Sub-classing an edit control (in full window, NOT dialogue) - c++

Question

I've been trying to figure this out for ages and I'm absolutely stumped! I'm trying to subclass an edit control so I can capture when the enter key is pressed.
I've seen lots of other posts about sub-classing with snippets of code to add to do it, but I can't seem to implement it into my application. I apologize if I'm making a stupid mistake, but I simply cannot figure this out.
I know this code is poorly written and has no error checking, but I wanted to post as little code as possible to convey the problem.
#include <Windows.h>
#include <wchar.h>
HWND editHWND;
WNDPROC wpOrigEditProc;
LRESULT APIENTRY EditSubclassProc(HWND hwnd,UINT uMsg,WPARAM wParam, LPARAM lParam)
{
if (uMsg == WM_CHAR)
{
//do my stuff
}
return CallWindowProc(wpOrigEditProc, hwnd, uMsg, wParam, lParam);
}
LRESULT WINAPI MsgProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
switch( msg )
{
case WM_CREATE:
wpOrigEditProc = (WNDPROC) SetWindowLong(editHWND,GWL_WNDPROC, (LONG) EditSubclassProc);
SetWindowLong(editHWND, GWL_WNDPROC,(LONG) wpOrigEditProc);
break;
case WM_DESTROY:
PostQuitMessage( 0 );
return 0;
}
return DefWindowProc( hWnd, msg, wParam, lParam );
}
int WINAPI wWinMain( HINSTANCE hInst,HINSTANCE,LPWSTR,INT )
{
WNDCLASSEX wc = { sizeof( WNDCLASSEX ),CS_CLASSDC,MsgProc,0,0,
GetModuleHandle( NULL ),NULL,NULL,NULL,NULL,
L"My Window",NULL };
RegisterClassEx( &wc );
HWND hWnd = CreateWindowW( L"My Window",L"test application",
WS_OVERLAPPEDWINDOW,100,100,800,600,
NULL,NULL,wc.hInstance,NULL );
editHWND = CreateWindow( L"edit",L"hi there",WS_VISIBLE | WS_CHILD | WS_BORDER,100,100,300,50,hWnd,(HMENU)17,0,0);
ShowWindow( hWnd,SW_SHOWDEFAULT );
MSG msg;
ZeroMemory( &msg,sizeof( msg ) );
while( msg.message != WM_QUIT )
{
if( PeekMessage( &msg,NULL,0,0,PM_REMOVE ) )
{
TranslateMessage( &msg );
DispatchMessage( &msg );
}
}
UnregisterClass( L"My Window",wc.hInstance );
return 0;
}

Answer 1

MsgProc() is the window procedure for the "My Window" window. When you are processing the WM_CREATE message, you are processing that window's creation, before the second CreateWindow() has been called to create the Edit window.
Worse, even if you were subclassing the Edit window correctly, you are removing the subclass immediately after setting it. So EditSubClassProc() would never have a change to be called anyway.
Since you are not defining a custom window procedure for the Edit window at the time it is being created, you cannot use a WM_CREATE message to subclass the Edit window (unless you use a message hook, which is overkill in this situation). Just call SetWindowLong() after CreateWindow() has exited.
Try this:
#include <Windows.h>
#include <wchar.h>
HWND editHWND = NULL;
WNDPROC wpOrigEditProc = NULL;
LRESULT APIENTRY EditSubclassProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
if (uMsg == WM_CHAR)
{
//do my stuff
}
return CallWindowProc(wpOrigEditProc, hwnd, uMsg, wParam, lParam);
}
LRESULT WINAPI MsgProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
switch( msg )
{
case WM_CLOSE:
DestroyWindow(hWnd);
return 0;
case WM_DESTROY:
PostQuitMessage( 0 );
return 0;
}
return DefWindowProc( hWnd, msg, wParam, lParam );
}
int WINAPI wWinMain( HINSTANCE hInst,HINSTANCE,LPWSTR,INT )
{
WNDCLASSEX wc = { sizeof( WNDCLASSEX ),CS_CLASSDC,MsgProc,0,0,
GetModuleHandle( NULL ),NULL,NULL,NULL,NULL,
TEXT("My Window"),NULL };
RegisterClassEx( &wc );
HWND hWnd = CreateWindowW( TEXT("My Window"),TEXT("test application"),
WS_OVERLAPPEDWINDOW,100,100,800,600,
NULL,NULL,wc.hInstance,NULL );
editHWND = CreateWindow( TEXT("edit"),TEXT("hi there"),WS_VISIBLE | WS_CHILD | WS_BORDER,100,100,300,50,hWnd,(HMENU)17,0,0);
wpOrigEditProc = (WNDPROC) SetWindowLongPtr(editHWND, GWL_WNDPROC, (LONG_PTR) EditSubclassProc);
ShowWindow( hWnd, SW_SHOWDEFAULT );
MSG msg;
while ( GetMessage( &msg,NULL,0,0 ) > 0 )
{
TranslateMessage( &msg );
DispatchMessage( &msg );
}
UnregisterClass( TEXT("My Window"),wc.hInstance );
return 0;
}
With that said, another way to subclass a window is to use SetWindowSubclass() instead:
#include <Windows.h>
#include <wchar.h>
HWND editHWND = NULL;
LRESULT CALLBACK EditSubclassProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam, UINT_PTR uIdSubclass, DWORD_PTR dwRefData)
{
if (uMsg == WM_CHAR)
{
//do my stuff
}
return DefSubclassProc(hWnd, uMsg, wParam, lParam);
}
LRESULT WINAPI MsgProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
switch( msg )
{
case WM_CLOSE:
DestroyWindow(hWnd);
return 0;
case WM_DESTROY:
PostQuitMessage( 0 );
return 0;
}
return DefWindowProc( hWnd, msg, wParam, lParam );
}
int WINAPI wWinMain( HINSTANCE hInst,HINSTANCE,LPWSTR,INT )
{
WNDCLASSEX wc = { sizeof( WNDCLASSEX ),CS_CLASSDC,MsgProc,0,0,
GetModuleHandle( NULL ),NULL,NULL,NULL,NULL,
TEXT("My Window"),NULL };
RegisterClassEx( &wc );
HWND hWnd = CreateWindowW( TEXT("My Window"),TEXT("test application"),
WS_OVERLAPPEDWINDOW,100,100,800,600,
NULL,NULL,wc.hInstance,NULL );
editHWND = CreateWindow( TEXT("edit"),TEXT("hi there"),WS_VISIBLE | WS_CHILD | WS_BORDER,100,100,300,50,hWnd,(HMENU)17,0,0);
SetWindowSubclass(editWND, EditSubclassProc, 0, 0);
ShowWindow( hWnd, SW_SHOWDEFAULT );
MSG msg;
while ( GetMessage( &msg,NULL,0,0 ) > 0 )
{
TranslateMessage( &msg );
DispatchMessage( &msg );
}
UnregisterClass( TEXT("My Window"),wc.hInstance );
return 0;
}