[Fonts] Restore the startup font when a config has no InterfaceDefault

- Capture the untouched application font next to the default palette and use
  it in previewFonts' else branch, so a config without InterfaceDefault
  restores the startup font instead of leaving the last preview applied.
- Drop the unpolish/polish loop from previewFonts: QApplication::setFont
  already notifies every widget, and the loop ran on every editor auto-apply.

cockatrice/src/interface/theme_config.cpp

@@ -304,4 +304,150 @@ QPalette PaletteConfig::apply(QPalette base) const
     }
 
     return base;
-}
+}
+
+bool FontConfig::hasFonts() const
+{
+    return !fonts.isEmpty();
+}
+
+QString FontConfig::toToml() const
+{
+    QMetaEnum roleEnum = QMetaEnum::fromType<AppFont::Role>();
+
+    QString entries;
+
+    for (auto it = fonts.cbegin(); it != fonts.cend(); ++it) {
+        const char *roleName = roleEnum.valueToKey(it.key());
+
+        if (!roleName) {
+            continue;
+        }
+
+        QString family = it.value().family().trimmed();
+        int pointSize = it.value().pointSize();
+
+        if (family.isEmpty() || pointSize <= 0) {
+            continue;
+        }
+
+        entries += QString("%1 = \"%2, %3\"\n").arg(QString(roleName), -20).arg(family).arg(pointSize);
+    }
+
+    if (entries.isEmpty()) {
+        return {};
+    }
+
+    return "[Fonts]\n" + entries + "\n";
+}
+
+QString FontConfig::fileName()
+{
+    return "fonts.toml";
+}
+
+FontConfig FontConfig::fromFile(const QString &filePath)
+{
+    FontConfig cfg;
+
+    QFile f(filePath);
+
+    if (!f.open(QIODevice::ReadOnly | QIODevice::Text)) {
+        return cfg;
+    }
+
+    QMetaEnum roleEnum = QMetaEnum::fromType<AppFont::Role>();
+
+    QString currentSection;
+
+    QTextStream in(&f);
+
+    while (!in.atEnd()) {
+        QString line = in.readLine().trimmed();
+
+        if (line.isEmpty() || line.startsWith('#') || line.startsWith(';')) {
+            continue;
+        }
+
+        if (line.startsWith('[') && line.endsWith(']')) {
+            currentSection = line.mid(1, line.length() - 2).trimmed();
+            continue;
+        }
+
+        if (currentSection.compare("Fonts", Qt::CaseInsensitive) != 0) {
+            continue;
+        }
+
+        int eq = line.indexOf('=');
+
+        if (eq < 0) {
+            continue;
+        }
+
+        QString key = line.left(eq).trimmed();
+        QString value = line.mid(eq + 1).trimmed();
+
+        // Strip inline comments if preceded by whitespace
+        for (int i = 1; i < value.size(); ++i) {
+            if ((value[i] == '#' || value[i] == ';') && value[i - 1].isSpace()) {
+                value = value.left(i).trimmed();
+                break;
+            }
+        }
+
+        // Strip surrounding quotes, if any
+        if (value.size() >= 2 &&
+            ((value.startsWith('"') && value.endsWith('"')) || (value.startsWith('\'') && value.endsWith('\'')))) {
+            value = value.mid(1, value.size() - 2).trimmed();
+        }
+
+        int comma = value.lastIndexOf(',');
+
+        if (comma < 0) {
+            continue;
+        }
+
+        QString family = value.left(comma).trimmed();
+
+        // Tolerate a partially-quoted family, e.g. "Inter", 10
+        if (family.size() >= 2 &&
+            ((family.startsWith('"') && family.endsWith('"')) || (family.startsWith('\'') && family.endsWith('\'')))) {
+            family = family.mid(1, family.size() - 2).trimmed();
+        }
+
+        bool ok = false;
+        int pointSize = value.mid(comma + 1).trimmed().toInt(&ok);
+
+        if (!ok || family.isEmpty() || pointSize <= 0) {
+            continue;
+        }
+
+        if (key.startsWith("AppFont::")) {
+            key = key.mid(QStringLiteral("AppFont::").size());
+        }
+
+        int roleInt = roleEnum.keyToValue(key.toUtf8().constData());
+
+        if (roleInt < 0) {
+            continue;
+        }
+
+        // Canonical family + point size only: a fresh QFont carries default
+        // (non-bold, non-italic) weight/style, so nothing caller-side leaks in.
+        // No validation against installed fonts; Qt substitution applies.
+        QFont font(family);
+        font.setPointSize(pointSize);
+        cfg.fonts[static_cast<AppFont::Role>(roleInt)] = font;
+    }
+
+    return cfg;
+}
+
+FontConfig FontConfig::fromThemeDir(const QString &themeDirPath)
+{
+    if (themeDirPath.isEmpty()) {
+        return {};
+    }
+
+    return fromFile(QDir(themeDirPath).absoluteFilePath(fileName()));
+}

