Thread: Creating an Edit Box (Subclassing)

The code below is my first attempt to create an edit box, i've used three files "SubClassedEditProc.cpp", "subclassing.cpp", and "SubclassedEditProc.h"

BTW these should be .c files, yet struggling to compile C files in VS 2005, get lots of errors.

Subclassing.cpp..

Code:

#include "stdafx.h"
#include <windows.h>

#include "SubclassedEditProc.h"		// we need the 'oldEditProcedure' variable

LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	switch (message)                 
	{
	case WM_CREATE:
		{
			/*
			First we create an edit control...
			*/
			HWND edit = CreateWindowEx (
				WS_EX_ACCEPTFILES,	//	Either set the flag here or call DragAcceptFiles (edit, TRUE); after creating the edit
				TEXT("EDIT"),
				TEXT("You can drag and drop a file here..."),
				WS_VISIBLE | WS_CHILD | WS_BORDER | ES_AUTOHSCROLL | ES_LEFT,
				10, 10,		//	position
				300, 22,	//	size
				hwnd,
				0,			//	no control ID (we don't need it in this example)
				(HINSTANCE)GetModuleHandle (0),
				0
				);

			oldEditProcedure = (WNDPROC)GetWindowLongPtr (edit, GWLP_WNDPROC);			

			SetWindowLongPtr (edit, GWLP_WNDPROC, (LONG_PTR)newEditProcedure);
			break;
		}

	case WM_DESTROY:
		PostQuitMessage (0);
		break;

	default:
		return DefWindowProc (hwnd, message, wParam, lParam);
	}

	return 0;
}

SubClassedEditProc.cpp

Code:

/*
	This is SubclassedEditProc.c
*/
#include "stdafx.h"
#include <ShellAPI.h>

#define WIN32_LEAN_AND_MEAN

#include "SubclassedEditProc.h"

//	the pointer to the edit's old window procedure
//	this will be used to call the old procedure inside the new window procedure
WNDPROC oldEditProcedure = 0;
 
//	the new edit's window procedure prototype
LRESULT CALLBACK newEditProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
 
	switch (message)
	{
		//	This is the message we want to handle...
		case WM_DROPFILES:
		{
			//	Now comes the code that retrieves the dropped file's path...
			//	I guess this is not relevant so you don't struggle understanding it.
			//	Just know that 'buffer' will store the dropped file's path.
			HDROP hDrop = (HDROP)wParam;
			TCHAR buffer[MAX_PATH];
			int nFilesDropped = DragQueryFile (hDrop, 0, buffer, MAX_PATH);
 
			if (nFilesDropped) {
				SetWindowText (hwnd, buffer);
			}
 
			DragFinish (hDrop);
			return 0;
		}
 
		//	The other message are simply forwarded to the old window procedure
		default:
			//	This is just me being too cautious... the 'oldEditProcedure' pointer will never be null if you're careful
			if (oldEditProcedure) {
				//	The CallWindowProc() API is responsible for calling the 'oldEditProcedure', we are not going to just call it directly, see MSDN for details
				return CallWindowProc (oldEditProcedure, hwnd, message, wParam, lParam);
			}
			else {
				//	Your application should never reach this point, because you were supposed to set the 'oldEditProcedure' pointer to point to the old window procedure.
				return DefWindowProc (hwnd, message, wParam, lParam);
			}
	}
}

headerfile...

Code:

/*
	This is SubclassedEditProc.h
*/
 
#ifndef __SUBCLASSED_EDIT_H_INCLUDED__
#define __SUBCLASSED_EDIT_H_INCLUDED__
 
#include <windows.h>
 
//	the pointer to the edit's old window procedure
//	this will be used to call the old procedure inside the new window procedure
extern WNDPROC oldEditProcedure;
 
//	the new edit's window procedure prototype
LRESULT CALLBACK newEditProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);
 
#endif

Problems... Link Error

Code:

 error LNK2019: unresolved external symbol _WinMain@16 referenced in function ___tmainCRTStartup

Not sure whether is looking for WinMain() or main() function????

Originally Posted by Elysia

What errors? Also, it's looking for WinMain, as the linker error says.

