1 files changed, 81 insertions, 0 deletions
diff --git a/go/ui/buffer.go b/go/ui/buffer.go
new file mode 100644
index 00000000..cc9f2377
--- /dev/null
+++ b/go/ui/buffer.go
@@ -0,0 +1,81 @@
+package ui
+
+import (
+	"image/color"
+
+	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/hajimehoshi/ebiten/v2/text"
+)
+
+var (
+	BUFFER_BACKGROUND = gray
+	BUFFER_FOREGROUND = color.White
+)
+
+type Buffer struct {
+	X, Y          int
+	Width, Height int
+	img           *ebiten.Image
+	lines         []string
+	pos           int
+}
+
+func NewBuffer(x, y int, width, height int) *Buffer {
+	return &Buffer{x, y, width, height, nil, []string{}, 0}
+}
+
+func (b *Buffer) render() {
+	img := ebiten.NewImage(b.Width, b.Height)
+	img.Fill(BUFFER_BACKGROUND)
+	y := 0
+	for _, line := range b.lines[b.pos:] {
+		bounds := text.BoundString(Font, line)
+		y += bounds.Dy()
+		if y > b.Height {
+			break
+		}
+		text.Draw(img, line, Font, 0, y, BUFFER_FOREGROUND)
+	}
+	b.img = img
+}
+
+func (b *Buffer) Draw(screen *ebiten.Image) {
+	if b.img == nil {
+		b.render()
+	}
+	op := &ebiten.DrawImageOptions{}
+	op.GeoM.Translate(float64(b.X), float64(b.Y))
+	screen.DrawImage(b.img, op)
+}
+
+func (b *Buffer) FindObjectAt(x, y int) interface{} {
+	return nil
+}
+
+func (b *Buffer) ForceRedraw() {
+	b.img = nil
+}
+
+func (b *Buffer) AddLines(lines []string) {
+	b.lines = append(b.lines, lines...)
+	b.ForceRedraw()
+}
+
+func (b *Buffer) AddLine(line string) {
+	b.AddLines([]string{line})
+}
+
+func (b *Buffer) ClearLines() {
+	b.lines = []string{}
+	b.ForceRedraw()
+}
+
+func (b *Buffer) RemoveLast() {
+	b.lines = b.lines[:len(b.lines)-1]
+	b.ForceRedraw()
+}
+
+func (b *Buffer) Remove(idx int) {
+	b.lines = append(b.lines[:idx], b.lines[idx+1:]...)
+	b.ForceRedraw()
+}