[VDS] Cache mana symbol renders and skip redundant resizes

- Render each mana symbol once at a bounded master size and derive every
  requested size from the cached master, avoiding repeated full-size SVG
  rasterization on the GUI thread
- Share scaled results through a process-wide cache keyed by symbol and
  size, so repeated widget creation and rescales don't redo the work
- Skip redundant resize work in ColorIdentityWidget and ManaSymbolWidget
  when sizes did not change

Took 8 minutes


Took 50 seconds

cockatrice/src/interface/widgets/cards/additional_info/color_identity_widget.cpp

@@ -41,6 +41,11 @@ void ColorIdentityWidget::populateManaSymbolWidgets()
     // clear old layout
     QtUtils::clearLayoutRec(layout);
 
+    // The freshly created symbols haven't been sized yet, so force the next resize pass
+    // to apply the symbol size again.
+    lastIconSize = -1;
+    lastWidth = -1;
+
     // populate mana symbols
     if (SettingsCache::instance().visualDeckStorage().getVisualDeckStorageDrawUnusedColorIdentities()) {
         for (const QString symbol : fullColorIdentity) {
@@ -73,23 +78,37 @@ void ColorIdentityWidget::toggleUnusedVisibility()
 void ColorIdentityWidget::resizeEvent(QResizeEvent *event)
 {
     QWidget::resizeEvent(event);
-    QList<ManaSymbolWidget *> manaSymbols = findChildren<ManaSymbolWidget *>();
 
-    if (!manaSymbols.isEmpty()) {
-        int totalWidth = event->size().width();
-        int totalHeight = totalWidth / 6; // Set height to 1/4 of the width
+    // Layout passes resize this widget repeatedly with identical sizes, so bail out before
+    // touching the children when neither the width nor the resulting symbol size changed.
+    const int totalWidth = event->size().width();
+    if (totalWidth == lastWidth && lastIconSize != -1) {
+        return;
+    }
+    lastWidth = totalWidth;
+
+    const int totalHeight = totalWidth / 6; // Set height to 1/4 of the width
     setFixedHeight(totalHeight);
 
-        int spacing = layout->spacing();
-        int count = manaSymbols.size();
-        int availableWidth = totalWidth - (spacing * (count - 1));
-        int iconSize = qMin(availableWidth / count, totalHeight); // Ensure icons fit within the new height
+    QList<ManaSymbolWidget *> manaSymbols = findChildren<ManaSymbolWidget *>();
+    if (manaSymbols.isEmpty()) {
+        return;
+    }
+
+    const int spacing = layout->spacing();
+    const int count = manaSymbols.size();
+    const int availableWidth = totalWidth - (spacing * (count - 1));
+    const int iconSize = qMin(availableWidth / count, totalHeight); // Ensure icons fit within the new height
+
+    if (iconSize == lastIconSize) {
+        return;
+    }
+    lastIconSize = iconSize;
 
     for (ManaSymbolWidget *manaSymbol : manaSymbols) {
         manaSymbol->setFixedSize(iconSize, iconSize);
     }
 }
-}
 
 QStringList ColorIdentityWidget::parseColorIdentity(const QString &manaString)
 {

cockatrice/src/interface/widgets/cards/additional_info/color_identity_widget.h

@@ -30,6 +30,8 @@ public slots:
 private:
     QString colorIdentity;
     QHBoxLayout *layout;
+    int lastIconSize = -1; ///< The symbol size last applied, to skip redundant resize passes.
+    int lastWidth = -1;    ///< The width last processed, to skip redundant resize passes.
 };
 
 #endif // COLOR_IDENTITY_WIDGET_H

cockatrice/src/interface/widgets/cards/additional_info/mana_symbol_widget.cpp

@@ -2,14 +2,56 @@
 
 #include "../../../../client/settings/cache_settings.h"
 
+#include <QHash>
+#include <QImageReader>
 #include <QResizeEvent>
 #include <libcockatrice/settings/visual_deck_storage_settings.h>
 
