API: Canvas (r1)

API	Uses canvas	Graphics libraries	AB framework	Worlds using this API	Starter Worlds
Canvas (r1)	Yes	None	No	7 Worlds	None

This API is for Worlds that use a canvas to do their own 2D or WebGL rendering. It does not come with a graphics library or with any Ancient Brain framework. Anything written in JS for a canvas should run using this API without change.

This API has the following features:

No graphics library.
No Ancient Brain framework.
The author has to do create canvas themselves and do their own 2D or WebGL rendering.
See 2D rendering documentation and WebGL rendering documentation.
Includes jQuery 1.12.4.
Loads up lots of CSS - all the CSS used on the AB login pages. At the risk of conflict with user CSS. (Later APIs load up minimal CSS.)
The screenshot assumes a canvas exists and takes a screenshot of that.
Run header on RHS. Many JS worlds use fixed small dimension canvas, which will go in top LHS. So this API puts run header on RHS.
If World uses Minds, World author must call the Mind themselves:
```
 AB.mind.getAction ( state );  
```

Templates

ABWorld

This API defines a global variable called "ABWorld" with not much in it:

 

 ABWorld;                 // instance of class ABWorldClass  
 

 ABWorld.canvas;          // a variable to point to the canvas   		
 
 // When making a screenshot, Ancient Brain will search for the canvas.
 // If it cannot find the canvas, set this variable to point to it.
 
 
 ABWorld.fullwidth();     // return full width of window on desktop / screen on mobile 
 ABWorld.fullheight();    // return full height of window on desktop / screen on mobile

getContext: preserveDrawingBuffer

The following is important if you are creating a "webgl" context.

Ancient Brain needs runs to be able to generate a screenshot.
If you are doing WebGL rendering (context "webgl"), you need in canvas.getContext to set "preserveDrawingBuffer" = true.
You need something like:

 
 ctx = canvas.getContext ( "webgl", { preserveDrawingBuffer: true } );

You might set it to true for "generate image" runs and false for normal runs:

 
 if ( AB.isScreenshotRun() )
	 ctx = canvas.getContext ( "webgl", { preserveDrawingBuffer: true } );	
 else                       
	 ctx = canvas.getContext ( "webgl", { preserveDrawingBuffer: false } );