[Icons] Add palette-aware themed icon engine

A QPixmap snapshot cannot follow palette changes, so an authored `currentColor`
glyph would freeze at whatever color it was first rendered with. Add a QIcon
engine that resolves the sentinel from the current palette on every pixmap
request, caches by resolved path/color/size/DPR, and falls back to Qt's normal
loader for authored multi-color art and raster overrides.

Purely additive. No behavior change yet.

cockatrice/CMakeLists.txt

@@ -172,6 +172,7 @@ set(cockatrice_SOURCES
     src/interface/widgets/utility/reversed_completer_model.cpp
     src/interface/pixel_map_generator.cpp
     src/interface/theme_config.cpp
+    src/interface/theme_icon.cpp
     src/interface/theme_manager.cpp
     src/interface/palette_editor/color_button.cpp
     src/interface/palette_editor/palette_generator.cpp

cockatrice/src/interface/theme_icon.cpp

@@ -0,0 +1,255 @@
+#include "theme_icon.h"
+
+#include "libcockatrice/utility/svg_recolor.h"
+#include "theme_manager.h"
+
+#include <QApplication>
+#include <QByteArray>
+#include <QColor>
+#include <QFile>
+#include <QHash>
+#include <QIODevice>
+#include <QIconEngine>
+#include <QPaintDevice>
+#include <QPainter>
+#include <QPointF>
+#include <QRect>
+#include <QRectF>
+#include <QSize>
+#include <QString>
+#include <QStringLiteral>
+#include <QStyle>
+#include <QSvgRenderer>
+#include <QtGlobal>
+#include <utility>
+
+namespace
+{
+/**
+ * @brief Palette color that replaces `currentColor`, following the icon mode.
+ */
+QByteArray sentinelColor(QIcon::Mode mode, QPalette::ColorRole role)
+{
+    const QPalette::ColorGroup group = mode == QIcon::Disabled ? QPalette::Disabled : QPalette::Active;
+    const QPalette::ColorRole effective =
+        mode == QIcon::Selected && role == QPalette::WindowText ? QPalette::HighlightedText : role;
+    return qApp->palette().color(group, effective).name(QColor::HexRgb).toLatin1();
+}
+
+/**
+ * @brief Reads an SVG through the `theme:` search path.
+ */
+QByteArray readSvg(const QString &resolvedPath)
+{
+    QFile file(QStringLiteral("theme:") + resolvedPath);
+    if (!file.open(QIODevice::ReadOnly)) {
+        return {};
+    }
+    return file.readAll();
+}
+
+/**
+ * @brief Renders SVG bytes, scaled to @p size when one is given.
+ *
+ * An empty size means the asset's intrinsic size; @p devicePixelRatio only
+ * applies in that case so HiDPI callers still get a crisp glyph.
+ */
+QPixmap renderSvg(const QByteArray &data, const QSize &size, qreal devicePixelRatio)
+{
+    QSvgRenderer renderer(data);
+    if (!renderer.isValid()) {
+        return {};
+    }
+
+    QSize renderSize = size;
+    if (renderSize.isEmpty()) {
+        renderSize = renderer.defaultSize();
+        renderSize =
+            QSize(qRound(renderSize.width() * devicePixelRatio), qRound(renderSize.height() * devicePixelRatio));
+    }
+    if (!renderSize.isValid() || renderSize.isEmpty()) {
+        return {};
+    }
+
+    QPixmap pixmap(renderSize);
+    pixmap.fill(Qt::transparent);
+    QPainter painter(&pixmap);
+    renderer.render(&painter);
+    return pixmap;
+}
+
+QString cacheKey(const QString &path, const QByteArray &color, const QSize &size, qreal devicePixelRatio)
+{
+    return path + QLatin1Char('|') + QString::fromLatin1(color) + QLatin1Char('|') + QString::number(size.width()) +