Got this code as an example which did not include WinMain()... If i add WinMain in my prog, where do i create a window (or call the CreateWindowEx())? Or could some1 give me a code example on how will WinMain() look like since i'm subclassing.. I know how to do WinMain() but my guesses it will be shorter than usual...

Originally Posted by Elysia

WinMain is no more special than main. It's just a function so you can create your window wherever you want, including WinMain.

I've added WinMain() to get the program to Build... It does build but does not run, obviously am missing something on my WinMain()

Code:

//Main window
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nShowCmd)
{
	InitCommonControls();

        // Missing code....??
	

}

What do i add... Or how do i call newEditProcedure()?

Originally Posted by P4R4N01D

From theForger's Win32 API Programming Tutorial , you will need something like this in WinMain:

Code:

    //Step 1: Registering the Window Class
    WNDCLASSEX wc;
    HWND hwnd;
    MSG Msg;

    wc.cbSize  = sizeof(WNDCLASSEX);
    .....

    if(!RegisterClassEx(&wc))
    {
        MessageBox(NULL, "Window Registration Failed!", "Error!",
            MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    // Step 2: Create the Window
      ...

    if(hwnd == NULL)
    {
        MessageBox(NULL, "Window Creation Failed!", "Error!",
            MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    ShowWindow(hwnd, nCmdShow);
    UpdateWindow(hwnd);

    // Step 3: The Message Loop
    while(GetMessage(&Msg, NULL, 0, 0) > 0)
    {
        TranslateMessage(&Msg);
        DispatchMessage(&Msg);
    }
    return Msg.wParam;
}

But may not apply the same for Subclassing!!!! Which is what am doing...

Originally Posted by P4R4N01D

Whether you are going to subclass a control or not, the WinMain function remains the same (except for controls that are created there).

Here's my attempt..

Code:

//Main window
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nShowCmd)
{
    WNDCLASSEX WndClsEx;
    HWND hwnd;
    MSG Msg;

     WndClsEx.cbSize        = sizeof(WNDCLASSEX);
     WndClsEx.style         = CS_HREDRAW | CS_VREDRAW;
     WndClsEx.lpfnWndProc   = WndProcedure;
     WndClsEx.cbClsExtra    = 0;
     WndClsEx.cbWndExtra    = 0;
     WndClsEx.hIcon		   = LoadIcon(hInstance, MAKEINTRESOURCE(400)); 
     WndClsEx.hCursor	   = LoadCursor(hInstance, MAKEINTRESOURCE(200)); 
     WndClsEx.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
     WndClsEx.lpszMenuName  = NULL;
     WndClsEx.lpszClassName = ClsName;
     WndClsEx.hInstance     = hInstance;
     WndClsEx.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);

    if(!RegisterClassEx(&WndClsEx))
    {
        MessageBox(NULL, "Window Registration Failed!", "Error!",
            MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    ShowWindow(hWnd, nCmdShow);
    UpdateWindow(hWnd);

     while( GetMessage(&Msg, NULL, 0, 0) )
     {
	TranslateMessage(&Msg);
	DispatchMessage(&Msg);
     }

     return 0;
}

In my code above, ShowWindow(hWnd, nCmdShow) expects hWnd of a created window... Since the window is created inside the windows procedure function as below...

Code:

case WM_INITDIALOG:
		{
			HWND edit = CreateWindowEx (
				WS_EX_ACCEPTFILES,	
				TEXT("EDIT"),
				TEXT("You can drag and drop a file here..."),
				WS_VISIBLE | WS_CHILD | WS_BORDER | ES_AUTOHSCROLL | ES_LEFT,
				10, 10,		//	position
				300, 22,	//	size
				hwnd,
				(HMENU)IDC_MY_SUBCLASSED_EDIT,	
				(HINSTANCE)GetModuleHandle (0),
				0
				);

			if(edit == NULL)
			{
				MessageBox(NULL, "Window Creation Failed!", "Error!",
					MB_ICONEXCLAMATION | MB_OK);
				return 0;
			}
			oldEditProcedure = (WNDPROC)GetWindowLongPtr (edit, GWLP_WNDPROC);			

			SetWindowLongPtr (edit, GWLP_WNDPROC, (LONG_PTR)newEditProcedure);
			break;
		}

How does WinMain() receive the handle of the edit window to show it? Or should i declare hWnd or HWND edit globally?

