Added mouse wheel support to the world selection screen.

src/client/gui/components/ScrollingPane.cpp

@@ -548,6 +548,14 @@ void ScrollingPane::stepThroughDecelerationAnimation(bool noAnimation) {
 	}
 }
 
+void ScrollingPane::scrollBy(float dx, float dy) {
+	// adjust the translation offsets fpx/fpy by the requested amount
+	float nfpx = fpx + dx;
+	float nfpy = fpy + dy;
+	// convert back to content offset (fpx = -contentOffset.x)
+	setContentOffset(Vec3(-nfpx, -nfpy, 0));
+}
+
 void ScrollingPane::setContentOffset(float x, float y) {
 	this->setContentOffsetWithAnimation(Vec3(x, y, 0), false);
 }

src/client/gui/components/ScrollingPane.h

@@ -51,6 +51,10 @@ public:
 	void tick();
 	void render(int xm, int ym, float alpha);
 
+	// scroll the content by the given amount (dx horizontal, dy vertical)
+	// positive values move content downward/rightward
+	void scrollBy(float dx, float dy);
+
 	bool getGridItemFor_slow(int itemIndex, GridItem& out);
 
 	void setSelected(int id, bool selected);