Thread: Windows CALLBACK

Having returned to dabbling in programming after some time, I am writing a simple text editor as refresh exercise.
Using Visual Studio 2019 to produce Windows programme
When I enter a character via the keyboard, WM_CHAR picks it up and displays it, but if I resize the window it is erased from the screen. If I put the TextOut function in WM_PAINT as well it works OK, BUT If I put the TextOut only in WM_PAINT the character is not displayed until the window is resized.
Relevant Code below

Code:

static struct NumEditStructure {    // structure for input fields
    TCHAR StrCha[SLEN];		    // characters in string
    int  StrCou;		    // total number of characters in string
} EditStru, * PtrES;	

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    int wmId, wmEvent;
    int lmId, lmEvent;

    PAINTSTRUCT ps;
    HDC hdc;
    TCHAR greeting[] = _T("Hello, Windows desktop!");

    switch (message){
    case WM_PAINT:                 // message    15
        hdc = BeginPaint(hWnd, &ps);

        // Here your application is laid out.
        // For this introduction, we just print out "Hello, Windows desktop!"
        // in the top left corner.

        hdc = BeginPaint(hWnd, &ps);
        TextOut(hdc,
            5, 5,
            greeting, _tcslen(greeting));

        //       Needed when paint called from ReSize etc
        TextOut(hdc,
            60, 60,
            EditStru.StrCha, _tcslen(EditStru.StrCha));

        EndPaint(hWnd, &ps);
        break;
        
    case WM_CHAR:                 // message VaLUE 0x0102
        hdc = GetDC(hWnd);

        wmId =      LOWORD(wParam);
        wmEvent =   HIWORD(wParam);
        lmId =      LOWORD(lParam);
        lmEvent =   HIWORD(lParam);

        EditStru.StrCha[EditStru.StrCou ] = wmId;
        EditStru.StrCha[EditStru.StrCou+1 ] = 0x00;
        EditStru.StrCou += 1;

//      Needed to display entry at initial entry, before paint called from ReSize etc   
        TextOut(hdc,
            60, 60,
            EditStru.StrCha, _tcslen(EditStru.StrCha));

        SendMessage(hWnd, WM_PAINT, 0, 0);
        break;
        
    case WM_DESTROY:                 // message 
        PostQuitMessage(0);
        break;
    default:                        // message 
        return DefWindowProc(hWnd, message, wParam, lParam);
        break;
    }

    return 0;
}