viewer: migrate to vue 3, general refactoring and cleanup

Non-exhaustive list of fixes and improvements done at the same time:

- html default background to grey (avoids white flash during init)
- unified links behavior
- added more theme variables
- removed the flex-expand transition (it wasn't working) and replaced it
  with a slide
- fixed LdLoading not centered on the content
- title on removable tags
- fixed an issue with encoded URI from vue-router
- unified Item resource URLs
- removed the iframe for PlainTextViewer (it wasn't working properly)
  and replaced it with a pre
- fixed clear and search buttons tabindex
- fixed the information panel bumping up during the fade animation of
  tag's dropdown
- fixed some focus outlines not appearing correctly
- moved CSS variables to the :root context
- Code cleaning

GitHub: closes #217
GitHub: closes #300
GitHub: closes #297
GitHub: closes #105
GitHub: closes #267
GitHub: closes #275
GitHub: closes #228
GitHub: closes #215
GitHub: closes #112

1 files changed, 37 insertions, 0 deletions

diff --git a/viewer/src/services/ui/ldSaveScroll.ts b/viewer/src/services/ui/ldSaveScroll.ts
new file mode 100644
index 0000000..34e277b
--- /dev/null
+++ b/viewer/src/services/ui/ldSaveScroll.ts
@@ -0,0 +1,37 @@
+/* ldgallery - A static generator which turns a collection of tagged
+--             pictures into a searchable web gallery.
+--
+-- Copyright (C) 2019-2022  Guillaume FOUET
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero General Public License as
+-- published by the Free Software Foundation, either version 3 of the
+-- License, or (at your option) any later version.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU Affero General Public License for more details.
+--
+-- You should have received a copy of the GNU Affero General Public License
+-- along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+import { MaybeElementRef, unrefElement } from '@vueuse/core';
+import { nextTick, watch } from 'vue';
+import { useRoute } from 'vue-router';
+
+type ScrollPosition = Record<string, number>;
+
+export const useLdSaveScroll = (element: MaybeElementRef) => {
+  const scrollPositions: ScrollPosition = {};
+  const route = useRoute();
+
+  watch(() => decodeURIComponent(route.path), (newRoute, oldRoute) => {
+    const el = unrefElement(element);
+    if (!el) return;
+
+    scrollPositions[oldRoute] = el.scrollTop / el.scrollHeight;
+    nextTick(() => (el.scrollTop = scrollPositions[newRoute] * el.scrollHeight));
+  });
+};