Continue the implementation of trigger rules (ex scene rules)

pkg/windowmanagerhandler/window_manager_handler_linux_xserver.go

@@ -0,0 +1,80 @@
+//go:build linux
+// +build linux
+
+package windowmanagerhandler
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/BurntSushi/xgb/xproto"
+	"github.com/BurntSushi/xgbutil"
+	"github.com/BurntSushi/xgbutil/ewmh"
+	"github.com/facebookincubator/go-belt/tool/logger"
+	"github.com/xaionaro-go/streamctl/pkg/observability"
+)
+
+type XWindowManagerHandler struct {
+	*xgbutil.XUtil
+}
+
+func (wmh *WindowManagerHandler) initUsingXServer() error {
+	x, err := xgbutil.NewConn()
+	if err != nil {
+		return fmt.Errorf("unable to connect to X-server using DISPLAY '%s': %w", os.Getenv("DISPLAY"), err)
+	}
+	wmh.XWMOrWaylandWM = &XWindowManagerHandler{
+		XUtil: x,
+	}
+	return nil
+}
+
+func (wmh *XWindowManagerHandler) WindowFocusChangeChan(ctx context.Context) <-chan WindowFocusChange {
+	logger.Debugf(ctx, "WindowFocusChangeChan")
+	ch := make(chan WindowFocusChange)
+
+	observability.Go(ctx, func() {
+		defer logger.Debugf(ctx, "/WindowFocusChangeChan")
+		defer func() {
+			close(ch)
+		}()
+
+		prevClientID := xproto.Window(0)
+		t := time.NewTicker(200 * time.Millisecond)
+		defer t.Stop()
+
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-t.C:
+			}
+
+			clientID, err := ewmh.ActiveWindowGet(wmh.XUtil)
+			if err != nil {
+				logger.Errorf(ctx, "unable to get active window: %w", err)
+				continue
+			}
+
+			if clientID == prevClientID {
+				continue
+			}
+			prevClientID = clientID
+
+			name, err := ewmh.WmNameGet(wmh.XUtil, clientID)
+			if err != nil {
+				logger.Errorf(ctx, "unable to get the name of the active window (%d): %w", clientID, err)
+				continue
+			}
+
+			ch <- WindowFocusChange{
+				WindowID:    WindowID(clientID),
+				WindowTitle: name,
+			}
+		}
+	})
+
+	return ch
+}