houseplan-card/docs/DECOR-EDITOR.md

Background editor: current contract

Status: implemented in v1.60.0. This document is the source of truth for the decorative layer. BACKDROP.md, LIVE-TEXT.md and FURNITURE.md describe the specialised parts.

Purpose and invariants

The Background editor is a visual annotation layer. Its shapes, furniture, text and plan image never participate in rooms, wall geometry, light routing, device state or Home Assistant actions.

Invariant	Contract
Coordinates	Axis-aligned positions and every box dimension are quantised to the space grid. A rotated resize keeps its opposite world-space corner fixed and quantises dimensions; its derived unrotated storage origin is not post-snapped, because that would translate the entire object. Shift never disables dimension snapping.
Physical values	Stroke and text sizes are stored in centimetres; the UI shows cm/in for small values and m/ft for object dimensions.
Undo	Decor and backdrop use the same named 50-command stack as plan geometry.
Cancel	Esc restores the state at the start of an active drag/draw/resize/rotate gesture. A completed gesture is reverted with Undo.
Selection	One click selects; drag moves; the selected object has one common transform frame; double click opens all editable properties.
Scale	Corner drag preserves aspect ratio. Hold Shift for independent axes.
Rotation	5° steps by default; Shift gives free rotation. Lines use endpoint handles instead of a rotation handle.
Magnet targets	Only other decor objects and room contours: corners, edge centres, centres and edges. The image, devices and openings are excluded.
Context emphasis	Decor and its editing chrome stay fully opaque. Rooms, labels, devices, openings, solid/thick walls and dashed virtual walls are contextual only and render at 35% opacity.
Compatibility	Legacy width, text size/scale and plan_scale remain readable. New writes use width_cm, size_cm and plan_scale_x/y.

Tools

Tool	Pointer action	Live feedback	Properties
Select	Select/move any decor object; corner handles resize; upper handle rotates	common selection frame and standard move/resize/rotate cursors	double click opens geometry, angle, contour/fill colour and opacity; text also exposes its content
Plan backdrop	Move the image by its body; resize/rotate by the frame	size badge; 5° rotation step	double click opens width, height and angle
Line	Drag between two grid points	length, angle, magnetic alignment guides	endpoint handles; length, angle, stroke colour/opacity/thickness
Rectangle	Drag a diagonal; Shift makes a square	width × height and area	size, angle, contour, optional independent fill colour/opacity
Oval	Drag its bounding box; Shift makes a circle	R for a circle, Rx × Ry for an oval	bounding size, angle, contour and optional fill
Text	Click to open the text form	the saved label is selected immediately	content, HA variables, colour/opacity, physical size and angle
Furniture	Pick a symbol, then click its centre	wall magnet unless Shift is held	size, angle and contour style; the common frame preserves ratio unless Shift is held
Erase	Click a decor object; text uses its whole logical bounding box, including spaces between glyphs	confirmation dialog, then atomic removal of the whole object	A miss changes nothing; Undo restores a removed object

The editor always opens on Select. If the space has an image, the Plan backdrop tool appears next to Select but is never armed implicitly.

Plan image behaviour

The plan image is interactive only while Plan backdrop is selected.

Context	Image opacity	Frame/body interaction
View, Plan editor, Device editor	1.0	none
Background editor, Select/drawing/furniture/erase	0.5	none; the stage remains available for pan/draw
Background editor, Plan backdrop	1.0	move, proportional/independent resize, rotate

Stored transform fields:

plan_x, plan_y                 top-left offset, normalised to the square canvas
plan_scale_x, plan_scale_y     independent positive multipliers
plan_angle                     degrees, normalised to -180..180

plan_scale is the legacy uniform fallback. The maintenance command converts it losslessly to both axis fields. Reset removes every transform field.

Style and units

New decor writes use:

color, opacity, width_cm
fill, fill_color, fill_opacity       rectangles and ovals only
size_cm                              text only

width_cm and text size_cm are independent physical styles. Resizing a rectangle or sofa does not make its outline thicker. A legacy object with render-unit width stays pixel-identical until edited or explicitly optimised; conversion is width_cm = width / GRID_PITCH × cell_cm.

The toolbar values are session defaults for newly drawn objects. Colour is a compact swatch; its popover owns both the native colour field and opacity, so alpha controls do not consume permanent toolbar space. Double-click properties edit an existing object without creating a second style model.

Interaction state machine

idle → draft/move/scale/rotate → release → named history command → debounced save
                          ↘ Esc → restore transaction start → idle

Only the active tool owns pointer events. Drawing tools can therefore start a new line or figure exactly on top of an existing object. Select and Erase are the general tools that target existing decor. The deliberate exception is Text: clicking an existing text label with Text opens that label's editor; clicking any non-text shape still starts a new label. The backdrop body belongs only to the Plan backdrop tool.

Ctrl/Cmd+Z first cancels an unfinished draft or live gesture, then walks the shared history. Ctrl+Shift+Z and Ctrl+Y obey the same transaction boundary: the first invocation cancels a live gesture, the next redoes. Native text-field history wins while focus is inside an input.

Code ownership

Concern	File
persisted decor types and future custom-image transform contract	src/editors/decor/types.ts
physical style conversion, oriented boxes, resize and snapping	src/editors/decor/geometry.ts
shared colour/opacity field	src/hp-color-opacity.ts
orchestration, dialogs and SVG transform frames	src/houseplan-card.ts
static/full-card backdrop rendering and content bounds	src/space-render.ts, src/space-geometry.ts
accepted persisted ranges	custom_components/houseplan/validation.py
explicit legacy conversion	src/plan-optimizer.ts

The current root card still owns orchestration. Future extraction should move it into src/editors/decor/decor-editor.ts without changing the typed model or geometry helpers.

Deferred custom images

User-provided decorative images are not exposed yet. The typed DecorImageTransform contract already matches the common selection controller (x/y/w/h/angle/opacity). A future image kind must additionally define safe upload/reference lifecycle, quotas, copy-on-write and deletion semantics before it is added to DecorShape; it must not reuse the plan backdrop file lifecycle implicitly.

Edge cases

• Degenerate drafts below half a cell are discarded and do not enter history.
• Unknown furniture symbols remain stored but render nothing in an older card.
• A rotated box contributes all four rotated corners to content bounds.
• A rotated backdrop is hit-tested in its own local coordinate system.
• Changing cell_cm changes the rendered width/font size of canonical physical styles, as expected: it changes the scale of the whole space. Legacy render-unit strokes/text retain their old pixels until migration.
• External config revisions clear the session history; undo never applies a command to a different server revision.