fix(viewport): pad width to contentWidth

[ivanvc]

I have an application that uses the viewport, and I added borders to the viewport. I noticed the width is not set to what can be set through .Width(), as I'm loading variable width content, which shrinks and grows depending on what it currently renders.

My initial workaround was to force the style from the viewport to set a fixed width. However, that didn't work. Then, I added spaces to the last line of the content to match the viewport's width, which worked, but I believe the end-user code shouldn't be handling this case.

So, with this PR, I'm padding the width of the viewport content to what has been specified in its width. Please look at the screenshots from a minimal application reproducing the issue.

Before:

After:

And this is the code that reproduces the issue:

package main

// An example program demonstrating the pager component from the Bubbles
// component library.

import (
	"fmt"
	"os"

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

type model struct {
	ready    bool
	viewport viewport.Model
}

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

func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	switch msg := msg.(type) {
	case tea.KeyMsg:
		if msg.String() == "ctrl+c" {
			return m, tea.Quit
		}

	case tea.WindowSizeMsg:
		if !m.ready {
			m.viewport = viewport.New(msg.Width, msg.Height)
			m.viewport.Style = lipgloss.NewStyle().BorderStyle(lipgloss.NormalBorder()).BorderForeground(lipgloss.Color("4")).Padding(0, 1)
			m.viewport.SetContent("testing")
			m.ready = true
		} else {
			m.viewport.Width = msg.Width
			m.viewport.Height = msg.Height
		}
	}

	var cmd tea.Cmd
	m.viewport, cmd = m.viewport.Update(msg)

	return m, cmd
}

func (m model) View() string {
	if !m.ready {
		return "\n  Initializing..."
	}
	return m.viewport.View()
}

func main() {
	p := tea.NewProgram(
		new(model),
		tea.WithAltScreen(),
	)

	if _, err := p.Run(); err != nil {
		fmt.Println("could not run program:", err)
		os.Exit(1)
	}
}

[holt-crews]

I just ran into the same issue and was going to suggest the same change. Any update on this @ivanvc? Did you find a fix/workaround or are you still waiting for this pr to get merged?

[maaslalani]

Thank you so much for the PR @ivanvc, great catch with this bug! Sorry for the delay in merging!