mathpad/MathPad/MPExpressionLayout.m

//
//  MPExpressionLayout.m
//  MathPad
//
//  Created by Kim Wittenburg on 07.08.14.
//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
//

#import "MPExpressionLayout.h"
#import "MPFunctionLayout.h"

@interface MPExpressionLayout (MPLineGeneration)

- (CTLineRef)lineForElementAtIndex:(NSUInteger)index;
- (CTLineRef)createLineForString:(NSString *)aString;

@end

@implementation MPExpressionLayout (MPLineGeneration)

- (CTLineRef)lineForElementAtIndex:(NSUInteger)index
{
    id element = [self.expression elementAtIndex:index];
    if (![element isString]) {
        return NULL;
    }
    NSString *string = element;
    id lineObject = [self cachableObjectForIndex:index generator:^id{
        CTLineRef line = [self createLineForString:string];
        return CFBridgingRelease(line);
    }];
    return (__bridge CTLineRef)lineObject;
}

- (CTLineRef)createLineForString:(NSString *)aString
{
    
    NSAttributedString *text = [[NSAttributedString alloc] initWithString:aString
                                                               attributes:@{NSFontAttributeName: [NSFont fontWithName:@"Lucida Grande" size:18.0]}];
    CFAttributedStringRef attributedString = CFBridgingRetain(text);
    CTLineRef line = CTLineCreateWithAttributedString(attributedString);
    CFRelease(attributedString); // TODO: Is this release appropriate?
    return line;
}

@end

@implementation MPExpressionLayout

# pragma mark Creation Methods
- (instancetype)initRootLayoutWithExpressionStorage:(MPExpressionStorage *)expressionStorage
{
    self = [super init];
    if (self) {
        _expressionStorage = expressionStorage;
        _expression = expressionStorage;
    }
    return self;
}

- (instancetype)initWithPath:(NSIndexPath *)path
                      parent:(MPLayout *)parent
{
    self = [super initWithPath:path
                        parent:parent];
    if (self) {
        _expression = [parent.expressionStorage elementAtIndexPath:path];
    }
    return self;
}

#pragma mark Properties
@synthesize expressionStorage = _expressionStorage;
- (MPExpressionStorage *)expressionStorage
{
    if (_expressionStorage) {
        return _expressionStorage;
    }
    return self.parent.expressionStorage;
}

//- (MPExpression *)expression
//{
//    return [self.expressionStorage elementAtIndexPath:self.path];
//}

#pragma mark Cache Methods
- (MPLayout *)childLayoutAtIndex:(NSUInteger)index
{
    id cachedObject = [self cachableObjectForIndex:index generator:^id{
        NSIndexPath *indexPath = [self.expression.indexPath indexPathByAddingIndex:index];
        MPFunctionLayout *layout = [MPFunctionLayout functionLayoutForFunctionAtIndexPath:indexPath
                                                                                   parent:self];
        return layout;
    }];
    if ([cachedObject isKindOfClass:[MPLayout class]]) {
        return cachedObject;
    }
    return nil;
}

- (NSSize)sizeForElementAtIndex:(NSUInteger)index
{
    id symbol = [self.expression elementAtIndex:index];
    if ([symbol isString]) {
        CTLineRef line = [self lineForElementAtIndex:index];
        CFRetain(line);
        CGRect bounds = CTLineGetBoundsWithOptions(line, /*kCTLineBoundsUseOpticalBounds*/ 0);
        CFRelease(line);
        return bounds.size;
    } else {
        return [self childLayoutAtIndex:index].size;
    }
}

#pragma mark Drawing Methods
- (NSSize)generateSize
{
    CGFloat width = 0, height = 0;
    for (NSUInteger index = 0; index < self.expression.numberOfElements; index++) {
        NSSize elementSize = [self sizeForElementAtIndex:index];
        width += elementSize.width;
        height = MAX(height, elementSize.height);
    }
    return NSMakeSize(width, height);
}

- (void)drawAtPoint:(NSPoint)point
{
    // Get the current context
    CGContextRef context =
        (CGContextRef)[[NSGraphicsContext currentContext] graphicsPort];
    CGContextSaveGState(context);
    
    // Set the text matrix
    CGContextSetTextMatrix(context, CGAffineTransformIdentity);
    
    // Track the x position
    CGFloat x = point.x;
    
    for (NSUInteger index = 0; index < self.expression.numberOfElements; index++) {
        // The current element
        id element = [self.expression elementAtIndex:index];
        NSSize elementSize = [self sizeForElementAtIndex:index];
        CGFloat dy = (self.size.height - elementSize.height) / 2;
        CGFloat y = point.y + dy;
        
        if ([element isString]) {
            // Get the line to draw
            CTLineRef line = [self lineForElementAtIndex:index];
            CFRetain(line);
            
            // Move to the appropriate position
            CGContextSetTextPosition(context, x, y);
                        
            // Perform the drawing
            CTLineDraw(line, context);

            CFRelease(line);
        } else {
            // Let the child layout draw itself
            MPLayout *layout = [self childLayoutAtIndex:index];
            [layout drawAtPoint:NSMakePoint(x, y)];
        }
        x += elementSize.width;
    }
    CGContextRestoreGState(context);
}

@end