Fix legend crash when defaults font changes between fit and draw

src/plugins/plugin.legend.js

@@ -392,6 +392,7 @@ export class Legend extends Element {
 
     const lineHeight = itemHeight + padding;
     this.legendItems.forEach((legendItem, i) => {
+      const legendHitBox = this.legendHitBoxes[i];
       ctx.strokeStyle = legendItem.fontColor; // for strikethrough effect
       ctx.fillStyle = legendItem.fontColor; // render in correct colour
 
@@ -409,10 +410,17 @@ export class Legend extends Element {
           cursor.line++;
           x = cursor.x = _alignStartEnd(align, this.left + padding, this.right - lineWidths[cursor.line]);
         }
-      } else if (i > 0 && y + lineHeight > this.bottom) {
-        x = cursor.x = x + columnSizes[cursor.line].width + padding;
-        cursor.line++;
-        y = cursor.y = _alignStartEnd(align, this.top + titleHeight + padding, this.bottom - columnSizes[cursor.line].height);
+      } else if (i > 0 && legendHitBox && legendHitBox.col !== cursor.line) {
+        const previousColSize = columnSizes[cursor.line];
+        const columnSize = columnSizes[legendHitBox.col];
+
+        if (!previousColSize || !columnSize) {
+          return;
+        }
+
+        x = cursor.x = x + previousColSize.width + padding;
+        cursor.line = legendHitBox.col;
+        y = cursor.y = _alignStartEnd(align, this.top + titleHeight + padding, this.bottom - columnSize.height);
       }
 
       const realX = rtlHelper.x(x);

test/specs/plugin.legend.tests.js

@@ -956,6 +956,49 @@ describe('Legend block tests', function() {
     expect(chart.legend.options.title.color).toBe('green');
   });
 
+  it('should not crash when defaults font changes before a render', function() {
+    const defaultFont = Object.assign({}, Chart.defaults.font);
+    const labels = Array.from({length: 8}, (_, i) => `L${i}`);
+    const datasets = labels.map((_, i) => ({
+      label: `dataset${i}`,
+      data: [i + 1]
+    }));
+
+    const chart = acquireChart({
+      type: 'bar',
+      data: {
+        labels: ['A'],
+        datasets
+      },
+      options: {
+        responsive: false,
+        maintainAspectRatio: false,
+        plugins: {
+          legend: {
+            position: 'right'
+          }
+        }
+      }
+    }, {
+      canvas: {
+        width: 256,
+        height: 180
+      }
+    });
+
+    try {
+      Object.assign(Chart.defaults.font, {
+        size: 42
+      });
+
+      expect(function() {
+        chart.render();
+      }).not.toThrow();
+    } finally {
+      Object.assign(Chart.defaults.font, defaultFont);
+    }
+  });
+
 
   describe('config update', function() {
     it('should update the options', function() {