Resizing truncates on terminal window's original size

[Zebbeni]

I'm doing a simple experiment to poll the terminal for size changes and update a bordered viewport to span the full window. (It's not an ideal solution but I can't rely on WindowSizeMsg events on Windows.) In some cases think I'm experiencing #573 but it tends to correct itself with subsequent resizes. The more consistent problem I'm finding is that the viewport gets truncated on the width the terminal window had at the time the program launched, and its y offset seems to get messed up if I enlarge the terminal window beyond its original height. I don't see the style MaxWidth or MaxHeight being set to anything unexpected so I wonder if this is a bug? Or is there something else I'm missing?

package main

import (
	"fmt"
	"os"
	"time"

	"golang.org/x/term"

	"github.com/charmbracelet/bubbles/viewport"
	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"
)

var borderStyle = lipgloss.NewStyle().BorderStyle(lipgloss.RoundedBorder())
var textStyle = lipgloss.NewStyle().Foreground(lipgloss.Color("45"))

type tickMsg int

type model struct {
	w, h int
	vp   viewport.Model
}

func tick() tea.Msg {
	time.Sleep(time.Second / 4)
	return tickMsg(1)
}

func (m *model) Init() tea.Cmd {
	return tick
}

func (m *model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	switch msg.(type) {
	case tickMsg:
		w, h, _ := term.GetSize(int(os.Stdout.Fd()))
		if w != m.w || h != m.h {
			m.updateSize(w, h)
		}
		return m, tick
	}
	return m, nil
}

func (m *model) View() string {
	return m.vp.View()
}

func (m *model) updateSize(w, h int) {
	m.w = w
	m.h = h

	m.vp = viewport.New(m.w, m.h)
	m.vp.Style = borderStyle

	text := fmt.Sprintf("Size: %d, %d", m.w, m.h)
	rendered := textStyle.Copy().Width(m.w).Height(m.h).Render(text)
	m.vp.SetContent(rendered)
}

func main() {
	m := &model{w: 1, h: 1, vp: viewport.New(1, 1)}
	p := tea.NewProgram(m)
	if _, err := p.Run(); err != nil {
		fmt.Print(err)
	}
}

[Zebbeni]

Okay, it looks like batching a WindowSizeMsg Cmd with my tick Cmd solves my problem. It'd be great if bubbletea comes up with a way to avoid polling for window resizes on Windows machines in the future but I'm happy with this for now.

previous:

func (m *model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	switch msg.(type) {
	case tickMsg:
		w, h, _ := term.GetSize(int(os.Stdout.Fd()))
		if w != m.w || h != m.h {
			m.updateSize(w, h)
		}
		return m, tick
	}
	return m, nil
}

solution:

func (m *model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	switch msg.(type) {
	case tickMsg:
		w, h, _ := term.GetSize(int(os.Stdout.Fd()))
		if w != m.w || h != m.h {
			m.updateSize(w, h)
		}
		return m, tea.Batch(tick, func() tea.Msg { return tea.WindowSizeMsg{Width: w, Height: h} })
	}
	return m, nil
}

[bashbunni]

What issues are you having with the tea.WindowSizeMsg on Windows? It should work cross-platform. The resizes also trigger the tea.WindowSizeMsg, so you shouldn't be having to trigger it manually

[Zebbeni]

I'm doing a simple experiment to poll the terminal for size changes and update a bordered viewport to span the full window. (It's not an ideal solution but I can't rely on WindowSizeMsg events on Windows.)

Ah, I meant that I can't listen for WindowSizeMsg events in the Update function to know when the terminal window has been resized, per the comment here:

bubbletea/screen.go

Lines 3 to 6 in 6b77c8f

	// WindowSizeMsg is used to report the terminal size. It's sent to Update once
	// initially and then on every terminal resize. Note that Windows does not
	// have support for reporting when resizes occur as it does not support the
	// SIGWINCH signal.

I can fire my own WindowSizeMsg message when I detect a window resize using term.GetSize(int(os.Stdout.Fd())) to trigger a bubbletea update but that's a little backward from how it ought to work.

[bashbunni]

Ah ok thank you! Looks like this was a duplicate of #538 🤔 Thank you for reporting it!