Ensure that cursor state change is always emitted upon restoring state

[aramikuto]

Fixes #203345

It seems that the distinction between cases where the scrollbar background appears and where it does not lies in whether onCursorStateChanged is called or not. When a file is opened, restoreCursorState fires events that initialize the cursor state, and _emitStateChangedIfNecessary determines whether the CursorStateChangedEvent should be fired by comparing the previous and current cursor states. However, it appears that the default value for the cursor position in a newly opened view is (1,1), which results in the CursorStateChangedEvent not being fired if the cursor position after restoration is also (1,1) – the cursor positioned before the first character on the first line. Without this event, certain parts of DecorationsOverviewRuler do not initialize properly, leading to the problem I linked above.

To address this, I've ensured that cursor events are emitted if they were caused by the restoreState.

[hediet]

Thanks for your analysis and bug report!

I think the bug fix is at the wrong location though. The event is correct, it should only fire when it changes. When the default value is (1,1) and the workbench restores the value to (1,1), no event should be fired.

However, the DecorationsOverviewRuler should not assume that this even is fired before it gets rendered!
So in the initialization of that class, it should copy over the necessary state.

[hediet]

See comment.

[aramikuto]

@hediet Thank you for reviewing my changes and providing feedback! I have adjusted my implementation according to the information provided.

This time, I explicitly added Position(1, 1) as the initial value for the cursor position in the DecorationsOverviewRuler constructor. This ensures that the initial value for the cursor position in both the newly opened view and the decorations overview are the same, allowing for proper rendering even when onCursorStateChanged is never called (such as when the editor's cursor is at its initial position (1,1)).

In cases where the cursor is not at the default position after state restoration, onCursorStateChanged is called, and everything should work as before.

[hediet]

Much nicer change! Thank you!