Input system
Description
The RATR0 input system decouples system-specific inputs and maps them into user-defined actions. By this, the engine can support customizable inputs that can be flexibly configured.
Design ideas
The input system is inspired by other game engines like Godot, but rather using string as identifiers, it uses integers to avoid costly comparison or mapping functions.
Rather than responding to specific inputs, the input system instead defines actions, and input types can be mapped to actions. With this not only can we remap inputs, but also map multiple input types to one action
Actions are represented with an ID that is allocated on demand at engine configuration time.
The input system is updated once per frame and synchronized to the video beam to ensure stable low latency, that means for Amiga that the input system is updated in the vertical blank interrupt.
Keyboard input
Keyboard input is performed through polling the keyboard.device in each iteration of the game loop. The status of the keyboard is obtained in a bit array called the keyboard matrix. The disadvantage is that only the raw keycode is available, and we would lose all the mapping information the user has provided to the operating system. Mapping is therefore performed by obtaining the current system keymap and obtaining the logical key through a lookup in the keymap, possibly incorporating one or more modifiers (shift, control, alt, etc.)