Initial patterm project

internal/app/tabbar.go

@@ -0,0 +1,70 @@
+package app
+
+import (
+	"fmt"
+	"os"
+	"strings"
+)
+
+const tabBarRows = 1
+
+// drawTabBar renders SPEC §4's top tab bar at row 1. Tabs are top-level
+// children (ParentID == ""); the focused tab is highlighted. The PTY
+// region begins at row 2.
+func (st *uiState) drawTabBar() {
+	st.mu.Lock()
+	palOpen := st.palette != nil
+	focus := st.focusedID
+	st.mu.Unlock()
+	if palOpen {
+		return
+	}
+	layout := st.layoutSnapshot()
+	width := int(layout.childCols())
+
+	var sessions []*Child
+	for _, c := range st.sess.Children() {
+		if c.ParentID == "" && c.Status() == StatusRunning {
+			sessions = append(sessions, c)
+		}
+	}
+
+	var b strings.Builder
+	b.WriteString("\x1b[1;1H")
+	cur := 0
+	for _, c := range sessions {
+		label := c.Name
+		seg := " " + label + " "
+		if cur+len(seg) > width-2 {
+			break
+		}
+		if c.ID == focus {
+			b.WriteString("\x1b[7m")
+		} else {
+			b.WriteString("\x1b[2m")
+		}
+		b.WriteString(seg)
+		b.WriteString("\x1b[0m")
+		cur += len(seg)
+	}
+	// "+" hint at end.
+	hint := "+"
+	if cur > 0 {
+		hint = "  +"
+	}
+	if cur+len(hint) <= width {
+		b.WriteString("\x1b[2m")
+		b.WriteString(hint)
+		b.WriteString("\x1b[0m")
+		cur += len(hint)
+	}
+	// Fill the rest of the tab-bar row so stale chars don't linger.
+	if width-cur > 0 {
+		b.WriteString(strings.Repeat(" ", width-cur))
+	}
+
+	st.outMu.Lock()
+	defer st.outMu.Unlock()
+	// Save cursor, paint, restore.
+	fmt.Fprintf(os.Stdout, "\x1b7%s\x1b8", b.String())
+}