fix(tui): skip Termux height redraws closes #2467

packages/tui/test/tui-render.test.ts

@@ -12,6 +12,47 @@ class TestComponent implements Component {
 	invalidate(): void {}
 }
 
+class LoggingVirtualTerminal extends VirtualTerminal {
+	private writes: string[] = [];
+
+	override write(data: string): void {
+		this.writes.push(data);
+		super.write(data);
+	}
+
+	getWrites(): string {
+		return this.writes.join("");
+	}
+
+	clearWrites(): void {
+		this.writes = [];
+	}
+}
+
+async function withEnv<T>(updates: Record<string, string | undefined>, run: () => Promise<T>): Promise<T> {
+	const previousValues = new Map<string, string | undefined>();
+	for (const [key, value] of Object.entries(updates)) {
+		previousValues.set(key, process.env[key]);
+		if (value === undefined) {
+			delete process.env[key];
+		} else {
+			process.env[key] = value;
+		}
+	}
+
+	try {
+		return await run();
+	} finally {
+		for (const [key, value] of previousValues) {
+			if (value === undefined) {
+				delete process.env[key];
+			} else {
+				process.env[key] = value;
+			}
+		}
+	}
+}
+
 function getCellItalic(terminal: VirtualTerminal, row: number, col: number): number {
 	const xterm = (terminal as unknown as { xterm: XtermTerminalType }).xterm;
 	const buffer = xterm.buffer.active;
@@ -24,28 +65,59 @@ function getCellItalic(terminal: VirtualTerminal, row: number, col: number): num
 
 describe("TUI resize handling", () => {
 	it("triggers full re-render when terminal height changes", async () => {
-		const terminal = new VirtualTerminal(40, 10);
-		const tui = new TUI(terminal);
-		const component = new TestComponent();
-		tui.addChild(component);
+		await withEnv({ TERMUX_VERSION: undefined }, async () => {
+			const terminal = new VirtualTerminal(40, 10);
+			const tui = new TUI(terminal);
+			const component = new TestComponent();
+			tui.addChild(component);
 
-		component.lines = ["Line 0", "Line 1", "Line 2"];
-		tui.start();
-		await terminal.flush();
+			component.lines = ["Line 0", "Line 1", "Line 2"];
+			tui.start();
+			await terminal.flush();
 
-		const initialRedraws = tui.fullRedraws;
+			const initialRedraws = tui.fullRedraws;
 
-		// Resize height
-		terminal.resize(40, 15);
-		await terminal.flush();
+			// Resize height
+			terminal.resize(40, 15);
+			await terminal.flush();
 
-		// Should have triggered a full redraw
-		assert.ok(tui.fullRedraws > initialRedraws, "Height change should trigger full redraw");
+			// Should have triggered a full redraw
+			assert.ok(tui.fullRedraws > initialRedraws, "Height change should trigger full redraw");
 
-		const viewport = terminal.getViewport();
-		assert.ok(viewport[0]?.includes("Line 0"), "Content preserved after height change");
+			const viewport = terminal.getViewport();
+			assert.ok(viewport[0]?.includes("Line 0"), "Content preserved after height change");
 
-		tui.stop();
+			tui.stop();
+		});
+	});
+
+	it("skips full re-render on height changes in Termux", async () => {
+		await withEnv({ TERMUX_VERSION: "1" }, async () => {
+			const terminal = new LoggingVirtualTerminal(40, 10);
+			const tui = new TUI(terminal);
+			const component = new TestComponent();
+			tui.addChild(component);
+
+			component.lines = Array.from({ length: 20 }, (_, i) => `Line ${i}`);
+			tui.start();
+			await terminal.flush();
+			terminal.clearWrites();
+
+			const initialRedraws = tui.fullRedraws;
+			for (const height of [15, 8, 14, 11]) {
+				terminal.resize(40, height);
+				await terminal.flush();
+			}
+
+			assert.strictEqual(tui.fullRedraws, initialRedraws, "Height change should not trigger full redraw");
+			assert.ok(!terminal.getWrites().includes("\x1b[2J"), "Height change should not clear the screen");
+			assert.ok(!terminal.getWrites().includes("\x1b[3J"), "Height change should not clear scrollback");
+
+			const viewport = terminal.getViewport();
+			assert.ok(viewport.join("\n").includes("Line 19"), "Latest content remains visible after resize");
+
+			tui.stop();
+		});
 	});
 
 	it("triggers full re-render when terminal width changes", async () => {