fix(tea): fall back to 80x24 when initial GetSize returns 0 (blank first frame under tmux)

[Ricardo-M-L]

Problem

Launching a Bubble Tea v2 program inside tmux (and some other pty setups) shows a blank screen until the first event — the user resizes the window or presses a key — at which point the UI finally paints. It looks like the program hung.

Root cause

Program.Run reads the terminal size once at startup and trusts the result, checking only the error:

w, h, err := term.GetSize(p.ttyOutput.Fd())
if err != nil {
    return p.initialModel, fmt.Errorf("bubbletea: error getting terminal size: %w", err)
}
width, height = w, h            // no check for w==0 / h==0

Under tmux the pty size often isn't negotiated yet at this instant, so term.GetSize returns (0, 0) with err == nil. Run then resizes the renderer to 0x0. Because the event loop only paints after it receives a message, and the only startup message is the resulting WindowSizeMsg{0,0}, the first frame is clipped to a 0x0 viewport — blank — until a real SIGWINCH arrives.

This is independent of the model's View(): even a view that ignores width entirely renders blank, because the renderer viewport is 0x0.

Fix

Fall back to a standard 80x24 for any zero dimension, mirroring what terminal apps conventionally do. The first frame then paints, and the genuine size replaces it via WindowSizeMsg a moment later.

width, height = fallbackZeroSize(w, h)

Adds fallbackZeroSize (a small pure helper) plus a unit test. The startup GetSize path itself is awkward to unit-test (it needs a real tty Fd), so the fallback logic is factored into a tested helper.

Testing

• go test . passes.
• Reproduction: a minimal v2 program launched in an early/detached tmux pane renders blank until the first event; with the fallback it paints immediately.

[Ricardo-M-L]

Gentle ping on this one 🙂

It's a small (+52/-1), self-contained fix with a unit test for a real tmux issue: term.GetSize returns (0, 0) with err == nil before the pty size is negotiated, so the renderer is sized to 0x0 and the first frame is blank until a real SIGWINCH arrives (looks like the program hung). The fallback lets the first frame paint, and the genuine size still replaces it via WindowSizeMsg a moment later — no behavior change for terminals that report a valid size.

Happy to adjust the fallback dimensions or take a different approach if you'd prefer. Thanks for taking a look when you get a chance!

[Ricardo-M-L]

Hi! Just a friendly ping on this PR. It's been open for a while — would appreciate a review when you get a chance. Thanks for your time!