cockatrice/src/interface/theme_config.h

@@ -2,6 +2,7 @@
 #define COCKATRICE_THEME_CONFIG_H
 
 #include <QColor>
+#include <QFont>
 #include <QMap>
 #include <QPalette>
 #include <QSharedPointer>
@@ -23,6 +24,23 @@ enum Role
 Q_ENUM_NS(Role)
 } // namespace AppColor
 
+// Application-specific font roles, one configurable family + point size per
+// purpose. Stored in a shared fonts.toml under a [Fonts] section (one file per
+// theme, not split by light/dark). Only family and point size are stored;
+// weight/italic are stripped on load and stay caller-side concerns.
+namespace AppFont
+{
+Q_NAMESPACE
+enum Role
+{
+    InterfaceDefault,
+    ChatLog,
+    CardText,
+    DeckList,
+};
+Q_ENUM_NS(Role)
+} // namespace AppFont
+
 struct ThemeConfig
 {
     QString colorScheme;
@@ -60,4 +78,33 @@ struct PaletteConfig
     QPalette apply(QPalette base) const;
 };
 
-#endif // COCKATRICE_THEME_CONFIG_H
+/** @brief Per-purpose font configuration, stored as family + point size only.
+ *
+ * Serialized to a shared fonts.toml file with a [Fonts] section, e.g.
+ * @code
+ * [Fonts]
+ * InterfaceDefault = "Inter, 10"
+ * @endcode
+ */
+struct FontConfig
+{
+    QMap<AppFont::Role, QFont> fonts;
+
+    bool operator==(const FontConfig &rhs) const
+    {
+        return fonts == rhs.fonts;
+    }
+    bool operator!=(const FontConfig &rhs) const
+    {
+        return !(*this == rhs);
+    }
+    bool hasFonts() const;
+    QString toToml() const;
+
+    static QString fileName();
+
+    static FontConfig fromFile(const QString &filePath);
+    static FontConfig fromThemeDir(const QString &themeDirPath);
+};
+
+#endif // COCKATRICE_THEME_CONFIG_H

cockatrice/src/interface/theme_manager.cpp

@@ -127,8 +127,10 @@ static QString usableDefaultStyle(const QString &style)
 ThemeManager::ThemeManager(QObject *parent) : QObject(parent)
 {
     defaultStyleName = usableDefaultStyle(qApp->style()->objectName());
-    // Capture the untouched application palette before any theme is applied.
+    // Capture the untouched application palette and font before any theme is
+    // applied.
     defaultPalette = qApp->palette();
+    defaultFont = qApp->font();
     ensureThemeDirectoryExists();
 #if (QT_VERSION >= QT_VERSION_CHECK(6, 5, 0))
     connect(QGuiApplication::styleHints(), &QStyleHints::colorSchemeChanged, this, [this] {
@@ -440,6 +442,34 @@ PaletteConfig ThemeManager::loadDefaultPaletteConfig(const QString &themeDirPath
     return cfg;
 }
 
