frontend/html: awesome rendering

[emersion]

For the moment, each time you type the whole file contents is re-rendered.

We should render only modified lines and lines where the syntax coloration has changed, like in the QML frontend.

I don't understand very well how to do this for now, could you help me a little please?

[quarnster]

Related to #303, #425.

The qml frontend currently first adds a BufferChangedCallback to the buffer, and then in the callback it counts the number of new lines in the region added.

It doesn't handle line removal efficiently yet as the number of new lines removed will already have been removed once the callback is called. Thus one will have to figure out in some other way how many lines to remove. I'm not too happy about that and I've opened up text#3 to improve this.

The qml frontend actually does a unneeded re-formatting of the whole file currently... #425 opened which would help improve that in the future.

[quarnster]

FYI text#3 has now been addressed. See
https://godoc.org/github.com/limetext/text#Buffer.AddObserver
https://godoc.org/github.com/limetext/text#BufferObserver

[erbridge]

Migrated to limetext/lime-html#1.