Conditional -> GUIObject and make all gui objects children of GUIObject

Signed-off-by: Vojtech Bocek <vbocek@gmail.com>

Change-Id: Ic0a7d6354dabe5919b83942f2f1aa0715625e522
diff --git a/gui/slider.cpp b/gui/slider.cpp
index af0c542..6926765 100644
--- a/gui/slider.cpp
+++ b/gui/slider.cpp
@@ -27,7 +27,7 @@
 #include "rapidxml.hpp"
 #include "objects.hpp"
 
-GUISlider::GUISlider(xml_node<>* node)
+GUISlider::GUISlider(xml_node<>* node) : GUIObject(node)
 {
 	xml_attribute<>* attr;
 	xml_node<>* child;
@@ -93,6 +93,9 @@
 
 int GUISlider::Render(void)
 {
+	if(!isConditionTrue())
+		return 0;
+
 	if (!sSlider || !sSlider->GetResource())
 		return -1;
 
@@ -113,6 +116,9 @@
 
 int GUISlider::Update(void)
 {
+	if(!isConditionTrue())
+		return 0;
+
 	if (sUpdate)
 		return 2;
 	return 0;
@@ -120,6 +126,9 @@
 
 int GUISlider::NotifyTouch(TOUCH_STATE state, int x, int y)
 {
+	if(!isConditionTrue())
+		return -1;
+
 	static bool dragging = false;
 
 	switch (state)