fix: canvas flickering due to resetting canvas on skipped frames (#6960)

src/components/canvases/StaticCanvas.tsx

@@ -37,10 +37,25 @@ const StaticCanvas = (props: StaticCanvasProps) => {
       canvas.classList.add("excalidraw__canvas", "static");
     }
 
-    canvas.style.width = `${props.appState.width}px`;
-    canvas.style.height = `${props.appState.height}px`;
-    canvas.width = props.appState.width * props.scale;
-    canvas.height = props.appState.height * props.scale;
+    const widthString = `${props.appState.width}px`;
+    const heightString = `${props.appState.height}px`;
+    if (canvas.style.width !== widthString) {
+      canvas.style.width = widthString;
+    }
+    if (canvas.style.height !== heightString) {
+      canvas.style.height = heightString;
+    }
+
+    const scaledWidth = props.appState.width * props.scale;
+    const scaledHeight = props.appState.height * props.scale;
+    // setting width/height resets the canvas even if dimensions not changed,
+    // which would cause flicker when we skip frame (due to throttling)
+    if (canvas.width !== scaledWidth) {
+      canvas.width = scaledWidth;
+    }
+    if (canvas.height !== scaledHeight) {
+      canvas.height = scaledHeight;
+    }
 
     renderStaticScene(
       {