Thread: No text appears on the screen with CreateFont() and DrawFont()?

Hello, to learn about Windows GUI objects, I have written the below code. Another main reason I have written it is to hopefully be able to have access to the API to make it easier to draw text on my SDL GUI's client window, since it should work as long as I own the process. In any case, my code displays absolutely nothing. It also receives no error messages, so I'm not sure what I got wrong in my window procedure. It seems to also be a little misbehaved on Windows XP, because although it handles the escape key message, it doesn't exit right away on Windows XP. It doesn't have this problem on Windows 7. Currently, no text appears on the screen and it is just plain black. I hope someone knows more about how to format GDI objects than I do, because I based my setup of my text object off of Microsoft's example.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>


#define WIN_32_LEAN_AND_MEAN
#include <windows.h>


#include <stdint.h>


#define GUI_WIDTH 500
#define GUI_HEIGHT 750


#define BACKGROUND_COLOR RGB( 0, 0, 0 )


void win_error( char * message, BOOL exit )
{
    char buffer[BUFSIZ] = { 0 };
    DWORD error_code = GetLastError( );


    FormatMessage
    (
        FORMAT_MESSAGE_FROM_SYSTEM,
        NULL,
        error_code,
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
        (LPTSTR) buffer,
        BUFSIZ,
        NULL
    );


    MessageBox(NULL, buffer, "Error from System :", MB_ICONWARNING | MB_OK );


    if ( exit ) ExitProcess( error_code );


    return;
}


LRESULT CALLBACK window_procedure( HWND window_handle, UINT message, WPARAM wParam, LPARAM lParam )
{
    static HDC window_device_context = NULL;
    HDC drawing_context = NULL;
    PAINTSTRUCT paint_struct = { 0 };
    RECT window_region = { 0 };
    RECT text_rect = { 0 };
    HBRUSH brush_object = CreateSolidBrush( BACKGROUND_COLOR );
    HFONT h_font = NULL;


    switch( message )
    {
        case WM_CREATE :
            if ( !( window_device_context = GetDC( window_handle ) ) )
                win_error( "GetDC( )", TRUE );
            GetWindowRect( window_handle, &window_region );
        break;


        case WM_PAINT :
            drawing_context = BeginPaint( window_handle, &paint_struct );


            h_font = CreateFont(
                                 0,
                                 0,
                                 0,
                                 0,
                                 FW_BOLD,
                                 FALSE,
                                 FALSE,
                                 FALSE,
                                 ANSI_CHARSET,
                                 OUT_OUTLINE_PRECIS,
                                 CLIP_DEFAULT_PRECIS,
                                 DEFAULT_QUALITY,
                                 VARIABLE_PITCH | FF_DECORATIVE,
                                 TEXT("Rockwell Ultra Bold")
                               );


            if ( !h_font )
            {
                win_error( "CreateFont( )", FALSE );
                PostQuitMessage( 0 );
            }


            text_rect = window_region;
            SelectObject( drawing_context, h_font );
            SetTextColor( drawing_context, RGB( 255, 255, 255 ) );


            if ( !DrawText( drawing_context, TEXT("Hello Windows!"), -1, &text_rect, DT_CENTER ) )
            {
                win_error( "DrawText( )", FALSE );
                PostQuitMessage( 0 );
            }


            DeleteObject( h_font );
            h_font = NULL;


            EndPaint( window_handle, &paint_struct );
        break;


        case WM_MOVE :
            GetWindowRect( window_handle, &window_region );
            UpdateWindow( window_handle );
        break;


        case WM_CLOSE :
            DestroyWindow( window_handle );
        break;


        case WM_DESTROY :
            ReleaseDC( window_handle, window_device_context );
            DeleteObject( brush_object );
        break;


        case WM_KEYDOWN :
            switch ( wParam )
            {
                case VK_ESCAPE :
                    PostQuitMessage( 0 );
                break;


                default :
                    printf( "Unhandled key message : %X\n", ( unsigned )wParam );
                    printf( "Character : %c\n\n", ( char )wParam );
                break;
            }
        break;


        case WM_LBUTTONDOWN :
            printf( "Left mouse click.\n" );
        break;


        case WM_RBUTTONDOWN :
            printf( "Right mouse click.\n" );
        break;


