How do I detect a WM_KEYDOWN on child window? - winapi

Question

For a standard control like button, edit, etc I can subclass it but how is this done for a child window(I'm using as a container)? I know the WM_KEYDOWN is sent to the parent window but I couldn't get it directly from the respective child window. I've tried subclassing it(not sure if this does make sense since it's a window and has its own window procedure already in the WNDCLASSW.lpfnWndProc member) but this subprocedure didn't get a WM_KEYDOWN message anyway. I can get the control's hwnd from the cursor position (I need to consider keyboard focus too) by using GetCursorPos() and WindowFromPoint() like below but I feel it's hacky. What's the proper way to do this?
currently it look like this:
case WM_KEYUP:
case WM_KEYDOWN:
{
POINT p;
if(GetCursorPos(&p))
{
HWND control = WindowFromPoint(p);
if(control)
{
// just testing it
int len = GetWindowTextLength(control);
wchar_t buffer[len + 1];
GetWindowText(control, buffer, sizeof(buffer));
MessageBox(NULL, buffer, L"", MB_OK);
}
}
}
break;
the window look like this:
the goal is catch the WM_KEYDOWN on the respective window where the user typed something, then call a function to deal with this event, like window1_onKeyDown(), window2_onKeyDown() and such.
Here's full code:
#pragma comment(lib, "user32.lib")
#pragma comment(lib, "Comctl32.lib")
#pragma comment(lib, "Gdi32.lib")
#define WIN32_LEAN_AND_MEAN
#define UNICODE
#define _UNICODE
#include <windows.h>
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK WndProc1(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);
LRESULT CALLBACK WndProc2(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);
void createWindow1(HWND);
void createWindow2(HWND);
HBRUSH hBrush1, hBrush2;
int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
PWSTR lpCmdLine, int nCmdShow) {
MSG msg;
WNDCLASSW wc = {0};
wc.lpszClassName = L"my window";
wc.hInstance = hInstance;
wc.hbrBackground = GetSysColorBrush(COLOR_3DFACE);
wc.lpfnWndProc = WndProc;
wc.hCursor = LoadCursor(0, IDC_ARROW);
hBrush1 = CreateSolidBrush(RGB(173, 164, 237));
hBrush2 = CreateSolidBrush(RGB(171, 171, 171));
RegisterClassW(&wc);
CreateWindowW(wc.lpszClassName, L"window",
WS_OVERLAPPEDWINDOW | WS_VISIBLE,
100, 100, 330, 270, NULL, 0, hInstance, 0);
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
DeleteObject(hBrush1);
DeleteObject(hBrush2);
return (int) msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg,
WPARAM wParam, LPARAM lParam) {
switch(msg)
{
case WM_CREATE:
createWindow1(hwnd);
createWindow2(hwnd);
break;
case WM_KEYUP:
case WM_KEYDOWN:
{
POINT p;
if(GetCursorPos(&p))
{
HWND control = WindowFromPoint(p);
if(control)
{
int len = GetWindowTextLength(control);
wchar_t buffer[len + 1];
GetWindowText(control, buffer, sizeof(buffer));
MessageBox(NULL, buffer, L"", MB_OK);
}
}
}
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
}
return DefWindowProcW(hwnd, msg, wParam, lParam);
}
void createWindow1(HWND hOwner)
{
WNDCLASSW wc = {0};
wc.lpszClassName = L"window2";
wc.hInstance = NULL;
wc.hbrBackground = hBrush1;
wc.lpfnWndProc = WndProc1;
wc.hCursor = LoadCursor(0, IDC_ARROW);
RegisterClassW(&wc);
CreateWindowW(wc.lpszClassName, L"window2",
WS_VISIBLE | WS_TABSTOP | WS_CHILD | WS_EX_CONTROLPARENT,
5, 5, 200, 100,
hOwner, 0, NULL, 0);
}
void createWindow2(HWND hOwner)
{
WNDCLASSW wc = {0};
wc.lpszClassName = L"window3";
wc.hInstance = NULL;
wc.hbrBackground = hBrush2;
wc.lpfnWndProc = WndProc2;
wc.hCursor = LoadCursor(0, IDC_ARROW);
RegisterClassW(&wc);
CreateWindowW(wc.lpszClassName, L"window3",
WS_VISIBLE | WS_TABSTOP | WS_CHILD,
5, 120, 200, 100,
hOwner, 0, NULL, 0);
}
LRESULT CALLBACK WndProc1(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch(msg)
{
case WM_CREATE:
CreateWindow(L"Button", L"Button A",
WS_VISIBLE | WS_TABSTOP | WS_CHILD,
5, 5, 80, 25,
hwnd, 0, NULL, 0);
break;
case WM_KEYUP:
case WM_KEYDOWN:
MessageBox(NULL, L"hello from proc1", L"", MB_OK);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
}
return DefWindowProcW(hwnd, msg, wParam, lParam);
}
LRESULT CALLBACK WndProc2(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch(msg)
{
case WM_CREATE:
CreateWindow(L"Button", L"Button ",
WS_VISIBLE | WS_TABSTOP | WS_CHILD,
5, 5, 80, 25,
hwnd, 0, NULL, 0);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
}
return DefWindowProcW(hwnd, msg, wParam, lParam);
}

Answer 1

You can use SetFocus in the child window.
Some code:
case WM_KEYDOWN:
{
POINT p;
HWND control = GetFocus();
if (control)
{
int len = GetWindowTextLength(control);
wchar_t* buffer = new wchar_t[len + 1];
GetWindowText(control, buffer, len + 1);
MessageBox(NULL, buffer, L"", MB_OK);
}
}
break;
LRESULT CALLBACK WndProc1(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch (msg)
{
case WM_CREATE:
CreateWindow(L"Button", L"Button A",
WS_VISIBLE | WS_TABSTOP | WS_CHILD,
5, 5, 80, 25,
hwnd, 0, NULL, 0);
break;
case WM_LBUTTONDOWN:
SetFocus(hwnd);
break;
case WM_KEYUP:
case WM_KEYDOWN:
MessageBox(NULL, L"hello from proc1", L"", MB_OK);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
}
return DefWindowProcW(hwnd, msg, wParam, lParam);
}
You can also use the current method, and then use PostMessage/SendMessage to forward the WM_KEYDOWN message to the child window:
if (control)
{
int len = GetWindowTextLength(control);
wchar_t* buffer = new wchar_t[len + 1];
GetWindowText(control, buffer, len + 1);
MessageBox(NULL, buffer, L"", MB_OK);
PostMessage(hwnd_child, msg, wParam, lParam);
}