Add example doing queries

examples/src/bin/queries.rs

@@ -0,0 +1,82 @@
+extern crate gstreamer as gst;
+use gst::*;
+
+extern crate glib;
+use glib::*;
+
+use std::env;
+
+fn main() {
+    let pipeline_str = env::args().collect::<Vec<String>>()[1..].join(" ");
+
+    gst::init().unwrap();
+
+    let main_loop = MainLoop::new(None, false);
+
+    let pipeline = gst::parse_launch(&pipeline_str).unwrap();
+    let bus = pipeline.get_bus().unwrap();
+
+    let ret = pipeline.set_state(gst::State::Playing);
+    assert_ne!(ret, gst::StateChangeReturn::Failure);
+
+    let main_loop_clone = main_loop.clone();
+
+    let pipeline_clone = pipeline.clone();
+    glib::timeout_add_seconds(1, move || {
+        let pipeline = &pipeline_clone;
+
+        //let pos = pipeline.query_position(Format::Time).unwrap_or(-1);
+        //let dur = pipeline.query_duration(Format::Time).unwrap_or(-1);
+        let pos = {
+            let mut q = Query::new_position(Format::Time);
+            pipeline.query(q.get_mut().unwrap());
+            match q.view() {
+                QueryView::Position(ref p) => {
+                    p.get().1
+                },
+                _ => unreachable!(),
+            }
+        };
+
+        let dur = {
+            let mut q = Query::new_duration(Format::Time);
+            pipeline.query(q.get_mut().unwrap());
+            match q.view() {
+                QueryView::Duration(ref p) => {
+                    p.get().1
+                },
+                _ => unreachable!(),
+            }
+        };
+
+        println!("{} / {}", pos, dur);
+
+        glib::Continue(true)
+    });
+
+    //bus.add_signal_watch();
+    //bus.connect_message(move |_, msg| {
+    bus.add_watch(move |_, msg| {
+        let main_loop = &main_loop_clone;
+        match msg.view() {
+            MessageView::Eos => main_loop.quit(),
+            MessageView::Error(err) => {
+                println!(
+                    "Error from {}: {} ({:?})",
+                    msg.get_src().get_path_string(),
+                    err.get_error(),
+                    err.get_debug()
+                );
+                main_loop.quit();
+            }
+            _ => (),
+        };
+
+        glib::Continue(true)
+    });
+
+    main_loop.run();
+
+    let ret = pipeline.set_state(gst::State::Null);
+    assert_ne!(ret, gst::StateChangeReturn::Failure);
+}