Summary

Add an optional "derive from measurements" mode to the config flow that computes FOV Left/Right and Window Depth from three physical inputs, so users with recessed covers in thick walls don't have to reverse-engineer the integration's coordinate model.

Today both parameters are a deterministic consequence of wall thickness, window width, and the cover-to-glass distance — but we leave the trig to the user. The wiki even shows the arctan example for a 60 cm wall without automating it, so most users keep the 90° FOV default, which is wrong for any recessed installation.

Proposed inputs

Derivation

FOV Left/Right = arctan((window_width / 2) / cover_depth_from_outer_wall)
Window Depth   = glass_depth - cover_depth

Behavior

• Manual FOV fields stay available and override the computed value. A value of 0 (or empty) means "use the auto-calculated value"; a non-zero manual value wins — this preserves the escape hatch for asymmetric reveals and external obstructions (neighbouring buildings, overhangs, etc.).
• All three new fields default to 0 / not set, so existing installations are unaffected.

Why

• Recessed covers in thick walls get correct values without understanding the internal model.
• FOV and Window Depth can no longer be silently inconsistent (e.g. deep wall + small window depth).
• The 90° FOV default stops being quietly wrong for the most common non-trivial case.

References

• Discussion Derive FOV and Window Depth automatically from physical wall/window measurements #489 (originated this proposal, with the 40 cm wall example to design against)
• Discussion Optional Window Depth #288 (same underlying confusion about optional Window Depth, from a different angle)