Show tooltip on invalid input in edit control

See more:

C++

WinAPI

I have subclassed edit control to accept only floating numbers. I would like to pop a tooltip when user makes an invalid input. The behavior I target is like the one edit control with ES_NUMBER has, please see this[^].

So far I was able to implement tracking tooltip and display it when user makes invalid input.

However, the tooltip is misplaced. I have tried to use ScreenToClient and ClientToScreen to fix this but have failed.

Here are the instructions for creating SCCE :

1) Create default Win32 project in Visual Studio.

2) Add the following includes in your stdafx.h, just under #include <windows.h> :

#include <windowsx.h>
#include <commctrl.h>

#pragma comment( lib, "comctl32.lib")

#pragma comment(linker, \
    "\"/manifestdependency:type='Win32' "\
    "name='Microsoft.Windows.Common-Controls' "\
    "version='6.0.0.0' "\
    "processorArchitecture='*' "\
    "publicKeyToken='6595b64144ccf1df' "\
    "language='*'\"")

3) Add these global variables:

HWND g_hwndTT;<br />
TOOLINFO g_ti;

4) Here is a simple subclass procedure for edit controls ( just for testing purposes ) :

LRESULT CALLBACK EditSubProc ( HWND hwnd, UINT message, 
    WPARAM wParam, LPARAM lParam, 
    UINT_PTR uIdSubclass, DWORD_PTR dwRefData )
{
    switch (message)
    {
    case WM_CHAR:
        {
            POINT pt;
            if( ! isdigit( wParam ) )  // if not a number pop a tooltip!
            {
                if (GetCaretPos(&pt))  // here comes the problem
                {
                    // coordinates are not good, so tooltip is misplaced
                    ClientToScreen( hwnd, &pt );
                    
                    /************************* EDIT : ****************************/
                    /******** After I delete this line x-coordinate is OK ********/
                    /*** y-coordinate could be a little lower, but is still OK ***/
                    /*************************************************************/
                    ScreenToClient( GetParent(hwnd), &pt );

                    SendMessage(g_hwndTT, TTM_TRACKACTIVATE, 
                        TRUE, (LPARAM)&g_ti);
                    SendMessage(g_hwndTT, TTM_TRACKPOSITION, 
                        0, MAKELPARAM(pt.x, pt.y));
                }
                return FALSE;
            }
            else
            {
                SendMessage(g_hwndTT, TTM_TRACKACTIVATE, 
                    FALSE, (LPARAM)&g_ti);
                return ::DefSubclassProc( hwnd, message, wParam, lParam );
            }
        }
        break;
    case WM_NCDESTROY:
        ::RemoveWindowSubclass( hwnd, EditSubProc, 0 );
        return DefSubclassProc( hwnd, message, wParam, lParam);
        break;
    }
    return DefSubclassProc( hwnd, message, wParam, lParam);
} 

5) Add the following WM_CREATE handler :

case WM_CREATE:
    {
        HWND hEdit = CreateWindowEx( 0, L"EDIT", L"edit", WS_CHILD | WS_VISIBLE |
            WS_BORDER | ES_CENTER, 150, 150, 100, 30, hWnd, (HMENU)1000, hInst, 0 );

        // try with tooltip
        g_hwndTT = CreateWindow(TOOLTIPS_CLASS, NULL,
            WS_POPUP | TTS_ALWAYSTIP | TTS_BALLOON,
            0, 0, 0, 0, hWnd, NULL, hInst, NULL);

        if( !g_hwndTT )
            MessageBeep(0);  // just to signal error somehow

        g_ti.cbSize = sizeof(TOOLINFO);
        g_ti.uFlags = TTF_TRACK | TTF_ABSOLUTE;
        g_ti.hwnd = hWnd;
        g_ti.hinst = hInst;
        g_ti.lpszText = TEXT("Hi there");

        if( ! SendMessage(g_hwndTT, TTM_ADDTOOL, 0, (LPARAM)&g_ti) )
            MessageBeep(0);  // just to have some error signal

        // subclass edit control
        SetWindowSubclass( hEdit, EditSubProc, 0, 0 );
    }
    return 0L;  

6) Initialize common controls in MyRegisterClass ( before return statement ) :

// initialize common controls
INITCOMMONCONTROLSEX iccex;
iccex.dwSize = sizeof(INITCOMMONCONTROLSEX);
iccex.dwICC = ICC_BAR_CLASSES | ICC_WIN95_CLASSES | 
    ICC_TAB_CLASSES | ICC_TREEVIEW_CLASSES | ICC_STANDARD_CLASSES ;

if( !InitCommonControlsEx(&iccex) ) 
    MessageBeep(0);   // signal error 

That's it, for the SSCCE.

My questions are following :

1. How can I properly position tooltip in my main window? How should I manipulate with caret coordinates?

2. Is there a way for tooltip handle and toolinfo structure to not be global?

Thank you for your time.

Best regards.

EDIT #1:

I have managed to achieve quite an improvement by deleting ScreenToClient call in the subclass procedure. The x-coordinate is good, y-coordinate could be slightly lower. I still would like to remove global variables somehow...

EDIT #2:

I was able to adjust y-coordinate by using EM_GETRECT[^] message and setting y-coordinate to the bottom of the formatting rectangle:

RECT rcClientRect;
Edit_GetRect( hwnd, &rcClientRect );
pt.y = rcClient.bottom;

Now the end-result is much better. All that is left is to remove global variables...

EDIT #3:

It seems that I have cracked it! The solution is in EM_SHOWBALLOONTIP and EM_HIDEBALLOONTIP messages! Tooltip is placed at the caret position, ballon shape is the same as the one on the picture, and it auto-dismisses itself properly. And the best thing is that I do not need global variables!

Here is my subclass procedure snippet:

case WM_CHAR:
    {
        // whatever... This condition is for testing purpose only
        if( ! IsCharAlpha( wParam ) && IsCharAlphaNumeric( wParam ) )
        {
            SendMessage(hwnd, EM_HIDEBALLOONTIP, 0, 0);
            return ::DefSubclassProc( hwnd, message, wParam, lParam );
        }
        else
        {
            EDITBALLOONTIP ebt;

            ebt.cbStruct = sizeof( EDITBALLOONTIP );
            ebt.pszText = L" Tooltip text! ";
            ebt.pszTitle = L" Tooltip title!!! ";
            ebt.ttiIcon = TTI_ERROR_LARGE;    // tooltip icon
				
            SendMessage(hwnd, EM_SHOWBALLOONTIP, 0, (LPARAM)&ebt);
       
            return FALSE;
        }
     }
     break;