+FontConfig ThemeManager::loadFontConfig(const QString &themeDirPath)
+{
+    if (themeDirPath.isEmpty()) {
+        return {};
+    }
+    return FontConfig::fromThemeDir(themeDirPath);
+}
+
+bool ThemeManager::saveFontConfig(const QString &themeDirPath, const FontConfig &cfg)
+{
+    if (themeDirPath.isEmpty()) {
+        return false;
+    }
+
+    QDir dir(themeDirPath);
+    if (!dir.exists()) {
+        dir.mkpath(".");
+    }
+
+    QFile f(dir.absoluteFilePath(FontConfig::fileName()));
+    if (!f.open(QIODevice::WriteOnly | QIODevice::Text | QIODevice::Truncate)) {
+        return false;
+    }
+
+    QTextStream(&f) << cfg.toToml();
+    return true;
+}
+
 bool ThemeManager::commitPalette(const QString &themeDirPath, const QString &colorScheme, const PaletteConfig &cfg)
 {
     if (!savePaletteConfig(themeDirPath, colorScheme, cfg)) {
@@ -488,6 +518,24 @@ void ThemeManager::previewPalette(const PaletteConfig &cfg, const QString &schem
     applyStyleAndPalette(themeName, themeCfg, cfg, scheme);
 }
 
+void ThemeManager::previewFonts(const FontConfig &cfg)
+{
+    currentFonts = cfg;
+
+    // QApplication::setFont already sends a font change to every widget, so a
+    // repolish pass is not needed for fonts (unlike the palette path).
+    const auto it = cfg.fonts.constFind(AppFont::InterfaceDefault);
+    if (it != cfg.fonts.constEnd()) {
+        qApp->setFont(it.value());
+    } else {
+        // A config without InterfaceDefault means "no override": restore the
+        // startup font instead of leaving the last preview applied.
+        qApp->setFont(defaultFont);
+    }
+
+    emit fontsChanged();
+}
+
 void ThemeManager::applyStyleAndPalette(const QString &themeName,
                                         const ThemeConfig &themeCfg,
                                         const PaletteConfig &palCfg,
@@ -591,6 +639,18 @@ QColor ThemeManager::appColor(AppColor::Role role) const
     return accent;
 }
 
+QFont ThemeManager::appFont(AppFont::Role role) const
+{
+    const auto it = currentFonts.fonts.constFind(role);
+    if (it != currentFonts.fonts.constEnd()) {
+        return it.value();
+    }
+
+    // No per-role scaling: every unset role resolves to the application font,
+    // so with no fonts.toml present the result is identical to before.
+    return qApp->font();
+}
+
 void ThemeManager::themeChangedSlot()
 {
     QString themeName = SettingsCache::instance().getThemeName();
@@ -642,6 +702,24 @@ void ThemeManager::themeChangedSlot()
 
     applyStyleAndPalette(themeName, themeCfg, palette, activeScheme);
 
+    // ── Load fonts: shared per theme, no light/dark split ───────────────────
+    FontConfig fonts = loadFontConfig(dirPath);
+    if (!fonts.hasFonts()) {
+        // The shipped fonts.toml may live in the system theme directory rather
+        // than the resolved (user) theme directory, so built-in themes still
+        // get their curated fonts.
+        const QString sysFontPath = QDir(systemThemesBasePath()).absoluteFilePath(themeName);
+        if (sysFontPath != dirPath) {
+            fonts = loadFontConfig(sysFontPath);
+        }
+    }
+    currentFonts = fonts;
+    const auto fontIt = currentFonts.fonts.constFind(AppFont::InterfaceDefault);
+    if (fontIt != currentFonts.fonts.constEnd()) {
+        qApp->setFont(fontIt.value());
+    }
+    emit fontsChanged();
+
     QStringList resources;
     if (!dirPath.isEmpty()) {
         resources << dir.absolutePath();

