feat: add window decoration that integrates with tiling

CMakeLists.txt

@@ -56,8 +56,20 @@ set(CMAKE_CXX_EXTENSIONS OFF)
 find_package(Qt5 ${QT_MIN_VERSION} CONFIG REQUIRED COMPONENTS DBus Quick Svg
                                                               Test)
 
-find_package(KF5 ${KF5_MIN_VERSION} REQUIRED
-             COMPONENTS I18n KCMUtils Declarative GlobalAccel Config)
+find_package(
+  KF5 ${KF5_MIN_VERSION} REQUIRED
+  COMPONENTS Config
+             ConfigWidgets
+             CoreAddons
+             Declarative
+             GlobalAccel
+             GuiAddons
+             IconThemes
+             KCMUtils
+             WindowSystem
+             I18n)
+
+find_package(KDecoration2 REQUIRED)
 
 include_directories("${PROJECT_SOURCE_DIR}/external")
 

src/CMakeLists.txt

@@ -1,7 +1,8 @@
-# SPDX-FileCopyrightText: 2021 Mikhail Zolotukhin <mail@gikari.com>
+# SPDX-FileCopyrightText: 2021-2022 Mikhail Zolotukhin <mail@gikari.com>
 # SPDX-License-Identifier: MIT
 
+add_subdirectory(config)
 add_subdirectory(core)
 add_subdirectory(kcm)
+add_subdirectory(kdecoration)
 add_subdirectory(kwinscript)
-add_subdirectory(config)

src/kdecoration/CMakeLists.txt

@@ -0,0 +1,18 @@
+# SPDX-FileCopyrightText: 2022 Mikhail Zolotukhin <mail@gikari.com>
+# SPDX-License-Identifier: MIT
+
+cmake_minimum_required(VERSION 3.16)
+
+project(bismuth-kdecoration)
+
+add_library(bismuth_kdecoration MODULE)
+
+target_sources(bismuth_kdecoration PRIVATE decoration.cpp decoration.hpp)
+
+target_link_libraries(
+  bismuth_kdecoration
+  PUBLIC Qt::Core
+  PRIVATE KDecoration2::KDecoration KF5::ConfigCore KF5::ConfigWidgets)
+
+install(TARGETS bismuth_kdecoration
+        DESTINATION ${KDE_INSTALL_PLUGINDIR}/org.kde.kdecoration2)

