Viewport Math (matrix.ts)

Stateless math functions for coordinate transformations, zoom anchoring, hit testing, and viewport interpolation.

Coordinate Conversion

screenToCanvas(pt, vp)

Converts viewport screen offset pixels to canvas (world) coordinates.

function screenToCanvas(pt: Vec2, vp: ViewportMatrix): Vec2

canvasToScreen(pt, vp)

Converts canvas coordinates to screen offset pixels.

function canvasToScreen(pt: Vec2, vp: ViewportMatrix): Vec2

Zoom & Pan

calculateZoomAnchor(pivot, oldScale, newScale, vp)

Computes translation parameters to scale around a cursor point (preventing cursor drift during zoom).

function calculateZoomAnchor(
  pivot: Vec2,
  oldScale: number,
  newScale: number,
  vp: ViewportMatrix
): ViewportMatrix

applyWheelZoom(e, vp, bounds)

Applies zoom modifications from a wheel event.

function applyWheelZoom(e: WheelEvent, vp: ViewportMatrix, bounds: DOMRect): ViewportMatrix

applyPan(e, vp, prev)

Accumulates pan offsets from a pointer event.

function applyPan(e: PointerEvent, vp: ViewportMatrix, prev: Vec2): ViewportMatrix

clampScale(scale)

Restricts zoom factor to bounds (ZOOM_MIN to ZOOM_MAX).

function clampScale(scale: number): number

Hit Testing

isPointInElement(pt, rect)

Collision test: returns true if the point is inside the rectangle.

function isPointInElement(pt: Vec2, rect: Rect): boolean

hitTestElements(pt, nodes)

Returns the ID of the topmost element covering the pointer position, or null.

function hitTestElements(pt: Vec2, nodes: ReadonlyArray<ResolvedNode>): string | null

getAnchorPositions(rect)

Gets the coordinate positions for all eight resize handle anchors.

function getAnchorPositions(rect: Rect): Record<ResizeAnchor, Vec2>

Interpolation

lerp(start, end, amt)

Standard linear interpolation helper.

function lerp(start: number, end: number, amt: number): number

lerpViewport(start, end, amt)

Smooth viewport transition interpolator for animated pans/zooms.

function lerpViewport(start: ViewportMatrix, end: ViewportMatrix, amt: number): ViewportMatrix