pipeline: Able to render a graph and check for error

If the pipeline can not be created, display an error dialog
when checking it.

TODO.md

@@ -32,6 +32,10 @@
 - [x] add a css class for pad (presence always or sometimes)
 - [ ] Add property to port to store some specific value(Caps)
 
+### GStreamer:
+
+- [ ] Implement pipeline unit test
+
 ### app
 
 - [x] check that a node accept to create a port on request (input/output)
@@ -41,20 +45,19 @@
   - [x] unable to connect a port which is already connected
   - [ ] Create a window for the video output
 - [ ] Add multiple graphviews with tabs.
-- [ ] Property window in the main window
+- [x] Property window in the main window
 - [ ] Connect the GPS status to GST status
 - [ ] Implement graph dot render/load
 - [ ] Implement a command line parser to graph
-- [ ] Render the parse launch line in a message box
-- [ ] Prevent to create a pad in an element without the template
-- [ ] Check the pipeline validity
-- [ ] Implement pipeline unit test
+- [x] Render the parse launch line in a message box
+- [x] Prevent to create a pad in an element without the template
+- [x] Check the pipeline validity
 - [x] Save node position in XML
 - [x] Autosave the graph
 - [x] Logger in file/app all over the app
 - [ ] handle the caps setter element
 - [ ] Add probes on each pad to monitor the pipeline
-- [ ] Display pad properties with tooltip hover
+- [x] Display pad properties with tooltip hover
 - [ ] Render a media file
 - [ ] Offer compatible element to a pad (autorender)
 - [ ] Display tags/meta/message detected

src/app.rs

@@ -537,7 +537,11 @@ impl GPSApp {
                         move |_,_| {
                             let app = upgrade_weak!(app_weak);
                             let render_parse_launch = app.pipeline.borrow().render_gst_launch(&app.graphview.borrow());
-                            GPSUI::message::display_message_dialog(&render_parse_launch,gtk::MessageType::Info, |_| {});
+                            if app.pipeline.borrow().create_pipeline(&render_parse_launch).is_ok() {
+                                GPSUI::message::display_message_dialog(&render_parse_launch,gtk::MessageType::Info, |_| {});
+                            } else {
+                                GPSUI::message::display_error_dialog(false, &format!("Unable to render:\n\n{}", render_parse_launch));
+                            }
                         }
                     );
                     pop_menu.show();

src/gps/pipeline.rs

@@ -80,12 +80,34 @@ impl Pipeline {
         Ok(pipeline)
     }
 
-    pub fn create_pipeline(&self, description: &str) -> anyhow::Result<()> {
+    pub fn create_pipeline(&self, description: &str) -> anyhow::Result<gstreamer::Pipeline> {
         GPS_INFO!("Creating pipeline {}", description);
 
         // Create pipeline from the description
         let pipeline = gst::parse_launch(&description.to_string())?;
-        if let Ok(pipeline) = pipeline.downcast::<gst::Pipeline>() {
+        let pipeline = pipeline.downcast::<gst::Pipeline>();
+        /* start playing */
+        if pipeline.is_err() {
+            GPS_ERROR!("Can not create a proper pipeline from gstreamer parse_launch");
+            return Err(anyhow::anyhow!(
+                "Unable to create a pipeline from the given parse launch {"
+            ));
+        }
+        Ok(pipeline.unwrap())
+    }
+
+    pub fn start_pipeline(
+        &self,
+        graphview: &GraphView,
+        new_state: PipelineState,
+    ) -> anyhow::Result<PipelineState> {
+        if self.state() == PipelineState::Stopped {
+            let pipeline = self
+                .create_pipeline(&self.render_gst_launch(graphview))
+                .map_err(|err| {
+                    GPS_ERROR!("Unable to start a pipeline: {}", err);
+                    err
+                })?;
             let bus = pipeline.bus().expect("Pipeline had no bus");
             let pipeline_weak = self.downgrade();
             bus.add_watch_local(move |_bus, msg| {
@@ -95,24 +117,6 @@ impl Pipeline {
             })?;
 
             *self.pipeline.borrow_mut() = Some(pipeline);
-            /* start playing */
-        } else {
-            GPS_ERROR!("Can not create a proper pipeline from gstreamer parse_launch");
-        }
-        Ok(())
-    }
-
-    pub fn start_pipeline(
-        &self,
-        graphview: &GraphView,
-        new_state: PipelineState,
-    ) -> anyhow::Result<PipelineState> {
-        if self.state() == PipelineState::Stopped {
-            self.create_pipeline(&self.render_gst_launch(graphview))
-                .map_err(|err| {
-                    GPS_ERROR!("Unable to start a pipeline: {}", err);
-                    err
-                })?;
         }
 
         self.set_state(new_state).map_err(|error| {

src/ui/message.rs

@@ -63,9 +63,13 @@ pub fn display_message_dialog<F: Fn(Application) + 'static>(
 
 #[allow(dead_code)]
 pub fn display_error_dialog(fatal: bool, message: &str) {
-    display_message_dialog(message, gtk::MessageType::Error, move |app| {
-        if fatal {
-            app.quit();
-        }
-    });
+    display_message_dialog(
+        &format!("Error: {}", message),
+        gtk::MessageType::Error,
+        move |app| {
+            if fatal {
+                app.quit();
+            }
+        },
+    );
 }