Child Windows and Messages

Below is my main message loop. I have created an Edit window as a child window of the main window. All I want to do is to be able to catch the keystrokes of the edit window (child window), but I cannot seem to figure out where to place the WM_KEYDOWN case. I have used spy++ to see the messages, and I know the WM_KEYDOWN, WM_CHAR, and WM_KEYUP messages are being fired, but I do not know where to put my message catcher. Please help me! Thanks!


LRESULT CALLBACK WndProc(HWND hWnd, UINT iMsg, WPARAM wParam, LPARAM lParam)
{
static HWND hwndEdit;
char buffer[20];
switch(iMsg)
{
case WM_CREATE:
{
hwndEdit = CreateWindow(TEXT("edit"), NULL, WS_CHILD | ES_WANTRETURN | WS_VISIBLE |
ES_MULTILINE | ES_AUTOVSCROLL | WS_VSCROLL, 0, 0, 0, 0,
hWnd, NULL, pWin->hInstance, NULL);
break;
}

case WM_SETFOCUS:
SetFocus (hwndEdit);
return 0;

case WM_SIZE:
MoveWindow(hwndEdit, 0, 0, LOWORD(lParam), HIWORD(lParam), TRUE);
return 0;

case WM_COMMAND:
{
//SetWindowText(hWnd, _itoa(LOWORD(wParam), buffer, 10));
switch (LOWORD(wParam))
{
case VK_RETURN:
//MessageBox(NULL, _itoa(LOWORD(wParam), buffer, 10), TEXT("Command"), MB_OK);
break;
}

return 0;
}

case WM_KEYDOWN:
{
SetWindowText(hWnd, TEXT("Sucker"));

switch (wParam)
{
case VK_RETURN:
MessageBox(NULL, _itoa(LOWORD(wParam), buffer, 10), TEXT("Command"), MB_OK);
break;
}
}

case WM_CHAR:
{
SetWindowText(hWnd, TEXT("Loser"));

// switch (wParam)
// {
// case VK_RETURN:
// MessageBox(NULL, _itoa(LOWORD(wParam), buffer, 10), TEXT("Command"), MB_OK);
// break;
// }
}

case WM_PAINT:
{
PAINTSTRUCT ps;
HDC hDC = BeginPaint(hWnd, &ps);

EndPaint(hWnd, &ps);
break;
}

case WM_DESTROY:
PostQuitMessage(0);
return 0;
}


return DefWindowProc(hWnd, iMsg, wParam, lParam);

}

To capture the messages like WM_KEYDOWN being sent to the edit control you must subclass the edit control. Try doing a board search on this because a few months ago I did a similiar subclass of an edit.

- Sean

I tried to subclass the edit control, and i can't even get my edit control to appear on the screen. I was just trying the minimum to see how it would work, and it just doesnt seem to work. What am I doing wrong? There is the header file that I made:

#include <afxwin.h>

class myEdit : public CEdit
{
public:
myEdit();
virtual ~myEdit();

};

Is there anything else that I need to do do subclass that control? I was just going to use all of CEdit's builtin functions, so I did not override them.

Assuming CEdit is an mfc class, just use the class wizard thingy with msvc to insert any message handler you need.

I tried that, and I didn't really want to use MFC. The little wizard thingy I dont really like, I want to have complete control over my code. I cannot stand generated code.

You cannot see the window because you sized it to zero ;)

In the main message loop, you can check if a WM_KEYDOWN message or WM_CHAR message is generated. If so, SendMessage right then and there to the child.

By subclassing what is meant is not C++ classes, but the act of setting one of several internal data structures of a given window using GetWindowLong(HWND hwnd, int which) and SetWindowLong(HWND hwnd, int which, long what). The variable GWL_USERDATA is typically used for the 'which' parameter, and the HWND or a pointer to a class instance for the 'what' parameter for the second function.

I change the size of my window in WM_SIZE, that way if the user resizes the window, the entire window will be resized as well.

When I check for WM_KEYDOWN or WM_CHAR in the main message loop, they are never getting called. I don't know how to trap them or catch them. Why are they not getting to my main message loop?

How would you use the GetWindowLong() and SetWindowLong()?

As sean345 suggested earlier, search the windows board as there have been numerous examples/discussions of windows subclassing before (ie using GetWindowLong() and SetWindowLong() ).

while(GetMessage(&messages, NULL, 0, 0) > 0)
{
DispatchMessage(&messages);

TranslateMessage(&messages);

if(messages.message == WM_KEYDOWN)
SendMessage(hEdit, messages.message, messages.wParam, messages.lParam);
}
}


Does it look something like that?

When you create a child window you should cast the HMENU param as the control ID (not NULL). Use 30,000 + to avoid any conflicts with the resouce editor (or check its last int ID allocation in resource.h).

ie

Code:

---

#define    IDC_EDIT_1      30001
hwndEdit = CreateWindow(TEXT("edit"), NULL,
WS_CHILD | ES_WANTRETURN | WS_VISIBLE | ES_MULTILINE | ES_AUTOVSCROLL | WS_VSCROLL,
 0, 0, 0, 0, hWnd, (HMENU)IDC_EDIT_1, pWin->hInstance, NULL);

---

then you can use IDC_EDIT_1 as a case in the WM_COMMAND switch and look for EN_CHANGE msg's.

ie

Code:

---

case IDC_EDIT_1:
  if (EN_CHANGE == HIWORD(wParam))
      GetDlgItemText(hWndEdit, IDC_EDIT_1, sBuffer, sizeof(sBuffer) );

---

//edited to try and make it more readable

Thanks for all of your help!! I looked again for the GetWindowLong() and SetWindowLong() posts on the board, and I found an example with code of what I needed to do!

DefEditProc = (WNDPROC)GetWindowLong(hwndEdit, GWL_WNDPROC);
SetWindowLong(hwndEdit, GWL_WNDPROC, (LONG)EditProc);



LRESULT CALLBACK EditProc(HWND hWnd,UINT message,WPARAM wParam,LPARAM lParam)
{
char lpszBuffer[20];

switch(message)
{
case WM_COMMAND:
{
case WM_KEYDOWN:
switch(wParam)
{
case VK_RETURN:
{
SetWindowText(pWin->hWnd, "Here");
break;
}

default:
{
SetWindowText(pWin->hWnd, "Socket Example");
break;
}
}
}


default: //Send all messages not processed to default edit proc
return CallWindowProc(DefEditProc,hWnd,message,
wParam,lParam);
}
}

This works exactly as I wanted it to!! Thanks for all of your help!