Scratch

Hi All,

I've been working with the Scratch source code to create a specialized set of blocks that are specific to a particular application and which should be as simplified as possible for the end user. I have some Arduino code written in Processing that listens for changes in specific variables by listening for broadcasts from Scratch and activates a particular electronic device. One of those is a 'BrewStatus' variable.  The goal is to have an end user be able to easily manipulate the 'BrewStatus' variable without any prior setup.  In order to accomplish this, I created a new entry in the blockspecs array:

          ('startBrew'       -       startBrew)

where startBrew is a function I defined in the ScriptableScratchMorphs's instance space which uses hard-coded values in Scratch's "broadcast" method passing "BrewStatus" as the thing to be broadcasted and "On" as the value.  Using this method, I have successfully communicated with the Arduino and a button-press connected to the startBrew block will successfully turn on the electronic device via the Arduino.

Scratch and Processing can also communicate the other way around: Processing code can simulate a variable broadcast, lets call it var1 here.If there is a "When I receive (var1)" broadcast listener setup in Scratch, the Scratch code will be triggered by the Processing code.  In order to provide the simplest interface for our end users, I need to create a block that is hardcoded to fire when the Processing code broadcasts a change to a variable, BrewStatus.  Therefore, I need a block that says "When BrewStatus Changes" and will not require any setup from the user (i.e. picking from a dropdown menu of broadcast events).  I was hoping I could simply mimic the technique used for my startBrew block, i.e. override a 'whenReceiveBroadcast' method with a hardcoded value of 'BrewStatus' and take it from there.  HOWEVER, the code for broadcast receivers in blockSpecs is:

('when I receive %e'    #E       #-)

It seems that the broadcast-receiving functionality is achieved through use of the #E identifier and in conjunction with the '%e' string which creates the dropdown of available events.  Does anyone know where this functionality is defined? There are a variety of possible solutions foreseeable here.  If I could override the '#E' mapping, that would work.  If I could hardcode what gets passed to it (instead of the '%e') that would also work.

I know this has been long-winded, I thoroughly appreciate anyone that has taken the time to read this and especially anyone that could provide some assistance.

Cheers!