This is the complete program, compiles, runs but no dialog/edit window is created! Oly the main blank window shows... It seems the subclass window is not even called because when i run on Debug mode and run to cursor where window's suppose to be created, program never jumps to there, any faults?

Code:

#include "stdafx.h"
#include <windows.h>
#include <ShellAPI.h>
#include <windowsx.h>
#include <commctrl.h>
#pragma comment( lib, "comctl32.lib" ) 

#define WIN32_LEAN_AND_MEAN
#define IDC_MY_SUBCLASSED_EDIT 2008

const char *ClsName = "SubClassing";
const char *WndName = "Edit Box";
WNDPROC oldEditProcedure = 0;

LRESULT CALLBACK newEditProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);
LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);

//Main window
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nShowCmd)
{
	WNDCLASSEX WndClsEx;
	HWND hWnd;
	MSG Msg;

	WndClsEx.cbSize        = sizeof(WNDCLASSEX);
	WndClsEx.style         = CS_HREDRAW | CS_VREDRAW;
	WndClsEx.lpfnWndProc   = WindowProcedure;
	WndClsEx.cbClsExtra    = 0;
	WndClsEx.cbWndExtra    = 0;
	WndClsEx.hIcon		   = LoadIcon(hInstance, MAKEINTRESOURCE(400)); 
	WndClsEx.hCursor	   = LoadCursor(hInstance, MAKEINTRESOURCE(200)); 
	WndClsEx.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
	WndClsEx.lpszMenuName  = NULL;
	WndClsEx.lpszClassName = ClsName;
	WndClsEx.hInstance     = hInstance;
	WndClsEx.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);

	if(!RegisterClassEx(&WndClsEx))
	{
		MessageBox(NULL, "Window Registration Failed!", "Error!",
			MB_ICONEXCLAMATION | MB_OK);
		return 0;
	}

	// Create the window object
	hWnd = CreateWindowEx(0,
		ClsName,
		WndName,
		WS_OVERLAPPEDWINDOW,
		CW_USEDEFAULT,
		CW_USEDEFAULT,
		CW_USEDEFAULT,
		CW_USEDEFAULT,
		NULL,
		NULL,
		hInstance,
		NULL);

	// Find out if the window was created
	if( !hWnd ) // If the window was not created,
		return FALSE; // stop the application

	ShowWindow(hWnd, nShowCmd);
	UpdateWindow(hWnd);

	while( GetMessage(&Msg, NULL, 0, 0) )
	{
		TranslateMessage(&Msg);
		DispatchMessage(&Msg);
	}

	return 0;
}

LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	switch (message)                 
	{
	case WM_CREATE:
		{
			HWND edit = CreateWindowEx (
				WS_EX_ACCEPTFILES,	
				TEXT("You can drag and drop a file here..."),
				TEXT("Edit/Browse"),
				WS_VISIBLE | WS_CHILD | WS_BORDER | ES_AUTOHSCROLL | ES_LEFT,
				10, 
				10,		//	position
				300, 
				22,	//	size
				hwnd,
				(HMENU)IDC_MY_SUBCLASSED_EDIT,
				(HINSTANCE)GetModuleHandle (0),
				0
				);

			oldEditProcedure = (WNDPROC)GetWindowLongPtr (edit, GWLP_WNDPROC);			
			SetWindowLongPtr (edit, GWLP_WNDPROC, (LONG_PTR)newEditProcedure);
			break;
		}

	case WM_DESTROY:
		PostQuitMessage (0);
		break;

	default:
		return DefWindowProc (hwnd, message, wParam, lParam);
	}

	return 0;
}

LRESULT CALLBACK newEditProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	switch (message)
	{
	case WM_DROPFILES:
		{
			HDROP hDrop = (HDROP)wParam;
			TCHAR buffer[MAX_PATH];
			int nFilesDropped = DragQueryFile (hDrop, 0, buffer, MAX_PATH);

			if (nFilesDropped) {
				SetWindowText (hwnd, buffer);
			}

			DragFinish (hDrop);
			return 0;
		}

	default:
		return DefWindowProc (hwnd, message, wParam, lParam);
	}

	return CallWindowProc (oldEditProcedure, hwnd, message, wParam, lParam);
}