputHwnd = URLInput(hwnd);
/* Error checking */
setOldURLInputProc((WNDPROC)SetWindowLongPtr (URLInputHwnd, GWLP_WNDPROC, (LONG_PTR)URLInputWndProc));
The Microsoft documentation helped: https://learn.microsoft.com/en-us/windows/desktop/controls/subclassing-overview
Everything works fine.