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


    return 0;
}


int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR CmdArgs, int nCmdShow )
{
    WNDCLASSEX window_class;
    HWND window_handle;
    MSG message;
    HBRUSH window_color = CreateSolidBrush( BACKGROUND_COLOR );


    window_class.cbSize = sizeof( WNDCLASSEX );
    window_class.style = 0;
    window_class.lpfnWndProc = window_procedure;
    window_class.cbClsExtra = 0;
    window_class.cbWndExtra = 0;
    window_class.hInstance = hInstance;
    window_class.hIcon = LoadIcon( NULL, IDI_APPLICATION );
    window_class.hCursor = LoadCursor( NULL, IDC_ARROW );
    window_class.hbrBackground = window_color;
    window_class.lpszMenuName = NULL;
    window_class.lpszClassName = "NewClass";
    window_class.hIconSm = NULL;


    if( !RegisterClassEx( &window_class ) )
        win_error( "RegisterClassEx( )", TRUE );


    window_handle = CreateWindowEx
                            (
                              WS_EX_CLIENTEDGE,
                             "NewClass",
                             "Hello",
                              WS_TILEDWINDOW,
                              CW_USEDEFAULT,
                              CW_USEDEFAULT,
                              GUI_HEIGHT,
                              GUI_WIDTH,
                              NULL,
                              NULL,
                              hInstance,
                              NULL
                            );


    if( !window_handle )
    {
        UnregisterClass( "NewClass", hInstance );
        win_error( "CreateWindowEx( )", TRUE );
    }


    ShowWindow( window_handle, SW_SHOW );
    UpdateWindow( window_handle );


    while( GetMessage( &message, window_handle, 0, 0 ) > 0 )
    {
        TranslateMessage( &message );
        DispatchMessage( &message );
    }


    UnregisterClass( "NewClass", hInstance );


    return 0;
}

The desired effect is for the text "Hello Windows" to be displayed in white in the Rockwell Ultra Bold font on the center of the screen, with the optional escape key exiting immediately.

Thanks, that helped me fix it. I also got the text to be transparent and flash different colors now using timers. I moved the deletion of the GDI objects to the proper place too.

In general your paint should not be creating objects or working out where to draw things. All that work should have already been done prior to you generating the paint message.

This is because other events on the PC will also generate ppaint messages and your code is too slow.

All my paint handlers are simply;

Code:

case WM_PAINT:
PAINTSTRUCT ps = {0};
BeginPaint(window_handle, &ps);	

BitBlt(	ps.hdc, 
	ps.rcPaint.left,
	ps.rcPaint.top,
	ps.rcPaint.right - ps.rcPaint.left,
	ps.rcPaint.bottom - ps.rcPaint.top,
	drawing_context,
	ps.rcPaint.left, 
	ps.rcPaint.top,
	SRCCOPY);

EndPaint(window_handle, &ps);
break;

>>text_rect = window_region;

Wrong area.

Use GetClientRect() as this is the area you can draw on. GetWindowRect() is the total area of your app, including the non client area (menu, toolbar, border, system menu, etc).

When you understand how to do GDI drawing properly (not the crap you are using in this code) then use the rect element in the PAINTSTRUCT.

Why are you using PostQuitMessage() outside of a WM_DESTROY handler?
You do understand that it will send a WM_QUIT to your message pump? (so no GDI clean up...)

>>HBRUSH brush_object = CreateSolidBrush( BACKGROUND_COLOR );

Do you understand that this creates a GDI object every message, including the hundreds of messages you do not process?

You are not managing your GDI objects correctly.

Code:

//create GDI object
HFONT hFont = CreateFont(.....);
HFONT *hDefault = NULL;

//select the font into the DC
//catching the current, default font
hDefault = SelectObject( memDc, hFont);

//write the text


//return the default GDI objects to the DC
SelectObject( memDC, hDefault); //no need to catch the font as it is hFont

//clean up any GDI we created
DeleteObject( hFont);

EDIT: Please note all code is from memory and so is wrong, full of bugs and may cause harm to your PC / pets / chances to have children.