Diff: GraphicsDisplay.h

Revision:

143:e872d65a710d

Parent:

142:6e9bff59878a

Child:

151:ae94daaaf8ad

Child:

152:a013ac0133e4

--- a/GraphicsDisplay.h	Sun Mar 19 21:41:24 2017 +0000
+++ b/GraphicsDisplay.h	Sun Mar 19 22:11:04 2017 +0000
@@ -170,9 +170,12 @@
     ///
     /// @param[in] layer is 0 or 1 to select the layer for subsequent 
     ///     commands.
-    /// @returns the previous drawing layer; 0 or 1.
+    /// @param[out] prevLayer is an optiona pointer to where the previous layer
+    ///     will be written, making it a little easer to restore layers.
+    ///     Writes 0 or 1 when the pointer is not NULL.
+    /// @returns success/failure code. See @ref RetCode_t.
     ///
-    virtual uint16_t SelectDrawingLayer(uint16_t layer) = 0;
+    virtual RetCode_t SelectDrawingLayer(uint16_t layer, uint16_t * prevLayer = NULL) = 0;
  
     
     /// Get the currently active drawing layer.
@@ -181,7 +184,8 @@
     /// and the currently active drawing layer.
     ///
     /// @code
-    ///     uint16_t prevLayer = lcd.SelectDrawingLayer(x);
+    ///     uint16_t prevLayer;
+    ///     lcd.SelectDrawingLayer(x, &prevLayer);
     ///     lcd.circle(400,25, 25, BrightRed);
     ///     lcd.SelectDrawingLayer(prevLayer);
     /// @endcode