TTrackbar working from right to left instead of left to right

  

I’m looking for a way to get a certain Delphi Firemonkey TTrackbar behavior change
in my Delphi 10.1 Seattle Android app.

What do I want to achieve?
The trackbar has a thumb the user can move. It runs on a track and the
side of the track left from the thumb until the left end of the track
will be colored by default to indicate the value chosen with the thumb.

I want it reversed: the track right from the thumb until the right end
of it shall have this color.

I was pointed into the direction of styles already but after learning a little bit about those I still don’t fully understand how to do it for my case and I start to doubt that just changing the style will work.

I dropped a TTrackbar on a form, right clicked on it and choose “edit
custom style”. I found that there is a htrack which consists of the
background, a TRectangle and the highlight, which is a TStyleObject.
Being a TStyleObject it is linked to a region in a png file via
SourceLookup and SourceLink. But there my wisdom stops.

how to find that png?
even if I find it, what to do next? I don’t want to change the
appearance of that “highlight” TStyleObject, I want to change its
position. I already tried to have it right anchored, but that’s of
course only part of the solution, as the width calculation at
runtime would need to be “inverted” (1-x) as well.

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