fix combobox style and disabled state handling for combobox

res/btn_background_transparent.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <selector xmlns:android="http://schemas.android.com/apk/res/android" >
   <item
-    android:drawable="btn_disabled"
+    android:drawable="@null"
     android:state_enabled="false"/>
   <item
     android:drawable="@null"
@@ -11,7 +11,7 @@
     android:state_pressed="true" />
   <item
     android:drawable="btn_hover"
-    android:state_hovered="true" />
+    android:state_hovered="true" android:state_enabled="true" />
   <item
     android:drawable="@null" />
 </selector>

res/theme_default.xml

@@ -190,6 +190,7 @@
         fontFamily="SansSerif"
         fontSize="16"
         />
+
     <style id="COMBO_BOX"
         backgroundImageId="btn_background"
         padding="2,2,2,2"
@@ -213,6 +214,7 @@
         backgroundImageId="btn_background_transparent"
         align="Center"
         />
+
     <style id="EDIT_BOX"
         backgroundImageId="editbox_background"
         padding="5,6,5,6"

src/dlangui/widgets/combobox.d

@@ -73,8 +73,18 @@ class ComboBoxBase : HorizontalLayout, OnClickHandler {
             onItemClickListener(this, index);
     }
 
+	/// change enabled state
+    override @property Widget enabled(bool flg) { 
+        super.enabled(flg);
+        _button.enabled = flg;
+        return this; 
+    }
+	/// return true if state has State.Enabled flag set
+    override @property bool enabled() { return super.enabled; }
+
     override bool onClick(Widget source) {
-        showPopup();
+        if (enabled)
+            showPopup();
         return true;
     }