47 lines
1.7 KiB
TypeScript
47 lines
1.7 KiB
TypeScript
 
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// The viewer context the drawing overlay reads: pointer to page fractions, mark drags, the page size.
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import { createContext, useContext, type PointerEvent as ReactPointerEvent } from "react";
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import type { Frac } from "../lib/geometry";
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/** The bitmap: at most 2.2 times the PDF size and at most 4200 px wide. */
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export function renderScale(pdfWidth: number): number {
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return Math.min(2.2, 4200 / Math.max(1, pdfWidth));
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}
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/** A pointer that moved less than this is a tap. */
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export const TAP_PX = 6;
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/** A mark drag starts after this. */
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export const DRAG_PX = 5;
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export interface DragHandlers {
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/** The pointer is at f (page fractions, not clamped). */
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onMove: (f: Frac) => void;
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/** The drag ended at f, or null when it never moved (a tap). */
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onEnd: (f: Frac | null) => void;
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}
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export interface ViewerApi {
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/** A client point as page fractions, and whether it lies inside the viewer frame. */
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toFrac: (clientX: number, clientY: number) => Frac & { inside: boolean };
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/** Starts a mark drag from a pointerdown. Moves and ends follow the window. */
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startDrag: (e: ReactPointerEvent, h: DragHandlers) => void;
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/** True for a short while after a drag ended, so the click that follows it is ignored. */
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justDragged: () => boolean;
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}
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export interface ViewerInfo extends ViewerApi {
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/** Page size in bitmap pixels; 0 until the page is drawn. */
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w: number;
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h: number;
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aspect: number;
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}
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export const ViewerCtx = createContext<ViewerInfo | null>(null);
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/** The viewer the overlay lives in. Marks use it to turn pointers into page fractions. */
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export function useViewer(): ViewerInfo {
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const v = useContext(ViewerCtx);
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if (!v) throw new Error("useViewer must be used inside MapViewer");
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return v;
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}
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