HUD hint buttons: Project shadow for better contrast

[manuq]

Use the same offset and color than the text label shadow.

Mouse and keyboard atlas: Remove rectangle of solid pixels

Which actually don't contain any icons. Because when cropping slices of this
atlas right below this area, the drop shadow shader does drop a shadow for the
pixels above.

[github-actions]

Play this branch at https://play.threadbare.game/branches/endlessm/hud-hints-contrast/.

(This launches the game from the start, not directly at the change(s) in this pull request.)

[manuq]

@wjt I remember we got feedback on having a better contrast in the HUD some time ago. I think it was in Discord. We could do the change in the assets themselves. Here I did it with a shader, at least for a quick try.

[manuq]

This is how hints on the right side look:

There is a problem with the mouse hint, it is projecting shadow at the top border:

The region is correct, I think. But the texture has pixels painted above. One way to fix it is by making those unused pixels transparent:

[manuq]

Fixed by just removing the solid rectangle from the atlas asset:

[wjt]

I think I saw another way to avoid this oversampling of the texture - let me check.

[wjt]

Found it. AtlasTexture has a filter_clip property:

I think that would work. But maybe it has a cost; and just deleting the extraneous pixels also works.

[manuq]

Found it. AtlasTexture has a filter_clip property:

Oh good to know!

I think that would work. But maybe it has a cost; and just deleting the extraneous pixels also works.

As you wish. I can revert the texture change. But yes we really don't need those pixels.