Introduction to Graphics Drivers

This chapter includes:

• Graphics drivers
• DDK source code

Graphics drivers

The graphics drivers are independent of the Photon microGUI; the driver that you supply is implemented as one or more shared objects (your choice) that can be used by Photon or by any other application requiring the services of a graphics driver.

You provide a set of well defined entry points, and the appropriate graphics system dynamically loads your driver and calls the entry points.

By way of example, this is how your driver interacts with Photon and the graphics driver subsystem, io-graphics, under QNX 6:

How a driver interacts with Photon.

As you can see from the above diagram, a set of Photon infrastructure components are responsible for the interface to Photon:

Connector

Presents the graphical region to Photon. This is the area that's defined to be shown on the graphical screen.

Draw stream interpreter

Interprets Photon's draw stream and decodes the graphical commands into scans, bitmaps, images, and fills, and passes them to the graphics driver. The interpreter also converts the draw stream from whatever endian format it's in to native-endian format.

Render library

Converts complex shapes (such as circles) into lower-level drawing primitives (scans, bitmaps, images, and fills) that the graphics driver can handle.

Font manager

Converts textual information into bitmaps.

Rasterizer (FFB)

Converts lower-level drawing primitives into a raster format, using the Flat Frame Buffer (FFB) library.

Graphics driver

Your graphics driver, supplied as one or more shared objects.

DDK source code

When you install the DDK package, the source is put into a directory under the /usr/src/ddk-6.2.0 directory. Currently, the directory structure for the Graphics DDK looks like this:

Directory structure for the Graphics DDK.