+           QLatin1Char('x') + QString::number(size.height()) + QLatin1Char('@') + QString::number(devicePixelRatio);
+}
+
+/**
+ * @brief QIcon engine rendering a `theme:` SVG with `currentColor` resolved on demand.
+ *
+ * Qt's SVG renderer has no ambient color, so the sentinel is substituted from
+ * the current palette on every pixmap request. The render cache is keyed by
+ * resolved path, palette color, pixel size and DPR, so a theme change produces
+ * new keys instead of reusing art built under the previous palette.
+ */
+class ThemeSvgIconEngine final : public QIconEngine
+{
+public:
+    ThemeSvgIconEngine(QString _prefix, QPalette::ColorRole _role) : prefix(std::move(_prefix)), role(_role)
+    {
+    }
+
+    QIconEngine *clone() const override
+    {
+        return new ThemeSvgIconEngine(prefix, role);
+    }
+
+    void paint(QPainter *painter, const QRect &rect, QIcon::Mode mode, QIcon::State) override
+    {
+        const qreal devicePixelRatio = painter->device() ? painter->device()->devicePixelRatioF() : 1.0;
+        const QSize logicalSize = fitToSize(rect.size());
+        if (logicalSize.isEmpty()) {
+            return;
+        }
+        const QSize pixelSize(qRound(logicalSize.width() * devicePixelRatio),
+                              qRound(logicalSize.height() * devicePixelRatio));
+        QPixmap pixmap = render(pixelSize, devicePixelRatio, mode);
+        if (!pixmap.isNull()) {
+            pixmap.setDevicePixelRatio(devicePixelRatio);
+            const QSizeF contentSize = pixmap.deviceIndependentSize();
+            const QRectF targetRect(
+                QPointF(rect.center()) - QPointF(contentSize.width() / 2.0, contentSize.height() / 2.0), contentSize);
+            painter->drawPixmap(targetRect, pixmap, QRectF(pixmap.rect()));
+        }
+    }
+
+    QPixmap pixmap(const QSize &size, QIcon::Mode mode, QIcon::State) override
+    {
+        return render(fitToSize(size), 1.0, mode);
+    }
+
+    QPixmap scaledPixmap(const QSize &size, QIcon::Mode mode, QIcon::State, qreal scale) override
+    {
+        const QSize logicalSize = fitToSize(size);
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+        const QSize pixelSize(qRound(logicalSize.width() * scale), qRound(logicalSize.height() * scale));
+#else
+        // Qt < 6.8 passes the device-dependent size to the engine.
+        const QSize pixelSize = logicalSize;
+#endif
+        QPixmap pixmap = render(pixelSize, scale, mode);
+        if (!pixmap.isNull()) {
+            pixmap.setDevicePixelRatio(scale);
+        }
+        return pixmap;
+    }
+
+    QSize actualSize(const QSize &size, QIcon::Mode, QIcon::State) override
+    {
+        return fitToSize(size);
+    }
+
+private:
+    void ensureResolved() const
+    {
+        const QString themePath = themeManager->getCurrentThemePath();
+        const bool darkMode = themeManager->isDarkModeActive();
+        if (!hasResolvedPath || themePath != resolvedThemePath || darkMode != resolvedDarkMode) {
+            resolvedPath = themeManager->assetPath(prefix);
+            resolvedThemePath = themePath;
+            resolvedDarkMode = darkMode;
+            hasResolvedPath = true;
+            hasIntrinsicSize = false;
+        }
+    }
+
+    QSize intrinsicSize() const
+    {
+        ensureResolved();
+        if (!hasIntrinsicSize) {
