feat: add monitor picker to the GUI settings

Enumerate monitors via hyprctl (Hyprland) and present them as a
dropdown in the settings window instead of a raw index. The picker is
enabled only for the screen source and persists the selected monitor as
stream_index. Falls back to a single indexed option when enumeration is
unavailable (non-Hyprland).

internal/capture/monitors.go

@@ -0,0 +1,79 @@
+// Monitor enumeration for the settings UI.
+//
+// The screen-capture backend itself selects a monitor by index; this file
+// provides a way to list the available monitors so the GUI can present a
+// friendly picker instead of a raw index.
+//
+// Hyprland exposes monitor info via the `hyprctl monitors` command. Other
+// Wayland compositors would need a portal-based enumeration; for now we only
+// implement the Hyprland path (the primary dev environment) and return a
+// clear error elsewhere.
+
+package capture
+
+import (
+	"encoding/json"
+	"errors"
+	"os/exec"
+)
+
+// Monitor describes one capturable output.
+type Monitor struct {
+	Index   int    // capture StreamIndex to pass to OpenPipeWire
+	Name    string // compositor name, e.g. "eDP-1"
+	Width   int
+	Height  int
+	Primary bool
+}
+
+// ErrNoMonitors is returned when monitor enumeration is unsupported or fails.
+var ErrNoMonitors = errors.New("capture: monitor enumeration unavailable on this compositor")
+
+// ListMonitors returns the available monitors for the GUI picker.
+func ListMonitors() ([]Monitor, error) {
+	if hyprctlAvailable() {
+		return hyprctlMonitors()
+	}
+	return nil, ErrNoMonitors
+}
+
+// hyprctlAvailable reports whether the Hyprland monitor command exists.
+func hyprctlAvailable() bool {
+	_, err := exec.LookPath("hyprctl")
+	return err == nil
+}
+
+// hyprctlMonitor is the JSON shape emitted by `hyprctl monitors -j`.
+type hyprctlMonitor struct {
+	ID          int    `json:"id"`
+	Name        string `json:"name"`
+	Width       int    `json:"width"`
+	Height      int    `json:"height"`
+	Description string `json:"description"`
+	Focused     bool   `json:"focused"`
+}
+
+// hyprctlMonitors lists monitors via the Hyprland IPC command.
+func hyprctlMonitors() ([]Monitor, error) {
+	out, err := exec.Command("hyprctl", "monitors", "-j").Output()
+	if err != nil {
+		return nil, ErrNoMonitors
+	}
+
+	var raw []hyprctlMonitor
+	if err := json.Unmarshal(out, &raw); err != nil {
+		return nil, ErrNoMonitors
+	}
+
+	monitors := make([]Monitor, 0, len(raw))
+	for _, m := range raw {
+		monitors = append(monitors, Monitor{
+			Index:   m.ID,
+			Name:    m.Name,
+			Width:   m.Width,
+			Height:  m.Height,
+			Primary: m.Focused,
+		})
+	}
+	return monitors, nil
+}

internal/capture/monitors_test.go

@@ -0,0 +1,42 @@
+package capture
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+// TestHyprctlMonitors parses a representative `hyprctl monitors -j` payload.
+func TestHyprctlMonitors(t *testing.T) {
+	payload := `[
+  {
+    "id": 0,
+    "name": "eDP-1",
+    "description": "BOE 0x094C",
+    "width": 1920,
+    "height": 1200,
+    "focused": true
+  },
+  {
+    "id": 1,
+    "name": "HDMI-A-1",
+    "description": "Samsung",
+    "width": 2560,
+    "height": 1440,
+    "focused": false
+  }
+]`
+
+	var raw []hyprctlMonitor
+	if err := json.Unmarshal([]byte(payload), &raw); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+	if len(raw) != 2 {
+		t.Fatalf("got %d monitors, want 2", len(raw))
+	}
+	if raw[0].ID != 0 || raw[0].Name != "eDP-1" || raw[0].Width != 1920 {
+		t.Errorf("monitor 0 wrong: %+v", raw[0])
+	}
+	if raw[1].ID != 1 || raw[1].Focused {
+		t.Errorf("monitor 1 wrong: %+v", raw[1])
+	}
+}

internal/gui/gui.go

@@ -8,6 +8,7 @@ package gui
 
 import (
 	"errors"
+	"fmt"
 	"image/color"
 	"log"
 	"strconv"
@@ -22,6 +23,7 @@ import (
 	"fyne.io/systray"
 
 	"teleportfling/assets"
+	"teleportfling/internal/capture"
 	"teleportfling/internal/config"
 	"teleportfling/internal/flinger"
 )
@@ -63,6 +65,8 @@ type App struct {
 	audioChk    *widget.Check
 	announceChk *widget.Check
 	srcSel      *widget.Select
+	monSel      *widget.Select
+	monitors    []capture.Monitor
 	statsDone   chan struct{}
 }
 
