OmaPhoto 1.0.0: the Linux port of Compositor

A layered image editor for Linux and Omarchy, ported from Compositor
(github.com/robbietilton/Compositor), whose Swift source is its
specification. It reads and writes Compositor's .comp projects.

Packages for Ubuntu, Fedora and Arch come from the release workflow;
scripts/install/ holds one install script per distribution family,
and flake.nix serves NixOS.

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

src/UI/EffectsSheet.h

@@ -0,0 +1,45 @@
+#pragma once
+#include "Document/EditorSession.h"
+#include <QWidget>
+#include <functional>
+#include <vector>
+
+class PickerField;
+class QButtonGroup;
+class QSlider;
+class QVBoxLayout;
+
+// Swift's EffectsSheet: one effect's controls, bound to its panel's layer.
+class EffectsSheet : public QWidget {
+    Q_OBJECT
+public:
+    EffectsSheet(EditorSession &session, LayerEffectKind kind, QWidget *parent = nullptr);
+
+private:
+    // Swift's slider: a title, a slider, a whole-number field.
+    struct Slider {
+        std::function<std::optional<double>(const LayerEffects &)> value;
+        std::function<void(LayerEffects &, double)> change;
+        double low;
+        double high;
+        QSlider *slider;
+        PickerField *field;
+    };
+    void header(const QString &title, bool position);
+    void colour(bool labelled);
+    void slider(const QString &title, std::function<std::optional<double>(const LayerEffects &)> value,
+                std::function<void(LayerEffects &, double)> change, double low, double high, const QString &unit);
+    // A value clamped to the slider's range, as Swift's binding.
+    void apply(const Slider &control, double value);
+    void synchronize();
+
+    EditorSession &m_session;
+    const LayerEffectKind m_kind;
+    QVBoxLayout *const m_column;
+    // What shows only while the effect is on its layer.
+    std::vector<QWidget *> m_controls;
+    std::vector<Slider> m_sliders;
+    QButtonGroup *m_position = nullptr;
+    // The picker's colour as last seen, Swift's onChange.
+    std::optional<PaletteColor> m_pickerColour;
+};