[R-SIG-Mac] Embedded R, event loops, GUI events, and OS X

[Miëtek Bak]

Hi Simon,

Thanks for the reply.  I’m looking into giving you access to the H repository.  Meanwhile, this is how we initialise embedded R, disabling stack limit checks:

    // NOTE: It is crucial to set the two R stack globals after calling
    // Rf_initialize_R() and before calling setup_Rmainloop().
    // H_initUnlimitedEmbeddedR() is based on Rf_initEmbeddedR(), found in
    // R 3.1.0 source code at src/gnuwin32/embeddedR.c:127.
    int H_initUnlimitedEmbeddedR(int argc, char **argv)
    {
        Rf_initialize_R(argc, argv);
        R_CStackLimit = -1;
        R_CStackStart = -1;
        setup_Rmainloop();
        return(1);
    }

We do use our own event loop.  In order to mesh the H loop and the R loop, we do two things every 0.03 seconds, depending on the platform, neither of which fixes the issue on OS X:

1. On Linux, we call the following:

    void processGUIEventsUnix(InputHandler** inputHandlers) {
      if (*inputHandlers == NULL)
          initStdinHandler();
      R_runHandlers(*inputHandlers, R_checkActivityEx(1000, 0, NULL));
    }

2. On Windows, we call `R_ProcessEvents`.

Can you say what exactly you have in mind when you say “run the R event loop”?

Best,

-- 
Miëtek




On 2014-07-02, at 15:06, Simon Urbanek <simon.urbanek at r-project.org> wrote:

> Miëtek,
> 
> On Jul 2, 2014, at 1:43 PM, Miëtek Bak <mietek at bak.io> wrote:
> 
>> Hello,
>> 
>> I’m helping with the development of an R-to-Haskell interoperability solution, called H.  The project allows Haskell functions to seamlessly call R functions and vice versa, making use of an embedded R interpreter.  H is developed in-house by Tweag I/O, and is soon to be open-sourced.
>> 
>> The project is stable on Linux and Windows, and I’m focussing on an OS X port.  Basic functionality is ready, but I’m having trouble with the GUI parts. Specifically, any graph window, e.g. the one expected for `plot(cars)`, appears blank and unresponsive when triggered from H.
>> 
>> I think the issue lies between the H loop, the R event loop, and the Cocoa event loop.  So far, I’ve pored over “Writing R Extensions” (chapter 8, “Linking GUIs and other front-ends to R”), the R 3.1.0 sources, (`./src/library/grDevices/src/qdCocoa.m`), and the R.app 1.6.4 sources (`./RController.m`, `./REngine/RCallbacks.m`, `./REngine/RInit.m`, and `./REngine/REngine.m`).  I’ve also found interesting notes in the R.app `./ReadMe.txt`, but unfortunately, they no longer seem to be in sync with the code.
>> 
>> As I’ve seemingly hit a wall, I’m looking for advice.  Are any of the developers of the OS X port of R subscribed to this list?
>> 
> 
> Yes.
> 
> In general, the trick is to make sure that you setup the R event loop. That is an extra step after initializing the embedded R. There is nothing special about the OS X port in that regard - as long as you run the R event loop all is well. It becomes more tricky if the app you use wants to use its own event loop - that can cause issues as you have to make sure the two loops mesh properly.
> 
> For more specific help you'll need to ask more specific questions - possibly with link to reproducible code.
> 
> Cheers,
> Simon
> 
> 
> 
>> Thanks, and kind regards,
>> 
>> -- 
>> Miëtek Bak
>> 
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