Added Function Chooser as a Popover

Improved Evaluation
Added Parenthesis Function

MathPad/MPExpressionLayout.m

@@ -13,6 +13,12 @@
 #import "NSIndexPath+MPAdditions.h"
 
 #define kMPEmptyBoxWidth (self.usesSmallSize ? 2.0 : 3.0)
+#define kMPEmptyBoxHeight (CTFontGetDescent((CTFontRef)self.font) + CTFontGetAscent((CTFontRef)self.font) + CTFontGetLeading((CTFontRef)self.font))
+#define kMPEmptyBoxYOrigin (-(CTFontGetDescent((CTFontRef)self.font) + CTFontGetLeading((CTFontRef)self.font)))
+
+#define kMPEmptyBoxDrawingWidth kMPEmptyBoxWidth
+#define kMPEmptyBoxDrawingHeight (CTFontGetDescent((CTFontRef)self.font) + CTFontGetAscent((CTFontRef)self.font))
+#define kMPEmptyBoxDrawingYOrigin (-(CTFontGetDescent((CTFontRef)self.font) + CTFontGetLeading((CTFontRef)self.font)/2))
 
 @interface MPExpressionLayout (MPLineGeneration)
 
@@ -86,7 +92,7 @@
 - (NSRect)generateBounds
 {
     if (self.expression.numberOfElements == 0) {
-        return NSMakeRect(0, [self.font descender], kMPEmptyBoxWidth, self.fontSize);
+        return NSMakeRect(0, kMPEmptyBoxYOrigin, kMPEmptyBoxWidth, kMPEmptyBoxHeight);
     }
     CGFloat x = 0, y = 0, width = 0, height = 0;
     for (NSUInteger index = 0; index < self.expression.numberOfElements; index++) {
@@ -211,10 +217,23 @@
         (CGContextRef)[[NSGraphicsContext currentContext] graphicsPort];
     CGContextSaveGState(context);
     
+#ifdef MPDEBUG_DRAW_ORIGIN
+    [[NSColor blueColor] set];
+    [[NSBezierPath bezierPathWithOvalInRect:NSMakeRect(-2, -2, 4, 4)] fill];
+#endif
+    
+    [[NSColor textColor] set];
+    
+#ifdef MPDEBUG_DRAW_BOUNDS
+        [[NSColor greenColor] set];
+        [[NSBezierPath bezierPathWithRect:self.bounds] stroke];
+        [[NSColor textColor] set];
+#endif
+
     if (self.expression.numberOfElements == 0) {
         
         CGContextRestoreGState(context);
-        NSBezierPath *path = [NSBezierPath bezierPathWithRect:NSMakeRect(0, 0 + self.font.descender, kMPEmptyBoxWidth, self.fontSize)];
+        NSBezierPath *path = [NSBezierPath bezierPathWithRect:NSMakeRect(0, kMPEmptyBoxDrawingYOrigin, kMPEmptyBoxDrawingWidth, kMPEmptyBoxDrawingHeight)];
         path.lineWidth = 0.5;
         [path stroke];
         return;
@@ -238,10 +257,16 @@
             
             // Move to the appropriate position
             CGContextSetTextPosition(context, x, 0);
-                        
+
+#ifdef MPDEBUG_DRAW_BASELINE
+            [[NSColor redColor] set];
+            NSRectFill(NSMakeRect(x, -1, elementBounds.size.width, 1));
+            [[NSColor textColor] set];
+#endif
+            
             // Perform the drawing
             CTLineDraw(line, context);
-
+            
             CFRelease(line);
         } else {
             // Let the child layout draw itself

MathPad/MPExpressionStorage.m

@@ -50,6 +50,7 @@
     [current clearCacheInRange:rangePath.rangeAtLastIndex
              replacementLength:replacementLength];
     [self.expressionView invalidateIntrinsicContentSize];
+    self.expressionView.error = nil;
     self.expressionView.needsDisplay = YES;
 }
 

MathPad/MPExpressionView.h

@@ -10,6 +10,8 @@
 
 #import <Cocoa/Cocoa.h>
 
+#import "MPParseError.h"
+
 @class MPExpressionView, MPExpressionStorage, MPExpressionLayout, MPRangePath;
 
 @interface MPExpressionView : NSView
@@ -23,7 +25,10 @@
 @property (readonly, nonatomic, strong) MPExpressionStorage *expressionStorage;
 
