Redesign idea (#343)

* Redisign idea

* Code cleanup

* Fixed to right container

* Reoredered layout

* Reordering panels

* Export dialog

* Removed redunant code

* Fixed not removing temp canvas

* Fixed preview not using only selected elements

* Returned file name on export

* Toggle export selected/all elements

* Hide copy to clipboard button if no support of clipboard

* Added border to swatches

* Fixed modal flickering

src/scene/data.ts

@@ -77,6 +77,59 @@ export function loadFromJSON() {
   });
 }
 
+export function getExportCanvasPreview(
+  elements: readonly ExcalidrawElement[],
+  {
+    exportBackground,
+    exportPadding = 10,
+    viewBackgroundColor
+  }: {
+    exportBackground: boolean;
+    exportPadding?: number;
+    viewBackgroundColor: string;
+  }
+) {
+  // calculate smallest area to fit the contents in
+  let subCanvasX1 = Infinity;
+  let subCanvasX2 = 0;
+  let subCanvasY1 = Infinity;
+  let subCanvasY2 = 0;
+
+  elements.forEach(element => {
+    const [x1, y1, x2, y2] = getElementAbsoluteCoords(element);
+    subCanvasX1 = Math.min(subCanvasX1, x1);
+    subCanvasY1 = Math.min(subCanvasY1, y1);
+    subCanvasX2 = Math.max(subCanvasX2, x2);
+    subCanvasY2 = Math.max(subCanvasY2, y2);
+  });
+
+  function distance(x: number, y: number) {
+    return Math.abs(x > y ? x - y : y - x);
+  }
+
+  const tempCanvas = document.createElement("canvas");
+  tempCanvas.width = distance(subCanvasX1, subCanvasX2) + exportPadding * 2;
+  tempCanvas.height = distance(subCanvasY1, subCanvasY2) + exportPadding * 2;
+
+  renderScene(
+    elements,
+    rough.canvas(tempCanvas),
+    tempCanvas,
+    {
+      viewBackgroundColor: exportBackground ? viewBackgroundColor : null,
+      scrollX: 0,
+      scrollY: 0
+    },
+    {
+      offsetX: -subCanvasX1 + exportPadding,
+      offsetY: -subCanvasY1 + exportPadding,
+      renderScrollbars: false,
+      renderSelection: false
+    }
+  );
+  return tempCanvas;
+}
+
 export function exportCanvas(
   type: ExportType,
   elements: readonly ExcalidrawElement[],