Bug 133569

Created attachment 161480 [details]
Dummy document with a comment for easier test

Original I found that Writer's comments ruler UI control in some KDE theme setting was highlighting on mouse over to use a black text on black background, which made it unreadable.

While looking into the code and testing the UI element, I found further problems with the design and implementation:

* swapping the arrow from left to right, as documented in the design wiki page, moves the text, which I find highly irritating
* in RTL mode, the label is right-aligned, resulting in completely hidden text and arrow, if the document space is small
* the arrow has a small, fixed size and padding, drawn with four consecutive lines, so it doesn't scale in HiDPI mode

Eventually the comments column should switch to the left side of the document, if the document itself is in RTL mode, as IMHO this follows the reading flow easier. But since I don't have any experience working with RTL environments, I didn't implement this. 

There is already a patch, which addresses all the mentioned problems: https://gerrit.libreoffice.org/c/core/+/75421

Design wiki page: https://wiki.documentfoundation.org/Design/Whiteboards/Comments_Ruler_Control
Implementation tracking: bug 38246

If some design people have additional comments, I'll try to address them, otherwise merge the patch end of next week.

To reproduce:
1. Open the attached document
2. Change the comments visibility via the ruler UI element

You can test the HiDPI setting with qt5 / kf5 starting LO with QT_SCALE_FACTOR=2.