Refactor Element Functions (#233)

* Remove `generatedraw` from element object

- Create a function that renders a single element
- Refactor rendering selected elements

* Replace getElementAbsoluteXY with getElementAbsoluteCoords

src/renderer/renderElement.ts

@@ -0,0 +1,142 @@
+import rough from "roughjs/bin/wrappers/rough";
+
+import { withCustomMathRandom } from "../random";
+
+import { ExcalidrawElement } from "../element/types";
+import { isTextElement } from "../element/typeChecks";
+import { getDiamondPoints, getArrowPoints } from "../element/bounds";
+import { RoughCanvas } from "roughjs/bin/canvas";
+import { SceneState } from "../scene/types";
+
+// Casting second argument (DrawingSurface) to any,
+// because it is requred by TS definitions and not required at runtime
+const generator = rough.generator(null, null as any);
+
+export function renderElement(
+  element: ExcalidrawElement,
+  rc: RoughCanvas,
+  context: CanvasRenderingContext2D,
+  { scrollX, scrollY }: SceneState
+) {
+  if (element.type === "selection") {
+    const fillStyle = context.fillStyle;
+    context.fillStyle = "rgba(0, 0, 255, 0.10)";
+    context.fillRect(
+      element.x + scrollX,
+      element.y + scrollY,
+      element.width,
+      element.height
+    );
+    context.fillStyle = fillStyle;
+  } else if (element.type === "rectangle") {
+    const shape = withCustomMathRandom(element.seed, () => {
+      return generator.rectangle(0, 0, element.width, element.height, {
+        stroke: element.strokeColor,
+        fill: element.backgroundColor,
+        fillStyle: element.fillStyle,
+        strokeWidth: element.strokeWidth,
+        roughness: element.roughness
+      });
+    });
+
+    context.globalAlpha = element.opacity / 100;
+    context.translate(element.x + scrollX, element.y + scrollY);
+    rc.draw(shape);
+    context.translate(-element.x - scrollX, -element.y - scrollY);
+    context.globalAlpha = 1;
+  } else if (element.type === "diamond") {
+    const shape = withCustomMathRandom(element.seed, () => {
+      const [
+        topX,
+        topY,
+        rightX,
+        rightY,
+        bottomX,
+        bottomY,
+        leftX,
+        leftY
+      ] = getDiamondPoints(element);
+      return generator.polygon(
+        [
+          [topX, topY],
+          [rightX, rightY],
+          [bottomX, bottomY],
+          [leftX, leftY]
+        ],
+        {
+          stroke: element.strokeColor,
+          fill: element.backgroundColor,
+          fillStyle: element.fillStyle,
+          strokeWidth: element.strokeWidth,
+          roughness: element.roughness
+        }
+      );
+    });
+    context.globalAlpha = element.opacity / 100;
+    context.translate(element.x + scrollX, element.y + scrollY);
+    rc.draw(shape);
+    context.translate(-element.x - scrollX, -element.y - scrollY);
+    context.globalAlpha = 1;
+  } else if (element.type === "ellipse") {
+    const shape = withCustomMathRandom(element.seed, () =>
+      generator.ellipse(
+        element.width / 2,
+        element.height / 2,
+        element.width,
+        element.height,
+        {
+          stroke: element.strokeColor,
+          fill: element.backgroundColor,
+          fillStyle: element.fillStyle,
+          strokeWidth: element.strokeWidth,
+          roughness: element.roughness
+        }
+      )
+    );
+
+    context.globalAlpha = element.opacity / 100;
+    context.translate(element.x + scrollX, element.y + scrollY);
+    rc.draw(shape);
+    context.translate(-element.x - scrollX, -element.y - scrollY);
+    context.globalAlpha = 1;
+  } else if (element.type === "arrow") {
+    const [x1, y1, x2, y2, x3, y3, x4, y4] = getArrowPoints(element);
+    const options = {
+      stroke: element.strokeColor,
+      strokeWidth: element.strokeWidth,
+      roughness: element.roughness
+    };
+
+    const shapes = withCustomMathRandom(element.seed, () => [
+      //    \
+      generator.line(x3, y3, x2, y2, options),
+      // -----
+      generator.line(x1, y1, x2, y2, options),
+      //    /
+      generator.line(x4, y4, x2, y2, options)
+    ]);
+
+    context.globalAlpha = element.opacity / 100;
+    context.translate(element.x + scrollX, element.y + scrollY);
+    shapes.forEach(shape => rc.draw(shape));
+    context.translate(-element.x - scrollX, -element.y - scrollY);
+    context.globalAlpha = 1;
+    return;
+  } else if (isTextElement(element)) {
+    context.globalAlpha = element.opacity / 100;
+    const font = context.font;
+    context.font = element.font;
+    const fillStyle = context.fillStyle;
+    context.fillStyle = element.strokeColor;
+    context.fillText(
+      element.text,
+      element.x + scrollX,
+      element.y + element.actualBoundingBoxAscent + scrollY
+    );
+    context.fillStyle = fillStyle;
+    context.font = font;
+    context.globalAlpha = 1;
+  } else {
+    throw new Error("Unimplemented type " + element.type);
+  }
+}