WinAPI text output in C

Question

I'm fairly new to WINAPI, and I need some help doing text output. I have an array of pixels that I write to with functions and then periodically blit onto the screen using the following functions:

DWORD WINAPI tickThreadProc(HANDLE handle) {
ShowWindow( hwnd, SW_SHOW );
HDC hdc = GetDC( hwnd );
hdcMem = CreateCompatibleDC( hdc );
HBITMAP hbmOld = (HBITMAP)SelectObject( hdcMem, hbmp );
int delay = 1000 / fps;
InitPhys();
LoadIMGs();
for ( ;; ) {
    onFrame( pixels );

    BitBlt( hdc, gLeft, gTop, width, height, hdcMem, 0, 0, SRCCOPY );
    // Wait
    Sleep( delay );
    // Physics
    SimPhys();  
}
SelectObject( hdcMem, hbmOld );
DeleteDC( hdc );
return 0;
}


void MakeSurface(HWND hwnd) {
BITMAPINFO bmi;
bmi.bmiHeader.biSize = sizeof(BITMAPINFO);
bmi.bmiHeader.biWidth = width;
bmi.bmiHeader.biHeight =  -height; // Order pixels from top to bottom
bmi.bmiHeader.biPlanes = 1;
bmi.bmiHeader.biBitCount = 32; // last byte not used, 32 bit for alignment
bmi.bmiHeader.biCompression = BI_RGB;
bmi.bmiHeader.biSizeImage = 0;
bmi.bmiHeader.biXPelsPerMeter = 0;
bmi.bmiHeader.biYPelsPerMeter = 0;
bmi.bmiHeader.biClrUsed = 0;
bmi.bmiHeader.biClrImportant = 0;
bmi.bmiColors[0].rgbBlue = 0;
bmi.bmiColors[0].rgbGreen = 0;
bmi.bmiColors[0].rgbRed = 0;
bmi.bmiColors[0].rgbReserved = 0;
HDC hdc = GetDC( hwnd );
// Create DIB section to always give direct access to pixels
hbmp = CreateDIBSection( hdc, &bmi, DIB_RGB_COLORS, (void**)&pixels, NULL, 0 );
DeleteDC( hdc );
// Create a new thread to use as a timer
hTickThread = CreateThread( NULL, 0, &tickThreadProc, NULL,0, NULL );
}

This is modified off some code I found on the internet. The pixel struct has 4 ints for r, g, b, and a.

I need to do text output and loading a picture for text is impractical. Any help?

Like the TextOut function?

Some programmer dude
– Some programmer dude

2013-06-20 16:06:17 +00:00
Commented Jun 20, 2013 at 16:06 — Some programmer dude
– Some programmer dude, Commented Jun 20, 2013 at 16:06
Yes, sort of. But I can't use the PAINSTRUCT stuff.

wrong answers only
– wrong answers only

2013-06-20 17:08:31 +00:00
Commented Jun 20, 2013 at 17:08 — wrong answers only
– wrong answers only, Commented Jun 20, 2013 at 17:08
+1 for 'PAINSTRUCT' :)

Martin James
– Martin James

2013-06-20 19:07:57 +00:00
Commented Jun 20, 2013 at 19:07 — Martin James
– Martin James, Commented Jun 20, 2013 at 19:07

Adrian McCarthy · Accepted Answer · 2013-06-20 17:19:22Z

1

First of all, if you use GetDC to get a handle to device context, you must use ReleaseDC when you're done with it. DeleteDC is only for device contexts that you created.

To draw text to this window, you can use functions like TextOut or DrawText using that DC (before you release it).

PAINTSTRUCT is for handling WM_PAINT messages (which is the more common way to draw to a Window). It looks like you're instead trying to draw directly from another thread on a regular basis. GDI isn't very good at dealing with multiple threads, so you might have some problems with this approach. But if your BitBlts are working, then a TextOut should work as well.

answered Jun 20, 2013 at 17:19

Adrian McCarthy

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2 Comments

wrong answers only Over a year ago

The loop in the thread is infinite; the deleteDC will never be called. I'm not sure why it's there (adapted this code). When the program exits, the loop does.

Adrian McCarthy Over a year ago

@Yuri Kahn: There's a DeleteDC in MakeSurface, near the botton of the code sample, just before it creates the thread. That should be a ReleaseDC. The DeleteDC in the thread proc was probably intended to clean up hdcMem rather than hdc, but, you're right that it will never be called.

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