From 6d5791eb3c5115c5d0623fc39f0c0b2b34e44202 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Fri, 16 Jan 2026 04:57:01 +0000
Subject: [PATCH] perf: hoist getBoundingClientRect out of render loop

- Moves `litegraphCanvas.getBoundingClientRect()` call outside the widget loop in `renderHtmlOverlays`.
- Reuses the `dpr` calculated at the top level.
- Adds regression test `tests/unit/MagnifyGlassRenderOptim.test.ts`.

Improves rendering performance by reducing forced reflows during magnification.
---
 src/magnify-glass/MagnifyGlass.ts          |   6 +-
 tests/unit/MagnifyGlassRenderOptim.test.ts | 131 +++++++++++++++++++++
 2 files changed, 134 insertions(+), 3 deletions(-)
 create mode 100644 tests/unit/MagnifyGlassRenderOptim.test.ts

diff --git a/src/magnify-glass/MagnifyGlass.ts b/src/magnify-glass/MagnifyGlass.ts
index 8cdd783..09305af 100644
--- a/src/magnify-glass/MagnifyGlass.ts
+++ b/src/magnify-glass/MagnifyGlass.ts
@@ -454,10 +454,10 @@ export class MagnifyGlass {
 
                 if (elementToProcess && (isTextElement || isVideoElement || isImageElement)) {
                     const widgetRect = elementToProcess.getBoundingClientRect();
-                    const canvasRect = this.litegraphCanvas!.getBoundingClientRect();
+                    // Optimization: Reuse canvasRect and dpr from top level scope
+                    const canvasRect = rect;
 
-                    // DPR = backing pixels / CSS pixels
-                    const dpr = canvasRect.width > 0 ? (this.litegraphCanvas!.width / canvasRect.width) : 1;
+                    // DPR is already calculated at function start
                     const currentScale = this.state.canvasScale;
                     const isVirtualZoomMode = currentScale < 0.7;
 
diff --git a/tests/unit/MagnifyGlassRenderOptim.test.ts b/tests/unit/MagnifyGlassRenderOptim.test.ts
new file mode 100644
index 0000000..372b8fa
--- /dev/null
+++ b/tests/unit/MagnifyGlassRenderOptim.test.ts
@@ -0,0 +1,131 @@
+
+import { describe, it, expect, beforeEach, vi, afterEach } from 'vitest';
+
+// Create hoisted mocks
+const { appMock } = vi.hoisted(() => {
+    return {
+        appMock: {
+            registerExtension: vi.fn(),
+            ui: {
+                settings: {
+                    getSettingValue: vi.fn(),
+                    setSettingValue: vi.fn(),
+                }
+            },
+            canvas: {
+                ds: {
+                    scale: 1,
+                    offset: [0, 0]
+                }
+            },
+            graph: {
+                _nodes: [] as any[]
+            }
+        }
+    };
+});
+
+// Attach to global for files that rely on global variable 'app'
+// @ts-ignore
+globalThis.app = appMock;
+
+vi.mock('/scripts/app.js', () => ({
+    app: appMock
+}));
+
+// Import after mocks are set up
+import { MagnifyGlass } from '../../src/magnify-glass/MagnifyGlass';
+
+describe('MagnifyGlass Rendering Optimization', () => {
+    let magnifyGlass: MagnifyGlass;
+    let canvasMock: HTMLCanvasElement;
+    let canvasGetBoundingClientRectSpy: any;
+
+    beforeEach(() => {
+        // Reset mocks
+        vi.clearAllMocks();
+
+        // Reset appMock state
+        appMock.graph._nodes = [];
+
+        // Setup document body
+        document.body.innerHTML = '<canvas id="graph-canvas" width="1000" height="800"></canvas>';
+        canvasMock = document.getElementById('graph-canvas') as HTMLCanvasElement;
+
+        // Mock getBoundingClientRect
+        canvasGetBoundingClientRectSpy = vi.spyOn(canvasMock, 'getBoundingClientRect').mockReturnValue({
+            x: 0, y: 0, width: 1000, height: 800, top: 0, left: 0, right: 1000, bottom: 800, toJSON: () => {}
+        });
+
+        // Initialize MagnifyGlass manually
+        magnifyGlass = new MagnifyGlass();
+        magnifyGlass.litegraphCanvas = canvasMock;
+
+        // Mock UI container
+        magnifyGlass.ui.htmlOverlayContainer = document.createElement('div');
+
+        // Setup state
+        magnifyGlass.state.active = true;
+        magnifyGlass.state.canvasScale = 1;
+        magnifyGlass.state.x = 500;
+        magnifyGlass.state.y = 400;
+
+        // Setup config
+        magnifyGlass.config.glassSize = 300;
+        magnifyGlass.config.zoomFactor = 2;
+
+        // Trigger calculateSourceRegion
+        magnifyGlass.calculateSourceRegion();
+    });
+
+    afterEach(() => {
+        vi.restoreAllMocks();
+        document.body.innerHTML = '';
+    });
+
+    it('should call getBoundingClientRect multiple times (inefficiently) before optimization', () => {
+        // Setup nodes and widgets
+        const numNodes = 5;
+        const widgetsPerNode = 3;
+
+        const nodes = [];
+        for (let i = 0; i < numNodes; i++) {
+            const widgets = [];
+            for (let j = 0; j < widgetsPerNode; j++) {
+                const el = document.createElement('div');
+                const videoEl = document.createElement('video');
+                el.appendChild(videoEl);
+
+                widgets.push({
+                    type: 'custom',
+                    element: el
+                });
+            }
+
+            nodes.push({
+                pos: [400, 300],
+                size: [200, 200],
+                widgets: widgets
+            });
+        }
+
+        appMock.graph._nodes = nodes;
+
+        // Mock widget getBoundingClientRect
+        vi.spyOn(HTMLElement.prototype, 'getBoundingClientRect').mockReturnValue({
+            x: 450, y: 350, width: 100, height: 100, top: 350, left: 450, right: 550, bottom: 450, toJSON: () => {}
+        });
+
+        // Run renderHtmlOverlays
+        magnifyGlass.renderHtmlOverlays();
+
+        // Calculate expected calls
+        // 1 call in setup (calculateSourceRegion)
+        // 1 call in renderHtmlOverlays (top level)
+        // 0 calls inside loop (optimization)
+        const expectedCalls = 2;
+
+        // After optimization, this should pass
+        expect(canvasGetBoundingClientRectSpy).toHaveBeenCalledTimes(expectedCalls);
+    });
+});