+            const QByteArray svg = readSvg(resolvedPath);
+            QSvgRenderer renderer(svg);
+            intrinsicSizeCache = renderer.isValid() ? renderer.defaultSize() : QSize(24, 24);
+            if (intrinsicSizeCache.isEmpty()) {
+                intrinsicSizeCache = QSize(24, 24);
+            }
+            hasIntrinsicSize = true;
+        }
+        return intrinsicSizeCache;
+    }
+
+    QSize fitToSize(const QSize &size) const
+    {
+        if (size.isEmpty()) {
+            return size;
+        }
+        return intrinsicSize().scaled(size, Qt::KeepAspectRatio);
+    }
+
+    QPixmap render(const QSize &pixelSize, qreal devicePixelRatio, QIcon::Mode mode) const
+    {
+        ensureResolved();
+        const QString themePath = resolvedThemePath;
+        const bool darkMode = resolvedDarkMode;
+
+        const QByteArray svg = readSvg(resolvedPath);
+        if (svg.isEmpty() || !QString::fromUtf8(svg).contains(QStringLiteral("currentColor"), Qt::CaseInsensitive)) {
+            // Authored art carries its own colors: use Qt's normal loader so
+            // raster overrides and non-SVG assets keep working.
+            QPixmap pixmap(QStringLiteral("theme:") + resolvedPath);
+            if (!pixelSize.isEmpty() && pixmap.size() != pixelSize) {
+                pixmap = pixmap.scaled(pixelSize, Qt::KeepAspectRatio, Qt::SmoothTransformation);
+            }
+            if (mode == QIcon::Disabled && !pixmap.isNull()) {
+                pixmap = QApplication::style()->generatedIconPixmap(QIcon::Disabled, pixmap, nullptr);
+            }
+            return pixmap;
+        }
+
+        const QByteArray color = sentinelColor(mode, role);
+        const QString key = cacheKey(resolvedPath, color, pixelSize, devicePixelRatio) + QLatin1Char('|') + themePath +
+                            (darkMode ? QLatin1Char('d') : QLatin1Char('l'));
+        const auto cached = cache.constFind(key);
+        if (cached != cache.constEnd()) {
+            return cached.value();
+        }
+
+        QPixmap pixmap = renderSvg(resolveSvgColorSentinel(svg, color), pixelSize, devicePixelRatio);
+        if (cache.size() >= 64) {
+            cache.clear();
+        }
+        cache.insert(key, pixmap);
+        return pixmap;
+    }
+
+    QString prefix;
+    QPalette::ColorRole role;
+    mutable QHash<QString, QPixmap> cache;
+    mutable QString resolvedPath;
+    mutable QString resolvedThemePath;
+    mutable QSize intrinsicSizeCache;
+    mutable bool resolvedDarkMode = false;
+    mutable bool hasResolvedPath = false;
+    mutable bool hasIntrinsicSize = false;
+};
+} // namespace
+
+QIcon loadThemedIcon(QStringView prefix, QPalette::ColorRole role)
+{
+    return QIcon(new ThemeSvgIconEngine(prefix.toString(), role));
+}
+
+QPixmap loadSentinelSvgPixmap(const QString &resolvedPath, QPalette::ColorRole role, const QSize &size)
+{
+    if (!resolvedPath.endsWith(QStringLiteral(".svg"), Qt::CaseInsensitive)) {
+        return {};
+    }
+
+    const QByteArray svg = readSvg(resolvedPath);
+    if (svg.isEmpty() || !QString::fromUtf8(svg).contains(QStringLiteral("currentColor"), Qt::CaseInsensitive)) {
+        return {};
+    }
+
+    const QByteArray color = qApp->palette().color(role).name(QColor::HexRgb).toLatin1();
+    return renderSvg(resolveSvgColorSentinel(svg, color), size, 1.0);
+}

