Make sure all UIElements descend from UIElement

- This way they all get the same default positionMode
  since they're all positioned as if they're TOPLEFT
  but these UI classes weren't descended from UIElement
  so their default positionMode was CENTER. It just
  happened to work because they themselves weren't
  displayed. Fixing this provides the knowledge needed
  to produce a proper concatenated screen position matrix.

Modules/Contents/UI/Include/PolyUIBox.h

@@ -23,11 +23,11 @@
 #pragma once
 #include "PolyGlobals.h"
 #include "PolyScreenImage.h"
-#include "PolyScreenEntity.h"
+#include "PolyUIElement.h"
 
 namespace Polycode {
 	
-	class _PolyExport UIBox : public ScreenEntity {
+	class _PolyExport UIBox : public UIElement {
 	public:
 		UIBox(String imageFile, Number t, Number r, Number b, Number l, Number boxWidth, Number boxHeight);
 		~UIBox();

Modules/Contents/UI/Include/PolyUIHScrollBar.h

@@ -23,10 +23,11 @@
 #pragma once
 #include "PolyGlobals.h"
 #include "PolyUIBox.h"
+#include "PolyUIElement.h"
 
 namespace Polycode {
 	
-	class _PolyExport UIHScrollBar : public ScreenEntity {
+	class _PolyExport UIHScrollBar : public UIElement {
 	public:
 		UIHScrollBar(Number width, Number height, Number initialRatio);
 		~UIHScrollBar();

Modules/Contents/UI/Include/PolyUITree.h

@@ -22,6 +22,7 @@
 
 #pragma once
 #include "PolyGlobals.h"
+#include "PolyUIElement.h"
 #include "PolyScreenLabel.h"
 #include "PolyScreenImage.h"
 #include "PolyScreenShape.h"
@@ -35,8 +36,10 @@ using std::vector;
 
 namespace Polycode {
 
-	class _PolyExport UITree : public ScreenEntity {
+	class _PolyExport UITree : public UIElement {
 		public:
+			using UIElement::Resize;
+
 			UITree(String icon, String text, Number treeWidth, Number treeOffset=0);
 			~UITree();
 			

Modules/Contents/UI/Include/PolyUIVScrollBar.h

@@ -22,12 +22,15 @@
 
 #pragma once
 #include "PolyGlobals.h"
+#include "PolyUIElement.h"
 #include "PolyUIBox.h"
 
 namespace Polycode {
 	
-	class _PolyExport UIVScrollBar : public ScreenEntity {
+	class _PolyExport UIVScrollBar : public UIElement {
 	public:
+		using UIElement::Resize;
+
 		UIVScrollBar(Number width, Number height, Number initialRatio);
 		~UIVScrollBar();
 		

Modules/Contents/UI/Source/PolyUIBox.cpp

@@ -24,7 +24,7 @@
 
 using namespace Polycode;
 
-UIBox::UIBox(String imageFile, Number t, Number r, Number b, Number l, Number boxWidth, Number boxHeight) : ScreenEntity() {
+UIBox::UIBox(String imageFile, Number t, Number r, Number b, Number l, Number boxWidth, Number boxHeight) : UIElement() {
 	
 	setPositionMode(ScreenEntity::POSITION_TOPLEFT);	
 	

Modules/Contents/UI/Source/PolyUIHScrollBar.cpp

@@ -29,7 +29,7 @@
 
 using namespace Polycode;
 
-UIHScrollBar::UIHScrollBar(Number width, Number height, Number initialRatio) : ScreenEntity() {
+UIHScrollBar::UIHScrollBar(Number width, Number height, Number initialRatio) : UIElement() {
 	
 	scrollValue = 0;
 	

Modules/Contents/UI/Source/PolyUITree.cpp

@@ -29,7 +29,7 @@
 
 using namespace Polycode;
 
-UITree::UITree(String icon, String text, Number treeWidth, Number treeOffset) : ScreenEntity() {
+UITree::UITree(String icon, String text, Number treeWidth, Number treeOffset) : UIElement() {
 		
 	processInputEvents = true;
 	willDrag = false;

Modules/Contents/UI/Source/PolyUIVScrollBar.cpp

@@ -30,7 +30,7 @@
 
 using namespace Polycode;
 
-UIVScrollBar::UIVScrollBar(Number width, Number height, Number initialRatio) : ScreenEntity() {
+UIVScrollBar::UIVScrollBar(Number width, Number height, Number initialRatio) : UIElement() {
 
 	scrollValue = 0;