[FEATURE] Optionally use a map theme to render terrain textures

[wonder-sk]

Often it is useful to have a different map theme for terrain in 3D view than the map theme used in the main map canvas.

[nyalldawson]

Do map themes apply to 3d render settings too?

Code here looks good, but could you add a test?

[wonder-sk]

Do map themes apply to 3d render settings too?

Themes are only applied as an override of map theme for terrain texture. 3D renerer settings of map layers are used from whatever is the current map theme.

Code here looks good, but could you add a test?

Added in afd3525 with few fixes

[nyalldawson]

. 3D renerer settings of map layers are used from whatever is the current map theme.

Is this by design? Or just due to not-yet-implemented features? I think as a user I'd expect the 3d canvas to behave similar to the 2d canvas here and switch to the entirety of the selected theme.

[wonder-sk]

Is this by design? Or just due to not-yet-implemented features?

To be honest I haven't thought much about 3D renderers of map layers. My aim really was to be able to use different texture for the terrain than what the main canvas displays, so for example some map layers with 3D renderers wouldn't get rendered in 2D map too. Having themes support for 3D map layer renderers could be nice, but that's a lower priority for me. So I guess that is a not-yet-implemented feature rather than unsupported by design.

[nyalldawson]

Ok. If it was by design I'd have an issue, but if it's just not implemented then I've no issue!