FN-7620: fix mobile terminal rendering blank via ResizeObserver recovery

Fixes the mobile dashboard terminal sometimes rendering completely blank on open by having TerminalModal recover from a zero/collapsed container box.

- TerminalModal now attaches a persistent ResizeObserver directly on the xterm container, mirroring SessionTerminal's existing pattern
- When the container reports a zero/collapsed box on the first post-open fit, it now re-fits once the real box settles instead of staying stuck at FitAddon's degenerate 2x1-cell floor
- Added regression tests covering TerminalModal and SessionTerminal zero-geometry recovery
- Documented the root cause and fix in docs/solutions/ui-bugs/mobile-terminal-blank-render-zero-geometry-container.md
- Added a patch changeset for @runfusion/fusion

Files changed:
 .changeset/fn-7620-mobile-terminal-blank-render.md |   7 +
 docs/solutions/ui-bugs/mobile-terminal-blank-render-zero-geometry-container.md | 112 +++++++
 packages/dashboard/app/components/TerminalModal.tsx |  49 +++
 packages/dashboard/app/components/__tests__/SessionTerminal.test.tsx |  66 ++++
 packages/dashboard/app/components/__tests__/TerminalModal.test.tsx |  358 +++++++++++++++++++++
 5 files changed, 592 insertions(+)

Fusion-Task-Id: FN-7620

Fusion-Task-Lineage: 103f5b17-9a6e-4e9a-ab61-65ccb2203a8d

Co-authored-by: Fusion (runfusion.ai) <noreply@runfusion.ai>
This commit is contained in:
gsxdsm
2026-07-06 19:35:27 -07:00
parent 1add12d703
commit 8d73b18c35
5 changed files with 592 additions and 0 deletions

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@@ -0,0 +1,7 @@
---
"@runfusion/fusion": patch
---
summary: Fix mobile dashboard terminal sometimes rendering completely blank on open.
category: fix
dev: TerminalModal now attaches a persistent ResizeObserver directly on the xterm container (mirroring SessionTerminal's existing pattern), so a container that reports a zero/collapsed box at the first post-open fit recovers as soon as its real box settles, instead of staying at FitAddon's degenerate 2x1-cell floor forever.

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@@ -0,0 +1,112 @@
---
title: "Mobile terminal renders nothing when the xterm container's own box is unwatched"
date: 2026-07-06
category: ui-bugs
module: packages/dashboard/app/components/TerminalModal
problem_type: ui_bug
component: frontend_terminal
applies_when: "A terminal/xterm surface is opened inside a container whose real box may be zero (or otherwise not yet settled) at the moment `terminal.open()`/`fitAddon.fit()` first runs, and no observer watches that CONTAINER element's own geometry independently of any ancestor."
symptoms:
- "The mobile terminal opens to a totally blank surface: no prompt, no output, no rows — a different, more severe failure than visible-but-mis-spaced ASCII."
- "The blank render happens on the INITIAL layout (keyboard open or closed) and does not repair itself from a keyboard toggle, orientation change, reconnect, or manual refit — because none of those events touch the terminal container's own box."
- "Desktop/docked/floating terminals are unaffected; only the mobile fullscreen shell (or any narrow/late-settling container) shows the blank symptom."
root_cause: real_fitaddon_proposedimensions_floors_to_a_degenerate_2x1_grid_on_a_zero_container_box_and_nothing_watched_the_container_itself_to_recover
resolution_type: code_fix
severity: high
related_components:
- packages/dashboard/app/components/TerminalModal.tsx
- packages/dashboard/app/components/SessionTerminal.tsx
- packages/dashboard/app/components/__tests__/TerminalModal.test.tsx
- packages/dashboard/app/components/__tests__/SessionTerminal.test.tsx
- FN-7620
tags:
- xterm
- fitaddon
- resize-observer
- mobile-safari
- blank-render
- geometry
---
# Mobile terminal renders nothing when the xterm container's own box is unwatched
## Problem
FN-7620 reported the mobile dashboard terminal opening to a completely blank surface — no prompt, no scrollback, no rows. This is a DIFFERENT failure class than the FN-7456→FN-7603 inter-character-spacing family (`xterm-options-noop-remeasure-after-font-settle.md`), which always rendered visible-but-mis-spaced ASCII. Here nothing renders at all.
