Either something is broken, or the information at http://processingjs.org/articles/jsQuickStart.html#accessingprocessingfromjs is not accurate.

It says:

By default, when a <canvas> has a data-processing-sources attribute, its id is used as a unique identifier for the Processing instance. If no id attribute is provided, you can use Processing.instances[0]

The second statement is untrue. I have tried Processing.instances and it always return an empty array (whether or not the canvas has an id); Processing.instances[0] is undefined.

Due to the default behavior of the floating point unit sometimes rounding upward, random(low, high) can return high when the interval low .. high is sufficiently small. Simply retrying in that case neither invalidates the uniformity of the resulting numbers, nor will it take very long (probabilistically) to produce a valid result.

The proposed fixed with assertion checking can be found here

If createGraphics is used in draw then it leaks memory quite heavily. I assume it saves graphics object somewhere in global object. It might be expected behaviour, I don't know, but documentation says nothing about it. I think it either should be fixed or documentation updated to state that createGraphics should be used only in setup.

There is clearly a lot of misunderstanding about what is and is not accepted in processing.js as a project, and a document that clearly states how the project falls apart (e.g. core vs. extensions) and "how to contribute what kind of code, where" will go a long way towards clearing those up.

Recent bugs that touch this subject are #140 and #145, starting with the text in those and creating a new document on the repo (and possibly the site) will be an important first step.

My sketch pre-loads an image and later, during run-time, requests another one asynchronously. When I copy the new image into the old image, nothing happens - This used to work in java processing.

Here an example - http://myzel.net/js/requestImage.html - After five seconds the display should alternate between showing an A and showing a B.

Did I miss something? Have I found a bug? Please share!

I'm reporting this here because https://github.com/processing-js/processing-js.github.io doesn't seem to have an issue tracker.

At http://processingjs.org/reference/ param() is marked as "not yet implemented" (and consistently, its documentation page is missing). But the method is implemented and it works.

I hope you're not planning to remove it.

The @pjs preload directive may be an acceptable solution for loading images which url is static and known at compile time, but any Processing sketch that loads images whose urls are determined at runtime will miserably break in Processing js and this cannot be solved with a @pjs preload directive.

I'm pretty sure there's a way to fix this. Basically by building into processing some of the hacky workarounds that people use in their sketches to have our sketches work in Processing.js.

I understand the downsides of having such workarounds bult-in (one that comes to my mind is to use a while loop to block execution until the image is really loaded, and that may trigger the unresponsive script warning), so perhaps another @pjs may be introduced to turn on or off "synchronous image loading" or "full Processing loadImage compatibility" mode or whatever you'd like to call it

plus unit test - note that it appears there is a bug in jsdom (or the version currently used for building Pjs) that prevents testing against <root><a/><b/><root> as input. For some reason, this is treated as unterminated elements a/ and b/...

Issue #99 : the withTouch() touchstart event handler was relying on direct access to the Processing.eventHandlers array to remove any existing mouse event handlers.

Instead of exposing Processing.eventHandlers array directly, this change exposes a method called detachEventHandlersByTypeMatch() which takes a regex of event types, iterates through the list of existing event handlers, and detaches the handlers that match.

The withTouch() touchstart handler then calls detachEventHandlersByTypeMatch() with a regex that matches the desired mouse events.

Lets 2D vectors add and subtract without worrying about the z-axis. Currently, the behavior is as follows, which is a little confusing.

var v = new PVector(3, 4);
v.add(2, 4); // v is now (5, 8, NaN), and this happens without any errors
v.limit(5); // limit, and other methods that operate on the vector, now don't work

Although the docs only suggest support for 3D adding and subtracting, since PVectors can be 2D as well, it'd be nice to handle this as well. Currently, it will do v.z += undefined, which causes errors for most of the other PVector methods, such as limit. If you had defined a 2D vector, you might expect to be able to perform operations on it as a 2D vector without considering the implicit z-axis.

This came up through an issue on another project.

I always get the same pattern, even though I'm applying random numbers to noiseSeed each time mouse is pressed. Even without calling the noiseSeed function the pattern is always the same each time I run the sketch. It seems that it's not a problem with the sketch, noiseSeed works as expected on Java mode.

Link for more information and code: http://forum.processing.org/two/discussion/8858/does-noiseseed-work-on-javascript-mode#Item_2

My skillset/background is mainly with JS/Node and Swift/iOS, but I have some experience using Processing (and processing.js!).

Any good spots to jump in currently?

I was doing some part time development work for myself ( which if it was not for the Processing I would never have had the skill to do ) and would like to contribute back.

What can I do to get this gear turning again?

npm install gives the following warnings indicated that some packages should be updated or installed differently

npm WARN deprecated [email protected]: please don't use. see readme (https://github.com/fizker/minifier) for details
npm WARN deprecated [email protected]: potential XSS vulnerability in autoescape mode, and with escape filter was fixed in v2.4.3
npm WARN deprecated [email protected]: Please update to minimatch 3.0.2 or higher to avoid a RegExp DoS issue
npm WARN deprecated [email protected]: connect 2.x series is deprecated
npm WARN deprecated [email protected]: Please update to minimatch 3.0.2 or higher to avoid a RegExp DoS issue
npm WARN deprecated [email protected]: CoffeeScript on NPM has moved to "coffeescript" (no hyphen)
npm WARN deprecated [email protected]: Please update to minimatch 3.0.2 or higher to avoid a RegExp DoS issue
npm WARN deprecated [email protected]: please upgrade to graceful-fs 4 for compatibility with current and future versions of Node.js
npm WARN deprecated [email protected]: Please update to minimatch 3.0.2 or higher to avoid a RegExp DoS issue
npm WARN prefer global [email protected] should be installed with -g
npm WARN prefer global [email protected] should be installed with -g

this processing program occurs the error because of the last line is commented out with close block token.

void setup() {
  any process ...
}
// }

But, next program doesn't occur the error.

void setup() {
  any process ...
}
// }
// hogehoge

The following API endpoints are missing and would allow for sharper images on retina screens.

displayDensity()

• should return window.devicePixelRatio

pixelDensity()

• should set canvas.style.width = width (same for height)
• should set canvas.width = width*density (same for height)
• should set mouseX = mouseX * density (same for Y)
• should scale drawing coords by density