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Testing for Sound CapabilitiesTesting for Sound Capabilities — Checking whether the library supports sound |
Before calling Glk sound functions, you should use the gestalt_Sound2
selector.
Earlier versions of the Glk spec defined separate selectors for various
optional capabilities. This has proven to be an unnecessarily confusing
strategy, and is no longer used. The gestalt_Sound, gestalt_SoundMusic,
gestalt_SoundVolume, and gestalt_SoundNotify selectors still exist, but you
should not need to test them; the gestalt_Sound2 selector covers all of
them.
#define GLK_MODULE_SOUND
You can perform a preprocessor test for the existence of GLK_MODULE_SOUND.
If this is defined, so are all the functions and constants described in this
section. If not, not.
#define GLK_MODULE_SOUND2
If you are writing a C program, there is an additional complication. A
library which does not support sound may not implement the sound functions at
all. Even if you put gestalt tests around your sound calls, you may get
link-time errors.
If the glk.h file is so old that it does not declare the sound functions
and constants, you may even get compile-time errors.
To avoid this, you can perform a preprocessor test for the existence of
GLK_MODULE_SOUND2. If this is defined, so are all the functions and constants
described in this section. If not, not.