Working with Graphics APIs - Essentials of Interactive Computer Graphics - page 96

scene geometries (e.g., the rectangles). TheAPI is the object representing our
interface to the graphics API. Because there should be only one interface to the
graphics API, we define a static singleton variable that is globally accessible. Now
we can examine the actual implementation of the GraphicsSystem class.

Tutorial 4.1. The D3D GraphicsSystem Class

Tutorial 4.1.
Project Name
D3D _ GraphicsSystem

• Goal. Increase the readability of our source code by hiding low-level graph-
ics API function calls.

• Approach. Design an abstraction for a graphics API based on the require- Tutorial 3.5. Recall that

in Tutorial 3.5 we worked
with the CRectangle2D and
CCircle2D classes to draw a
scene with a rectangle and a
circle.

ments of our applications. For example, in this tutorial we will implement
the GraphicsSystem class of Listing 4.5 based on the D3D graphics API.
We will integrate the new class into the source code of Tutorial 3.5.

Figure 4.4 is a screenshot of running Tutorial 4.1. Not surprisingly, this out-
put is identical to that of Tutorial 3.5. However, if we compare the source code of

class GraphicsSystemD3D {
A: // class variable for representation of singleton interface to the D3D API.
public : static GraphicsSystemD3D& GetSystem();
private : static GraphicsSystemD3D m _ TheAPI;

Source file.
D3DGraphicsSystem.h file
in the GraphicsSystem folders
of the D3D _ GraphicsSystem
project.

B: // public interface for initialization/termination/accessing
public : bool CreateGraphicsContext(HWND hWindow);

void ShutDown();
LPDIRECT3DDEVICE9 GetActiveDevice();

C: // public interface initializing the device for drawing
bool BeginDraw( float width, float height);
bool EndDrawAndShow();

D: // private representation of the D3D interface.
private :
// This is the D3D Interface (GHC)
LPDIRECT3D9 m _ pD3D;
// This is one drawing pipeline (RC)
LPDIRECT3DDEVICE9 m _ pD3DDevice;

};

Listing 4.7. The D3D GraphicsSystem class.