### The actual mechanism
Real `@xterm/addon-fit@0.10.0`'s `FitAddon.proposeDimensions()` reads `getComputedStyle(terminal.element.parentElement)` height/width (the xterm container, i.e. `TerminalModal`'s `terminalRef` div):
```js
proposeDimensions() {
...
const o = parseInt(computedStyle(parentElement).height);
const s = Math.max(0, parseInt(computedStyle(parentElement).width));
...
return {
cols: Math.max(2, Math.floor(availableWidth / cellWidth)),
rows: Math.max(1, Math.floor(availableHeight / cellHeight)),
};
}
```
Crucially, this does **not** bail out on a zero box — it floors to a degenerate `{cols: 2, rows: 1}` grid. If the container's real box is genuinely `0` at the moment of the first post-open `fitAddon.fit()` (plausible on a real mobile device on the very first paint — the mobile fullscreen `.terminal-modal--mobile` + `[style*="--keyboard-overlap"]` height cascade, `100dvh` support, or general layout/font settle can all delay the container's real box by a frame or more), xterm silently resizes to a near-invisible 2×1 grid clipped inside a container whose own box is *also* still ~0px — visually indistinguishable from "nothing renders".
The defect that made this **permanent** (not a one-frame flicker): only the OUTER MODAL (`modalRef`) had a `ResizeObserver`. A modal already sized to `100dvh`/the keyboard-constrained box does not re-fire that observer when only *inner* content (the xterm container) later settles to its real size — nothing else watched the container (`terminalRef`) itself. The prior "one opportunistic deferred re-fit" (added 2026-06-22 for the FN-7461 fold-transition spacing fix) only recovers if `clientWidth > 0` at the SINGLE scheduled rAF check; if the container is still zero at that moment, no later trigger ever re-measures it, and the terminal stays a degenerate grid forever — matching the report that no reconnect/orientation/keyboard-toggle/manual refit repaired it.
## Why this survived FN-7456→FN-7603
Every prior fix in this subsystem targeted the CHARACTER-measurement pipeline (font metrics, DOM-vs-Canvas divergence) — none of them touched CONTAINER-level geometry observation. A total blank render is a fundamentally different failure surface (container box, not glyph metrics) and none of the prior regressions modeled a zero/degenerate container box at all.
`SessionTerminal.tsx` (the sibling embedded CLI-agent terminal) never had this defect: it already attaches `resizeObserver.observe(containerRef.current)` directly on its own xterm container right after init.
## Fix
Add a persistent `ResizeObserver` directly on the xterm CONTAINER element (`terminalRef.current`), established for the life of each xterm instance and re-established whenever the container remounts (tab switch uses `key={activeTab?.sessionId}` on the container div), calling the existing `fitAndResizeForSession(sessionId)` on any change to the container's OWN box:
```tsx
// packages/dashboard/app/components/TerminalModal.tsx
useEffect(() => {
if (!isOpen) return;
const node = terminalRef.current;
if (!node || typeof ResizeObserver === "undefined") return;
let pendingFrame: number | null = null;
const observer = new ResizeObserver(() => {
if (pendingFrame !== null) cancelAnimationFrame(pendingFrame);
pendingFrame = requestAnimationFrame(() => {
pendingFrame = null;
const sessionId =
typeof xtermInitializedRef.current === "string" ? xtermInitializedRef.current : undefined;
fitAndResizeForSession(sessionId);
});
});
observer.observe(node);
return () => {
observer.disconnect();
if (pendingFrame !== null) cancelAnimationFrame(pendingFrame);
};
}, [fitAndResizeForSession, isOpen, activeTab?.sessionId]);
```
This mirrors the pattern `SessionTerminal.tsx` already uses. Per the ResizeObserver spec, an initial notification fires shortly after `observe()` is called even if the box hasn't changed since — so this also catches the very first zero-to-real transition, not just later changes. No arbitrary frame-polling loop, timeout, hardcoded cell/column count, or disabling of the mobile fullscreen path is used.
