Hi all,
in the attached GIF, the slentando and Andante tranquillo markings do not line up. It seems this has to do with the letter “q”, because when I add it, the alignment is corrected.
Can you reproduce this, or is there something I am missing?
I think adding the “q” aligns it to the other by accident. Non-continuous tempo markings do not currently align vertically.
It’s moving it higher because of the q, but that has nothing to do with the mark that follows. Tempo marks might align on a system or they might not, but they generally require manual adjustment.
But the next marking also has a q. If I take that away, the whole marking goes down. My logic is that since the protruding items to avoid are the same, they should be on the same vertical level as specified in the engraving settings.
The text items are set to appear a certain number of spaces above the stave, and to avoid colliding with other objects (again, by being a certain number of spaces above the tops of those items). Dorico’s calculating from the bottom of the letters that are actually included in the text item. If you add a letter that has a baseline descender (such as a j, p or q) then Dorico considers the bottom of that letter to be the bottom of the text item. You could argue that Dorico ought to consider the potential for baseline extenders in tempo items, but then the many tempo markings that don’t contain them wouldn’t comply with the Engraving Options!
I would not like to argue for that, but rather that this was handled in a way similar to the tucking in of accidentals. The baseline descender in “q” should not cause the whole text to move up since the descender does not actually collide with anything. The bounding box for the text marking should not be a rectangle, but rather a polygon. Sorry for the cryptic explanation but maybe you understand what I mean 
I understand exactly what you mean. With any luck someone from the development team will chime in sooner rather than later.
You simply redefine the Engraving Options to consistently mean “distance below baseline to whatever” for text above objects and “distance above text X-height to whatever” for text below them.
Of course however you do this it will potentially change the format of old projects, but if it doesn’t change anything there is no point in doing it!
This doesn’t only apply to tempo text. One of my peeves is that families of ornaments like the various baroque trill signs don’t line up when there is no collision with notes, because some of them have “descenders” in the symbols and others don’t.
Typography doesn’t change the interline spacing for text because there may or may not be ascenders and descenders in the characters in a line. It seems illogical to me that Dorico doesn’t follow the same principle in avoiding collisions. The only “reason” not to is if you want to have extremely tight spacing - but most of the time that just reduces readability.
Unfortunately it’s not easy to get a raggedy bounding shape around a complex text item in order to tuck it in the way that we do other things we draw. I wouldn’t rule out that for the future but it’s not simple to do for text.