Mirror cursors

[xorye]

Here is some work for #130

Everything that works for the html mirror tags, should work with this PR.

Toggle is available with ctrl+shift+f2.

How it works:
There is a listener that listens for changes in the xml.mirrorCursorOnMatchingTag config. This listener is active as long as vscode-xml is activated.

If xml.mirrorCursorOnMatchingTag is turned on, a MirrorCursors object is created. This object creates more listeners.
When xml.mirrorCursorOnMatchingTag is turned off, the MirrorCursors object (if exists) is disposed, along with the listeners it created.

I must clean the code and play around with it more.
Please feel free to test things out as it is.

[angelozerr]

@xorye IMHO (but not sure if it's possible?), I think we should keep the original mirrorCursor.ts from vscode and update it by adding comments (// updated for vscode-xml) because:

• it will be more easy to review your PR (just comparing original vscode mirrorCursor.ts with your mirrorCursor.ts)
• when vscode will fix something in mirrorCursor.ts, it will be easy to fix it in vscode-xml if we have the same code.

@fbricon what do you think about that?

[fbricon]

new version seems way safer

[xorye]

fixed

[fbricon]

We still have that completion issue, that the html server doesn't have:

[xorye]

The reason why it works for the HTML language server is that for their completion requests, the new text that is being inserted is only the tag name (ie, div).

LSP4XML provides the brackets, start tag and end tag on completion, (ie <div></div>). One solution would be to have LSP4XML do the same thing as the HTML language server and just send back the tag names, but maybe that's not feasible in the context of LSP4XML?

[angelozerr]

As @xorye LSP4XML generate the start and end tag when completion is applied (like Eclipse WTP) although HTML Language server generates only the start tag.

An idea of fix is to check if mirror cursor is activated and send this settings to the LSP4XML. In this case, the end tag should not be generated and we will have the same context than HTML language server.

[fbricon]

I think you can check whether the tag is closed or not, whether mirror cursors is enabled or not

[angelozerr]

I think you can check whether the tag is closed or not

Ideally we should do that, but I don't know if it's possible to do that, need more investigation.

[fbricon]

See related microsoft/vscode#88424

[xorye]

Closing in favour of #304, since HTML doesn't use the old mirror cursors implementation that this PR was based on.