Engine
From DaphneWiki
Contents |
DAPHNE Engine
This information applies mostly to the unreleased Daphne v2.0 code base. I am making notes as I develop it. This info is subject to change.
Program Entry
Program entry must be implemented on a platform-specific basis. It can be something like a main() function which loops and calls Daphne functions or whatever you need it to be. In short, these daphne-specific functions must be called regardless of the platform:
- daphne_init (parses command line and returns an instance of the IGenericLoop interface)
- IGenericLoop->Go() (call this over and over again until get_quitflag() returns true; this value returns the number of milliseconds before calling Go() again; this value must be respected in order for Daphne to run at the proper speed)
- daphne_shutdown (when get_quitflag() has returned true)
Platform-specific
Platform-specific code inherits from the IPlatform interface and lives in the src/platform folder. It is responsible for providing the following functions:
- Platform input event handling (keyboard, mouse, joystick, any other abstract means of input)
- Sound (providing a mechanism to stream PCM audio to audio device)
- Video (can be as simple as providing platform initialization to OpenGL code to as complex as providing a complete video object)
- Timing (millisecond precision)
Video
All video functionality is inherits from the IVideoObject interface. The IPlatform interface returns an instance of IVideoObject. So you can extend pre-written IVideoObject classes or write your own from scratch. Very flexible.
TODO: The IVideoObject interface needs to be split up into smaller interfaces because it currently tries to do too many things.
Sound
The IPlatform interface has a SoundInit method, one argument of which is AudioStreamCallback. Your platform specific code must call this callback regularly (when audio buffer needs to be filled) to grab PCM audio generated by Daphne's sound code. Daphne's sound code currently is hard-coded to generate audio at 44.1khz, 16-bit stereo.
Input
The platform-specific code is responsible for returning an implementation of the IGenericInput interface. As of right now, it appears it is safe for all platforms to just return an instance of GenericInput.
The platform-specific code must implement some event handler to call the IGenericInput methods input_enable, input_disable to indicate that input has come in. The platform-specific code may optionally also support mouse motion by capturing mouse events and then calling IGenericInput->OnMouseMotion. The platform-specific code may optionally also support keyboard events (to handle Thayer's Quest and SINGE games) by calling IGenericInput->key_enable and IGenericInput->key_disable.
