RFR: JDK-8293480: IGV: Update Bytecode and ControlFlow Component immediately when opening a new graph [v6]

[Tobias Holenstein]

On Fri, 16 Sep 2022 14:58:04 GMT, Tobias Holenstein <tholenstein at openjdk.org> wrote:

>> The `BytecodeViewTopComponent` and `ControlFlowTopComponent` represent information depending on which graph is opened in `EditorTopComponent`. Previously `BytecodeViewTopComponent` and `ControlFlowTopComponent` did not update their contents immediately when a new graph from another group was opened in `EditorTopComponent`. They were also not updated when switching between two tabs of an open graph. 
>> `OutlineTopComponent` had the same problem to update the selected graphs according to the `EditorTopComponent`
>> 
>> <img width="1291" alt="Update" src="https://user-images.githubusercontent.com/71546117/188860123-825a67fd-aab3-4500-8a47-8fa56eb9aeed.png">
>> 
>> **Analysis**
>> `BytecodeViewTopComponent`, `ControlFlowTopComponent` and `OutlineTopComponent` each represent information that depends on the `InputGraph` of the currently or last active `EditorTopComponent`. This information is made available globally by adding a new `InputGraphProvider` to the `Lookup` of `EditorTopComponent` each time the `InputGraph` changes. `BytecodeViewTopComponent`, `ControlFlowTopComponent` and `OutlineTopComponent` implement a `LookupListener` that calls `resultChanged(LookupEvent lookupEvent)` whenever a `InputGraphProvider` changes in in the lookup of `Utilities.actionsGlobalContext()`. When such a change happens the last active `InputGraphProvider` is retrieved from the `LookupHistory` by the listening components. 
>> 
>> **Problem** 
>> First, we missed to `fire()` a `diagramChangedEvent` in the constructor of `EditorTopComponent` which trigger to add the `InputGraphProvider` to the `Lookup`
>> 
>> Second, `Utilities.actionsGlobalContext()` returns a `Lookup` of the active (focused) `TopComponent's` `Lookup`. Unfortunately, when the last `EditorTopComponent` the `LookupListener` does not get called and there is no way to call is manually. 
>> 
>> **New Approach**
>> We extends the `LookupHistory` class such that we can add a `ChangedListener` that gets called whenever the last active `InputGraphProvider` is cached. So instead of listening to changes in `Utilities.actionsGlobalContext()` and then consulting the `LookupHistory`, now  `BytecodeViewTopComponent`, `ControlFlowTopComponent` and `OutlineTopComponent` listen to changes in the `LookupHistory` directly. This way we can now call `terminate` in the `LookupHistory` whenever we close a `EditorTopComponent`, which directly notifies the listeners.
>
> Tobias Holenstein has updated the pull request incrementally with four additional commits since the last revision:
> 
>  - Fix for: parent is null for DiffGraph
>  - remove DiagramProvider
>  - add ChangedListener to LookupHistory
>  - update OutlineTopComponent graph closed

> fix



> Thanks for this UI improvement, Tobias, looks good to me! There is one more case where the Bytecode and Control Flow windows get out of sync: after removing all graphs and groups in the Outline, they still show the content of the graph that was last active:
> 
> ![bytecode-and-cfg-leftovers](https://user-images.githubusercontent.com/8792647/189114719-770ba617-e94c-4492-a5ab-81047b8a0b98.png)
> 
> This problem existed before the changeset, so it might be addressed here or in a separate issue, whatever you think makes more sense.

You are right, @robcasloz, my last fix didn't solve the problem. There was a fundamental problem with using `Utilities.actionsGlobalContext()` - I pushed a new version and updated the PR. 

Thanks!

-------------

PR: https://git.openjdk.org/jdk/pull/10196