panel.go

package term

import (
	"fmt"
	"strings"

	"github.com/deref/exo/internal/util/mathutil"
)

// Zero value is ready to use. Operations on panel affect Stdout.
// Must call Close() when done, to restore terminal settings.
type BottomPanel struct {
	content string
	// Desired panel height.
	height int
	// Current terminal margin.
	margin int
	// Current terminal size.
	termHeight int
}

func (p *BottomPanel) Height() int {
	return p.margin
}

// Set the panel height. The rendered height may be smaller than the requested
// height, if the requested height exceeds the terminal height minus ScrollOff.
func (p *BottomPanel) SetHeight(value int) {
	p.height = value
	p.render()
}

// Minimum number of scrolling terminal lines to display, no matter the
// requested panel size.
const ScrollOff = 4

// Set the content to appear at the bottom of the scrollback buffer.
// Will be truncated if it is larger than the panel's height.
func (p *BottomPanel) SetContent(value string) {
	p.content = value
	p.render()
}

func (p *BottomPanel) render() {
	termWidth, termHeight := GetSize()

	// Save and restore cursor.
	fmt.Printf("%c7", Esc)
	defer func() {
		fmt.Printf("%c8", Esc)
	}()

	// Set margin.
	margin := mathutil.IntMin(p.height, termHeight-ScrollOff)
	bottom := termHeight - margin
	if margin != p.margin || termHeight != p.termHeight {
		x := bottom
		if p.height == 0 {
			x = 0
		}
		fmt.Printf("%c[0;%dr", Esc, x)
		p.margin = margin
		p.termHeight = termHeight
	}

	// Fill content with trailing blank lines.
	lines := strings.Split(p.content, "\n")
	for i := 0; i < margin; i++ {
		line := ""
		if i < len(lines) {
			line += TrimToVisualLength(lines[i], termWidth)
		}
		// Move cursor, write string, then erase to end of line.
		fmt.Printf("%c[%d;1H%s%c[0K", Esc, bottom+i+1, line, Esc)
	}

}

func (p *BottomPanel) Close() {
	p.height = 0
	p.content = ""
	p.render()
}

there are various bugs left in this impl, do not use