Do not:
- Replace this with a fixed cell/column count or an arbitrary mobile-only min-height — that masks the symptom instead of fixing the missing observation.
- Assume the outer modal's `ResizeObserver` is sufficient — it is not, because the modal's own box can stay constant (`100dvh`) while only the container's box changes.
- Gate this fix to mobile only — it is a general container-geometry gap; desktop/docked/floating benefit from the same additive fix with no observed regression.
## Regression coverage (rendered geometry, not init/fit call presence)
jsdom cannot exercise real CSS layout, so the regression models the exact mechanism directly:
- Override the xterm container's (`data-testid="terminal-xterm"`) `clientWidth`/`clientHeight` getters to report `0` at the moment of the first post-open fit, then flip them to a real, stable nonzero box a moment later — with NO reconnect/orientation/keyboard-toggle/manual-refit call.
- Swap the shared `FitAddon.fit()` mock's implementation (scoped to this describe block only) for a variant that mirrors real `proposeDimensions()`'s degenerate-floor formula (`Math.max(2, floor(width/cellWidth))` / `Math.max(1, floor(height/cellHeight))`) against the REAL container element, instead of the fixed-width mock the spacing-family tests use.
- Capture every `new ResizeObserver(cb)` instance/target via a `MockResizeObserver`, then fire the SAME notification a real browser delivers for the container element specifically — this is the decisive step: pre-fix, no ResizeObserver is ever attached to `terminal-xterm` (only the modal), so this assertion fails outright; post-fix it recovers to a real, non-degenerate grid.
- Covers keyboard-CLOSED and keyboard-OPEN initial layouts, tab-switch remount (the container's `key={sessionId}` swap must re-target the new node), and duplicate/rapid resize notification coalescing.
- `SessionTerminal.tsx` gets a parallel regression proving it already has (and keeps) this same container-level observer.
- Run: `pnpm --filter @fusion/dashboard exec vitest run app/components/__tests__/TerminalModal.test.tsx app/components/__tests__/SessionTerminal.test.tsx app/components/__tests__/SessionTerminal.mobile.test.tsx --silent=passed-only --reporter=dot`.
- Real mobile Safari/Chrome sanity check remains the strongest signal for this class of bug; a real-device screenshot was not obtainable in this execution environment (headless coding agent, no physical device access) — this gap is recorded explicitly (task document key="repro" on FN-7620) rather than treating jsdom/desktop WebKit as proof. See `docs/ios-acceptance.md`.

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@@ -1038,6 +1038,55 @@ export function TerminalModal({ isOpen, onClose, initialCommand, initialCommandG
replaceActiveTabSession, replaceActiveTabSession,
} = useTerminalSessions(projectId); } = useTerminalSessions(projectId);
/*
FNXC:Terminal 2026-07-06-09:15:
FN-7620 root cause: the mobile terminal could render BLANK (not merely
mis-spaced) because nothing ever watched the xterm CONTAINER's (`terminalRef`)
own box. Real `FitAddon.proposeDimensions()` (@xterm/addon-fit@0.10.0) reads
`getComputedStyle(terminal.element.parentElement)` height/width and, when that
resolves to 0 (e.g. the mobile fullscreen/keyboard-overlap height cascade,
dvh support, or web-font/layout settle has not finished by the time the first
`fitAddon.fit()` call in `initTerminal` runs), floors to a degenerate
`{cols: 2, rows: 1}` grid rather than bailing out — xterm silently resizes
into a near-invisible box. Only `modalRef` (the whole modal) had a
ResizeObserver; a modal that is already sized to 100dvh/the keyboard box does
not re-fire that observer when only INNER content (the terminal container)
later settles to its real size, so the degenerate grid could persist forever
with no reconnect/orientation/keyboard-toggle/manual-refit path able to catch
it. `SessionTerminal.tsx` already observes its own container this way (see
its `resizeObserver.observe(containerRef.current)`); TerminalModal did not.
