v0.1.0 initial commit

internal/ui/overlay.go

@@ -0,0 +1,107 @@
+package ui
+
+import (
+	"github.com/lixenwraith/terminal"
+	"github.com/lixenwraith/terminal/tui"
+)
+
+// Panel is a modal overlay with a scrollable body. It owns the frame, the
+// scroll state and the scrollbar; the caller renders rows into the region
+// Render returns, starting at Scroll.
+type Panel struct {
+	Title  string
+	Hint   string
+	Status string // line inside the bottom of the frame, e.g. a full filename
+	W, H   int    // 0 = 80% of the screen
+	Cursor bool   // track a selected row rather than scrolling freely
+
+	Sel    int
+	Scroll int
+	Rows   int // content rows, set by the caller before Render
+	View   int // visible rows, set by Render
+}
+
+// Move advances the selection, or the scroll offset when Cursor is unset.
+func (p *Panel) Move(d int) {
+	if p.Cursor {
+		p.Sel += d
+	} else {
+		p.Scroll += d
+	}
+	p.clamp()
+}
+
+// Page moves by n screens.
+func (p *Panel) Page(n int) { p.Move(n * max(1, p.View)) }
+
+// Half moves by n half screens.
+func (p *Panel) Half(n int) { p.Move(n * max(1, p.View/2)) }
+
+// First jumps to the top.
+func (p *Panel) First() { p.Sel, p.Scroll = 0, 0 }
+
+// Last jumps to the bottom.
+func (p *Panel) Last() {
+	p.Sel, p.Scroll = p.Rows-1, p.Rows
+	p.clamp()
+}
+
+// Reset returns the panel to the top, for new content.
+func (p *Panel) Reset() { p.Sel, p.Scroll = 0, 0 }
+
+func (p *Panel) clamp() {
+	if p.Rows <= 0 {
+		p.Sel, p.Scroll = 0, 0
+		return
+	}
+	p.Sel = tui.ClampCursor(p.Sel, p.Rows)
+	if p.Cursor {
+		p.Scroll = tui.AdjustScroll(p.Sel, p.Scroll, p.View, p.Rows)
+	}
+	p.Scroll = tui.ClampScroll(p.Scroll, p.View, p.Rows)
+}
+
+// Render draws the frame and returns the body region, scrollbar excluded.
+// A zero-width result means the screen is too small to show the panel.
+func (p *Panel) Render(root tui.Region, th *Theme) tui.Region {
+	w, h := p.W, p.H
+	if w <= 0 {
+		w = root.W * 80 / 100
+	}
+	if h <= 0 {
+		h = root.H * 80 / 100
+	}
+	w, h = min(w, root.W-4), min(h, root.H-2)
+	if w < 24 || h < 6 {
+		return tui.Region{}
+	}
+
+	t, hint := p.Title, p.Hint
+	if t != "" {
+		t = " " + t + " "
+	}
+	if hint != "" {
+		hint = " " + hint + " "
+	}
+
+	content := tui.Center(root, w, h).Modal(tui.ModalOpts{
+		Title: t, Hint: hint, Border: tui.LineDouble,
+		BorderFg: th.Accent, TitleFg: th.HeaderFg, HintFg: th.HintFg, Bg: th.FocusBg,
+	})
+
+	body := content
+	if p.Status != "" && content.H > 3 {
+		body = content.Sub(0, 0, content.W, content.H-2)
+		content.HLine(content.H-2, tui.LineSingle, th.Border)
+		content.Text(0, content.H-1, tui.Truncate(p.Status, content.W),
+			th.HintFg, th.FocusBg, terminal.AttrDim)
+	}
+
+	p.View = body.H
+	p.clamp()
+	if p.Rows > body.H && body.W > 2 {
+		body.Sub(body.W-1, 0, 1, body.H).ScrollBar(0, p.Scroll, body.H, p.Rows, th.Border)
+		body = body.Sub(0, 0, body.W-1, body.H)
+	}
+	return body
+}