When typing characters such as É, È or Ô (from range U+00C0 to U+00DD) that extend above the font ascent, the part above the current line is not drawn (until the previous line is redrawn). In a similar way, garbage remains when the character is deleted. Steps to reproduce : 0) Use Oxygen font 1) Make sure the cursor is at least on the second line 2) Paste ÉÈÔ : the accents are not visible 3) Move the cursor up : the accents appear 4) Delete the characters : the accents remain 5) Move the cursor up : the accents disappear I can't send a screenshot, because the whole window is redrawn when focused out. This is closely related to #335079, which describes similar (though more serious) problems when the characters extend below the font's descent.
Known issue: since the painting is line-based fonts whose characters exceed the lower or upper bound of their own line height draw in the area of neighboring lines. When neighboring lines are drawn, these parts are lost. Mostly a problem in the fonts, but then again, would be nice, if Kate could handle it correctly. *** This bug has been marked as a duplicate of bug 335079 ***