Mirror that: observe the xterm container itself for the life of each xterm
instance so ANY change in its OWN box (not just the outer modal's box) —
including the very first zero-to-real transition — triggers a corrective
fit via the existing `fitAndResizeForSession`. Re-established whenever the
container remounts (tab switch uses `key={activeTab?.sessionId}` on the
container div). See docs/solutions/ui-bugs/mobile-terminal-blank-render-zero-geometry-container.md.
*/
useEffect(() => {
if (!isOpen) return;
const node = terminalRef.current;
if (!node || typeof ResizeObserver === "undefined") return;
let pendingFrame: number | null = null;
const observer = new ResizeObserver(() => {
if (pendingFrame !== null) cancelAnimationFrame(pendingFrame);
pendingFrame = requestAnimationFrame(() => {
pendingFrame = null;
const sessionId =
typeof xtermInitializedRef.current === "string"
? xtermInitializedRef.current
: undefined;
fitAndResizeForSession(sessionId);
});
});
observer.observe(node);
return () => {
observer.disconnect();
if (pendingFrame !== null) cancelAnimationFrame(pendingFrame);
};
}, [fitAndResizeForSession, isOpen, activeTab?.sessionId]);
const { const {
projectName: terminalWorkspaceProjectName, projectName: terminalWorkspaceProjectName,
workspaces: terminalWorkspaces, workspaces: terminalWorkspaces,

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@@ -776,3 +776,69 @@ describe("SessionTerminal", () => {
await waitFor(() => expect(screen.queryByText("Not yet")).toBeNull()); await waitFor(() => expect(screen.queryByText("Not yet")).toBeNull());
}); });
}); });
/*
FNXC:Terminal 2026-07-06-09:20:
FN-7620 investigated whether `SessionTerminal` (the embedded CLI-agent
terminal) shares `TerminalModal`'s mobile blank-render defect (a zero-geometry
xterm container with no recovery path once collapsed to FitAddon's degenerate
{cols:2, rows:1} floor). It does NOT: `SessionTerminal` already attaches
`resizeObserver.observe(containerRef.current)` directly on its own xterm
container (`cli-terminal-viewport`) right after init — the SAME container-level
observer pattern `TerminalModal` was missing and this task added. This proves
that invariant with the same "fire the exact ResizeObserver notification a real
browser delivers, without any reconnect/keyboard-toggle/orientation trigger"
model used in `TerminalModal.test.tsx`'s FN-7620 coverage.
*/
describe("SessionTerminal — FN-7620 mobile blank render (container geometry recovery, unaffected surface)", () => {
type CapturedEntry = { target: Element; callback: ResizeObserverCallback };
let captured: CapturedEntry[] = [];
let originalGlobalResizeObserver: unknown;
class CapturingResizeObserver {
private readonly callback: ResizeObserverCallback;
constructor(callback: ResizeObserverCallback) {
this.callback = callback;
}
observe(target: Element): void {
captured.push({ target, callback: this.callback });
}
unobserve(): void {}
disconnect(): void {}
}
beforeEach(() => {
captured = [];
originalGlobalResizeObserver = (globalThis as unknown as { ResizeObserver?: unknown }).ResizeObserver;
(globalThis as unknown as { ResizeObserver: unknown }).ResizeObserver = CapturingResizeObserver;
});
afterEach(() => {
(globalThis as unknown as { ResizeObserver: unknown }).ResizeObserver = originalGlobalResizeObserver;
});
it("observes its own xterm container (not just relying on an outer/ancestor observer) so a zero-then-real geometry transition recovers without any external trigger", async () => {
render(<SessionTerminal sessionId="s1" />);
await waitFor(() => expect(FakeWS.instances.length).toBe(1));
await waitFor(() => expect(mockTerm.open).toHaveBeenCalled());
const container = screen.getByTestId("cli-terminal-viewport");
const matches = captured.filter((entry) => entry.target === container);
// Decisive invariant: SessionTerminal already wires a ResizeObserver
// directly onto its own xterm container element (unlike pre-fix
// TerminalModal, which only observed the outer modal box).
