API: Canvas (AB) (r2)

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. It comes with an Ancient Brain framework to make writing Worlds easier.

This API has the following features:

• No graphics library.
• Creates a canvas in the run window.
• The author has to do their own 2D or WebGL rendering.
• See 2D rendering documentation and WebGL rendering documentation.
• Includes jQuery 3.6.0.
• Loads up minimal CSS that should not conflict with user CSS.
• The screenshot assumes a canvas exists and takes a screenshot of that.

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Templates

• World with no Mind

• World with Mind
• Mind

ABWorld

This API defines a global variable called "ABWorld" as follows.

 

 ABWorld;       // instance of class ABWorldClass - basic functionality for this API
 
 
  // A canvas that may be drawn on using getContext("2d") or getContext("webgl")

	ABWorld.canvas;		
		  
		
  // create canvas:		

	ABWorld.init ( color );   
		
		
  // get drawing context:
  
	ABWorld.getContext ( type );
	

Custom getContext

ABWorld.getContext creates a drawing context of a certain type, with other arguments set to default:

 
 var ctx = ABWorld.getContext ( "2d" );
 var ctx = ABWorld.getContext ( "webgl" );

If you want to customise the drawing context, do this:

 

 var ctx = ABWorld.canvas.getContext ( type, args );
 

Custom getContext: preserveDrawingBuffer

The following is important if you are (1) creating a customised drawing context, for (2) "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.
If you use ABWorld.getContext, this is taken care of for you.

If you use your own custom getContext, then to make sure your run can generate a screenshot, you need to do something like this:

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

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

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

Examples

Examples of Worlds that use this API: