imageView: Use custom slide widget and IndexSet

Use IndexSet to allow direct access by Path and also allow
an arbitrary ordering that was not possible with Vec. Also
add monitoring of file changes in the directory.

Use a custom LpSlidingView instead of AdwCarousel because
Carousel was never designed for this job and suffered of
bugs. LpSlidingView does not support swiping gestures yet
since they currently don't work yet anyways #24.

Use a new algorithm to fill the LpSlidingView that is
stateless and covers all potential changes in the directory.
This not only fixes bugs but would also work with changed
sorting orders.

This also adds build time template XML validation since it
was useful for the refactoring #46.

Closes #9, #11, #30, #33, #42

src/widgets/image_page.rs

@@ -18,24 +18,23 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 use crate::deps::*;
+use crate::widgets::LpImage;
 
 use adw::subclass::prelude::*;
 use glib::clone;
 use gtk::prelude::*;
 use gtk::CompositeTemplate;
-
 use gtk_macros::spawn;
+use once_cell::sync::Lazy;
 
-use once_cell::sync::{Lazy, OnceCell};
 use std::cell::RefCell;
-
-use crate::widgets::LpImage;
+use std::path::{Path, PathBuf};
 
 mod imp {
     use super::*;
 
     #[derive(Debug, Default, CompositeTemplate)]
-    #[template(resource = "/org/gnome/Loupe/gtk/image_page.ui")]
+    #[template(file = "../../data/gtk/image_page.ui")]
     pub struct LpImagePage {
         #[template_child]
         pub(super) stack: TemplateChild<gtk::Stack>,
@@ -54,8 +53,6 @@ mod imp {
         #[template_child]
         pub(super) press_gesture: TemplateChild<gtk::GestureLongPress>,
 
-        pub(super) file: OnceCell<gio::File>,
-
         /// set if an error has occured and is shown on error_page
         pub(super) error: RefCell<Option<String>>,
     }
@@ -97,6 +94,7 @@ mod imp {
                 name => unimplemented!("property {name}"),
             }
         }
+
         fn constructed(&self) {
             let obj = self.instance();
 
@@ -128,17 +126,20 @@ glib::wrapper! {
 }
 
 impl LpImagePage {
-    pub fn from_file(file: &gio::File) -> Self {
+    pub fn from_path(path: &Path) -> Self {
         let obj = glib::Object::new::<Self>(&[]);
-        obj.imp().file.set(file.clone()).unwrap();
+        let path = path.to_path_buf();
+        let file = gio::File::for_path(&path);
+
+        obj.imp().image.set_file(&file);
 
         // This doesn't work properly for items not explicitly selected
         // via the file chooser portal. I'm not sure how to make this work.
         gtk::RecentManager::default().add_item(&file.uri());
 
-        spawn!(clone!(@weak obj, @weak file => async move {
+        spawn!(clone!(@weak obj, @strong path => async move {
             let imp = obj.imp();
-            match imp.image.load(&file).await {
+            match imp.image.load(&path).await {
                 Ok(()) => {
                     imp.stack.set_visible_child(&*imp.scrolled_window);
                     imp.spinner.set_spinning(false);
@@ -156,8 +157,8 @@ impl LpImagePage {
         obj
     }
 
-    pub fn file(&self) -> Option<gio::File> {
-        self.imp().file.get().cloned()
+    pub fn path(&self) -> PathBuf {
+        self.image().path().unwrap()
     }
 
     pub fn image(&self) -> LpImage {