expect(matches.length).toBeGreaterThan(0);
mockFitAddon.fit.mockClear();
// Fire the same notification a real browser delivers the instant the
// container's box changes — not a manual fit()/reconnect call.
act(() => {
for (const entry of matches) {
entry.callback([] as unknown as ResizeObserverEntry[], entry as unknown as ResizeObserver);
}
});
await waitFor(() => expect(mockFitAddon.fit).toHaveBeenCalled());
});
});

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@@ -7988,3 +7988,361 @@ describe("TerminalModal — FN-7603 mobile inter-character spacing (Canvas vs DO
}); });
}); });
}); });
/*
FNXC:Terminal 2026-07-06-09:15:
FN-7620: "terminal renders nothing on mobile" is a DIFFERENT symptom than the
FN-7456->FN-7603 inter-character-spacing family above — a total blank render,
not visible-but-spaced ASCII. Root cause: real `FitAddon.proposeDimensions()`
(@xterm/addon-fit@0.10.0) reads `getComputedStyle(terminal.element.
parentElement)` height/width and floors to a degenerate `{cols: 2, rows: 1}`
grid — rather than bailing out — whenever that resolves to a zero box (e.g.
the mobile fullscreen/keyboard-overlap CSS height cascade has not settled by
the time the first post-open `fitAddon.fit()` runs). Only the WHOLE MODAL
(`modalRef`) had a ResizeObserver; nothing watched the xterm CONTAINER
(`terminalRef`) itself, so if the container's OWN box was still zero at the
single scheduled deferred-fit check, no later trigger ever re-measured it —
the terminal stayed a near-invisible 2x1 grid clipped inside a genuinely
zero-height box. This models that exact mechanism: `mockFitAddonFit`'s
implementation is temporarily swapped for a variant that reads the REAL
container's clientWidth/clientHeight (mirroring the real addon's
`getComputedStyle(...).width/height` read) instead of the shared fixed-width
constant the spacing-family tests above use, and a captured
`new ResizeObserver(cb)` lets the test fire the SAME notification a real
browser would deliver the instant the container's box changes size — without
calling any keyboard-toggle/orientation/reconnect/manual-refit production
handler. See docs/solutions/ui-bugs/mobile-terminal-blank-render-zero-geometry-container.md.
*/
describe("TerminalModal — FN-7620 mobile blank render (zero-geometry xterm container)", () => {
const mockOnClose = vi.fn();
const mockSendInput = vi.fn();
const mockResize = vi.fn();
const mockReconnect = vi.fn();
const createMockTerminalState = (overrides = {}) => ({
connectionStatus: "connected" as const,
sendInput: mockSendInput,
resize: mockResize,
onData: vi.fn(() => vi.fn()),
onExit: vi.fn(() => vi.fn()),
onConnect: vi.fn(() => vi.fn()),
onScrollback: vi.fn(() => vi.fn()),
reconnect: mockReconnect,
onSessionInvalid: vi.fn(() => vi.fn()),
...overrides,
});
type CapturedResizeObserverEntry = { target: Element; callback: ResizeObserverCallback };
let capturedResizeObservers: CapturedResizeObserverEntry[] = [];
class MockResizeObserver {
private readonly callback: ResizeObserverCallback;
constructor(callback: ResizeObserverCallback) {
this.callback = callback;
}
observe(target: Element): void {
capturedResizeObservers.push({ target, callback: this.callback });
}
unobserve(): void {}
disconnect(): void {}
}
/**
* Fires the captured ResizeObserver callback(s) for the element with the
* given `data-testid`, mirroring exactly what a real browser delivers when
* that element's own box changes size. Returns false if no ResizeObserver
* ever observed that element (the pre-fix state for "terminal-xterm").
