Collapse and expand sections

[aisbergde]

I tested some Android editors, including Acode and code-editor, and I was surprised about built-in syntax highlight for many languages, including Markdown and AsciiDoc. What I really like: they support line numbers and a feature to collapse and expand sections. Maybe this would be also a good idea for Markor?

[harshad1]

One problem is that we use a plain old EditText as the underlying interface. Collapsing and expanding sections can be challenging to do well without changing to a mode powerful underlying view.

One option which may work even with an EditText is this - https://developer.android.com/reference/android/text/style/DynamicDrawableSpan

[gsantner]

#922