propertiesView: Show basic EXIF data

Use libgweather to determine the city for EXIF GPS coordinates.
Make ImageMetadata a GObject to use it's properties in UI.

src/image_metadata/obj.rs

@@ -0,0 +1,107 @@
+use gio::prelude::*;
+
+use super::{GPSLocation, ImageMetadata, Orientation};
+
+use glib::subclass::prelude::*;
+use gtk::glib;
+use once_cell::sync::Lazy;
+
+use std::cell::RefCell;
+
+glib::wrapper! {
+    pub struct LpImageMetadata(ObjectSubclass<imp::LpImageMetadata>);
+}
+
+impl LpImageMetadata {
+    pub fn load(file: &gio::File) -> Self {
+        let obj = glib::Object::new::<Self>(&[]);
+
+        let metadata = ImageMetadata::load(file);
+        obj.imp().metadata.replace(metadata);
+
+        obj
+    }
+
+    pub fn orientation(&self) -> Orientation {
+        self.imp().metadata.borrow().orientation()
+    }
+
+    pub fn gps_location(&self) -> Option<GPSLocation> {
+        self.imp().metadata.borrow().gps_location()
+    }
+}
+
+impl From<ImageMetadata> for LpImageMetadata {
+    fn from(metadata: ImageMetadata) -> Self {
+        let obj = glib::Object::new::<Self>(&[]);
+
+        obj.imp().metadata.replace(metadata);
+
+        obj
+    }
+}
+
+impl Default for LpImageMetadata {
+    fn default() -> Self {
+        glib::Object::new(&[])
+    }
+}
+
+mod imp {
+    use super::*;
+
+    #[derive(Default)]
+    pub struct LpImageMetadata {
+        pub(super) metadata: RefCell<ImageMetadata>,
+    }
+
+    #[glib::object_subclass]
+    impl ObjectSubclass for LpImageMetadata {
+        const NAME: &'static str = "LpImageMetadata";
+        type Type = super::LpImageMetadata;
+        type ParentType = glib::Object;
+    }
+
+    impl ObjectImpl for LpImageMetadata {
+        fn properties() -> &'static [glib::ParamSpec] {
+            static PROPERTIES: Lazy<Vec<glib::ParamSpec>> = Lazy::new(|| {
+                let mut vec = vec![glib::ParamSpecBoolean::builder("has-information").build()];
+
+                vec.append(
+                    &mut [
+                        "originally-created",
+                        "location",
+                        "f-number",
+                        "exposure-time",
+                        "iso",
+                        "focal-length",
+                        "camera-model",
+                    ]
+                    .iter()
+                    .map(|name| glib::ParamSpecString::builder(name).read_only().build())
+                    .collect(),
+                );
+
+                vec
+            });
+
+            PROPERTIES.as_ref()
+        }
+
+        fn property(&self, _id: usize, pspec: &glib::ParamSpec) -> glib::Value {
+            //let obj = self.instance();
+            let metadata = self.metadata.borrow();
+            match pspec.name() {
+                "has-information" => (!metadata.is_none()).to_value(),
+                "originally-created" => metadata.originally_created().to_value(),
+                "location" => metadata.gps_location().map(|x| x.display()).to_value(),
+                "f-number" => metadata.f_number().to_value(),
+                "exposure-time" => metadata.exposure_time().to_value(),
+                "iso" => metadata.iso().to_value(),
+                "focal-length" => metadata.focal_length().to_value(),
+                "camera-model" => metadata.camera_model().to_value(),
+                name => unimplemented!("property {name}"),
+            }
+        }
+    }
+}