endContour() throws error in WEBGL mode

[davepagurek]

Most appropriate sub-area of p5.js?

• Accessibility
• Color
• Core/Environment/Rendering
• Data
• DOM
• Events
• Image
• IO
• Math
• Typography
• Utilities
• WebGL
• Build Process
• Unit Testing
• Internalization
• Friendly Errors
• Other (specify if possible)

p5.js version

1.5.0

Web browser and version

Firefox 108.0

Operating System

MacOS 12.5.1

Steps to reproduce this

Currently, if you add a createCanvas(100, 100, WEBGL) to the start of the beginContour example in the docs, we get an type error in endContour: d[0] is undefined.

We're able in theory to support this in beginShape(TESS) mode (the default on the main branch currently) by supplying multiple contours to libtess. I have an example of using that to extrude text in 3D in https://openprocessing.org/sketch/1721124 on extrudeText:52 and it triangulates the cutouts correctly, so implementing this would be a matter of mapping begin/endContour shapes to an array in the parameters of our _triangulate call.

[aditya-shrivastavv]

According to documentation

createCanvas method should be called only once at the start of setup(). Calling createCanvas more than once in a sketch will result in very unpredictable behavior. If you want more than one drawing canvas you could use createGraphics() | Link

another point i could think of is that createCanvas() is a function from the p5.js library, and beginContour() is a function from the p5.js WebGL library. They are different libraries and need to be used with the corresponding mode (either 2D or WEBGL) specified in the createCanvas()

[davepagurek]

@aditya-shrivastavv for clarification, I'm suggesting replacing the existing 2D createCanvas call with the WebGL one.

While beginContour is currently only functional in 2D mode, it is not documented as such. We're hoping that we can eventually get this implemented in WebGL mode to match the feature set of 2D mode to increase predictability for new users of WebGL mode.

[aditya-shrivastavv]

Please assign this issue to me, I want to work on this

[davepagurek]

Thanks @aditya-shrivastavv! I'll assign this one to you.