-ManaSymbolWidget::ManaSymbolWidget(QWidget *parent, QString _symbol, bool _isActive, bool _mayBeToggled)
-    : QLabel(parent), symbol(_symbol), isActive(_isActive), mayBeToggled(_mayBeToggled)
+namespace
 {
-    loadManaIcon();
-    setPixmap(manaIcon.scaled(50, 50, Qt::KeepAspectRatio, Qt::SmoothTransformation));
+/// Longest side mana symbols are rendered at before being scaled to their final size.
+constexpr int MASTER_ICON_SIZE = 128;
+
+QHash<QString, QPixmap> &scaledIconCache()
+{
+    static QHash<QString, QPixmap> cache;
+    return cache;
+}
+
+/**
+ * @brief Renders \a symbol once at a fixed moderate size, so repeated scalings never
+ * re-rasterize the source file (SVG sources can be very expensive to rasterize).
+ */
+const QPixmap &masterIcon(const QString &symbol)
+{
+    static QHash<QString, QPixmap> cache;
+    auto it = cache.constFind(symbol);
+    if (it != cache.constEnd()) {
+        return it.value();
+    }
+
+    QImageReader reader("theme:icons/mana/" + symbol);
+    QSize sourceSize = reader.size();
+    if (!sourceSize.isEmpty()) {
+        sourceSize.scale(QSize(MASTER_ICON_SIZE, MASTER_ICON_SIZE), Qt::KeepAspectRatio);
+        reader.setScaledSize(sourceSize);
+    }
+    const QPixmap rendered = QPixmap::fromImageReader(&reader);
+
+    return cache.insert(symbol, rendered).value();
+}
+
+QString cacheKey(const QString &symbol, const QSize &size)
+{
+    return symbol + QLatin1Char('|') + QString::number(size.width()) + QLatin1Char('x') +
+           QString::number(size.height());
+}
+} // namespace
+
+ManaSymbolWidget::ManaSymbolWidget(QWidget *parent, QString _symbol, bool _isActive, bool _mayBeToggled)
+    : QLabel(parent), symbol(std::move(_symbol)), isActive(_isActive), mayBeToggled(_mayBeToggled)
+{
+    setPixmap(getCachedScaledIcon(symbol, QSize(50, 50)));
     setMaximumWidth(50);
 
     // Initialize opacity effect
@@ -22,6 +64,24 @@ ManaSymbolWidget::ManaSymbolWidget(QWidget *parent, QString _symbol, bool _isAct
             &ManaSymbolWidget::updateOpacity);
 }
 
+QPixmap ManaSymbolWidget::getCachedScaledIcon(const QString &symbol, const QSize &size)
+{
+    const QString key = cacheKey(symbol, size);
+    auto it = scaledIconCache().constFind(key);
+    if (it != scaledIconCache().constEnd()) {
+        return it.value();
+    }
+
+    const QPixmap &icon = masterIcon(symbol);
+    if (icon.isNull()) {
+        return {};
+    }
+
+    QPixmap scaled = icon.scaled(size, Qt::KeepAspectRatio, Qt::SmoothTransformation);
+    scaledIconCache().insert(key, scaled);
+    return scaled;
+}
+
 void ManaSymbolWidget::toggleSymbol()
 {
     setColorActive(!isActive);
@@ -64,16 +124,13 @@ void ManaSymbolWidget::mousePressEvent(QMouseEvent *event)
 void ManaSymbolWidget::resizeEvent(QResizeEvent *event)
 {
     QLabel::resizeEvent(event);
-    setPixmap(manaIcon.scaled(event->size(), Qt::KeepAspectRatio, Qt::SmoothTransformation));
+    const QSize newSize = event->size();
+
+    // Skip the rescale when the size didn't actually change: layout passes resize these
+    // widgets repeatedly with identical sizes.
+    if (newSize.isEmpty() || pixmap().size() == newSize) {
+        return;
     }
 
-void ManaSymbolWidget::loadManaIcon()
-{
-    QString filename = "theme:icons/mana/";
-
-    if (symbol == "W" || symbol == "U" || symbol == "B" || symbol == "R" || symbol == "G") {
-        filename += symbol;
-    }
-
-    manaIcon = QPixmap(filename);
+    setPixmap(getCachedScaledIcon(symbol, newSize));
 }

cockatrice/src/interface/widgets/cards/additional_info/mana_symbol_widget.h

@@ -33,7 +33,14 @@ public:
         return symbol[0];
     }
 
-    void loadManaIcon();
+    /**
+     * @brief Returns a smooth-scaled rendering of the given mana symbol icon.
+     *
+     * Results are shared between all instances via a process-wide cache keyed by symbol
+     * and size, so scaling work is done once per distinct combination instead of once per
+     * widget creation or resize.
+     */
+    static QPixmap getCachedScaledIcon(const QString &symbol, const QSize &size);
 
 public slots:
     void resizeEvent(QResizeEvent *event) override;
@@ -44,7 +51,6 @@ signals:
 
 private:
     QString symbol;
-    QPixmap manaIcon;
     bool isActive;
     bool mayBeToggled;
     QGraphicsOpacityEffect *opacityEffect;