Add compiler or related tech to solve call back functions

[gaocegege]

related issues: #166

There are some functions which will be defined in R but it is called in Java. Actually we have limited implementation for these functions, for example, draw and settings. But some libraries and some other built-in functions need to be supported.

Built-in functions includes: mouse related functions.

[gaocegege]

COPY from #166 (comment)

I've tried using the importLibrary() function to create a second library example using the Processing Video library ("video"), and specifically its Loop.pde demo sketch.

I was successful -- video plays in a loop in Processing.R -- however I ran into a problem redefining the Video library's movieEvent function hook. My demo sketch works around this problem by dropping the framerate and reading the video each frame no matter what. This creates rough, choppy, low-framerate video. I wonder if there is a way to do this right.

To set up this test sketch, install the Video library in PDE, save the test sketch in Processing.R mode, then copy transit.mov from the video library example into the sketch /data folder.

settings <- function() {
    # Please install the video before you run the example.
    importLibrary("video")
    size(640, 360)
}

setup <- function() {
    frameRate(10) # hack -- drop the framerate to give video more time to load
    # copy transit.mov from video library example into sketch /data folder
    movie = Movie$new(processing, "transit.mov");
    movie$loop()
}

draw <- function() {
    background(0)
    movie$read() # hack -- reads regardless of whether the next frame is ready or not
    image(movie, 0, 0, width, height)
}

## The video library uses the movieEvent() function
## to manage when the movie object reads the next frame.
## However I'm not sure how to redefine this hook
## in R mode. For the original Java video library example, see:
##   /libraries/video/examples/Movie/Loop/Loop.pde

## doesn't work
# movieEvent <- function(m) {
#     m$read()
# }

## also doesn't work
# movieEvent <- function() {
#     movie$read()
# }

## also doesn't work
# Movie$movieEvent <- function(m) {
#     m$read()
# }

## also doesn't work
# Movie$movieEvent <- function() {
#     movie$read()
# }

[jeremydouglass]

Also related issue: #163 Support the event function.

All the interactive keyboard and mouse functions are hooks / callbacks

• mouseClicked()
• mouseDragged()
• mouseMoved()
• mousePressed()
• mouseReleased()
• mouseWheel()
• keyPressed()
• keyReleased()
• keyTyped()

[jeremydouglass]

I wonder if this can be separated into two issues.

1. API hooks: manually implement the known list of 9 special API functions above (mouseClicked() keyPressed() etc.) with the same method that is already used to support draw() setup() and settings().

2. Library hooks: research methods that could be used to discover hook / callback functions in libraries, e.g. movieEvent() in the Processing video library. This is feasibility research. There might be a way to do this dynamically, for example with a compiler. Or it might turn out that any library with hooks / callbacks will need a special mapping in order to be supported.

[gaocegege]

It is a good idea! I agree with you. If we could implement the library hooks then we could deprecate the original API hooks.

[jeremydouglass]

The first half of this -- API hooks -- was resolved by #187 Fix the callback function.