Internal Redesign:

- Combined MPExpression and MPMutableExpression
- Abstracted children of MPExpression into MPExpressionElement protocol
- Abstracted most of MPExpressionLayout and MPFunctionLayout into common superclass MPLayout

MathPad/MPLayout.m

@@ -0,0 +1,159 @@
+//
+//  MPLayout.m
+//  MathPad
+//
+//  Created by Kim Wittenburg on 11.08.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import "MPLayout.h"
+
+@interface MPLayout ()
+
+// Querying Caches
+- (BOOL)hasCacheForElementAtIndex:(NSUInteger)index;
+
+// Storing Caches
+- (void)cacheObject:(id)anObject
+  forElementAtIndex:(NSUInteger)index;
+- (void)ensureCacheSizeForIndex:(NSUInteger)index;
+
+@end
+
+@implementation MPLayout {
+    NSMutableArray *_cache;
+    NSBezierPath *_cachedPath;
+}
+
+#pragma mark Creation Methods
+- (id)init
+{
+    self = [super init];
+    if (self) {
+        _cache = [[NSMutableArray alloc] init];
+        _cachedPath = nil;
+        _path = [[NSIndexPath alloc] init];
+    }
+    return self;
+}
+
+- (id)initWithPath:(NSIndexPath *)path
+            parent:(MPLayout *)parent
+{
+    self = [self init];
+    if (self) {
+        _path = path;
+        _parent = parent;
+    }
+    return self;
+}
+
+#pragma Text System Objects
+- (MPExpressionStorage *)expressionStorage
+{
+    return self.parent.expressionStorage;
+}
+
+- (NSLayoutManager *)layoutManager
+{
+    return self.expressionStorage.layoutManager;
+}
+
+- (NSTextContainer *)textContainer
+{
+    return self.expressionStorage.textContainer;
+}
+
+- (NSTextStorage *)textStorage
+{
+    return self.expressionStorage.textStorage;
+}
+
+#pragma mark Cache Tree
+// Querying Caches
+- (BOOL)hasCacheForElementAtIndex:(NSUInteger)index
+{
+    if (index >= _cache.count) {
+        return NO;
+    }
+    return _cache[index] != MPNull;
+}
+
+- (id)cachableObjectForIndex:(NSUInteger)index
+                   generator:(id (^)())generator
+{
+    if ([self hasCacheForElementAtIndex:index]) {
+        return _cache[index];
+    }
+    id object = generator();
+    [self cacheObject:object
+    forElementAtIndex:index];
+    return object;
+}
+
+// Storing Caches
+- (void)cacheObject:(id)anObject
+  forElementAtIndex:(NSUInteger)index
+{
+    [self ensureCacheSizeForIndex:index];
+    _cache[index] = anObject;
+}
+
+- (void)ensureCacheSizeForIndex:(NSUInteger)index
+{
+    while (index >= _cache.count) {
+        [_cache addObject:MPNull];
+    }
+}
+
+// Clearing Caches
+- (void)clearCacheInRange:(NSRange)range
+        replacementLength:(NSUInteger)replacementLength
+{
+    NSMutableArray *placeholders = [[NSMutableArray alloc] initWithCapacity:replacementLength];
+    while (placeholders.count < replacementLength) {
+        [placeholders addObject:MPNull];
+    }
+    [_cache replaceObjectsInRange:range
+             withObjectsFromArray:placeholders];
+    [self invalidate];
+}
+
+- (void)invalidate
+{
+    _cachedPath = nil;
+    [self.parent invalidate];
+}
+
+#pragma mark Calculation Methods
+- (NSSize)size
+{
+    return self.bezierPath.bounds.size;
+}
+
+- (NSBezierPath *)bezierPath
+{
+    if (!_cachedPath) {
+        _cachedPath = [self generateBezierPath];
+    }
+    return _cachedPath;
+}
+
+- (NSBezierPath *)bezierPathAtOrigin:(NSPoint)point
+{
+    NSAffineTransform *transform = [NSAffineTransform transform];
+    [transform translateXBy:point.x
+                        yBy:point.y];
+    NSBezierPath *path = [NSBezierPath bezierPath];
+    [path appendBezierPath:self.bezierPath];
+    [path transformUsingAffineTransform:transform];
+    return path;
+}
+
+- (void)drawAtPoint:(NSPoint)point
+{
+    NSBezierPath *path = [self bezierPathAtOrigin:point];
+    [path fill];
+}
+
+@end