Backspace is pressed

[abdul]

How do I know when the Backspace is pressed in a combobox?

[kedaman]

you should get a WM_KEYDOWN 8

[abdul]

Yes I should, but I is a combobox so I don't get that message. I may need to subclass it but I don't know.

[kedaman]

yeah, that would do

[Vlatko]

What do you mean you don't know how to subclass it. It is not VB.
Just handle that message in the WindowProc.

[Megatron]

Try this:

Add these to your globals

LRESULT CALLBACK ComboBoxProc(HWND, UINT, WPARAM, LPARAM); 		
WNDPROC wOldProc;

Add these to the WM_CREATE and WM_CLOSE events of your main WinProc.

case WM_CREATE: 
{
	hCbo = CreateWindowEx(NULL, "ComboBox", NULL, CBS_DROPDOWNLIST | WS_CHILD | WS_VISIBLE, 32, 32, 128, 128, hWnd, NULL,gInst,NULL);
	SendMessage(hCbo, CB_ADDSTRING, 0, (LPARAM) "Zero");
	SendMessage(hCbo, CB_ADDSTRING, 0, (LPARAM) "One");
	SendMessage(hCbo, CB_ADDSTRING, 0, (LPARAM) "Two");
                // Subclass it
	wOldProc = (WNDPROC)SetWindowLong(hCbo, GWL_WNDPROC, (LONG) &ComboBoxProc);
	return 0;
}
case WM_CLOSE:
	SetWindowLong(hCbo, GWL_WNDPROC, (LONG)wOldProc);
	DestroyWindow(hWnd);
	return 0;

This will be your ComBox procedure:

LRESULT CALLBACK ComboBoxProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
	if( (uMsg == WM_KEYDOWN) && (wParam == 8) )
	{
		// Add code here
		MessageBox(NULL, "Backspace pressed", NULL, NULL);
	}

	return CallWindowProc(wOldProc, hWnd, uMsg, wParam, lParam);
}

[Megatron]

Originally posted by Vlatko
What do you mean you don't know how to subclass it. It is not VB.
Just handle that message in the WindowProc.

No, you can't capture the messages of the combobox from the window procedure of the parent.

[abdul]

Thanks megatron. I think I was doing some think wrong when handling the "WM_KEYDOWN" message after subclassing.
It is almost autocomplete now but there is just one more problem:

First look at the image

I have some words in the combobox like "C:\", "C:\windows". When I type "C", it completes with the mathcing word which is "C:\", and then it heighlights ":\" as it does in the other autocomplete comboboxes.

Now the problem is that I can't move the caret using the left/right arrow keys...you know

Here is the code I am using in the CB_EDITUPDATE message that actually completes the word:

           char edtext[2];
           USHORT theindex;
           
        case CBN_EDITCHANGE:
            if(!isback)
            {
                GetWindowText(cbhwnd, edtext, GetWindowTextLength(cbhwnd) + 1);
                if(SendMessage(cbhwnd, CB_FINDSTRING, (WPARAM)-1, (LPARAM)(LPCSTR)edtext) != CB_ERR)
                {
                    theindex = GetWindowTextLength(cbhwnd);
                    SendMessage(cbhwnd,CB_SETCURSEL, SendMessage(cbhwnd, CB_FINDSTRING, (WPARAM)-1, (LPARAM)(LPCSTR)edtext), 0);
                    SendMessage(cbhwnd, CB_SETEDITSEL,0, MAKELPARAM(theindex,GetWindowTextLength(cbhwnd)));
                }
            }
            
       return TRUE; 

isback is a global variable that tells if the backspace is pressed or not. Here is code that I am using to tell if it is pressed or not using the subclassing technique:

switch(msg)
    {
    case WM_KEYDOWN:
        if(wparam == 8)
        {
            isback = TRUE;
        }
        else
        {
            isback = FALSE;
        }
        return 0;
    } 

So, why can't I move the caret using the arrow keys so that I don't have to type the whole word if it highlights it?

[abdul]

It is ok now. I used the message "WM_KEYUP" instead of "WM_KEYDOWN" and it is all working now

Thanks a lot!

[abdul]

Ohhh NO!

I got the caret thingy working but then I lots the backspace handling. How do I get both at a time?

I am using the same code except that I am handling the "WM_KEYUP" message instead of "WM_KEYDOWN"

[Vlatko]

No, you can't capture the messages of the combobox from the window procedure of the parent.

I know that Megatron. I didn't mean the WindowProc of the parent but the combobox's own procedure.

[abdul]

this thread is stopped Come on guys, it is not finished yet. I still have the above problem

[TadaTensai]

For some reason, my subclassing isnt working right. I'm trying to do this too, but for some reason, it isnt working. Code:

#include <windows.h>

const char g_szClassName[] = "myWindowClass";

#define IDC_COMBOBOX	9001
#define FixFonts(control) {SendDlgItemMessage(hwnd, control, WM_SETFONT, (WPARAM)GetStockObject(DEFAULT_GUI_FONT), MAKELPARAM(TRUE, 0));}

HINSTANCE hInstance;
WNDPROC wOldProc;

