pluginlist: avoid mulitple init

Allow only one initialization of the plugin
list.

src/app.rs

@@ -24,6 +24,7 @@ use gtk::{
     AboutDialog, Application, ApplicationWindow, Builder, Button, FileChooserAction,
     FileChooserDialog, PopoverMenu, ResponseType, Statusbar, Viewport,
 };
+use once_cell::unsync::OnceCell;
 use std::cell::RefCell;
 use std::collections::HashMap;
 use std::rc::{Rc, Weak};
@@ -40,6 +41,7 @@ pub struct GPSAppInner {
     pub graphview: RefCell<GraphView>,
     pub builder: Builder,
     pub pipeline: RefCell<Pipeline>,
+    pub plugin_list_initialized: OnceCell<bool>,
 }
 
 // This represents our main application window.
@@ -82,6 +84,7 @@ impl GPSApp {
             graphview: RefCell::new(GraphView::new()),
             builder,
             pipeline: RefCell::new(pipeline),
+            plugin_list_initialized: OnceCell::new(),
         }));
         Ok(app)
     }

src/plugindialogs.rs

@@ -62,6 +62,7 @@ pub fn display_plugin_list(app: &GPSApp, elements: &[ElementInfo]) {
         .object("dialog-plugin-list")
         .expect("Couldn't get window");
 
+    if app.plugin_list_initialized.get().is_none() {
         dialog.set_title(Some("Plugin list"));
         dialog.set_default_size(640, 480);
 
@@ -118,6 +119,10 @@ pub fn display_plugin_list(app: &GPSApp, elements: &[ElementInfo]) {
                 }
             }),
         );
+        app.plugin_list_initialized
+            .set(true)
+            .expect("Should never happen");
+    }
 
     dialog.show();
 }