Selection highlight settings

[SerCarciofini]

Issue Type: Bug

Looks like setting selection highlight this way
"editor.selectionHighlight": false,
"editor.occurrencesHighlight": true
disables occurrencesHighlight anyway, no matter if it's true or false

VS Code version: Code 1.24.1 (24f6262, 2018-06-13T17:47:35.732Z)
OS version: Linux x64 4.15.0-23-generic

System Info

Item	Value
CPUs	Intel(R) Core(TM) i3-4005U CPU @ 1.70GHz (4 x 1332)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: disabled_software rasterization: disabled_software video_decode: unavailable_software video_encode: enabled vpx_decode: unavailable_software webgl: enabled webgl2: enabled
Load (avg)	0, 1, 1
Memory (System)	7.71GB (0.93GB free)
Process Argv	/usr/share/code/code /tmp/fz3temp-2/archivio.php
Screen Reader	no
VM	0%

Extensions (4)

Extension	Author (truncated)	Version
jshint	dba	0.10.19
svn-scm	joh	1.29.2
vscode-language-pack-it	MS-	1.24.3
vscode-code-outline	pat	0.2.1

[vscodebot]

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[alexdima]

@SerCarciofini This depends from language to language.

It is a bit complicated, but here goes:

---

• extensions can contribute a DocumentHighlightProvider for their language. This should be a semantic highlighter which highlights, for example, the same variable. You can see this in action in a .js file (notice how nn is highlighted semantically, the first occurrence is not highlighted):
  
• this feature can be turned off via editor.occurrencesHighlight

---

• there is another feature called selection highlighting. This kicks in when making a selection and is non semantic (it will highlight all occurences of the selection):
  
• this feature can be turned off via editor.selectionHighlight

---

Now, there is a long tail of languages which we also want to support. For a lot of them, we don't have rich extensions that can implemented semantic highlights. So, if a language does not register a DocumentHighlightProvider, we fall back to the selection highlighter even when there is no selection. You can see this kicking in for example in plain text:

• you can think of this fallback as an implementation of a very simple DocumentHighlightProvider. Currently, this gets disabled when either editor.occurrencesHighlight or editor.selectionHighlight are set to false.

Would you expect that this last one should be disabled only when configuring editor.occurrencesHighlight to false?

[SerCarciofini]

Would you expect that this last one should be disabled only when configuring editor.occurrencesHighlight to false?

Actually yes because with the current logic, there's no way to disable editor.occurrencesHighlight while keeping the fallback you described. Or it might make sense add an additional explicit setting for this fallback.

[alexdima]

To verify, configure:

"editor.selectionHighlight": false,
"editor.occurrencesHighlight": true

Then open a plain text file and check that words are still highlighted, even if selectionHighlight is turned off.