src/kdecoration/decoration.cpp

@@ -0,0 +1,123 @@
+// SPDX-FileCopyrightText: 2022 Mikhail Zolotukhin <mail@gikari.com>
+// SPDX-License-Identifier: MIT
+
+#include "decoration.hpp"
+
+#include <QPainter>
+
+#include <KConfigGroup>
+#include <KDecoration2/DecoratedClient>
+#include <KDecoration2/DecorationSettings>
+#include <KPluginFactory>
+#include <KSharedConfig>
+
+K_PLUGIN_FACTORY_WITH_JSON(BismuthDecorationFactory, "metadata.json", registerPlugin<Bismuth::Decoration>();)
+
+namespace Bismuth
+{
+Decoration::Decoration(QObject *parent, const QVariantList &args)
+    : KDecoration2::Decoration(parent, args)
+{
+}
+
+void Decoration::init()
+{
+    m_kdeglobalsWatcher = KConfigWatcher::create(KSharedConfig::openConfig("kdeglobals"));
+
+    setBorderSizes();
+    connectEvents();
+    updateColors();
+}
+
+void Decoration::paint(QPainter *painter, const QRect &repaintRegion)
+{
+    paintBorders(*painter);
+}
+
+void Decoration::paintBorders(QPainter &p)
+{
+    auto client = this->client().lock();
+    auto windowRect = rect();
+
+    p.save();
+    p.setPen(Qt::NoPen);
+
+    if (client->isActive()) {
+        p.setBrush(m_activeColor);
+    } else {
+        p.setBrush(m_inactiveColor);
+    }
+
+    p.drawRect(windowRect);
+    p.restore();
+}
+
+void Decoration::updateColors()
+{
+    auto colorsConfig = KSharedConfig::openConfig("kdeglobals");
+    auto group = colorsConfig->group("Colors:Window");
+    m_activeColor = group.readEntry("DecorationFocus", QColor(255, 0, 0));
+    m_inactiveColor = group.readEntry("BackgroundNormal", QColor(0, 0, 0));
+}
+
+void Decoration::setBorderSizes()
+{
+    const auto client = this->client().lock();
+
+    const int left = (settings()->borderSize() == KDecoration2::BorderSize::NoSides) ? 0 : borderSize();
+    const int top = borderSize();
+    const int right = (settings()->borderSize() == KDecoration2::BorderSize::NoSides) ? 0 : borderSize();
+    const int bottom = borderSize();
+
+    setBorders(QMargins(left, top, right, bottom));
+}
+
+void Decoration::connectEvents()
+{
+    auto clientPtr = this->client().lock().data();
+    auto settingsPtr = settings().data();
+
+    // No idea why regular connection does not work
+    connect(clientPtr, &KDecoration2::DecoratedClient::activeChanged, this, [&](bool value) {
+        this->update();
+    });
+    connect(settingsPtr, &KDecoration2::DecorationSettings::borderSizeChanged, this, &Decoration::setBorderSizes);
+
+    connect(m_kdeglobalsWatcher.data(), &KConfigWatcher::configChanged, [&](const KConfigGroup &group, const QByteArrayList &names) {
+        if (group.name() == QStringLiteral("General")) {
+            if (names.contains(QByteArrayLiteral("ColorScheme")) || names.contains(QByteArrayLiteral("AccentColor"))) {
+                updateColors();
+                this->update();
+            }
+        }
+    });
+}
+
+int Decoration::borderSize() const
+{
+    const int baseSize = settings()->smallSpacing();
+    switch (settings()->borderSize()) {
+    case KDecoration2::BorderSize::Oversized:
+        return baseSize * 10;
+    case KDecoration2::BorderSize::VeryHuge:
+        return baseSize * 6;
+    case KDecoration2::BorderSize::Huge:
+        return baseSize * 5;
+    case KDecoration2::BorderSize::VeryLarge:
+        return baseSize * 4;
+    case KDecoration2::BorderSize::NoSides:
+    case KDecoration2::BorderSize::Normal:
+        return baseSize * 2;
+    case KDecoration2::BorderSize::Large:
+        return baseSize * 3;
+    case KDecoration2::BorderSize::None:
+        return 0;
+    case KDecoration2::BorderSize::Tiny:
+    default:
+        return baseSize;
+    }
+}
+
+}
+
+#include "decoration.moc"

src/kdecoration/decoration.hpp

@@ -0,0 +1,49 @@
+// SPDX-FileCopyrightText: 2022 Mikhail Zolotukhin <mail@gikari.com>
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <QVariant>
+
+#include <KConfigWatcher>
+#include <KDecoration2/Decoration>
+
+namespace Bismuth
+{
+class Decoration : public KDecoration2::Decoration
+{
+    Q_OBJECT
+public:
+    explicit Decoration(QObject *parent = nullptr, const QVariantList &args = QVariantList());
+
+    /**
+     * Provides the rendering.
+     *
+     * The painter is set up to paint on an internal QPaintDevice. The painting is implicitly double buffered.
+     */
+    void paint(QPainter *painter, const QRect &repaintRegion) override;
+
+public Q_SLOTS:
+    /**
+     * This method gets invoked once the Decoration is created and completely setup.
+     *
+     * All initialization must be performed in this method instead of the constructor.
+     */
+    void init() override;
+
+private:
+    void paintBorders(QPainter &painter);
+
+    void updateColors();
+    void setBorderSizes();
+    void connectEvents();
+
+    int borderSize() const;
+
+    QColor m_activeColor;
+    QColor m_inactiveColor;
+
+    KConfigWatcher::Ptr m_kdeglobalsWatcher;
+};
+
+}

src/kdecoration/metadata.json

@@ -0,0 +1,13 @@
+{
+  "KPlugin": {
+    "Id": "org.kde.bismuth.decoration",
+    "Description": "Window decoration, that integrates with Bismuth Tiling Window extension for the Plasma Desktop",
+    "Name": "Bismuth",
+    "ServiceTypes": ["org.kde.kdecoration2"]
+  },
+  "org.kde.kdecoration2": {
+    "blur": false,
+    "kcmodule": false,
+    "recommendedBorderSize": "Normal"
+  }
+}