feat: add system theme on Qt 6.5 and up (#5118)

* feat: add system theme on Qt 6.5

* chroe: add changelog entry

* refactor: add separate settings

* fix: qt 5

* Update changelog entry

---------

Co-authored-by: Rasmus Karlsson <rasmus.karlsson@pajlada.com>

CHANGELOG.md

@@ -26,6 +26,7 @@
 - Minor: Normalized the input padding between light & dark themes. (#5095)
 - Minor: Add `--activate <channel>` (or `-a`) command line option to activate or add a Twitch channel. (#5111)
 - Minor: Chatters from recent-messages are now added to autocompletion. (#5116)
+- Minor: Added a _System_ theme that updates according to the system's color scheme (requires Qt 6.5). (#5118)
 - Minor: Added support for the `{input.text}` placeholder in the **Split** -> **Run a command** hotkey. (#5130)
 - Bugfix: Fixed an issue where certain emojis did not send to Twitch chat correctly. (#4840)
 - Bugfix: Fixed capitalized channel names in log inclusion list not being logged. (#4848)

src/singletons/Theme.cpp

@@ -6,6 +6,7 @@
 #include "common/QLogging.hpp"
 #include "singletons/Paths.hpp"
 #include "singletons/Resources.hpp"
+#include "singletons/WindowManager.hpp"
 
 #include <QColor>
 #include <QDir>
@@ -13,6 +14,9 @@
 #include <QFile>
 #include <QJsonDocument>
 #include <QSet>
+#if QT_VERSION >= QT_VERSION_CHECK(6, 5, 0)
+#    include <QStyleHints>
+#endif
 
 #include <cmath>
 
@@ -219,6 +223,11 @@ bool Theme::isLightTheme() const
     return this->isLight_;
 }
 
+bool Theme::isSystemTheme() const
+{
+    return this->themeName == u"System"_s;
+}
+
 void Theme::initialize(Settings &settings, const Paths &paths)
 {
     this->themeName.connect(
@@ -227,15 +236,51 @@ void Theme::initialize(Settings &settings, const Paths &paths)
             this->update();
         },
         false);
+    auto updateIfSystem = [this](const auto &) {
+        if (this->isSystemTheme())
+        {
+            this->update();
+        }
+    };
+    this->darkSystemThemeName.connect(updateIfSystem, false);
+    this->lightSystemThemeName.connect(updateIfSystem, false);
 
     this->loadAvailableThemes(paths);
 
+#if QT_VERSION >= QT_VERSION_CHECK(6, 5, 0)
+    QObject::connect(qApp->styleHints(), &QStyleHints::colorSchemeChanged,
+                     &this->lifetime_, [this] {
+                         if (this->isSystemTheme())
+                         {
+                             this->update();
+                             getIApp()->getWindows()->forceLayoutChannelViews();
+                         }
+                     });
+#endif
+
     this->update();
 }
 
 void Theme::update()
 {
-    auto oTheme = this->findThemeByKey(this->themeName);
+    auto currentTheme = [&]() -> QString {
+#if QT_VERSION >= QT_VERSION_CHECK(6, 5, 0)
+        if (this->isSystemTheme())
+        {
+            switch (qApp->styleHints()->colorScheme())
+            {
+                case Qt::ColorScheme::Light:
+                    return this->lightSystemThemeName;
+                case Qt::ColorScheme::Unknown:
+                case Qt::ColorScheme::Dark:
+                    return this->darkSystemThemeName;
+            }
+        }
+#endif
+        return this->themeName;
+    };
+
+    auto oTheme = this->findThemeByKey(currentTheme());
 
     constexpr const double nsToMs = 1.0 / 1000000.0;
     QElapsedTimer timer;

src/singletons/Theme.hpp

@@ -46,6 +46,7 @@ public:
     void initialize(Settings &settings, const Paths &paths) final;
 
     bool isLightTheme() const;
+    bool isSystemTheme() const;
 
     struct TabColors {
         QColor text;
@@ -153,6 +154,9 @@ public:
     pajlada::Signals::NoArgSignal updated;
 
     QStringSetting themeName{"/appearance/theme/name", "Dark"};
+    QStringSetting lightSystemThemeName{"/appearance/theme/lightSystem",
+                                        "Light"};
+    QStringSetting darkSystemThemeName{"/appearance/theme/darkSystem", "Dark"};
 
 private:
     bool isLight_ = false;
@@ -164,6 +168,8 @@ private:
     // This will only be populated when auto-reloading themes
     QJsonObject currentThemeJson_;
 
+    QObject lifetime_;
+
     /**
      * Figure out which themes are available in the Themes directory
      *

src/widgets/settingspages/GeneralPage.cpp

@@ -122,16 +122,49 @@ void GeneralPage::initLayout(GeneralPageView &layout)
 
     layout.addTitle("Interface");
 
-    layout.addDropdown<QString>(
-        "Theme", getIApp()->getThemes()->availableThemes(),
-        getIApp()->getThemes()->themeName,
-        [](const auto *combo, const auto &themeKey) {
-            return combo->findData(themeKey, Qt::UserRole);
-        },
-        [](const auto &args) {
-            return args.combobox->itemData(args.index, Qt::UserRole).toString();
-        },
-        {}, Theme::fallbackTheme.name);
+    {
+        auto *themes = getIApp()->getThemes();
+        auto available = themes->availableThemes();
+#if QT_VERSION >= QT_VERSION_CHECK(6, 5, 0)
+        available.emplace_back("System", "System");
+#endif
+
+        auto addThemeDropdown = [&](auto name, auto &setting,
+                                    const auto &options,
+                                    const QString &tooltip = {}) {
+            return layout.addDropdown<QString>(
+                name, options, setting,
+                [](const auto *combo, const auto &themeKey) {
+                    return combo->findData(themeKey, Qt::UserRole);
+                },
+                [](const auto &args) {
+                    return args.combobox->itemData(args.index, Qt::UserRole)
+                        .toString();
+                },
+                tooltip, Theme::fallbackTheme.name);
+        };
+
+        addThemeDropdown("Theme", themes->themeName, available);
+
+#if QT_VERSION >= QT_VERSION_CHECK(6, 5, 0)
+        auto *darkDropdown = addThemeDropdown(
+            "Dark system theme", themes->darkSystemThemeName,
+            themes->availableThemes(),
+            "This theme is selected if your system is in a dark theme and you "
+            "enabled the adaptive 'System' theme.");
+        auto *lightDropdown = addThemeDropdown(
+            "Light system theme", themes->lightSystemThemeName,
+            themes->availableThemes(),
+            "This theme is selected if your system is in a light theme and you "
+            "enabled the adaptive 'System' theme.");
+
+        auto isSystem = [](const auto &s) {
+            return s == "System";
+        };
+        layout.enableIf(darkDropdown, themes->themeName, isSystem);
+        layout.enableIf(lightDropdown, themes->themeName, isSystem);
+#endif
+    }
 
     layout.addDropdown<QString>(
         "Font", {"Segoe UI", "Arial", "Choose..."},

src/widgets/settingspages/GeneralPageView.hpp

@@ -306,6 +306,15 @@ public:
         return combo;
     }
 
+    void enableIf(QComboBox *widget, auto &setting, auto cb)
+    {
+        auto updateVisibility = [cb = std::move(cb), &setting, widget]() {
+            auto enabled = cb(setting.getValue());
+            widget->setEnabled(enabled);
+        };
+        setting.connect(updateVisibility, this->managedConnections_);
+    }
+
     DescriptionLabel *addDescription(const QString &text);
 
     void addSeperator();