Page 215 - DCAP408_WEB_PROGRAMMING

Unit 13: Windows GDI

Notes

Notes In GDI calls screen position 0,0 is the top left of the window. If you need to work out
the window width and height follow this link here: Window size
An example application showing these GDI functions can be downloaded here: WinGDIdemo.exe.
In addition the source code for this demo can also be downloaded: WinGDIDemoCode.zip
The different GDI capabilities:

 Displaying Text
 Displaying Pixels
 Drawing Lines
 Drawing Filled Shapes

 Pens & Brushes
 Window size
 Forcing a redraw

13.1.1 Displaying Text

To display some text you can use the TextOut function. In order to use this you need to obtain a
handle to the device, an HDC and release it after use.
To obtain the handle you call: BeginPaint, it takes your window handle and a pointer to a
PAINTSTRUCT that you have declared. This structure is just used by windows so you don't need
to do anything apart from pass it on to functions.
The definition of the TextOut function is:
BOOL TextOut(HDC hdc, int x, int y, LPCSTR lpString, int cbString);

It takes the handle you were returned from BeginPaint, the x, y position on screen, a pointer to
some text and the number of characters you want to display.
After displaying your text you must call EndPaint to release the handle.

For example, to display 'Hello World' at screen position 10,10 you could do this:
PAINTSTRUCT ps;
HDC hdc = BeginPaint(hWnd, &ps);
TextOut(hdc,10,10,"Hello World",11);

EndPaint(hWnd, &ps);

Did u know? What is GDI +?
Windows GDI+ is a class-based API for C/C++ programmers. It enables applications to
use graphics and formatted text on both the video display and the printer.

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