*/
function fireResizeObserverFor(testId: string): boolean {
const target = screen.getByTestId(testId);
const matches = capturedResizeObservers.filter((entry) => entry.target === target);
if (matches.length === 0) return false;
for (const entry of matches) {
entry.callback(
[] as unknown as ResizeObserverEntry[],
entry as unknown as ResizeObserver,
);
}
return true;
}
// Mirrors real FitAddon.proposeDimensions()'s degenerate-floor formula
// (`Math.max(2, floor(width/cellWidth))` / `Math.max(1, floor(height/
// cellHeight))`) against the REAL xterm container element's clientWidth/
// clientHeight — unlike the shared fixed-width mock the spacing-family
// tests above use, this is what lets the test distinguish "the container is
// still a zero/degenerate box" from "the container has settled to a real,
// usable box".
const CHAR_WIDTH_PX = 9;
const CHAR_HEIGHT_PX = 17;
const geometryAwareFitAddonFit = vi.fn(() => {
const container = screen.queryByTestId("terminal-xterm");
const width = container?.clientWidth ?? 0;
const height = container?.clientHeight ?? 0;
mockTerminalInstance.cols = Math.max(2, Math.floor(width / CHAR_WIDTH_PX));
mockTerminalInstance.rows = Math.max(1, Math.floor(height / CHAR_HEIGHT_PX));
});
const originalMockFitAddonFitImpl = mockFitAddonFit.getMockImplementation();
let previousInnerWidth: number;
let previousOntouchstart: unknown;
let originalWindowResizeObserver: unknown;
let originalGlobalResizeObserver: unknown;
beforeEach(() => {
vi.clearAllMocks();
resetMockTerminalGeometry();
resetFontRemeasureCount();
capturedResizeObservers = [];
mockFitAddonFit.mockImplementation(geometryAwareFitAddonFit);
originalWindowResizeObserver = (window as unknown as { ResizeObserver?: unknown }).ResizeObserver;
originalGlobalResizeObserver = (globalThis as unknown as { ResizeObserver?: unknown }).ResizeObserver;
(window as unknown as { ResizeObserver: unknown }).ResizeObserver = MockResizeObserver;
(globalThis as unknown as { ResizeObserver: unknown }).ResizeObserver = MockResizeObserver;
vi.spyOn(window, "matchMedia").mockImplementation((query: string) => ({
matches: false,
media: query,
onchange: null,
addListener: vi.fn(),
removeListener: vi.fn(),
addEventListener: vi.fn(),
removeEventListener: vi.fn(),
dispatchEvent: vi.fn(),
}));
previousInnerWidth = window.innerWidth;
previousOntouchstart = window.ontouchstart;
// Real reported device: a narrow touch-primary mobile viewport.
Object.defineProperty(window, "innerWidth", { value: 390, configurable: true });
Object.defineProperty(window, "ontouchstart", { value: null, configurable: true });
window.localStorage.removeItem(TERMINAL_FONT_SIZE_KEY);
window.localStorage.removeItem(TERMINAL_PREFERENCES_KEY);
mockTerminalInstance.options.fontFamily = XTERM_FONT_FAMILY;
mockTerminalInstance.options.fontSize = 14;
mockTerminalInstance.cols = 80;
mockTerminalInstance.rows = 24;
mockUseTerminal.mockReturnValue(createMockTerminalState());
mockUseTerminalSessions.mockReturnValue(defaultSessionState);
mockUseWorkspaces.mockReturnValue({
projectName: "kb",
workspaces: [],
loading: false,
error: null,
});
mockCreateTerminalSession.mockResolvedValue({
sessionId: "test-session-123",
shell: "/bin/bash",
cwd: "/project",
});
});
afterEach(() => {
Object.defineProperty(window, "innerWidth", { value: previousInnerWidth, configurable: true });
if (previousOntouchstart === undefined) {
delete (window as unknown as { ontouchstart?: unknown }).ontouchstart;
} else {
Object.defineProperty(window, "ontouchstart", { value: previousOntouchstart, configurable: true });
