Interpolating RGB between activeTint and inactiveColor produced a
visibly muddy intermediate color that read as a hard cut inside the
button rather than a soft fade. Switched to a pure alpha gradient of
inactiveColor itself (0.0 -> 0.85): at alpha 0 it exactly matches the
header container's own tint sitting behind it, so the seam disappears
entirely, and the color only ever mixes with itself. Also pushed the
stop from 30% to 45% of the button's width for more breathing room
before the solid fill starts.
Constantin Leue
4485c1644e