feat: polish envelopes (#2090)

## Description

The rest of the owl

packages/lib/client-only/hooks/use-page-renderer.ts

@@ -0,0 +1,126 @@
+import { useEffect, useMemo, useRef } from 'react';
+
+import Konva from 'konva';
+import type { RenderParameters } from 'pdfjs-dist/types/src/display/api';
+import { usePageContext } from 'react-pdf';
+
+type RenderFunction = (props: { stage: Konva.Stage; pageLayer: Konva.Layer }) => void;
+
+export function usePageRenderer(renderFunction: RenderFunction) {
+  const pageContext = usePageContext();
+
+  if (!pageContext) {
+    throw new Error('Unable to find Page context.');
+  }
+
+  const { page, rotate, scale } = pageContext;
+
+  if (!page) {
+    throw new Error('Attempted to render page canvas, but no page was specified.');
+  }
+
+  const canvasElement = useRef<HTMLCanvasElement>(null);
+  const konvaContainer = useRef<HTMLDivElement>(null);
+
+  const stage = useRef<Konva.Stage | null>(null);
+  const pageLayer = useRef<Konva.Layer | null>(null);
+
+  /**
+   * The raw viewport with no scaling. Basically the actual PDF size.
+   */
+  const unscaledViewport = useMemo(
+    () => page.getViewport({ scale: 1, rotation: rotate }),
+    [page, rotate, scale],
+  );
+
+  /**
+   * The viewport scaled according to page width.
+   */
+  const scaledViewport = useMemo(
+    () => page.getViewport({ scale, rotation: rotate }),
+    [page, rotate, scale],
+  );
+
+  /**
+   * Viewport with the device pixel ratio applied so we can render the PDF
+   * in a higher resolution.
+   */
+  const renderViewport = useMemo(
+    () => page.getViewport({ scale: scale * window.devicePixelRatio, rotation: rotate }),
+    [page, rotate, scale],
+  );
+
+  /**
+   * Render the PDF and create the scaled Konva stage.
+   */
+  useEffect(
+    function drawPageOnCanvas() {
+      if (!page) {
+        return;
+      }
+
+      const { current: canvas } = canvasElement;
+      const { current: kContainer } = konvaContainer;
+
+      if (!canvas || !kContainer) {
+        return;
+      }
+
+      canvas.width = renderViewport.width;
+      canvas.height = renderViewport.height;
+
+      canvas.style.width = `${Math.floor(scaledViewport.width)}px`;
+      canvas.style.height = `${Math.floor(scaledViewport.height)}px`;
+
+      const renderContext: RenderParameters = {
+        // eslint-disable-next-line @typescript-eslint/consistent-type-assertions
+        canvasContext: canvas.getContext('2d', { alpha: false }) as CanvasRenderingContext2D,
+        viewport: renderViewport,
+      };
+
+      const cancellable = page.render(renderContext);
+      const runningTask = cancellable;
+
+      cancellable.promise.catch(() => {
+        // Intentionally empty
+      });
+
+      void cancellable.promise.then(() => {
+        stage.current = new Konva.Stage({
+          container: kContainer,
+          width: scaledViewport.width,
+          height: scaledViewport.height,
+          scale: {
+            x: scale,
+            y: scale,
+          },
+        });
+
+        // Create the main layer for interactive elements.
+        pageLayer.current = new Konva.Layer();
+
+        stage.current.add(pageLayer.current);
+
+        renderFunction({
+          stage: stage.current,
+          pageLayer: pageLayer.current,
+        });
+      });
+
+      return () => {
+        runningTask.cancel();
+      };
+    },
+    [page, scaledViewport],
+  );
+
+  return {
+    canvasElement,
+    konvaContainer,
+    stage,
+    pageLayer,
+    unscaledViewport,
+    scaledViewport,
+    pageContext,
+  };
+}