cockatrice/src/interface/theme_icon.h

@@ -0,0 +1,50 @@
+/**
+ * @file theme_icon.h
+ * @ingroup Interface
+ */
+
+#ifndef THEME_ICON_H
+#define THEME_ICON_H
+
+#include <QIcon>
+#include <QPalette>
+#include <QPixmap>
+#include <QSize>
+#include <QString>
+#include <QStringView>
+
+/**
+ * @brief Builds a palette-aware icon from a `theme:` asset.
+ *
+ * SVG glyphs may use the `currentColor` sentinel. A plain QPixmap snapshot
+ * cannot follow palette changes, so this returns a QIcon whose engine resolves
+ * the sentinel from the current palette every time it is asked for a pixmap.
+ * Icons therefore stay legible when the user switches between light and dark
+ * themes without recreating any actions or buttons.
+ *
+ * @param prefix Asset prefix relative to the `theme:` search path, with no file
+ *               extension (for example `icons/search`), matching themePixmap().
+ * @param role Palette role whose color replaces the sentinel. Selected glyphs
+ *             use HighlightedText unless a role other than WindowText is given.
+ * @return An icon that follows the application palette.
+ */
+QIcon loadThemedIcon(QStringView prefix, QPalette::ColorRole role = QPalette::WindowText);
+
+/**
+ * @brief Renders a resolved theme SVG when it carries the `currentColor` sentinel.
+ *
+ * Non-SVG assets and SVGs without the sentinel return a null pixmap so callers
+ * can fall back to their usual loading path (including legacy inversion).
+ *
+ * @param resolvedPath Asset path relative to the `theme:` search path, as
+ *                     returned by ThemeManager::assetPath (includes extension).
+ * @param role Palette role whose color replaces the sentinel.
+ * @param size Pixel size to render at; an empty size uses the SVG's intrinsic size.
+ * @return The recolored pixmap, or a null pixmap when the asset is not a
+ *         sentinel-carrying SVG.
+ */
+QPixmap loadSentinelSvgPixmap(const QString &resolvedPath,
+                              QPalette::ColorRole role = QPalette::WindowText,
+                              const QSize &size = {});
+
+#endif // THEME_ICON_H

libcockatrice_utility/CMakeLists.txt

@@ -12,6 +12,7 @@ set(UTILITY_SOURCES
     libcockatrice/utility/passwordhasher.cpp
     libcockatrice/utility/report_categories.cpp
     libcockatrice/utility/server_rate_limiter.cpp
+    libcockatrice/utility/svg_recolor.cpp
     libcockatrice/utility/translation_loader.cpp
     libcockatrice/utility/user_data_backup.cpp
     libcockatrice/utility/warning_categories.cpp
@@ -35,6 +36,7 @@ set(UTILITY_HEADERS
     libcockatrice/utility/zone_names.h
     libcockatrice/utility/days_years_between.h
     libcockatrice/utility/server_rate_limiter.h
+    libcockatrice/utility/svg_recolor.h
     libcockatrice/utility/translation_loader.h
     libcockatrice/utility/user_data_backup.h
     libcockatrice/utility/warning_categories.h

libcockatrice_utility/libcockatrice/utility/svg_recolor.cpp

@@ -0,0 +1,15 @@
+#include "svg_recolor.h"
+
+#include <QString>
+
+QByteArray resolveSvgColorSentinel(const QByteArray &svg, const QByteArray &color)
+{
+    const QString source = QString::fromUtf8(svg);
+    if (!source.contains(QStringLiteral("currentColor"), Qt::CaseInsensitive)) {
+        return svg;
+    }
+
+    QString resolved = source;
+    resolved.replace(QStringLiteral("currentColor"), QString::fromLatin1(color), Qt::CaseInsensitive);
+    return resolved.toUtf8();
+}

libcockatrice_utility/libcockatrice/utility/svg_recolor.h

@@ -0,0 +1,26 @@
+/**
+ * @file svg_recolor.h
+ * @ingroup Core
+ */
+
+#ifndef SVG_RECOLOR_H
+#define SVG_RECOLOR_H
+
+#include <QByteArray>
+
+/**
+ * @brief Resolves the `currentColor` sentinel in authored SVG data.
+ *
+ * Qt's SVG renderer has no CSS cascade or ambient color context, so the
+ * sentinel is not resolved by Qt. Callers pass the concrete color they want
+ * (for example a QPalette role serialized to #RRGGBB) and receive SVG bytes
+ * that are safe to hand to QSvgRenderer.
+ *
+ * @param svg UTF-8 SVG source. Every `currentColor` occurrence, in any case,
+ *            is replaced.
+ * @param color Concrete SVG color (for example "#ff00ff"), as ASCII bytes.
+ * @return The recolored SVG source; the input is left untouched.
+ */
+QByteArray resolveSvgColorSentinel(const QByteArray &svg, const QByteArray &color);
+
+#endif // SVG_RECOLOR_H

