56 lines
2.5 KiB
TypeScript
56 lines
2.5 KiB
TypeScript
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/**
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* Shared pan/zoom viewport math — the "fit floor" semantics harvested from
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* the plan popup (plan-graph rounds 2–4) so the session overlays (the plan
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* focus, the mermaid focus) run the SAME geometry: fully zoomed out IS the
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* fit (whichever axis binds), panning locks at the floor (nothing to move),
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* wheel zooms to the cursor. Pure on purpose: the overlays are render-tested
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* in static markup (no live pointer events), so the math lives here where
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* tests can pin it (tests/pan-zoom.test.ts).
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*/
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/** Zoom ceiling for every surface that uses this math (raised 2×→4× for
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* reading node titles closely, owner, plan-graph round 3). */
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export const ZOOM_MAX = 4;
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/** Viewport breathing room subtracted by the fit. */
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export const FIT_PAD = 16;
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/** The fit never zooms IN past this — a tiny diagram must not blow up. */
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export const FIT_ZOOM_MAX = 1.5;
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/** A pan/zoom viewport state (translate + scale; origin top-left). */
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export interface Viewport {
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zoom: number;
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x: number;
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y: number;
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}
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/** The fit zoom for a box in a viewport: never below a true fit (the old
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* 0.15 floor could sit ABOVE the fit for wide graphs — the epsilon only
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* guards degenerate viewports), never above FIT_ZOOM_MAX. Pure. */
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export function fitZoomFor(box: { w: number; h: number }, viewport: { w: number; h: number }): number {
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if (!viewport.w || !viewport.h || box.w === 0) return 1;
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return Math.max(0.02, Math.min((viewport.w - FIT_PAD) / box.w, (viewport.h - FIT_PAD) / box.h, FIT_ZOOM_MAX));
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}
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/** Centers a box (at the given zoom) in the viewport. Pure. */
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export function fitGraphView(box: { w: number; h: number }, viewport: { w: number; h: number }, zoom: number): Viewport {
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return { zoom, x: (viewport.w - box.w * zoom) / 2, y: (viewport.h - box.h * zoom) / 2 };
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}
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/** Zoom by `factor` keeping `focus` (viewport coordinates) visually fixed,
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* clamped to [floor, ZOOM_MAX]. At the floor the view re-fits + RE-CENTERS
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* (the fit IS the floor — a locked view there has nothing to move). Pure. */
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export function zoomedGraphView(
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view: Viewport,
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factor: number,
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floor: number,
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focus: { x: number; y: number },
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box: { w: number; h: number },
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viewport: { w: number; h: number },
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): Viewport {
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const zoom = Math.min(Math.max(view.zoom * factor, floor), ZOOM_MAX);
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if (zoom === view.zoom) return view;
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if (zoom <= floor) return fitGraphView(box, viewport, floor);
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const k = zoom / view.zoom;
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return { zoom, x: focus.x - (focus.x - view.x) * k, y: focus.y - (focus.y - view.y) * k };
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}
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