feat(android): detect focused-window package via dumpsys window

internal/android/android.go

@@ -251,8 +251,26 @@ func ForegroundPackage(ctx context.Context) (string, error) {
 	return parseForegroundPackage(string(output)), nil
 }
 
+// FocusedWindowPackage returns the package owning the currently focused window,
+// or "" when no window is focused (e.g. mid-launch, before the app has drawn).
+// Unlike ForegroundPackage, this reflects what is actually on screen:
+// ResumedActivity flips to a newly launched app before its first frame renders,
+// while mCurrentFocus only names the app once its window is up.
+func FocusedWindowPackage(ctx context.Context) (string, error) {
+	adb, err := AdbBinary()
+	if err != nil {
+		return "", err
+	}
+	output, err := exec.CommandContext(ctx, adb, "shell", "dumpsys", "window").Output()
+	if err != nil {
+		return "", err
+	}
+	return parseFocusedWindowPackage(string(output)), nil
+}
+
 // resumedActivityPackage matches the "<package>/<activity>" component name that
-// dumpsys prints on ResumedActivity lines, capturing the package.
+// dumpsys prints on ResumedActivity and mCurrentFocus lines, capturing the
+// package.
 var resumedActivityPackage = regexp.MustCompile(`([a-zA-Z][a-zA-Z0-9_.]*)/[a-zA-Z0-9_.$]+`)
 
 // parseForegroundPackage extracts the foreground package from `dumpsys activity
@@ -269,6 +287,21 @@ func parseForegroundPackage(dumpsys string) string {
 	return ""
 }
 
+// parseFocusedWindowPackage extracts the focused-window package from
+// `dumpsys window` output by reading the mCurrentFocus component name. A
+// "mCurrentFocus=null" line (no focused window) yields "".
+func parseFocusedWindowPackage(dumpsys string) string {
+	for line := range strings.SplitSeq(dumpsys, "\n") {
+		if !strings.Contains(line, "mCurrentFocus") {
+			continue
+		}
+		if match := resumedActivityPackage.FindStringSubmatch(line); match != nil {
+			return match[1]
+		}
+	}
+	return ""
+}
+
 func bootCompleted(ctx context.Context) (bool, error) {
 	adb, err := AdbBinary()
 	if err != nil {

internal/android/android_test.go

@@ -127,3 +127,39 @@ func TestParseForegroundPackage(t *testing.T) {
 		})
 	}
 }
+
+func TestParseFocusedWindowPackage(t *testing.T) {
+	cases := []struct {
+		name    string
+		dumpsys string
+		want    string
+	}{
+		{
+			name:    "folio focused",
+			dumpsys: "  mCurrentFocus=Window{e00f63a u0 app.folio/app.folio.MainActivity}\n  mFocusedApp=ActivityRecord{c0 u0 app.folio/.MainActivity t202}",
+			want:    "app.folio",
+		},
+		{
+			name:    "settings focused",
+			dumpsys: "  mCurrentFocus=Window{709 u0 com.android.settings/com.android.settings.SubSettings}",
+			want:    "com.android.settings",
+		},
+		{
+			name:    "no focused window mid-launch",
+			dumpsys: "  mCurrentFocus=null\n  mFocusedApp=null",
+			want:    "",
+		},
+		{
+			name:    "no focus line",
+			dumpsys: "  some unrelated dumpsys window output\n",
+			want:    "",
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := parseFocusedWindowPackage(tc.dumpsys); got != tc.want {
+				t.Errorf("parseFocusedWindowPackage = %q, want %q", got, tc.want)
+			}
+		})
+	}
+}