List: Support a different navigation mode where focus and selection move together

[joaomoreno]

• When focus === selection && size 1
• Else, navigation should only move focus

[rebornix]

I found that some of the tree is already doing that, for example the Problems View, which is an ObjectTree, will move both focus and select down when arrow down key is pressed, even if we turn on multipleSelectionSupport for it.

This is because focusDown command already has a special logic for tree: pass in a fake keyboard event

vscode/src/vs/workbench/browser/actions/listCommands.ts

Line 51 in e9533c2

tree.focusNext(count, loop, fakeKeyboardEvent);

and then openOnFocus option will decide if selection should be set to the same as focus

vscode/src/vs/platform/list/browser/listService.ts

Lines 617 to 619 in 828f99e

	if (this.openOnFocus) {
	this._register(Event.filter(this.widget.onDidChangeFocus, e => e.browserEvent instanceof KeyboardEvent)(e => this.onFocusFromKeyboard(e)));
	}

vscode/src/vs/platform/list/browser/listService.ts

Lines 631 to 633 in 828f99e

	private onFocusFromKeyboard(event: ITreeEvent<any>): void {
	const focus = this.widget.getFocus();
	this.widget.setSelection(focus, event.browserEvent);

The problem with this special logic is, shift+arrowdown doesn't work anymore, even with "multipleSelectionSupport": true. It will move the focus down and then move the selection down as well.

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As we discussed this morning, a new flag/option will be introduced for this behavior and we should get rid of focused instanceof List || focused instanceof PagedList || focused instanceof Table checks in the list commands, and use the new option to decide what's the expected behavior. And also make sure shift+arrowdown still works.

[joaomoreno]

The new selectionNavigation list/tree/table option will make selection move along with focus, when navigation commands are executed: ie UpArrow, PageUp, Home, et al.

@roblourens @sandy081 This can now be adopted in Search and Problems and you can very likely remove some annoying code you must have created to keep both focus and selection in sync.

@rebornix When adopted, can you mark as verified?

[roblourens]

I forgot that the openOnFocus flag exists, which opens and selects items when they become focused, so I already get this behavior. Any benefit to using both flags?

[joaomoreno]

Oh I forgot about that, that's exactly what search, problems, etc are using. Let me see if I can clean up that one, I do look at it more as a hack, and adopt the new one instead.