Animation API

[erisco]

This issue outlines the proposed Animation API.

The intent of the Animation API is to facilitate the animation of in-game Sprites.

Implementation details, such as the usage of spritesheets and xml definition files, are intentionally hidden.

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Publicly accessible class: Animator

Public attributes of Animator: none

Public methods of Animator:

• void begin(string animation, uint playTimeMS) Sets the animation to animation with a play time of playTimeMS milliseconds.
• SDL_Surface *getFrame(uint timeMS) Returns the frame that should be displayed at timeMS milliseconds. In particular, timeMS = 0 will return the first frame of the current animation.
• void transition(string animation, uint transTimeMS, uint playTimeMS) Takes transTimeMS milliseconds to transition to animation animation. Animation animation will then play with a play time of playTimeMS. After transition(...) is called, getFrame(timeMS = 0) will return the first frame of the transition for transTimeMS > 0.
• bool hasAnimation(string animation) Intended for testing and debugging purposes, this returns true iff animation animation exists.

Errors:

• In exception to hasAnimation(...), passing a non-existent animation name as an animation argument will assert(...).

Notes:

• uint playTimeMS: If the animation is a loop, playTimeMS is how long a cycle takes. If the animation is a sequence, playTimeMS is how long the sequence takes (before stopping on the last frame).
• string animation: Animation name. This name is agreed upon between the developers and the art department. For example, the string ship.idle may refer to the idle animation of the player's ship.

[StephenNu]

Will there be a function access to set the correct x y coords to display, or will this be coded depending from which class it is called?

[erisco]

Corrected the return value of getFrame(...) from SDL_image * to SDL_Surface *.

@StephenNu: Animator returns pointers to instances of SDL_Surface via getFrame(...). You can draw an SDL_Surface wherever you want, since it is independent of coordinate systems.