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

build-aux/flatpak/libadwaita-issue-597.patch

@@ -1,59 +0,0 @@
-From b2c52f258757e37a74a95c109431f6af8cda8f91 Mon Sep 17 00:00:00 2001
-From: Sophie Herold <sophie@hemio.de>
-Date: Wed, 7 Dec 2022 17:42:06 +0100
-Subject: [PATCH] carousel: give new child a snap_point immediately
-
-Fixes #457, #597
----
- src/adw-carousel.c | 21 ++++++++++++++++++++-
- 1 file changed, 20 insertions(+), 1 deletion(-)
-
-diff --git a/src/adw-carousel.c b/src/adw-carousel.c
-index 47ea9475..5a9816f9 100644
---- a/src/adw-carousel.c
-+++ b/src/adw-carousel.c
-@@ -1207,6 +1207,8 @@ adw_carousel_insert (AdwCarousel *self,
- {
-   ChildInfo *info;
-   GList *next_link = NULL;
-+  double snap_point = 0;
-+  GList *children;
- 
-   g_return_if_fail (ADW_IS_CAROUSEL (self));
-   g_return_if_fail (GTK_IS_WIDGET (widget));
-@@ -1214,7 +1216,8 @@ adw_carousel_insert (AdwCarousel *self,
- 
-   info = g_new0 (ChildInfo, 1);
-   info->widget = widget;
--  info->size = 0;
-+  // set a minimal size to give child it's own snap_point from the beginning
-+  info->size = 0.00001;
-   info->adding = TRUE;
- 
-   if (position >= 0)
-@@ -1230,6 +1233,22 @@ adw_carousel_insert (AdwCarousel *self,
-     gtk_widget_set_parent (widget, GTK_WIDGET (self));
-   }
- 
-+  // work around this usually happening in measure which can be too late
-+  for (children = self->children; children; children = children->next) {
-+    ChildInfo *child_info = children->data;
-+
-+    child_info->snap_point = snap_point + child_info->size - 1;
-+
-+    snap_point += child_info->size;
-+
-+    if (child_info == self->animation_target_child)
-+      adw_spring_animation_set_value_to (ADW_SPRING_ANIMATION (self->animation),
-+                                         child_info->snap_point);
-+  }
-+
-+  // start animation from correct size
-+  info->size = 0;
-+
-   gtk_widget_queue_allocate (GTK_WIDGET (self));
- 
-   animate_child_resize (self, info, 1, self->reveal_duration);
--- 
-GitLab
-

build-aux/flatpak/org.gnome.Loupe.Devel.json

@@ -91,22 +91,6 @@
                 }
             ]
         },
-        /* Use patched libadwaita version to test the fix */
-        {
-            "name": "libadwaita",
-            "buildsystem": "meson",
-            "sources": [
-                {
-                    "type": "git",
-                    "url": "https://gitlab.gnome.org/GNOME/libadwaita.git",
-                    "branch": "main"
-                },
-                {
-                    "type": "patch",
-                    "path": "libadwaita-issue-597.patch"
-                }
-            ]
-        },
         {
             "name" : "loupe",
             "builddir" : true,