}
if (originalWindowResizeObserver) {
(window as unknown as { ResizeObserver: unknown }).ResizeObserver = originalWindowResizeObserver;
} else {
delete (window as unknown as { ResizeObserver?: unknown }).ResizeObserver;
}
if (originalGlobalResizeObserver) {
(globalThis as unknown as { ResizeObserver: unknown }).ResizeObserver = originalGlobalResizeObserver;
} else {
delete (globalThis as unknown as { ResizeObserver?: unknown }).ResizeObserver;
}
mockFitAddonFit.mockImplementation(originalMockFitAddonFitImpl ?? (() => {}));
Object.defineProperty(window, "visualViewport", { value: undefined, writable: true, configurable: true });
vi.useRealTimers();
vi.restoreAllMocks();
});
function overrideContainerBox(container: HTMLElement, box: { width: number; height: number }): void {
Object.defineProperty(container, "clientWidth", { configurable: true, get: () => box.width });
Object.defineProperty(container, "clientHeight", { configurable: true, get: () => box.height });
}
it("recovers from a zero-geometry xterm container on the INITIAL mobile layout with the keyboard CLOSED — no reconnect/orientation/refit", async () => {
let capturedDataCallback: ((data: string) => void) | null = null;
let capturedScrollbackCallback: ((data: string) => void) | null = null;
mockUseTerminal.mockReturnValue(
createMockTerminalState({
onData: vi.fn((cb: (data: string) => void) => {
capturedDataCallback = cb;
return vi.fn();
}),
onScrollback: vi.fn((cb: (data: string) => void) => {
capturedScrollbackCallback = cb;
return vi.fn();
}),
}),
);
render(<TerminalModal isOpen={true} onClose={mockOnClose} />);
await waitFor(() => expect(mockTerminalInstance.open).toHaveBeenCalled());
const container = screen.getByTestId("terminal-xterm");
const box = { width: 0, height: 0 };
overrideContainerBox(container, box);
// Let the initial fit()+deferred-refit sequence run against a genuinely
// zero container box — the real-device race this task fixes.
await act(async () => {
await new Promise((resolve) => setTimeout(resolve, 60));
await Promise.resolve();
});
// Pre-condition: with the container still reporting 0x0, xterm has
// collapsed to FitAddon's degenerate floor — exactly the "nothing
// renders" mechanism (a 2x1 grid clipped inside a 0px box).
expect(mockTerminalInstance.cols).toBe(2);
expect(mockTerminalInstance.rows).toBe(1);
// The real device settles the container to its actual, stable box a
// moment later — no user action, CSS/layout/font settle only.
box.width = 360;
box.height = 480;
// Decisive step: fire the SAME notification a real browser's
// ResizeObserver would deliver for THIS container the instant its box
// changed — not a manual fitAddon.fit()/reconnect/keyboard-toggle call.
// Pre-fix, no ResizeObserver ever observes this container (only the
// whole modal), so this assertion fails outright.
const observed = fireResizeObserverFor("terminal-xterm");
expect(observed).toBe(true);
await waitFor(() => {
expect(mockTerminalInstance.cols).toBeGreaterThan(2);
expect(mockTerminalInstance.rows).toBeGreaterThan(1);
});
// Rendered-state invariant: a non-zero, stable measured box AND real
// (non-degenerate) rows/cols — not merely that fit()/open() was
// attempted.
expect(container.clientWidth).toBe(360);
expect(container.clientHeight).toBe(480);
expect(mockTerminalInstance.cols).toBe(Math.max(2, Math.floor(360 / CHAR_WIDTH_PX)));
expect(mockTerminalInstance.rows).toBe(Math.max(1, Math.floor(480 / CHAR_HEIGHT_PX)));
// Output/prompt actually renders (write() receives real data), not just
// an init attempt.
