Update documentation.md

Author: acbart

documentation.md

@@ -2,6 +2,20 @@ This is an attempt to summarize key parts of BlockPy's execution model. Expect m
 
 # Execution Pipeline
 
-The interface is done via KnockoutJS. That was a mistake but here we are. It's at least not hard to see where how it binds the Run button:
+The interface is done via KnockoutJS. That was a mistake but here we are. The UI is broken off into separate components, one of which is the list of possible `Editor` instances. The most critical one is the Python Editor (`editor/python.js`). You bind the `click` event handler to `ui.execute.run`:
 
-[src/editor/python.js#L37](src/editor/python.js#L37)
+https://github.com/blockpy-edu/blockpy/blob/1e3c26ff6ce37e8c1865b1b3898b861a11db1201/src/editor/python.js#L35-L41
+
+That function is stuffed into the big main `blockpy.js` file, because apparently Past Me chose to forget everything he knew about modular design:
+
+https://github.com/blockpy-edu/blockpy/blob/1e3c26ff6ce37e8c1865b1b3898b861a11db1201/src/blockpy.js#L1019-L1027
+
+That is really just dispatching to `delayedRun` (there are performance reasons for this, believe it or not), which in turn is responsible for calling `run` (there are not performance reasons for that, it's just leftover structure from an older hack):
+
+https://github.com/blockpy-edu/blockpy/blob/master/src/engine.js#L98-L134
+
+Okay the actual `run` function finally gets a little interesting. This is in `engine.js` and requires you to understand the `Configuration` hierarchy that we use.
+
+![image](https://user-images.githubusercontent.com/897227/235737132-08fa2911-1ccb-4ea4-87ba-f9af884cb5b4.png)
+
+We need to be able to run the user's code in various ways. The different `Configuration` classes allow us to reuse functionality between those "various ways". In addition to the methods shown, they also have a bunch of methods like `print()`, `input()`, `openFile()`, etc. that work differently depending on how the code is meant to be executed (e.g., the `Student` variant's `print` puts text on the BlockPy console, the `Instructor` variant's `print` puts it in the developer console). Anyway, the critical thing is that if you