optimization: don't create page if it won't be navigated to

ui/browsing/browsingpane.go

@@ -209,7 +209,10 @@ func (b *BrowsingPane) Reload() {
 	}
 }
 
-func (b *BrowsingPane) CurPage() controller.Route {
+func (b *BrowsingPane) CurrentPage() controller.Route {
+	if b.curPage == nil {
+		return controller.Route{Page: controller.Blank}
+	}
 	return b.curPage.Route()
 }
 

ui/browsing/router.go

@@ -7,6 +7,7 @@ import (
 
 type NavigationHandler interface {
 	SetPage(Page)
+	CurrentPage() controller.Route
 }
 
 type Router struct {
@@ -53,5 +54,7 @@ func (r Router) CreatePage(rte controller.Route) Page {
 }
 
 func (r Router) NavigateTo(rte controller.Route) {
-	r.Nav.SetPage(r.CreatePage(rte))
+	if rte != r.Nav.CurrentPage() {
+		r.Nav.SetPage(r.CreatePage(rte))
+	}
 }

ui/mainwindow.go

@@ -65,7 +65,7 @@ func NewMainWindow(fyneApp fyne.App, appName, appVersion string, app *backend.Ap
 	// inject controller dependencies
 	m.Controller.NavHandler = m.Router.NavigateTo
 	m.Controller.ReloadFunc = m.BrowsingPane.Reload
-	m.Controller.CurPageFunc = m.BrowsingPane.CurPage
+	m.Controller.CurPageFunc = m.BrowsingPane.CurrentPage
 
 	m.BottomPanel = NewBottomPanel(app.Player, m.Controller)
 	m.BottomPanel.SetPlaybackManager(app.PlaybackManager)