cockatrice/src/interface/theme_manager.h

@@ -11,6 +11,7 @@
 
 #include <QBrush>
 #include <QColor>
+#include <QFont>
 #include <QLoggingCategory>
 #include <QMap>
 #include <QObject>
@@ -47,10 +48,15 @@ private:
     // palette is applied. Used as the base when a theme supplies no palette, so
     // switching away from a custom palette restores the original colours.
     QPalette defaultPalette;
+    // Pristine application font captured at startup, before any theme font is
+    // applied. Restored when a theme (or a preview) supplies no InterfaceDefault
+    // font, so switching away from a themed font cannot leave it behind.
+    QFont defaultFont;
     QString currentThemePath;
     std::array<QBrush, Role::MaxRole + 1> brushes;
     QStringMap availableThemes;
     QMap<AppColor::Role, QColor> currentAppColors;
+    FontConfig currentFonts;
     /*
       Internal cache for multiple backgrounds
     */
@@ -105,6 +111,9 @@ public:
     // Load/save per-scheme palette colors
     static PaletteConfig loadPaletteConfig(const QString &themeDirPath, const QString &colorScheme);
     static bool savePaletteConfig(const QString &themeDirPath, const QString &colorScheme, const PaletteConfig &cfg);
+    // Load/save shared per-theme fonts (fonts.toml, not split by scheme)
+    static FontConfig loadFontConfig(const QString &themeDirPath);
+    static bool saveFontConfig(const QString &themeDirPath, const FontConfig &cfg);
     // Resolve prefix to a scheme-qualified "theme:" path. Existence is probed
     // internally across the formats themes may ship (.png/.jpg/.svg), so
     // callers load the returned path directly. Prefers "<prefix>-<dark|light>"
@@ -132,10 +141,14 @@ public:
 
     void reloadCurrentTheme();
     void previewPalette(const PaletteConfig &cfg, const QString &scheme);
+    void previewFonts(const FontConfig &cfg);
 
     // Resolves an application color role: the theme's stored [AppColors] value
     // when present, otherwise a palette-accent-derived fallback.
     QColor appColor(AppColor::Role role) const;
+    /** @brief Resolves an application font role: the theme's stored [Fonts]
+     *         value when present, otherwise the application font. */
+    QFont appFont(AppFont::Role role) const;
 
     QBrush &getBgBrush(Role zone);
     QBrush getExtraBgBrush(Role zone, int zoneId = 0);
@@ -144,6 +157,7 @@ protected slots:
 signals:
     void themeChanged();
     void paletteChanged();
+    void fontsChanged();
 };
 
 extern ThemeManager *themeManager;

tests/CMakeLists.txt

@@ -412,6 +412,15 @@ cockatrice_add_test(
   INCLUDE_DIRS
   ${CMAKE_SOURCE_DIR}/cockatrice/src
 )
+cockatrice_add_test(
+  NAME
+  font_config_test
+  SOURCES
+  ${CMAKE_SOURCE_DIR}/cockatrice/src/interface/theme_config.cpp
+  font_config_test.cpp
+  INCLUDE_DIRS
+  ${CMAKE_SOURCE_DIR}/cockatrice/src
+)
 cockatrice_add_test(
   NAME
   loader_local_matching_test

