Add basic image cache to scripting API

include/scripting.h

@@ -25,6 +25,7 @@ public:
     static Tile toTile(QJSValue obj);
     static QJSValue dimensions(int width, int height);
     static QJSEngine *getEngine();
+    static QImage getImage(QString filepath);
     static void init(MainWindow *mainWindow);
     static void registerAction(QString functionName, QString actionName);
     static int numRegisteredActions();
@@ -41,6 +42,7 @@ private:
     QStringList filepaths;
     QList<QJSValue> modules;
     QMap<QString, QString> registeredActions;
+    QMap<QString, const QImage*> imageCache;
 
     void loadModules(QStringList moduleFiles);
     void invokeCallback(CallbackType type, QJSValueList args);

src/scripting.cpp

@@ -193,3 +193,12 @@ QJSValue Scripting::fromTile(Tile tile) {
 QJSEngine *Scripting::getEngine() {
     return instance->engine;
 }
+
+QImage Scripting::getImage(QString filepath) {
+    const QImage * image = instance->imageCache.value(filepath, nullptr);
+    if (!image) {
+        image = new QImage(filepath);
+        instance->imageCache.insert(filepath, image);
+    }
+    return QImage(*image);
+}

src/ui/overlay.cpp

@@ -1,4 +1,5 @@
 #include "overlay.h"
+#include "scripting.h"
 #include "log.h"
 
 void OverlayText::render(QPainter *painter) {
@@ -53,7 +54,7 @@ void Overlay::addRect(int x, int y, int width, int height, QString color, bool f
 }
 
 bool Overlay::addImage(int x, int y, QString filepath, int width, int height, unsigned offset, bool hflip, bool vflip, bool setTransparency) {
-    QImage image = QImage(filepath);
+    QImage image = Scripting::getImage(filepath);
     if (image.isNull()) {
         logError(QString("Failed to load image '%1'").arg(filepath));
         return false;