app: support multiple preview in a Notebook

The preview is now a NoteBook and if multiple video
gtk4sink are available, a page is created for each of it.

src/app.rs

@@ -410,17 +410,30 @@ impl GPSApp {
         status_bar.push(status_bar.context_id("Description"), &state.to_string());
     }
 
-    pub fn set_app_preview(&self, paintable: &gdk::Paintable) {
+    pub fn set_app_preview(&self, paintable: &gdk::Paintable, n_sink: usize) {
         let picture = gtk::Picture::new();
         picture.set_paintable(Some(paintable));
-        let box_preview: gtk::Box = self
+        let notebook_preview: gtk::Notebook = self
             .builder
-            .object("box-preview")
+            .object("notebook-preview")
             .expect("Couldn't get box_preview");
-        while let Some(child) = box_preview.first_child() {
-            box_preview.remove(&child);
+        if n_sink == 0 {
+            loop {
+                let i = notebook_preview.n_pages();
+                if i == 0 {
+                    break;
+                }
+                notebook_preview.remove_page(Some(i - 1));
+            }
         }
+        let box_preview = gtk::Box::builder()
+            .orientation(gtk::Orientation::Vertical)
+            .halign(gtk::Align::Center)
+            .valign(gtk::Align::Center)
+            .build();
         box_preview.append(&picture);
+        let label = gtk::Label::new(Some(&format!("Preview{}", n_sink)));
+        notebook_preview.insert_page(&box_preview, Some(&label), None);
     }
 
     pub fn build_ui(&self, application: &Application) {

src/gps/element.rs

@@ -223,26 +223,28 @@ impl ElementInfo {
         None
     }
 
-    pub fn search_fo_element(bin: &gst::Bin, element_name: &str) -> Option<gst::Element> {
+    pub fn search_fo_element(bin: &gst::Bin, element_name: &str) -> Vec<gst::Element> {
         let mut iter = bin.iterate_elements();
-        let element = loop {
+        let mut elements: Vec<gst::Element> = Vec::new();
+        let elements = loop {
             match iter.next() {
                 Ok(Some(element)) => {
                     if element.is::<gst::Bin>() {
                         let bin = element.dynamic_cast::<gst::Bin>().unwrap();
-                        break ElementInfo::search_fo_element(&bin, element_name);
+                        let mut bin_elements = ElementInfo::search_fo_element(&bin, element_name);
+                        elements.append(&mut bin_elements);
                     } else {
                         GPS_INFO!("Found factory: {}", element.factory().unwrap().name());
                         if element.factory().unwrap().name() == element_name {
                             GPS_INFO!("Found {}", element_name);
-                            break Some(element);
+                            elements.push(element);
                         }
                     }
                 }
                 Err(gst::IteratorError::Resync) => iter.resync(),
-                _ => break None,
+                _ => break elements,
             }
         };
-        element
+        elements
     }
 }

src/gps/pipeline.rs

@@ -113,16 +113,18 @@ impl Pipeline {
 
     pub fn check_for_gtk4sink(&self, pipeline: &gst::Pipeline) {
         let bin = pipeline.clone().dynamic_cast::<gst::Bin>().unwrap();
-        let gtksink = ElementInfo::search_fo_element(&bin, "gtk4paintablesink");
-        if let Some(gtksink) = gtksink {
+        let gtksinks = ElementInfo::search_fo_element(&bin, "gtk4paintablesink");
+
+        for (first_sink, gtksink) in gtksinks.into_iter().enumerate() {
             let paintable = gtksink.property::<gdk::Paintable>("paintable");
             self.app
                 .borrow()
                 .as_ref()
                 .expect("App should be available")
-                .set_app_preview(&paintable);
+                .set_app_preview(&paintable, first_sink);
         }
     }
+
     pub fn start_pipeline(
         &self,
         graphview: &GraphView,

src/ui/gps.ui

@@ -295,6 +295,10 @@
                   </object>
                 </child>
                 <child>
+                 <object class="GtkNotebook" id="notebook-preview">
+                 <child>
+                 <object class="GtkNotebookPage">
+                  <property name="child">
                   <object class="GtkScrolledWindow">
                     <property name="hexpand">True</property>
                     <property name="vexpand">True</property>
@@ -309,6 +313,10 @@
                       </object>
                     </property>
                   </object>
+                  </property>
+                  </object>
+                  </child>
+                  </object>
                 </child>
               </object>
               </child>