tests/font_config_test.cpp

@@ -0,0 +1,195 @@
+#include "interface/theme_config.h"
+
+#include <QDir>
+#include <QFile>
+#include <QFileInfo>
+#include <QFont>
+#include <QIODevice>
+#include <QString>
+#include <QStringLiteral>
+#include <QTemporaryDir>
+#include <QTextStream>
+#include <gtest/gtest.h>
+
+namespace
+{
+// Writes content to a file inside tmp, creating parents as needed.
+QString writeTempFile(QTemporaryDir &tmp, const QString &relativePath, const QString &content)
+{
+    const QString filePath = QDir(tmp.path()).absoluteFilePath(relativePath);
+    EXPECT_TRUE(QDir().mkpath(QFileInfo(filePath).absolutePath()));
+    QFile file(filePath);
+    EXPECT_TRUE(file.open(QIODevice::WriteOnly | QIODevice::Text));
+    QTextStream out(&file);
+    out << content;
+    file.close();
+    return filePath;
+}
+
+QFont makeFont(const QString &family, int pointSize)
+{
+    QFont font(family);
+    font.setPointSize(pointSize);
+    return font;
+}
+} // namespace
+
+TEST(FontConfigTest, FileNameIsFontsToml)
+{
+    EXPECT_EQ(FontConfig::fileName(), QStringLiteral("fonts.toml"));
+}
+
+TEST(FontConfigTest, EmptyByDefault)
+{
+    FontConfig cfg;
+    EXPECT_FALSE(cfg.hasFonts());
+    EXPECT_TRUE(cfg.toToml().isEmpty());
+    EXPECT_EQ(cfg, FontConfig());
+    EXPECT_EQ(cfg, FontConfig::fromFile("/nonexistent/path/fonts.toml"));
+    EXPECT_EQ(cfg, FontConfig::fromThemeDir(QString()));
+}
+
+TEST(FontConfigTest, RoundTripPreservesFamilyAndSize)
+{
+    QTemporaryDir tmp;
+    ASSERT_TRUE(tmp.isValid());
+
+    FontConfig cfg;
+    cfg.fonts[AppFont::InterfaceDefault] = makeFont("Inter", 10);
+    cfg.fonts[AppFont::ChatLog] = makeFont("JetBrains Mono", 9);
+    cfg.fonts[AppFont::CardText] = makeFont("Noto Serif", 11);
+    cfg.fonts[AppFont::DeckList] = makeFont("Roboto", 12);
+    ASSERT_TRUE(cfg.hasFonts());
+
+    const QString filePath = writeTempFile(tmp, "fonts.toml", cfg.toToml());
+    const FontConfig loaded = FontConfig::fromFile(filePath);
+
+    EXPECT_EQ(loaded, cfg);
+    EXPECT_EQ(loaded.fonts[AppFont::InterfaceDefault].family(), QStringLiteral("Inter"));
+    EXPECT_EQ(loaded.fonts[AppFont::InterfaceDefault].pointSize(), 10);
+    EXPECT_EQ(loaded.fonts[AppFont::ChatLog].family(), QStringLiteral("JetBrains Mono"));
+    EXPECT_EQ(loaded.fonts[AppFont::ChatLog].pointSize(), 9);
+    EXPECT_EQ(loaded.fonts[AppFont::CardText].family(), QStringLiteral("Noto Serif"));
+    EXPECT_EQ(loaded.fonts[AppFont::CardText].pointSize(), 11);
+    EXPECT_EQ(loaded.fonts[AppFont::DeckList].family(), QStringLiteral("Roboto"));
+    EXPECT_EQ(loaded.fonts[AppFont::DeckList].pointSize(), 12);
+}
+
+TEST(FontConfigTest, RoundTripStripsWeightAndItalic)
+{
+    QTemporaryDir tmp;
+    ASSERT_TRUE(tmp.isValid());
+
+    QFont styled("Inter");
+    styled.setPointSize(10);
+    styled.setBold(true);
+    styled.setItalic(true);
+
+    FontConfig cfg;
+    cfg.fonts[AppFont::ChatLog] = styled;
+
+    const QString filePath = writeTempFile(tmp, "fonts.toml", cfg.toToml());
+    const FontConfig loaded = FontConfig::fromFile(filePath);
+
+    ASSERT_TRUE(loaded.fonts.contains(AppFont::ChatLog));
+    EXPECT_EQ(loaded.fonts[AppFont::ChatLog].family(), QStringLiteral("Inter"));
+    EXPECT_EQ(loaded.fonts[AppFont::ChatLog].pointSize(), 10);
+    EXPECT_FALSE(loaded.fonts[AppFont::ChatLog].bold());
+    EXPECT_FALSE(loaded.fonts[AppFont::ChatLog].italic());
+    EXPECT_EQ(loaded.fonts[AppFont::ChatLog], makeFont("Inter", 10));
+}
+
+TEST(FontConfigTest, ToTomlFormat)
+{
+    FontConfig cfg;
+    cfg.fonts[AppFont::InterfaceDefault] = makeFont("Inter", 10);
+
+    const QString toml = cfg.toToml();
+    EXPECT_TRUE(toml.contains(QStringLiteral("[Fonts]")));
