Add XNAListBoxItem.Visible property for support of hiding list box it…

…ems without needing to remove them from the list box

XNAControls/XNAListBox.cs

@@ -497,7 +497,10 @@ private int GetTotalLineCount()
         int lineCount = 0;
 
         foreach (XNAListBoxItem item in Items)
-            lineCount += item.TextLines.Count;
+        {
+            if (item.Visible)
+                lineCount += item.TextLines.Count;
+        }
 
         return lineCount;
     }
@@ -728,6 +731,9 @@ private void ScrollUp()
 
         for (int i = SelectedIndex - 1; i > -1; i--)
         {
+            if (!Items[i].Visible)
+                continue;
+
             if (Items[i].Selectable)
             {
                 SelectedIndex = i;
@@ -750,6 +756,9 @@ private void ScrollDown()
         int scrollLineCount = 1;
         for (int i = SelectedIndex + 1; i < Items.Count; i++)
         {
+            if (!Items[i].Visible)
+                continue;
+
             if (Items[i].Selectable)
             {
                 SelectedIndex = i;
@@ -759,6 +768,7 @@ private void ScrollDown()
                 ScrollBar.RefreshButtonY(ViewTop);
                 return;
             }
+
             scrollLineCount++;
         }
 
@@ -883,6 +893,9 @@ private int GetItemIndexOnCursor(Point mouseLocation)
         {
             XNAListBoxItem lbItem = Items[i];
 
+            if (!lbItem.Visible)
+                continue;
+
             height += lbItem.TextLines.Count * LineHeight;
 
             if (height > mouseLocation.Y)
@@ -998,6 +1011,9 @@ public override void Draw(GameTime gameTime)
         {
             XNAListBoxItem lbItem = Items[i];
 
+            if (!lbItem.Visible)
+                continue;
+
             DrawListBoxItem(i, height);
 
             height += lbItem.TextLines.Count * LineHeight;

XNAControls/XNAListBoxItem.cs

@@ -93,5 +93,11 @@ public float Alpha
         }
     }
 
+    /// <summary>
+    /// Whether this list box item is visible.
+    /// Invisible list box items are not drawn and cannot be selected.
+    /// </summary>
+    public bool Visible { get; set; } = true;
+
     public List<string> TextLines;
 }