screenshot: add window capture for Hyprland

core/cmd/dms/commands_screenshot.go

@@ -35,6 +35,7 @@ Modes:
   full        - Capture the focused output
   all         - Capture all outputs combined
   output      - Capture a specific output by name
+  window      - Capture the focused window (Hyprland only)
   last        - Capture the last selected region
 
 Output format (--format):
@@ -47,6 +48,7 @@ Examples:
   dms screenshot full                # Full screen of focused output
   dms screenshot all                 # All screens combined
   dms screenshot output -o DP-1      # Specific output
+  dms screenshot window              # Focused window (Hyprland)
   dms screenshot last                # Last region (pre-selected)
   dms screenshot --no-clipboard      # Save file only
   dms screenshot --no-file           # Clipboard only
@@ -86,6 +88,14 @@ If no previous region exists, falls back to interactive selection.`,
 	Run: runScreenshotLast,
 }
 
+var ssWindowCmd = &cobra.Command{
+	Use:   "window",
+	Short: "Capture the focused window",
+	Long: `Capture the currently focused window.
+Currently only supported on Hyprland.`,
+	Run: runScreenshotWindow,
+}
+
 var ssListCmd = &cobra.Command{
 	Use:   "list",
 	Short: "List available outputs",
@@ -117,6 +127,7 @@ func init() {
 	screenshotCmd.AddCommand(ssAllCmd)
 	screenshotCmd.AddCommand(ssOutputCmd)
 	screenshotCmd.AddCommand(ssLastCmd)
+	screenshotCmd.AddCommand(ssWindowCmd)
 	screenshotCmd.AddCommand(ssListCmd)
 
 	screenshotCmd.Run = runScreenshotRegion
@@ -347,6 +358,11 @@ func runScreenshotLast(cmd *cobra.Command, args []string) {
 	runScreenshot(config)
 }
 
+func runScreenshotWindow(cmd *cobra.Command, args []string) {
+	config := getScreenshotConfig(screenshot.ModeWindow)
+	runScreenshot(config)
+}
+
 func runScreenshotList(cmd *cobra.Command, args []string) {
 	outputs, err := screenshot.ListOutputs()
 	if err != nil {

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
+}

core/internal/screenshot/screenshot.go

@@ -77,6 +77,8 @@ func (s *Screenshoter) Run() (*CaptureResult, error) {
 		return s.captureLastRegion()
 	case ModeRegion:
 		return s.captureRegion()
+	case ModeWindow:
+		return s.captureWindow()
 	case ModeOutput:
 		return s.captureOutput(s.config.OutputName)
 	case ModeFullScreen:
@@ -119,6 +121,27 @@ func (s *Screenshoter) captureRegion() (*CaptureResult, error) {
 	return result, nil
 }
 
+func (s *Screenshoter) captureWindow() (*CaptureResult, error) {
+	geom, err := GetActiveWindow()
+	if err != nil {
+		return nil, err
+	}
+
+	region := Region{
+		X:      geom.X,
+		Y:      geom.Y,
+		Width:  geom.Width,
+		Height: geom.Height,
+	}
+
+	output := s.findOutputForRegion(region)
+	if output == nil {
+		return nil, fmt.Errorf("could not find output for window")
+	}
+
+	return s.captureRegionOnOutput(output, region)
+}
+
 func (s *Screenshoter) captureFullScreen() (*CaptureResult, error) {
 	output := s.findFocusedOutput()
 	if output == nil {