Added isOpaque

git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/gui/trunk@5216 72102866-910b-0410-8b05-ffd578937521

Source/NSSliderCell.m

@@ -152,6 +152,11 @@
   [controlView unlockFocus];
 }
 
+- (BOOL) isOpaque
+{
+  return YES;
+}
+
 - (float) knobThickness
 {
   NSImage* image = [_knobCell image];

Source/NSText.m

@@ -3192,7 +3192,20 @@ _relocLayoutArray (NSMutableArray *lineLayoutInformation,
 }
 
 // text lays out from top to bottom
-- (BOOL) isFlipped {return YES;}
+- (BOOL) isFlipped 
+{
+  return YES;
+}
+
+- (BOOL) isOpaque
+{ 
+  if (draws_background == NO 
+      || background_color == nil 
+      || [background_color alphaComponent] < 1.0)
+    return NO;
+  else
+    return YES; 
+}
 
 //
 // Copy and paste