Derive FOV and Window Depth automatically from physical wall/window measurements

[FredM67]

Background

While configuring my setup (a window mid-wall in a 40 cm thick wall, cover mounted on the window's outer face — see #288), I found that the current parameters require understanding the integration's internal coordinate model to set correctly. Specifically:

• FOV Left/Right must be estimated in degrees, but they are a direct geometric consequence of the window width and how deep the cover sits from the outer wall face. Most users will guess or use the 90° default, which is wrong for any recessed installation.
• Window Depth is documented as "distance from outer wall surface to glass", but only makes sense if the cover is at the outer wall surface. If the cover is recessed (as mine is), users will set it incorrectly.

The wiki even acknowledges this relationship (arctan example for a 60 cm wall), but leaves the calculation to the user.

Proposal

Add optional physical measurement inputs:

Parameter	Description
Window opening width	Width of the opening in the outer wall face
Cover depth from outer wall face	How far inward the cover hangs
Glass depth from outer wall face	How far inward the window glass sits

When these are provided, auto-calculate:

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

FOV Left/Right would remain manually overridable (keep the existing fields, but pre-populate them from the formula). A value of 0 — or leaving the fields empty — signals "use auto-calculated value". Non-zero manual values override the calculation, which handles asymmetric reveals and external obstructions (neighbouring buildings, overhangs, etc.).

What this solves

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

Backward compatibility

No impact on existing installations. All three new fields default to 0 / not set, preserving current behaviour exactly.

Reference

Discussion #288 (Optional Window Depth) covers the same underlying confusion from a different angle.

[jrhubott]

You've described the calculation exactly right — for a cover mounted on the outer face of a 40 cm wall, FOV and effective window depth are both deterministic consequences of wall thickness, window width, and cover-to-glass distance. I can add a "derive from measurements" mode to the config flow that takes those three physical inputs and computes FOV and Window Depth automatically, with the manual fields still available for users who already know their angles. I'll log this as a config-flow UX improvement — the 40 cm wall example is a concrete enough case to design against.

[FredM67]

That'd great, thx a lot.
May be as suggested, simply set the FOV defaults to 0, which would mean "derive from measurements". So you don't need to add any new check box or so.

[FredM67]

Hi @jrhubott
Do you have any timeline, when you'll implement this improvement?
No pressure at all, it's just to know if I calculate all my 24 pair of FOV (I've 24 windows with shutters), or if I wait until it's implemented ;-)

[jrhubott]

Logged this as #550 to track the work. Thanks for the clear write-up, @FredM67 — the 40 cm wall case gives me a concrete target to design the config-flow mode against.

[FredM67]

In fact, the most important measure is how "deep" the window is inside the wall.
The inner part, in my case 20cm, is only important if the user wants to allow some direct sun light inside the room.