It would be nice if we had the ability to choose the line height of the editor so that text becomes more readable in some fonts.

So I come up with a set of changes that add a new option in the configurations UI to let the user specify a line height multiplier. In the renderer, when setting m_fontHeight, I also multiply it by the chosen value. I am happy with the results (see screenshots).

There's a problem, though: selection gets inconsistent. I know that we let Qt draw the selected text background by passing a list of FormatRanges to it specifying decorations for the selected text. For selected parts that are not text (e.g, when there's whole lines selected), we draw the selection background by ourselves. Qt's text rendering doesn't know of the new height so it doesn't render the selected background in whe whole height, but katepart does so it renders the selection background in the whole height.

I've come up with some ideas: Make Qt's text rendering aware of the new height (I don't think this is going to happen as I searched a lot but couldn't find how to do it) or draw the text background ourselves, but this involves calculations like the selected range, where the characters are, etc, that I don't feel versed enough in kate's code to do that.

So my solution was, when rendering the selected background, use the original font height instead of the multiplied one. It doesn't look very pretty but at least is consistent.

It would be nice if someone helped me fixed the selection in these cases, but, I am happy enough with the results to use it in my day-to-day life.

Reproducible: Always

Steps to Reproduce:
Open Kate
Go to Settings->Configure Kate->Editing
Actual Results:  
No option to change the line height

Expected Results:  
Option to configure the line height or the line height multiplier

Please see patches/screenshots