 // @property (nonatomic, getter = isEditable) BOOL editable;
+@property (nonatomic) BOOL allowsIntelligentReplacements;
+
 @property (nonatomic, strong) MPRangePath *selection;
+@property (nonatomic, strong) MPParseError *error;
 
 @property (nonatomic, weak) id target;
 @property (nonatomic) SEL action;

MathPad/MPExpressionView.m

@@ -16,12 +16,17 @@
 #import "NSIndexPath+MPAdditions.h"
 
 #import "MPSumFunction.h"
+#import "MPParenthesisFunction.h"
+#import "MPParenthesisFunctionLayout.h"
 
+#import "MPFunctionsViewController.h"
 
 
 @interface MPExpressionView ()
 
 @property (nonatomic, weak) NSButton *functionsButton;
+@property (nonatomic, strong) NSPopover *functionsPopover;
+@property (nonatomic, strong) MPFunctionsViewController *functionsViewController;
 
 @property (nonatomic, strong) NSTimer *caretTimer;
 @property (nonatomic) NSTimeInterval caretBlinkRate;
@@ -303,7 +308,7 @@
 - (void)initializeExpressionView
 {
     // Setup the Expression Storage
-    MPExpressionStorage *expressionStorage = [[MPExpressionStorage alloc] initWithElements:@[@"12345", [[MPSumFunction alloc] init], [[MPSumFunction alloc] init]]];
+    MPExpressionStorage *expressionStorage = [[MPExpressionStorage alloc] init];
     expressionStorage.expressionView = self;
     _expressionStorage = expressionStorage;
     
@@ -347,18 +352,40 @@
     self.needsDisplay = YES;
 }
 
+- (void)setError:(MPParseError *)error
+{
+    _error = error;
+    self.needsDisplay = YES;
+}
+
 #pragma mark Actions
 - (void)showFunctions:(id)sender
 {
-    NSViewController *controller = [[NSViewController alloc] initWithNibName:nil
+    if (self.functionsPopover == nil || self.functionsViewController == nil) {
-                                                                      bundle:nil];
+        self.functionsViewController = [[MPFunctionsViewController alloc] init];
-    controller.view = [[NSView alloc] init];
+        self.functionsViewController.target = self;
-    NSPopover *popover = [[NSPopover alloc] init];
+        self.functionsViewController.action = @selector(insertFunction:);
-    popover.contentSize = NSMakeSize(100.0, 100.0);
+        self.functionsPopover = [[NSPopover alloc] init];
-    popover.contentViewController = controller;
+        self.functionsPopover.contentViewController = self.functionsViewController;
-    popover.animates = YES;
+        self.functionsPopover.animates = YES;
-    popover.behavior = NSPopoverBehaviorSemitransient;
+        self.functionsPopover.behavior = NSPopoverBehaviorSemitransient;
-    [popover showRelativeToRect:[sender bounds] ofView:sender preferredEdge:NSMaxYEdge];
+    }
+    if (self.functionsPopover.isShown) {
+        [self.functionsPopover close];
+    } else {
+        [self.functionsPopover showRelativeToRect:[sender bounds] ofView:sender preferredEdge:NSMaxYEdge];
+    }
+}
+
+- (void)insertFunction:(MPFunction *)function
+{
+    [self.functionsPopover close];
+    [self.expressionStorage replaceSymbolsInRangePath:self.selection withElements:@[function]];
+    MPExpression *targetExpression = [self.expressionStorage elementAtIndexPath:[self.selection.location indexPathByRemovingLastIndex]];
+    NSIndexPath *functionPath = [self.selection.location indexPathByReplacingLastIndexWithIndex:[targetExpression indexOfElementAtLocation:self.selection.location.lastIndex
+                                                                                                                                    offset:NULL]];
+    MPFunctionLayout *functionLayout = (MPFunctionLayout *)[self.expressionStorage.rootLayout childLayoutAtIndexPath:functionPath];
+    self.selection = MPMakeRangePath([[functionPath indexPathByAddingIndex:functionLayout.indexOfLeadingChild] indexPathByAddingIndex:0], 0);
 }
 
