Asynchronously decorate quick outline view via DecorationManager #1922

[HeikoKlare]

What it does

The Quick Outline View currently applies (i.e., calculates and draws) decorations for override indicators synchronously. In case the calculation of the indicator takes long, it blocks the UI. The ordinary Outline View defers the responsibility of calculating and applying decorations to the DecorationManager. This ensures that (1) that task is performed asynchronously via a dedicated job and (2) that the DecorationManager takes care of the current user configuration (i.e., whether those indicators shall be shown or not), which the Quick Outline View currently replicates.

With this change, the Quick Outline View uses the same label decorator as the ordinary Outline View, which makes the DecorationManager process the override label decorator asynchronously instead of applying it synchronously.

Contributes to #1922

This complements #1926, which improves performance of the business logic used for calculating labels of the view, while this one ensures that the business logic is completely moved outside of the UI thread to be executed asynchronously.

How to test

A reproducer has been kindly provided by @fedejeanne in:

• Poor Performance of Quick Outline View #1922

To reproduce, do the following:

• Import this Java project: reproducer.zip
• Make sure the "Java Method Overwrite Indicator" is active
• Go to the class Broke1 and click Ctrl + O twice

Without this patch, the quick outline view will take a high amout of time to open and block the UI while with this patch it will open immediately and stay responsible.

Author checklist

• I have thoroughly tested my changes
• The change is following the coding conventions
• I have signed the Eclipse Contributor Agreement (ECA)

[HeikoKlare]

@jukzi @fedejeanne this one complements #1926, which improves business logic of the quick outline view image calculation, while this one extracts the business logic out of the UI thread. Would be great if you could have a look and integrate this as well.

[jukzi]

I am not familiar with that code, does this PR still fix https://bugs.eclipse.org/bugs/show_bug.cgi?id=62896 (which introduced that code)?

[HeikoKlare]

Yes, it still fixes that PR. Here is a screencast to demonstrate the behavior:

The asynchronously executed decorator has been introduced to the ordinary outline view in 2008, so quite some time after the mentioned issue has been resolved:

eclipse.jdt.ui/org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaOutlinePage.java

Line 949 in 35d2546

fOutlineViewer.setLabelProvider(new DecoratingJavaLabelProvider(lprovider));

Maybe the quick outline was just forgotten to be adapted as well.

[jukzi]

ok, if nobody complains i would merge it tomorrow.