overlays/utils: Add simple utility to center align a child component

rpcs3/Emu/RSX/Overlays/overlay_controls.cpp

@@ -684,6 +684,20 @@ namespace rsx
 			width = static_cast<u16>(ceilf(max_w));
 		}
 
+		u16 overlay_element::compute_vertically_centered(u16 element_height)
+		{
+			const u16 half_height = h / 2;
+			const u16 element_half_height = element_height / 2;
+			return std::max(half_height, element_half_height) - element_half_height;
+		}
+
+		u16 overlay_element::compute_horizontally_centered(u16 element_width)
+		{
+			const u16 half_width = h / 2;
+			const u16 element_half_width = element_width / 2;
+			return std::max(half_width, element_half_width) - element_half_width;
+		}
+
 		layout_container::layout_container()
 		{
 			// Transparent by default

rpcs3/Emu/RSX/Overlays/overlay_controls.h

@@ -224,6 +224,16 @@ namespace rsx
 			virtual void set_visible(bool visible) { this->visible = visible; m_is_compiled = false; }
 			virtual bool is_visible() const { return visible; }
 
+			// Calculate the vertical offset for an element of height Y if it were to be placed as a child of this element
+			u16 compute_vertically_centered(u16 element_height);
+
+			// Calculate the horizontal offset for an element of width X if it were to be placed as a child of this element
+			u16 compute_horizontally_centered(u16 element_width);
+
+			// Wrappers for the placement functions
+			u16 compute_vertically_centered(const overlay_element* other) { return compute_vertically_centered(other->h); }
+			u16 compute_horizontally_centered(const overlay_element* other) { return compute_horizontally_centered(other->w); }
+
 		protected:
 			bool m_is_compiled = false; // Only use m_is_compiled as a getter in is_compiled() if possible
 		};