+    EXPECT_TRUE(toml.contains(QStringLiteral("InterfaceDefault")));
+    EXPECT_TRUE(toml.contains(QStringLiteral("\"Inter, 10\"")));
+}
+
+TEST(FontConfigTest, MalformedLinesAreSkipped)
+{
+    QTemporaryDir tmp;
+    ASSERT_TRUE(tmp.isValid());
+
+    const QString filePath = writeTempFile(tmp, "fonts.toml",
+                                           "# a comment\n"
+                                           "; another comment\n"
+                                           "\n"
+                                           "StrayBeforeSection = \"Inter, 10\"\n"
+                                           "\n"
+                                           "[Other]\n"
+                                           "ChatLog = \"ShouldBeIgnored, 10\"\n"
+                                           "\n"
+                                           "[Fonts]\n"
+                                           "InterfaceDefault = \"Inter, 10\"\n"
+                                           "ChatLog = \"JetBrains Mono\", 9 # inline comment\n"
+                                           "CardText = Noto Serif, 11\n"
+                                           "AppFont::DeckList = \"Roboto, 12\"\n"
+                                           "UnknownRole = \"Inter, 10\"\n"
+                                           "QPalette::Window = \"Inter, 10\"\n"
+                                           "NoComma = \"Inter\"\n"
+                                           "EmptyFamily = \", 10\"\n"
+                                           "ZeroSize = \"Inter, 0\"\n"
+                                           "NegativeSize = \"Inter, -3\"\n"
+                                           "NotANumber = \"Inter, big\"\n"
+                                           "NotAnEntry\n");
+
+    const FontConfig loaded = FontConfig::fromFile(filePath);
+
+    ASSERT_TRUE(loaded.hasFonts());
+    EXPECT_EQ(loaded.fonts.size(), 4);
+    EXPECT_EQ(loaded.fonts[AppFont::InterfaceDefault], makeFont("Inter", 10));
+    EXPECT_EQ(loaded.fonts[AppFont::ChatLog], makeFont("JetBrains Mono", 9));
+    EXPECT_EQ(loaded.fonts[AppFont::CardText], makeFont("Noto Serif", 11));
+    EXPECT_EQ(loaded.fonts[AppFont::DeckList], makeFont("Roboto", 12));
+}
+
+TEST(FontConfigTest, FromThemeDirReadsFontsToml)
+{
+    QTemporaryDir tmp;
+    ASSERT_TRUE(tmp.isValid());
+
+    const QString themeDir = QDir(tmp.path()).absoluteFilePath("MyTheme");
+    ASSERT_TRUE(QDir().mkpath(themeDir));
+
+    FontConfig cfg;
+    cfg.fonts[AppFont::CardText] = makeFont("Noto Serif", 11);
+    writeTempFile(tmp, "MyTheme/fonts.toml", cfg.toToml());
+
+    const FontConfig loaded = FontConfig::fromThemeDir(themeDir);
+    EXPECT_EQ(loaded, cfg);
+
+    // A theme directory without fonts.toml loads as empty.
+    const QString bareDir = QDir(tmp.path()).absoluteFilePath("BareTheme");
+    ASSERT_TRUE(QDir().mkpath(bareDir));
+    EXPECT_FALSE(FontConfig::fromThemeDir(bareDir).hasFonts());
+}
+
+TEST(FontConfigTest, InequalityComparesRoles)
+{
+    FontConfig left;
+    left.fonts[AppFont::InterfaceDefault] = makeFont("Inter", 10);
+
+    FontConfig right = left;
+    EXPECT_EQ(left, right);
+    EXPECT_FALSE(left != right);
+
+    right.fonts[AppFont::InterfaceDefault] = makeFont("Inter", 11);
+    EXPECT_NE(left, right);
+
+    right = left;
+    right.fonts[AppFont::ChatLog] = makeFont("Inter", 10);
+    EXPECT_NE(left, right);
+}
+
+// Every test brings its own main(): GTest is not guaranteed to be found on the build machines, and
+// the fallback then links the bare gtest library without gtest_main.
+int main(int argc, char **argv)
+{
+    ::testing::InitGoogleTest(&argc, argv);
+    return RUN_ALL_TESTS();
+}