See-through keyboard background with optional blur

- Opacity slider for the panel behind the keys (10–100%); keys stay opaque
- Blur Behind: asks the compositor (KWin) to blur under the rounded panel
  via KF6 WindowSystem; skipped at full opacity
- Settings panel draws over the window background so changes show live,
  and scrolls when it doesn't fit

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

src/CMakeLists.txt

@@ -39,6 +39,7 @@ set(SLOPOSK_QML_FILES
     SettingsButton.qml
     SettingsPanel.qml
     ToggleRow.qml
+    SliderRow.qml
     Theme.qml
 )
 list(TRANSFORM SLOPOSK_QML_FILES PREPEND ${PROJECT_SOURCE_DIR}/qml/ OUTPUT_VARIABLE sloposk_qml_paths)
@@ -98,6 +99,7 @@ target_link_libraries(sloposk PRIVATE
     Qt6::DBus
     Qt6::WaylandClient
     LayerShellQt::Interface
+    KF6::WindowSystem
     PkgConfig::WAYLAND
 )
 

src/settings/Settings.cpp

@@ -11,6 +11,8 @@ constexpr auto HoldKeysKey = "typing/holdKeys";
 constexpr auto VisibleSectionsKey = "layout/visibleSections";
 constexpr auto FullKeyboardKey = "layout/fullKeyboard";
 constexpr auto AlwaysVisibleKey = "window/alwaysVisible";
+constexpr auto BackgroundOpacityKey = "appearance/backgroundOpacity";
+constexpr auto BlurBackgroundKey = "appearance/blurBackground";
 }
 
 Settings::Settings(QObject *parent)
@@ -26,6 +28,27 @@ Settings::Settings(QObject *parent)
         m_visibleSections = {MainSectionId};
     m_fullKeyboard = store.value(FullKeyboardKey, false).toBool();
     m_alwaysVisible = store.value(AlwaysVisibleKey, false).toBool();
+    m_backgroundOpacity = qBound(MinBackgroundOpacity, store.value(BackgroundOpacityKey, 1.0).toReal(), 1.0);
+    m_blurBackground = store.value(BlurBackgroundKey, true).toBool();
+}
+
+void Settings::setBackgroundOpacity(qreal opacity)
+{
+    opacity = qBound(MinBackgroundOpacity, opacity, 1.0);
+    if (qFuzzyCompare(opacity, m_backgroundOpacity))
+        return;
+    m_backgroundOpacity = opacity;
+    QSettings().setValue(BackgroundOpacityKey, opacity);
+    Q_EMIT appearanceChanged();
+}
+
+void Settings::setBlurBackground(bool blur)
+{
+    if (blur == m_blurBackground)
+        return;
+    m_blurBackground = blur;
+    QSettings().setValue(BlurBackgroundKey, blur);
+    Q_EMIT appearanceChanged();
 }
 
 void Settings::setAlwaysVisible(bool always)

src/settings/Settings.h

@@ -22,6 +22,10 @@ class Settings : public QObject
     Q_PROPERTY(bool fullKeyboard READ fullKeyboard WRITE setFullKeyboard NOTIFY fullKeyboardChanged)
     // Shown even without a focused text field, to type into any window.
     Q_PROPERTY(bool alwaysVisible READ alwaysVisible WRITE setAlwaysVisible NOTIFY alwaysVisibleChanged)
+    // Opacity of the panel behind the keys (MinBackgroundOpacity–1); keys stay opaque.
+    Q_PROPERTY(qreal backgroundOpacity READ backgroundOpacity WRITE setBackgroundOpacity NOTIFY appearanceChanged)
+    // Blurs what shows through a translucent background (needs compositor support, e.g. KWin).
+    Q_PROPERTY(bool blurBackground READ blurBackground WRITE setBlurBackground NOTIFY appearanceChanged)
 
 public:
     explicit Settings(QObject *parent = nullptr);
@@ -44,11 +48,18 @@ public:
     bool alwaysVisible() const { return m_alwaysVisible; }
     void setAlwaysVisible(bool always);
 
+    static constexpr qreal MinBackgroundOpacity = 0.1;
+    qreal backgroundOpacity() const { return m_backgroundOpacity; }
+    void setBackgroundOpacity(qreal opacity);
+    bool blurBackground() const { return m_blurBackground; }
+    void setBlurBackground(bool blur);
+
 Q_SIGNALS:
     void typingOptionsChanged();
     void visibleSectionsChanged();
     void fullKeyboardChanged();
     void alwaysVisibleChanged();
+    void appearanceChanged();
 
 private:
     void setTypingOptions(const TypingOptions &options);
@@ -57,4 +68,6 @@ private:
     QStringList m_visibleSections;
     bool m_fullKeyboard = false;
     bool m_alwaysVisible = false;
+    qreal m_backgroundOpacity = 1.0;
+    bool m_blurBackground = true;
 };

src/window/FloatingWindow.cpp

@@ -1,6 +1,8 @@
 #include "FloatingWindow.h"
 
+#include <KWindowEffects>
 #include <LayerShellQt/Window>
+#include <QPainterPath>
 #include <QGuiApplication>
 #include <QScreen>
 #include <QWindow>
@@ -81,6 +83,17 @@ void FloatingWindow::setInputRegion(const QRectF &region)
     m_window->setMask(QRegion(region.toAlignedRect()));
 }
 
+void FloatingWindow::setBlurRegion(const QRectF &region, qreal radius)
+{
+    if (region.isEmpty()) {
+        KWindowEffects::enableBlurBehind(m_window, false);
+        return;
+    }
+    QPainterPath path;
+    path.addRoundedRect(region, radius, radius);
+    KWindowEffects::enableBlurBehind(m_window, true, QRegion(path.toFillPolygon().toPolygon()));
+}
+
 void FloatingWindow::show()
 {
     m_window->setVisible(true);

src/window/FloatingWindow.h

@@ -28,6 +28,8 @@ public:
     Q_INVOKABLE void resizeBy(qreal dw, qreal dh);
     // Only this part of the window takes input; the rest passes through.
     Q_INVOKABLE void setInputRegion(const QRectF &region);
+    // Asks the compositor to blur behind this rounded rect; an empty rect turns blur off.
+    Q_INVOKABLE void setBlurRegion(const QRectF &region, qreal radius);
     Q_INVOKABLE void show();
     Q_INVOKABLE void hide();