Comment 8 for bug 1772451

Description:
Arabic is sometimes written with diacritical vowel marks, which are placed either above or below each letter of the word. Many multipurpose fonts, which are not designed specifically for Arabic, place some of these marks in the empty space between lines, outside of the space reserved for line height. Writing Arabic in LibreOffice Writer, these marks don't become visible while typing but only after the page view has changed once.

See the attached series of screenshots, where the first screenshot has been taken while typing. The first letter of the first word (reading from right to left) should have two diacritical marks: ء and a diagonal line above the letter: أَ. Only the lower half of the ء mark is visible and the diagonal line not at all. The second letter of the same word has a circle on top of it but only the lower half of it is visible. Equally so for the third word of the sentence بِبَرْنَامِجِ, where the last letter of the word has a diagonal line below, but it is not visible at all. The second screenshot has been taken after I scrolled the page down by a couple of screens and then scrolled back. Now all the diacritics are shown as they should. In the third screenshot I have deleted all of the text I typed but as you can see, some parts of the diacritics are still visible above the line. If I scroll down and back, they would disappear. If you want to test it yourself, the sentence I wrote reads "أَكْتُبُ هُنَا بِبَرْنَامِجِ لِيبَرْ أُفِيسْ".

This problem is similar to https://bugs.documentfoundation.org/show_bug.cgi?id=85426 but does not involve fixing line spaces. Even the font I'm using is different (DejaVu Sans).

This bug was first reported on Launchpad for LO 5.4.6.2 on Ubuntu 17.10 at: https://bugs.launchpad.net/ubuntu/+source/libreoffice/+bug/1772451 . After my initial report, I have upgraded to LO 6.0.3.2 and can still reproduce the problem. On Launchpad, I was advised to file this report separately from 85426, as I was not sure whether it is exactly the same issue or just related to it.

Steps to Reproduce:
1. Type Arabic text with full vowel marks, including low diacritics under letters extending below the baseline and high diacritics on top of high letters.
2. Remove the text by pressing backspace.

Actual Results:
Many vowel diacritics or parts of them become visible only after the view is changed, and removing a character sometimes leaves the diacritic or part of it visible on the screen, although textually it doesn't exist anymore.

Expected Results:
All diacritics should become visible as the user is typing and be removed from the screen as soon as the characters are removed.

Reproducible: Always

User Profile Reset: No

Additional Info: