[p5.js 2.0 Docs] Change in return value for load functions that use callbacks needs to be documented

[sidwellr]

Topic

In version 1.x, the load... functions (loadImage, loadJSON, etc.) always returned the loaded data, whether or not callbacks were used. This changed in version 2: now when load.. functions are used with callbacks, they now return the value returned by the callback instead of the loaded item. This is a nice feature that allows a successCallback to dynamically modify the loaded data. It also allows an errorCallback to return some default data. But this feature needs to be described in the documentation for the various load... functions. The need for this was noted by @limzykenneth in a comment on a previous issue, but it looks like it was missed.

This is a breaking change from version 1 to 2 since most version 1 sketches that use both an assignment and a callback function won't return the desired data from the callback function (this has actually broken one of the examples on the p5.js website; see /processing/p5.js-website#1033), so this should be emphasized in the documentation.

[limzykenneth]

Most load functions should already mention this feature, I think it is only loadFont() that does not mention this behavior, unless you found others?

[sidwellr]

I noticed it with loadTable from one of the examples on the p5.js website. I checked a few others (the first few found when searching for "load") and none of them mentioned it either, so I created this issue.

The load functions that need this update are loadBlob, loadBytes, loadFilterShader, loadFont, and loadTable.

[sidwellr]

I looked at the code for loadFilterShader, and it doesn't appear to return the value from the callback functions. It probably should for consistency with the other functions. Can fixing this be included with this issue? Or should a separate issue be created for it?