Zoom using the mouse wheel (#59)

src/fabric-object/custom_canvas.ts

@@ -11,6 +11,60 @@ export class CustomCanvas extends fabric.Canvas {
   private readonly MIRROR_GHOST_COLOR = "rgba(0, 0, 0, 0.3)";
   private customBackground: boolean = true;
   private highlightMirror: boolean = true;
+  private virtualZoomRatio: number = 1;
+
+  constructor(el?: string | HTMLCanvasElement, options?: fabric.TOptions<fabric.CanvasOptions>) {
+    super(el, options);
+    this.setupZoom();
+  }
+
+  private setupZoom() {
+    this.on("mouse:wheel", (opt) => {
+      const event = opt.e as WheelEvent;
+      event.preventDefault();
+
+      const delta = event.deltaY;
+      if (delta > 0) {
+        this.virtualZoomOut();
+      } else {
+        this.virtualZoomIn();
+      }
+    });
+    this.on("mouse:down:before", (opt) => {
+      const event = opt.e as MouseEvent;
+      if (event.button == 1) {
+        event.preventDefault();
+        this.resetVirtualZoom();
+      }
+    });
+  }
+
+  public virtualZoom(newZoom: number) {
+    this.virtualZoomRatio = Math.min(Math.max(0.25, newZoom), 4);
+    this.setDimensions(
+      {
+        width: this.virtualZoomRatio * this.getWidth() + "px",
+        height: this.virtualZoomRatio * this.getHeight() + "px",
+      },
+      { cssOnly: true }
+    );
+  }
+
+  public virtualZoomIn() {
+    this.virtualZoom(this.virtualZoomRatio * 1.05);
+  }
+
+  public virtualZoomOut() {
+    this.virtualZoom(this.virtualZoomRatio * 0.95);
+  }
+
+  public getVirtualZoom(): number {
+    return this.virtualZoomRatio;
+  }
+
+  public resetVirtualZoom() {
+    this.virtualZoom(1);
+  }
 
   setLabelProps(value: LabelProps) {
     this.labelProps = value;

src/lib/ImageEditor.svelte

@@ -141,6 +141,7 @@
   const onUpdateLabelProps = (newProps: LabelProps) => {
     labelProps = newProps;
     fabricCanvas.setDimensions(labelProps.size);
+    fabricCanvas.virtualZoom(fabricCanvas.getVirtualZoom());
     try {
       LocalStoragePersistence.saveLastLabelProps(labelProps);
       undo.push(fabricCanvas, labelProps);

src/utils/file_utils.ts

@@ -11,6 +11,7 @@ import { OBJECT_DEFAULTS, THUMBNAIL_HEIGHT, THUMBNAIL_QUALITY } from "../default
 import { z } from "zod";
 import { FileSharer } from "@byteowls/capacitor-filesharer";
 import { Toasts } from "./toasts";
+import { CustomCanvas } from "../fabric-object/custom_canvas";
 
 export class FileUtils {
   static timestamp(): number {
@@ -140,6 +141,9 @@ export class FileUtils {
     await canvas.loadFromJSON(state, (_, obj) => {
       if ("set" in obj) obj.set({ snapAngle: OBJECT_DEFAULTS.snapAngle });
     });
+    if (canvas instanceof CustomCanvas) {
+      canvas.virtualZoom(canvas.getVirtualZoom())
+    }
     canvas.requestRenderAll();
   }
 }