Fix terminal font size bounds checking in mouse wheel zoom (microsoft#253010)

Author: Copilot

src/vs/workbench/contrib/terminalContrib/zoom/browser/terminal.zoom.contribution.ts

@@ -57,6 +57,10 @@ class TerminalMouseWheelZoomContribution extends Disposable implements ITerminal
 		return this._configurationService.getValue(TerminalSettingId.FontSize);
 	}
 
+	private _clampFontSize(fontSize: number): number {
+		return clampTerminalFontSize(fontSize);
+	}
+
 	private _setupMouseWheelZoomListener(raw: RawXtermTerminal) {
 		// This is essentially a copy of what we do in the editor, just we modify font size directly
 		// as there is no separate zoom level concept in the terminal
@@ -72,7 +76,8 @@ class TerminalMouseWheelZoomContribution extends Disposable implements ITerminal
 			if (classifier.isPhysicalMouseWheel()) {
 				if (this._hasMouseWheelZoomModifiers(browserEvent)) {
 					const delta = browserEvent.deltaY > 0 ? -1 : 1;
-					this._configurationService.updateValue(TerminalSettingId.FontSize, this._getConfigFontSize() + delta);
+					const newFontSize = this._clampFontSize(this._getConfigFontSize() + delta);
+					this._configurationService.updateValue(TerminalSettingId.FontSize, newFontSize);
 					// EditorZoom.setZoomLevel(zoomLevel + delta);
 					browserEvent.preventDefault();
 					browserEvent.stopPropagation();
@@ -96,7 +101,8 @@ class TerminalMouseWheelZoomContribution extends Disposable implements ITerminal
 					const deltaAbs = Math.ceil(Math.abs(gestureAccumulatedDelta / 5));
 					const deltaDirection = gestureAccumulatedDelta > 0 ? -1 : 1;
 					const delta = deltaAbs * deltaDirection;
-					this._configurationService.updateValue(TerminalSettingId.FontSize, gestureStartFontSize + delta);
+					const newFontSize = this._clampFontSize(gestureStartFontSize + delta);
+					this._configurationService.updateValue(TerminalSettingId.FontSize, newFontSize);
 					gestureAccumulatedDelta += browserEvent.deltaY;
 					browserEvent.preventDefault();
 					browserEvent.stopPropagation();
@@ -128,7 +134,8 @@ registerTerminalAction({
 		const configurationService = accessor.get(IConfigurationService);
 		const value = configurationService.getValue(TerminalSettingId.FontSize);
 		if (isNumber(value)) {
-			await configurationService.updateValue(TerminalSettingId.FontSize, value + 1);
+			const newFontSize = clampTerminalFontSize(value + 1);
+			await configurationService.updateValue(TerminalSettingId.FontSize, newFontSize);
 		}
 	}
 });
@@ -140,7 +147,8 @@ registerTerminalAction({
 		const configurationService = accessor.get(IConfigurationService);
 		const value = configurationService.getValue(TerminalSettingId.FontSize);
 		if (isNumber(value)) {
-			await configurationService.updateValue(TerminalSettingId.FontSize, value - 1);
+			const newFontSize = clampTerminalFontSize(value - 1);
+			await configurationService.updateValue(TerminalSettingId.FontSize, newFontSize);
 		}
 	}
 });
@@ -153,3 +161,7 @@ registerTerminalAction({
 		await configurationService.updateValue(TerminalSettingId.FontSize, defaultTerminalFontSize);
 	}
 });
+
+export function clampTerminalFontSize(fontSize: number): number {
+	return Math.max(6, Math.min(100, fontSize));
+}

src/vs/workbench/contrib/terminalContrib/zoom/test/browser/terminal.zoom.test.ts

@@ -0,0 +1,37 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { strictEqual } from 'assert';
+import { ensureNoDisposablesAreLeakedInTestSuite } from '../../../../../../base/test/common/utils.js';
+import { clampTerminalFontSize } from '../../browser/terminal.zoom.contribution.js';
+
+suite('Terminal Mouse Wheel Zoom', () => {
+	ensureNoDisposablesAreLeakedInTestSuite();
+
+	test('clamps font size to minimum value when below bounds', () => {
+		const result = clampTerminalFontSize(3 + (-2)); // 3 - 2 = 1, clamped to 6
+		strictEqual(result, 6, 'Font size should be clamped to minimum value of 6');
+	});
+
+	test('clamps font size to maximum value when above bounds', () => {
+		const result = clampTerminalFontSize(99 + 5); // 99 + 5 = 104, clamped to 100
+		strictEqual(result, 100, 'Font size should be clamped to maximum value of 100');
+	});
+
+	test('preserves font size when within bounds', () => {
+		const result = clampTerminalFontSize(12 + 3); // 12 + 3 = 15, within bounds
+		strictEqual(result, 15, 'Font size should remain unchanged when within bounds');
+	});
+
+	test('clamps font size when going below minimum', () => {
+		const result = clampTerminalFontSize(6 + (-1)); // 6 - 1 = 5, clamped to 6
+		strictEqual(result, 6, 'Font size should be clamped when going below minimum');
+	});
+
+	test('clamps font size when going above maximum', () => {
+		const result = clampTerminalFontSize(100 + 1); // 100 + 1 = 101, clamped to 100
+		strictEqual(result, 100, 'Font size should be clamped when going above maximum');
+	});
+});