PureBasic integrated commandset relies on available OS libraries. Sometimes, there is different way to achieve the same goal and when it makes sense, PureBasic offers the possibility to change the used underlying libraries for specific commands, without changing one line of source code. For example, on Windows there is the 'OpenGL' subsystem available, which will use OpenGL functions to render sprites, instead of DirectX (which is the default subsystem). It can be useful to use OpenGL instead of DirectX when writing a crossplatform game, as OS X and Linux use OpenGL as default. It also allows to use raw OpenGL commands directly on screen.
To enable a subsystem, its name has to be set in the IDE compiler options, or through the /SUBSYSTEM command-line switch. This is a compile time option, which means an executable can not embed more than one subsystem at once. If multiple support is needed (for example shipping an OpenGL and DirectX version of a game), two executables needs to be created.
The available subsystems are located in the PureBasic 'subsystems' folder. Any residents or libraries found in this drawer will have precedency over the default libraries and residents, when a subsystem is specified. Any number of different subsystems can be specified (as long it doesn't affect the same libraries).
The Subsystem compiler function can be used to detect if a specific subsystem is used for the compilation.
Here is a list of available subsystems, and the affected libraries:
WindowsOpenGL: use OpenGL instead of DirectX. Affected libraries: - Sprite - Sprite3D - Screen - All 3D engine related libraries
Linuxgtk2: Affected libraries: - 2D Drawing - AudioCD - Clipboard - Desktop - Drag & Drop - Font - Gadget - Image - Menu - Movie - Printer - Requester - Scintilla - StatusBar - SysTray - Toolbar - Window