Module zoom 

EXP-1586: the ZoomableImage native’s maths (catalog/style.json zoomableImage, whose $comment is the spec). Pure: every painter feeds its pointer, wheel, pinch and key input through these functions, so a zoom, a pan or a double tap lands on the same view everywhere. Mirrors src/zoom.ts; fixtures/zoom.json locks it.

Structs

ZoomBounds

ZoomFrame

What every function needs to know about the picture and its box.

ZoomLimits

ZoomMenuItem

ZoomPanRoom

ZoomPillSpec

The pill’s geometry (style.json zoomableImage.pill).

ZoomPoint

ZoomSize

ZoomSpec

style.json zoomableImage.

ZoomView

scale = displayed px per image px (1 = 100%); x/y = the picture’s top-left in the viewport.

Enums

WheelDeltaMode

ZoomInitial

The initial prop (catalog enum zoomInitial); anything else = Auto.

Statics

ZOOM

Functions

zoom_at_rest

Whether the view sits at its rest scale.

zoom_bounds

The pill’s disabled ends.

zoom_centre

The viewport’s centre, the anchor of keys and the pill.

zoom_clamp

The view inside its bounds (scale within the limits, no letterbox).

zoom_double_tap

Double click / tap: at rest → zoom in about the point; else → rest.

zoom_double_tap_scale

The scale a double tap at rest jumps to.

zoom_drag

A drag from start by (dx, dy) while held: past an edge the overshoot rubber-bands. The release is zoom_clamp of the last view.

zoom_fit_scale

The whole picture inside the viewport, never upscaled: the minimum.

zoom_is_tall

A picture taller than 1 / tallAspect times its width.

zoom_key

A key while the picture has focus; None = not a zoom key.

zoom_ladder

The ladder steps walk: the presets plus the rest scale, inside the limits, ascending.

zoom_limits

The scale range: [fit, max(fit, maxScale)].

zoom_menu

The % button’s Menu: Fit, then the menu presets inside the limits.

zoom_momentum

Mouse-drag momentum t ms after a release at velocity (px/ms), exponential decay, stopping at the edges.

zoom_momentum_active

Whether momentum t ms after a release is still moving (above 0.01 px/ms).

zoom_pan_room

The axes the picture can pan on: an axis without room hands a swipe to the host (paging).

zoom_percent

The pill’s label: round(scale × 100) + % (JS Math.round: halves up).

zoom_pinch

A pinch from start by the raw factor about anchor while held: past the min/max the scale rubber-bands (d = the limit). The release is zoom_clamp of the last view.

zoom_request

THE JSON entry (the FFI’s zoom_json, the fixture replays ×4): {op, frame: {natural, viewport, initial?, maxScale?}, from?: view | "rest", …} with the op named like the fixtures/zoom.json group it answers: rest, clamp {view}, zoomTo {scale, anchor}, wheel {deltaY, mode, anchor}, scroll {deltaX, deltaY}, ladder, steps {scale, direction}, step {direction} (a view), doubleTap {point}, keys {key}, rubberBand {overshoot, extent}, drag {dx, dy}, pinch {factor, anchor}, momentum {vx, vy, t}, momentumActive {vx, vy, t}, panRoom, resize {fromViewport} (from: "rest" = the rest view at the OLD viewport), percent {scale}, menu {fitLabel?}, bounds.

zoom_resize

A new viewport: at rest = the new rest view; zoomed = the same scale about the viewport centre, clamped.

zoom_rest_scale

The scale the picture opens at (and a double tap / 0 / the fit button returns to), inside the limits.

zoom_rest_view

The opening view: the rest scale, centred; a taller-than-the-viewport picture starts at its top.

zoom_rubber_band

The overshoot past an edge, damped: (1 − 1 / (o·c/d + 1))·d.

zoom_scroll

A plain wheel / two-finger scroll: pans by the deltas, clamped.

zoom_step

/ − (keys and the pill) about the viewport centre.

zoom_step_scale

The next ladder scale strictly above (1) or below (-1) the current one, or the current one at the end.

zoom_to

Zoom to scale (clamped) keeping the image point under anchor fixed.

zoom_wheel

One ⌘/ctrl-wheel event about the cursor.

zoom_wheel_factor

⌘/ctrl + wheel (or a trackpad pinch delivered as a wheel): the scale factor of one wheel event.