This patch does nothing but alter how the playhead scrubber is drawn in the timeline (and other editors).
The left of the following image shows how it looks now. The right side is after this patch is applied:
The width gets a minimum so it won't get too small.
It stays centered over the vertical frame line no matter how wide that line is.
It has a nicer almost-AA edge...
Our current GL drawing routines allow us to draw with smooth AA edges or with solid opaqueness, but not both. The current playhead drawing code opts for opaque coverage (since it overlaps other numbers) but doing so the edges are not anti-aliased.
This version draws the middle opaque in one pass and then adds an anti-aliased outline. It's not perfect. It is an AA outline smoothing out the rough edges of a non-AA shape. But it is much better than we have now.
I have made the outline slightly lighter than the interior. This is not strictly necessary, and I could remove that if you wish. But I find that this feature helps mask the non-perfect nature of implementation.