wallpaper: one monitor to preview, a line per transition

Selecting was unclear with a tile doing both jobs. A mock monitor now
plays whatever line is clicked, and a click changes nothing else; the
choice is an Active mark per line, and Random's pool a Switch beside it.
Each line shows a frame caught halfway through its transition.

MockScreen takes children, drawn on its panel.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/desktop/modules/appearance/TransitionView.qml b/desktop/modules/appearance/TransitionView.qml
new file mode 100644
index 0000000..44511a8
--- /dev/null
+++ b/desktop/modules/appearance/TransitionView.qml
@@ -0,0 +1,51 @@
+// Copyright (C) 2026 Danilo M. <danix@danix.xyz>
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License version 2 as
+// published by the Free Software Foundation.
+//
+// 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 General Public License for more details.
+
+import QtQuick
+import "../.."
+
+// The two current wallpapers with a transition at `progress`, laid out as the
+// cover lays them out in WallpaperSpread.qml, for the transitions page. Draws
+// nothing while either wallpaper is unknown.
+Item {
+    id: view
+    property string name: "burn"
+    property real progress: 0
+    property point origin: Qt.point(0.5, 0.5)
+    readonly property bool shows: Wallpapers.currentH !== "" && Wallpapers.currentV !== ""
+
+    Image {
+        id: newImg
+        visible: view.shows
+        anchors.fill: parent
+        source: view.shows ? "file://" + Wallpapers.currentV : ""
+        fillMode: Image.PreserveAspectCrop
+        sourceSize: Qt.size(view.width, view.height)
+        asynchronous: true
+        layer.enabled: view.shows
+    }
+    Image {
+        visible: view.shows
+        anchors.fill: parent
+        source: view.shows ? "file://" + Wallpapers.currentH : ""
+        fillMode: Image.PreserveAspectCrop
+        sourceSize: Qt.size(view.width, view.height)
+        asynchronous: true
+        layer.enabled: view.shows
+        layer.effect: WallShader {
+            name: view.name
+            target: newImg
+            progress: view.progress
+            aspect: view.width / Math.max(1, view.height)
+            origin: view.origin
+        }
+    }
+}