fix screens

v3/pkg/application/screen_linux.go

@@ -3,12 +3,20 @@
 package application
 
 import (
-	"fmt"
 	"sync"
 )
 
 func (a *linuxApp) getPrimaryScreen() (*Screen, error) {
-	return nil, fmt.Errorf("not implemented")
+	var wg sync.WaitGroup
+	var screen *Screen
+	var err error
+	wg.Add(1)
+	InvokeSync(func() {
+		screen, err = getPrimaryScreen()
+		wg.Done()
+	})
+	wg.Wait()
+	return screen, err
 }
 
 func (a *linuxApp) getScreens() ([]*Screen, error) {