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A monad for WebGL functions in PureScript
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README.md

Graphics.WebGL

A monad wrapping raw WebGL methods and common sets of interactions, providing access to the WebGL context and error checking and handling.

See the module documentation for all available types and methods.

Intention

A good library should educate the user about the subject matter and assist them in writing readable, error-free code without forcing them into an opinionated programming flow. Meanwhile, WebGL is raging chimera of poor interaction models:

  • the WebGL context is an impenetrable state machine
  • types are represented as constants and passed as method arguments
  • shader programs are passed as strings and compiled ad-hoc
  • errors must be checked via method call or null value inspection
  • the list goes on...

As much as is possible, this library attempts to help authors avoid the most common pitfalls of WebGL without restricting access to low-level polymorphic methods like vertexAttribPointer, which are desirable for high-performance cases.

Implementation

The WebGL a monad is an alias for ReaderT WebGLContext (ErrorT WebGLError (Eff (canvas :: Canvas))) a, providing the WebGL context and error-handling without restricting arbitrary function usage.

Modules are divided as follows:

  • Graphics.WebGL.Context provides functions for obtaining and using the WebGL canvas context
  • Graphics.WebGL.Methods provides all wrapped raw WebGL methods with nominal type-checking
  • Graphics.WebGL.Types provides the WebGL monad and represents various WebGL enums/constants as datatypes
  • Graphics.WebGL.Shaders provides helpers for common shader interactions, such as obtaining the active bindings or compiling sets of shaders into a WebGL program

Any complex behaviors are (as much as is possible) constructed by composing methods and types, simultaneously allowing authors convenience and the ability to perform lower-level operations (usually the expense of some type-safety).

Future Plans

I'd like to wrap any complex sets of behaviors, such as loading/compiling/retrieving-bindings-of shaders, binding/drawing arrays, etc. with helper functions. I'm a relative newcomer to graphics programming, however, so I don't know what all of these common uses are.

That's where you come in. Help me implement common patterns by raising Github issues or providing pull requests! Together we can rein this chimeric state machine into some semblance of respectability.

Differences from purescript-webgl

This library contains some foundational differences that currently render it incompatible with purescript-webgl. For example, purescript-webgl:

  • replies upon a hidden gl global variable for all WebGL methods calls :(
  • doesn't provide direct access to raw WebGL methods, meaning...
  • complex behaviors aren't composed from otherwise provided functionality
  • contains its own WebGL effect, meaning canvas methods from purescript-canvas must be reimplemented (this library maintains type-safety via the provided context rather than the type of effect)

It's my sincere hope that this library and purescript-webgl can merge sometime in the future, so that our efforts can become cumulative.

Credits

This library is inspired and informed by the hard work done by Jurgen Nicklisch-Franken, the author of purescript-webgl. Also, I'd never have figured out the (simple in retrospect) WebGL monad without Phil Freeman handing it to me on a silver platter. Thanks for getting me to ask for help sooner!

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