Working with Graphics APIs - Essentials of Interactive Computer Graphics - page 95

Source file. Pseudocode; no
corresponding source file.

class GraphicsSystem {
Functionality demanded by OnCreate() of Listings 4.3 and 4.4.
CreateGraphicsContext(); // Create and Initialize GHC and RC

Functionality demanded by the OnPaint() of Listings 4.1 and 4.2.
// Select and initialize the RC for drawing
BeginDraw();
// Present the drawn results on the GUI drawing area
EndDrawAndShow();

};

GraphicsSystem TheAPI

Listing 4.5. The GraphicsSystem class.

bool OnCreate() {
. // Initialize GUI system
// Create and Initialize GHC and RC
if (! TheAPI .CreateGraphicsContext() )
return false ;

Source file. Pseudocode; no
corresponding source file.

.
return true ;

}

void OnPaint() {
TheAPI .BeginDraw(); // Initialize RC for drawing
m _ LargeSquare.Draw(); // Draw the large square

.
TheAPI .EndDrawAndShow();
// Present the drawn results on the application window

};

Listing 4.6. Pseudocode for OnCreate() and OnPaint() .

The functionality presented in Listing 4.5 is driven entirely by our experience
from working with graphics APIs. The CreateGraphicsContext() function
should create/initialize the GHC and create one instance of RC. The BeginDraw()
and EndDrawAndShow() functions are designed to encapsulate graphics API ini-
tialization and configuration calls. As we can see from the OnPaint() function
in Listing 4.6, in this way, application programmers can focus on specifying the