screenshot: add window capture for Hyprland

core/internal/screenshot/compositor.go

@@ -0,0 +1,69 @@
+package screenshot
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/exec"
+)
+
+type Compositor int
+
+const (
+	CompositorUnknown Compositor = iota
+	CompositorHyprland
+)
+
+func DetectCompositor() Compositor {
+	if os.Getenv("HYPRLAND_INSTANCE_SIGNATURE") != "" {
+		return CompositorHyprland
+	}
+	return CompositorUnknown
+}
+
+type WindowGeometry struct {
+	X      int32
+	Y      int32
+	Width  int32
+	Height int32
+}
+
+func GetActiveWindow() (*WindowGeometry, error) {
+	compositor := DetectCompositor()
+
+	switch compositor {
+	case CompositorHyprland:
+		return getHyprlandActiveWindow()
+	default:
+		return nil, fmt.Errorf("window capture requires Hyprland (other compositors not yet supported)")
+	}
+}
+
+type hyprlandWindow struct {
+	At   [2]int32 `json:"at"`
+	Size [2]int32 `json:"size"`
+}
+
+func getHyprlandActiveWindow() (*WindowGeometry, error) {
+	cmd := exec.Command("hyprctl", "-j", "activewindow")
+	output, err := cmd.Output()
+	if err != nil {
+		return nil, fmt.Errorf("hyprctl activewindow: %w", err)
+	}
+
+	var win hyprlandWindow
+	if err := json.Unmarshal(output, &win); err != nil {
+		return nil, fmt.Errorf("parse activewindow: %w", err)
+	}
+
+	if win.Size[0] <= 0 || win.Size[1] <= 0 {
+		return nil, fmt.Errorf("no active window")
+	}
+
+	return &WindowGeometry{
+		X:      win.At[0],
+		Y:      win.At[1],
+		Width:  win.Size[0],
+		Height: win.Size[1],
+	}, nil
+}