Make dashboard updateable

terminal_cursor.go

@@ -0,0 +1,86 @@
+package main
+
+import (
+	"bytes"
+	"io"
+	"os"
+	"sync"
+
+	"github.com/charmbracelet/x/ansi"
+)
+
+// terminalCursorOutput decorates Bubble Tea's completed frame writes with a
+// hardware cursor position. Bubble Tea otherwise parks the cursor at the
+// bottom of every frame, which prevents a real insertion caret inside a custom
+// editor.
+type terminalCursorOutput struct {
+	file *os.File
+
+	mu      sync.Mutex
+	visible bool
+	column  int
+	row     int
+}
+
+func newTerminalCursorOutput(file *os.File) *terminalCursorOutput {
+	return &terminalCursorOutput{file: file}
+}
+
+func (o *terminalCursorOutput) SetCursor(visible bool, column, row int) {
+	o.mu.Lock()
+	defer o.mu.Unlock()
+	o.visible, o.column, o.row = visible, column, row
+}
+
+func (o *terminalCursorOutput) FrameMarker() string {
+	o.mu.Lock()
+	defer o.mu.Unlock()
+	if !o.visible {
+		return ""
+	}
+	// This zero-width sequence makes frames at different insertion positions
+	// distinct, preventing Bubble Tea from skipping a hardware-cursor-only
+	// update. The output wrapper reasserts the same position after Bubble Tea
+	// parks its cursor at the bottom of the frame.
+	return ansi.CursorPosition(o.column, o.row)
+}
+
+func (o *terminalCursorOutput) Write(value []byte) (int, error) {
+	o.mu.Lock()
+	defer o.mu.Unlock()
+
+	written, err := o.file.Write(value)
+	if err != nil || written != len(value) {
+		return written, err
+	}
+	// Let Bubble Tea restore the cursor normally during startup/shutdown.
+	if bytes.Equal(value, []byte(ansi.ShowCursor)) || bytes.Equal(value, []byte(ansi.HideCursor)) {
+		if bytes.Equal(value, []byte(ansi.ShowCursor)) {
+			_, _ = io.WriteString(o.file, ansi.SetCursorStyle(0))
+		}
+		return written, nil
+	}
+	if !o.visible {
+		_, err = io.WriteString(o.file, ansi.HideCursor)
+		return written, err
+	}
+	_, err = io.WriteString(
+		o.file,
+		ansi.SetCursorStyle(5)+
+			ansi.CursorPosition(o.column, o.row)+
+			ansi.ShowCursor,
+	)
+	return written, err
+}
+
+func (o *terminalCursorOutput) Read(value []byte) (int, error) {
+	return o.file.Read(value)
+}
+
+func (o *terminalCursorOutput) Close() error {
+	return nil
+}
+
+func (o *terminalCursorOutput) Fd() uintptr {
+	return o.file.Fd()
+}