mockTerminalInstance.write.mockClear();
act(() => {
capturedScrollbackCallback?.("user@host:~$ ");
capturedDataCallback?.("ls\r\n");
});
expect(mockTerminalInstance.write).toHaveBeenCalledWith("user@host:~$ ");
expect(mockTerminalInstance.write).toHaveBeenCalledWith("ls\r\n");
});
it("recovers from a zero-geometry xterm container on the INITIAL mobile layout with the keyboard already OPEN", async () => {
const mockVV = {
width: 360,
height: 300,
offsetTop: 0,
offsetLeft: 0,
addEventListener: vi.fn(),
removeEventListener: vi.fn(),
};
Object.defineProperty(window, "visualViewport", { value: mockVV, writable: true, configurable: true });
Object.defineProperty(window, "innerHeight", { value: 300, writable: true, configurable: true });
render(<TerminalModal isOpen={true} onClose={mockOnClose} />);
await waitFor(() => expect(mockTerminalInstance.open).toHaveBeenCalled());
const container = screen.getByTestId("terminal-xterm");
const box = { width: 0, height: 0 };
overrideContainerBox(container, box);
await act(async () => {
await new Promise((resolve) => setTimeout(resolve, 60));
await Promise.resolve();
});
expect(mockTerminalInstance.cols).toBe(2);
expect(mockTerminalInstance.rows).toBe(1);
box.width = 360;
box.height = 260;
const observed = fireResizeObserverFor("terminal-xterm");
expect(observed).toBe(true);
await waitFor(() => {
expect(mockTerminalInstance.cols).toBeGreaterThan(2);
expect(mockTerminalInstance.rows).toBeGreaterThan(1);
});
expect(container.clientWidth).toBe(360);
expect(container.clientHeight).toBe(260);
expect(mockTerminalInstance.cols).toBe(Math.max(2, Math.floor(360 / CHAR_WIDTH_PX)));
expect(mockTerminalInstance.rows).toBe(Math.max(1, Math.floor(260 / CHAR_HEIGHT_PX)));
});
it("re-establishes the container ResizeObserver against the NEW container node after a tab-switch remount", async () => {
const secondTab = {
id: "tab-2",
sessionId: "session-2",
title: "Terminal 2",
isActive: true,
createdAt: Date.now(),
};
const { rerender } = render(<TerminalModal isOpen={true} onClose={mockOnClose} />);
await waitFor(() => expect(mockTerminalInstance.open).toHaveBeenCalledTimes(1));
const firstContainer = screen.getByTestId("terminal-xterm");
expect(fireResizeObserverFor("terminal-xterm")).toBe(true);
mockUseTerminalSessions.mockReturnValue({
...defaultSessionState,
tabs: [{ ...defaultTab, isActive: false }, secondTab],
activeTab: secondTab,
});
rerender(<TerminalModal isOpen={true} onClose={mockOnClose} />);
await waitFor(() => expect(mockTerminalInstance.open).toHaveBeenCalledTimes(2));
const secondContainer = screen.getByTestId("terminal-xterm");
expect(secondContainer).not.toBe(firstContainer);
// The container remounted with a new sessionId key — the observer must
// now target the NEW node, not the stale/unmounted one.
expect(fireResizeObserverFor("terminal-xterm")).toBe(true);
});
it("coalesces duplicate/rapid container resize notifications into a single settled fit", async () => {
render(<TerminalModal isOpen={true} onClose={mockOnClose} />);
await waitFor(() => expect(mockTerminalInstance.open).toHaveBeenCalled());
const container = screen.getByTestId("terminal-xterm");
const box = { width: 0, height: 0 };
overrideContainerBox(container, box);
await act(async () => {
await new Promise((resolve) => setTimeout(resolve, 60));
await Promise.resolve();
});
expect(mockTerminalInstance.cols).toBe(2);
expect(mockTerminalInstance.rows).toBe(1);
box.width = 640;
box.height = 400;
// Two rapid duplicate notifications (e.g. layout + font settle firing in
// the same tick) must coalesce to one corrective fit, not double-apply.
mockFitAddonFit.mockClear();
expect(fireResizeObserverFor("terminal-xterm")).toBe(true);
expect(fireResizeObserverFor("terminal-xterm")).toBe(true);
await waitFor(() => {
expect(mockTerminalInstance.cols).toBe(Math.max(2, Math.floor(640 / CHAR_WIDTH_PX)));
expect(mockTerminalInstance.rows).toBe(Math.max(1, Math.floor(400 / CHAR_HEIGHT_PX)));
});
});
});