@@ -133,6 +137,7 @@ func (g *App) buildUI() {
 	// Source.
 	g.srcSel = widget.NewSelect([]string{"screen", "pattern"}, func(string) {})
 	g.srcSel.SetSelected(g.cfg.Source)
+	g.setupMonitorPicker()
 
 	// Quality.
 	g.qualitySel = widget.NewSelect([]string{"50", "60", "70", "80", "90", "100"}, func(string) {})
@@ -167,6 +172,7 @@ func (g *App) buildUI() {
 			{Text: "Name", Widget: g.nameEnt},
 			{Text: "Port", Widget: g.portEnt},
 			{Text: "Source", Widget: g.srcSel},
+			{Text: "Monitor", Widget: g.monSel},
 			{Text: "Quality", Widget: g.qualitySel},
 			{Text: "Frame rate", Widget: g.fpsSel},
 			{Text: "", Widget: g.audioChk},
@@ -185,6 +191,56 @@ func (g *App) buildUI() {
 	g.win.Resize(fyne.NewSize(380, 0))
 }
 
+// setupMonitorPicker populates the monitor dropdown and ties its visibility
+// to the source selector. When monitor enumeration is unavailable (non-
+// Hyprland), it falls back to a raw index entry driven by the saved config.
+func (g *App) setupMonitorPicker() {
+	// Populate monitor names for the picker.
+	g.monitors, _ = capture.ListMonitors()
+	names := make([]string, 0, len(g.monitors))
+	for _, m := range g.monitors {
+		names = append(names, fmt.Sprintf("%s (%dx%d)", m.Name, m.Width, m.Height))
+	}
+
+	// If we could not enumerate, present the saved index as a single option.
+	if len(names) == 0 {
+		names = []string{fmt.Sprintf("Monitor %d", g.cfg.StreamIndex)}
+		g.monitors = []capture.Monitor{{Index: g.cfg.StreamIndex, Name: fmt.Sprintf("Monitor %d", g.cfg.StreamIndex)}}
+	}
+
+	g.monSel = widget.NewSelect(names, func(string) {})
+	if len(g.monitors) > 0 {
+		// Preselect the configured index if it's within range.
+		for i, m := range g.monitors {
+			if m.Index == g.cfg.StreamIndex {
+				g.monSel.SetSelectedIndex(i)
+				break
+			}
+		}
+	}
+
+	// Monitor picker only applies to the "screen" source.
+	g.srcSel.OnChanged = func(string) {
+		g.monSel.Disable()
+		if g.srcSel.Selected == "screen" {
+			g.monSel.Enable()
+		}
+	}
+	g.monSel.Disable()
+	if g.cfg.Source == "screen" {
+		g.monSel.Enable()
+	}
+}
+
+// selectedMonitorIndex returns the monitor index chosen in the picker, or the
+// saved config value when the picker is unavailable/disabled.
+func (g *App) selectedMonitorIndex() int {
+	if g.monSel != nil && g.monSel.SelectedIndex() >= 0 && g.monSel.SelectedIndex() < len(g.monitors) {
+		return g.monitors[g.monSel.SelectedIndex()].Index
+	}
+	return g.cfg.StreamIndex
+}
+
 // toggleStream starts or stops the engine based on current UI state.
 func (g *App) toggleStream() {
 	if g.lock {
@@ -211,7 +267,7 @@ func (g *App) start() {
 		FPS:         fps,
 		Source:      g.srcSel.Selected,
 		Audio:       g.audioChk.Checked,
-		StreamIndex: g.cfg.StreamIndex,
+		StreamIndex: g.selectedMonitorIndex(),
 		Announce:    &announce,
 	}
 	if g.configPath != "" {
@@ -258,7 +314,16 @@ func (g *App) watchStats() {
 				// Fyne UI calls must run on the main thread.
 				fyne.Do(func() {
 					g.statusLab.SetText(formatStatus(st))
-					g.setTrayState(true, "TeleportFling · "+frames+" frames, "+dropped+" dropped")
+					if st.Err != nil {
+						g.statusLab.Importance = widget.DangerImportance
+					} else {
+						g.statusLab.Importance = widget.SuccessImportance
+					}
+					tip := "TeleportFling · " + frames + " frames, " + dropped + " dropped"
+					if st.Err != nil {
+						tip += " · error"
+					}
+					g.setTrayState(true, tip)
 				})
 			case <-done:
 				return
@@ -273,6 +338,9 @@ func formatStatus(st flinger.Status) string {
 	if st.Dropped > 0 {
 		base += " · " + itoa(int(st.Dropped)) + " dropped"
 	}
+	if st.Err != nil {
+		base += "\nError: " + st.Err.Error()
+	}
 	return base
 }