Corrected MVC Implementation

MathKit/MPExpressionStorage.h

@@ -21,38 +21,17 @@
 
 /*!
     @class      MPExpressionStorage
-    @abstract   An expression storage manages the contents of an expression view
+    @abstract   An expression storage manages the contents of an expression view.
-                and notifies it when the underlying expression changes.
  */
 @interface MPExpressionStorage : MPExpression
 
-/*!
-    @property   expressionView
-    @abstract   The receiver's expression view.
- 
-    @discussion The expression view is the view that displays the contents of an
-                expression storage. Normally you should not call the setter of
-                this property. It is automatically assigned when the <code>@link
-                //apple_ref/occ/instp/MPExpressionView/expressionStorage@/link</code>
-                property of the respective <code>@link
-                //apple_ref/occ/cl/MPExpressionView@/link</code> instance is set.
- 
-                When this property is set the receiver assumes that the
-                displaying expression view has changed (regardless of wether the
-                actual value of the property changed or not). It then adapts to
-                the properties of the new expression view and discards the
-                current root layout.
- */
-@property (nonatomic, weak) MPExpressionView *expressionView;
-
-
 /*!
     @property   rootLayout
     @abstract   The receiver's root layout.
  
     @discussion The root layout is the root node of the layout tree that draws
-                the receiver's contents. For more information see the
+                the receiver's contents in an expression view. For more
-                documentation on the <code>@link
+                information see the documentation on the <code>@link
                 //apple_ref/occ/cl/MPLayout@/link</code> class.
  */
 @property (nonatomic, strong) MPExpressionLayout *rootLayout;

MathKit/MPExpressionStorage.m

@@ -37,14 +37,6 @@
 }
 
 
-- (void)setExpressionView:(MPExpressionView *)expressionView
-{
-    _expressionView = expressionView;
-    self.rootLayout = [[MPExpressionLayout alloc] initWithExpression:self parent:nil];
-    self.rootLayout.flipped = expressionView.flipped;
-}
-
-
 - (void)changedElementsInRangePath:(MPRangePath *)rangePath
                    replacementLength:(NSUInteger)replacementLength
 {
@@ -58,8 +50,6 @@
     }
     [current clearCacheInRange:rangePath.rangeAtLastIndex
              replacementLength:replacementLength];
-    [self.expressionView invalidateIntrinsicContentSize];
-    self.expressionView.needsDisplay = YES;
 }
 
 @end

MathKit/MPExpressionView.m

@@ -348,7 +348,7 @@
 {
     // Setup the Expression Storage
     MPExpressionStorage *expressionStorage = [[MPExpressionStorage alloc] init];
-    expressionStorage.expressionView = self;
+    expressionStorage.rootLayout.expressionView = self;
     _expressionStorage = expressionStorage;
     
     [self initializeButtons];
@@ -472,9 +472,9 @@
 
 - (void)setExpressionStorage:(MPExpressionStorage *)expressionStorage
 {
-    _expressionStorage.expressionView = nil;
+    _expressionStorage.rootLayout.expressionView = nil;
     _expressionStorage = expressionStorage;;
-    _expressionStorage.expressionView = self;
+    _expressionStorage.rootLayout.expressionView = self;
     [self invalidateIntrinsicContentSize];
 }
 

MathKit/MPLayout.h

@@ -86,7 +86,7 @@
 
 
 
-@class MPLayout, MPRangePath;
+@class MPLayout, MPExpressionView, MPRangePath;
 
 
 /*!
@@ -149,6 +149,21 @@
  */
 
 
+/*!
+    @property   expressionView
+    @abstract   The receiver's expression view.
+ 
+    @discussion The expression view is the view in which the receivin
+                <code>MPLayout</code> instance draws itself into. Normally you
+                should not call the setter of this property. It is automatically
+                assigned when the <code>@link
+                //apple_ref/occ/instp/MPExpressionView/expressionStorage@/link</code>
+                property of the respective <code>@link
+                //apple_ref/occ/cl/MPExpressionView@/link</code> instance is set.
+ */
+@property (nonatomic, weak) MPExpressionView *expressionView;
+
+
 /*!
     @method     font
     @abstract   Returns the receiver's context inferred font.

MathKit/MPLayout.m

@@ -8,6 +8,8 @@
 
 #import "MPLayout.h"
 
+#import "MPExpressionView.h"
+
 #import "MPRangePath.h"
 #import "NSIndexPath+MPAdditions.h"
 
@@ -54,6 +56,14 @@
 #pragma mark Properties
 
 
+- (void)setExpressionView:(MPExpressionView *)expressionView
+{
+    self.flipped = expressionView.flipped;
+    [_cache removeAllObjects];
+    [self invalidate];
+}
+
+
 - (NSFont *)normalFontWithSize:(CGFloat)size
 {
     return [NSFont fontWithName:@"CMU Serif"
@@ -135,6 +145,8 @@
     [_cache replaceObjectsInRange:range
              withObjectsFromArray:placeholders];
     [self invalidate];
+    [self.expressionView invalidateIntrinsicContentSize];
+    self.expressionView.needsDisplay = YES;
 }