oracle/CMakeLists.txt

@@ -30,6 +30,7 @@ set(oracle_SOURCES
     ../cockatrice/src/client/network/update/client/release_channel.cpp
     ../cockatrice/src/interface/pixel_map_generator.cpp
     ../cockatrice/src/interface/theme_config.cpp
+    ../cockatrice/src/interface/theme_icon.cpp
     ../cockatrice/src/interface/theme_manager.cpp
     ${VERSION_STRING_CPP}
 )

tests/CMakeLists.txt

@@ -177,6 +177,7 @@ cockatrice_add_test(NAME test_age_formatting SOURCES test_age_formatting.cpp LIB
 cockatrice_add_test(NAME user_data_backup_test SOURCES user_data_backup_test.cpp LIBS libcockatrice_utility)
 cockatrice_add_test(NAME password_hash_test SOURCES password_hash_test.cpp LIBS libcockatrice_utility)
 cockatrice_add_test(NAME report_categories_test SOURCES report_categories_test.cpp LIBS libcockatrice_utility)
+cockatrice_add_test(NAME svg_recolor_test SOURCES svg_recolor_test.cpp LIBS libcockatrice_utility)
 cockatrice_add_test(NAME warning_categories_test SOURCES warning_categories_test.cpp LIBS libcockatrice_utility)
 cockatrice_add_test(
   NAME

tests/svg_recolor_test.cpp

@@ -0,0 +1,53 @@
+#include "libcockatrice/utility/svg_recolor.h"
+
+#include <QByteArray>
+#include <gtest/gtest.h>
+
+namespace
+{
+
+TEST(SvgRecolor, ReplacesEverySentinel)
+{
+    const QByteArray svg = R"(<svg><path fill="currentColor"/><path stroke="currentColor"/></svg>)";
+    const QByteArray result = resolveSvgColorSentinel(svg, "#ff8800");
+
+    EXPECT_EQ(result.count("#ff8800"), 2);
+    EXPECT_FALSE(result.contains("currentColor"));
+}
+
+TEST(SvgRecolor, ReplacesSentinelRegardlessOfCase)
+{
+    const QByteArray svg = R"(<svg><path fill="CurrentColor"/><path stroke="CURRENTCOLOR"/></svg>)";
+
+    EXPECT_EQ(resolveSvgColorSentinel(svg, "#ff8800").count("#ff8800"), 2);
+}
+
+TEST(SvgRecolor, LeavesTheRestOfTheDocumentIntact)
+{
+    const QByteArray svg =
+        R"(<svg viewBox="0 0 24 24"><!-- an ordinary comment --><path d="M0 0h24v24" fill="currentColor"/></svg>)";
+    const QByteArray result = resolveSvgColorSentinel(svg, "#123456");
+
+    EXPECT_TRUE(result.contains(R"(viewBox="0 0 24 24")"));
+    EXPECT_TRUE(result.contains(R"(d="M0 0h24v24")"));
+    EXPECT_TRUE(result.contains("an ordinary comment"));
+}
+
+TEST(SvgRecolor, DoesNotModifyTheInput)
+{
+    const QByteArray svg = R"(<svg><path fill="currentColor"/></svg>)";
+    const QByteArray original = svg;
+
+    resolveSvgColorSentinel(svg, "#000000");
+
+    EXPECT_EQ(svg, original);
+}
+
+TEST(SvgRecolor, NoSentinelIsANoOp)
+{
+    const QByteArray svg = R"(<svg><path fill="#abcdef"/></svg>)";
+
+    EXPECT_EQ(resolveSvgColorSentinel(svg, "#ffffff"), svg);
+}
+
+} // namespace