LRESULT CALLBACK ComboBoxProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
	switch(uMsg)
	{
	case WM_KEYUP:
		MessageBox(hwnd,"","",0);
		break;
	default:
		return(DefWindowProc(hwnd,uMsg,wParam,lParam));
	}
	return(0);
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch(msg)
    {
        case WM_CLOSE:
			SetWindowLong(GetDlgItem(hwnd,IDC_COMBOBOX), GWL_WNDPROC, (LONG)wOldProc);
            DestroyWindow(hwnd);
			break;
        case WM_DESTROY:
            PostQuitMessage(0);
			break;
		case WM_CREATE:
			CreateWindow("COMBOBOX","",WS_CHILD | WS_VISIBLE | CBS_DROPDOWN,0,0,100,100,hwnd,(HMENU)IDC_COMBOBOX,hInstance,0);
			FixFonts(IDC_COMBOBOX);
			SendMessage(GetDlgItem(hwnd,IDC_COMBOBOX), CB_ADDSTRING, 0, (LPARAM) "Zero");
			SendMessage(GetDlgItem(hwnd,IDC_COMBOBOX), CB_ADDSTRING, 0, (LPARAM) "One");
			SendMessage(GetDlgItem(hwnd,IDC_COMBOBOX), CB_ADDSTRING, 0, (LPARAM) "Two");
			wOldProc = (WNDPROC)SetWindowLong(GetDlgItem(hwnd,IDC_COMBOBOX), GWL_WNDPROC, (LONG) &ComboBoxProc);
			SetWindowLong(GetDlgItem(hwnd,IDC_COMBOBOX), GWL_STYLE	, WS_CHILD | WS_VISIBLE | CBS_DROPDOWN);
			break;
        default:
            return DefWindowProc(hwnd, msg, wParam, lParam);
    }
    return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
    LPSTR lpCmdLine, int nCmdShow)
{
    WNDCLASSEX wc;
    HWND hwnd;
    MSG Msg;
    ::hInstance=hInstance;
    wc.cbSize        = sizeof(WNDCLASSEX);
    wc.style         = 0;
    wc.lpfnWndProc   = WndProc;
    wc.cbClsExtra    = 0;
    wc.cbWndExtra    = 0;
    wc.hInstance     = hInstance;
    wc.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_BTNFACE+1);
    wc.lpszMenuName  = NULL;
    wc.lpszClassName = g_szClassName;
    wc.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);

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

    hwnd = CreateWindowEx(
        0,
        g_szClassName,
        "Autocomplete Combobox Test",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, 240, 120,
        NULL, NULL, hInstance, NULL);

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

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

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

Any ideas?

[abdul]

Try this code. I have put the comments on which line is added or changed:

#include <windows.h>

const char g_szClassName[] = "myWindowClass";

#define IDC_COMBOBOX    9001
#define FixFonts(control) {SendDlgItemMessage(hwnd, control, WM_SETFONT, (WPARAM)GetStockObject(DEFAULT_GUI_FONT), MAKELPARAM(TRUE, 0));}

HINSTANCE hInstance;
WNDPROC wOldProc;
//A new declaration for the Handle of the editbox in the combobox
HWND edhwnd;

LRESULT CALLBACK ComboBoxProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch(uMsg)
    {
    case WM_KEYUP:
        MessageBox(hwnd,"","",0);
        break;
    default:
        return CallWindowProc(wOldProc, hwnd,uMsg,wParam,lParam); //Changed to CallWindowProc
    }
    return(0);
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch(msg)
    {
        case WM_CLOSE:
            //This is also changed. Changed the handle to editbox handle
            SetWindowLong(edhwnd, GWL_WNDPROC, (LONG)wOldProc);
            DestroyWindow(hwnd);
            break;
        case WM_DESTROY:
            PostQuitMessage(0);
            break;
        case WM_CREATE:
            CreateWindow("COMBOBOX","",WS_CHILD | WS_VISIBLE | CBS_DROPDOWN,0,0,100,100,hwnd,(HMENU)IDC_COMBOBOX,hInstance,0);
            FixFonts(IDC_COMBOBOX);
            SendMessage(GetDlgItem(hwnd,IDC_COMBOBOX), CB_ADDSTRING, 0, (LPARAM) "Zero");
            SendMessage(GetDlgItem(hwnd,IDC_COMBOBOX), CB_ADDSTRING, 0, (LPARAM) "One");
            SendMessage(GetDlgItem(hwnd,IDC_COMBOBOX), CB_ADDSTRING, 0, (LPARAM) "Two");
            //New Stuff Added here
            //We get the handle of the editbox in the combobox because that
            //is the window in which WM_KEYUP message occurs
            POINT pt;
            pt.x = 3;
            pt.y = 3;
            edhwnd = ChildWindowFromPoint(GetDlgItem(hwnd,IDC_COMBOBOX), pt);
            //-----------------------------------------------------------
            //Now we use the editbox handle - not the combobox handle
            wOldProc = (WNDPROC)SetWindowLong(edhwnd, GWL_WNDPROC, (LONG) &ComboBoxProc);
            SetWindowLong(GetDlgItem(hwnd,IDC_COMBOBOX), GWL_STYLE    , GetWindowLong(GetDlgItem(hwnd,IDC_COMBOBOX), GWL_STYLE) | WS_CHILD | WS_VISIBLE | CBS_DROPDOWN); //Changed this line
            break;
        default:
            return DefWindowProc(hwnd, msg, wParam, lParam);
    }
    return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
    LPSTR lpCmdLine, int nCmdShow)
{
    WNDCLASSEX wc;
    HWND hwnd;
    MSG Msg;
    ::hInstance=hInstance;
    wc.cbSize        = sizeof(WNDCLASSEX);
    wc.style         = 0;
    wc.lpfnWndProc   = WndProc;
    wc.cbClsExtra    = 0;
    wc.cbWndExtra    = 0;
    wc.hInstance     = hInstance;
    wc.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_BTNFACE+1);
    wc.lpszMenuName  = NULL;
    wc.lpszClassName = g_szClassName;
    wc.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);

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

    hwnd = CreateWindowEx(
        0,
        g_szClassName,
        "Autocomplete Combobox Test",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, 240, 120,
        NULL, NULL, hInstance, NULL);

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

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

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