fix(dom): update canvas style on resize to allow chart to grow

When the chart's container grows, the canvas style width/height
were not being updated because they were already set (from initial
render). This caused the chart to shrink correctly but not grow
when the window was enlarged.

This fix updates the canvas style width/height during resize when
they differ from the current chart dimensions, allowing the chart
to properly resize in both directions.

Fixes #12177

Author: jonathan-fulton

src/helpers/helpers.dom.ts

@@ -222,9 +222,22 @@ export function retinaScale(
   // If no style has been set on the canvas, the render size is used as display size,
   // making the chart visually bigger, so let's enforce it to the "correct" values.
   // See https://github.com/chartjs/Chart.js/issues/3575
+  // Also update styles when resizing to ensure the canvas grows with its container.
+  // See https://github.com/chartjs/Chart.js/issues/12177
   if (canvas.style && (forceStyle || (!canvas.style.height && !canvas.style.width))) {
     canvas.style.height = `${chart.height}px`;
     canvas.style.width = `${chart.width}px`;
+  } else if (canvas.style) {
+    // Update styles on resize if they were previously set by Chart.js
+    // This ensures the canvas can grow when its container grows
+    const currentStyleHeight = parseFloat(canvas.style.height);
+    const currentStyleWidth = parseFloat(canvas.style.width);
+    if (!isNaN(currentStyleHeight) && currentStyleHeight !== chart.height) {
+      canvas.style.height = `${chart.height}px`;
+    }
+    if (!isNaN(currentStyleWidth) && currentStyleWidth !== chart.width) {
+      canvas.style.width = `${chart.width}px`;
+    }
   }
 
   const canvasHeight = Math.floor(deviceHeight);