mathpad/MathPad/MPLayout.m

//
//  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