ScrollView: Add a subtle drop shadow to the top.

Common/UI/ScrollView.cpp

@@ -239,6 +239,23 @@ void ScrollView::Draw(UIContext &dc) {
 	// For debugging layout issues, this can be useful.
 	// dc.FillRect(Drawable(0x60FF00FF), bounds_);
 	views_[0]->Draw(dc);
+
+	// If not anchored at the top of the screen exactly, and not scrolled to the top,
+	// draw a subtle drop shadow to indicate scrollability.
+	if (bounds_.y > 0.0f && orientation_ == ORIENT_VERTICAL) {
+		float radius = 20.0f;
+
+		Bounds shadowBounds = bounds_;
+		shadowBounds.x -= radius;
+		shadowBounds.w += radius * 2;
+		shadowBounds.y -= radius * 2;
+		shadowBounds.h = radius * 2;
+
+		float fade = std::clamp(scrollPos_ * 0.1f, 0.0f, 0.6f);
+
+		dc.DrawRectDropShadow(shadowBounds, radius, fade);
+	}
+
 	dc.PopScissor();
 
 	// Vertical scroll bob. We don't support a horizontal yet.