--- a/doodle/tk/pixel_model.d	Sun Aug 15 01:36:22 2010 +0930
+++ b/doodle/tk/pixel_model.d	Sun Aug 15 15:19:14 2010 +0930
@@ -9,6 +9,7 @@
 }
 
 // This class manages the relationship between screen space and model space.
+// Screen is defined as the current window/viewport into the model
 // It provides convenient high-level operations.
 //
 // x and y run right and up respectively for screen and model space
@@ -62,11 +63,11 @@
     private {
         static double clampZoom(in double zoom) { return clamp(zoom, 0.1, 10.0); }
 
-        // Screen units are screens
+        // Screen units are pixels
         // Model units are millimetres
-        double    _zoom;                // screens-per-millimetre
-        Rectangle _viewBoundsScreen;    // bounds of the viewport in screens
-        Point     _viewCentreModel;     // where in the model is the centre of our view
-        Rectangle _canvasBoundsModel;   // the bounds of the canvas in millimetres
+        double    _zoom;                // pixels-per-millimetre
+        Rectangle _viewBoundsScreen;    // bounds of the viewport in screen space
+        Point     _viewCentreModel;     // where in the model is the centre of our screen
+        Rectangle _canvasBoundsModel;   // the bounds of the canvas in model space
     }
 }