 #pragma mark NSView Stuff
@@ -372,6 +399,20 @@
     return YES;
 }
 
+- (BOOL)becomeFirstResponder
+{
+    [self restartCaretTimer];
+    return [super becomeFirstResponder];
+}
+
+- (BOOL)resignFirstResponder
+{
+    [self.caretTimer invalidate];
+    self.caretVisible = NO;
+    self.needsDisplay = YES;
+    return [super resignFirstResponder];
+}
+
 - (BOOL)isFlipped
 {
     return NO;
@@ -415,17 +456,40 @@
 - (void)keyDown:(NSEvent *)theEvent
 {
     NSString *characters = theEvent.characters;
+    
+    if ([characters isEqualToString:@"("]) {
+        [self insertParenthesisFunction];
+        return;
+    }
+    
+    
+    
+    NSString *decimalSeparator = [NSRegularExpression escapedPatternForString:[[NSLocale currentLocale] objectForKey:NSLocaleDecimalSeparator]];
     NSMutableCharacterSet *allowedCharacters = [NSMutableCharacterSet alphanumericCharacterSet];
-    [allowedCharacters addCharactersInString:@"+-*= "];
+    [allowedCharacters addCharactersInString:[NSString stringWithFormat:@"+-*= %@", decimalSeparator]];
+    
     if (characters.length == 1 && [characters stringByTrimmingCharactersInSet:allowedCharacters].length == 0) {
-        MPExpression *targetExpression = [self.expressionStorage elementAtIndexPath:[self.selection.location indexPathByRemovingLastIndex]];
+        [self.expressionStorage replaceSymbolsInRangePath:self.selection withElements:@[characters]];
-        [targetExpression replaceSymbolsInRange:self.selection.rangeAtLastIndex withElements:@[characters]];
         self.selection = MPMakeRangePath([self.selection.location indexPathByIncrementingLastIndex], 0);
     } else {
         [self interpretKeyEvents:@[theEvent]];
     }
 }
 
+- (void)insertParenthesisFunction
+{
+    MPExpression *selectedElementsExpression = [self.expressionStorage subexpressionWithRangePath:self.selection];
+    MPParenthesisFunction *function = [[MPParenthesisFunction alloc] init];
+    function.expression = selectedElementsExpression;
+    [self.expressionStorage replaceSymbolsInRangePath:self.selection
+                                         withElements:@[function]];
+    
+    MPExpression *targetExpression = [self.expressionStorage elementAtIndexPath:[self.selection.location indexPathByRemovingLastIndex]];
+    NSIndexPath *functionPath = [self.selection.location indexPathByReplacingLastIndexWithIndex:[targetExpression indexOfElementAtLocation:self.selection.location.lastIndex
+                                                                                                                                    offset:NULL]];
+    self.selection = MPMakeRangePath([[functionPath indexPathByAddingIndex:0] indexPathByAddingIndex:0], self.selection.length);
+}
+
 - (void)insertNewline:(id)sender
 {
     if (self.target && self.action) {
@@ -571,6 +635,30 @@
     self.selection = MPMakeRangePath(location, maxLocation.lastIndex-location.lastIndex);
 }
 
+- (void)moveUp:(id)sender
+{
+    NSIndexPath *targetExpressionPath = [self.selection.location indexPathByRemovingLastIndex];
+    MPExpression *targetExpression = [self.expressionStorage elementAtIndexPath:targetExpressionPath];
+    if (targetExpression.parent != nil) {
+        NSIndexPath *functionPath = [targetExpressionPath indexPathByRemovingLastIndex];
+        MPFunctionLayout *functionLayout = (MPFunctionLayout *)[self.expressionStorage.rootLayout childLayoutAtIndexPath:functionPath];
+        NSUInteger newChildIndex = [functionLayout indexOfChildAboveChildAtIndex:targetExpressionPath.lastIndex];
+        self.selection = MPMakeRangePath([[targetExpressionPath indexPathByReplacingLastIndexWithIndex:newChildIndex] indexPathByAddingIndex:0], 0);
+    }
+}
+
+- (void)moveDown:(id)sender
+{
+    NSIndexPath *targetExpressionPath = [self.selection.location indexPathByRemovingLastIndex];
+    MPExpression *targetExpression = [self.expressionStorage elementAtIndexPath:targetExpressionPath];
+    if (targetExpression.parent != nil) {
+        NSIndexPath *functionPath = [targetExpressionPath indexPathByRemovingLastIndex];
+        MPFunctionLayout *functionLayout = (MPFunctionLayout *)[self.expressionStorage.rootLayout childLayoutAtIndexPath:functionPath];
+        NSUInteger newChildIndex = [functionLayout indexOfChildBelowChildAtIndex:targetExpressionPath.lastIndex];
+        self.selection = MPMakeRangePath([[targetExpressionPath indexPathByReplacingLastIndexWithIndex:newChildIndex] indexPathByAddingIndex:0], 0);
+    }
+}
+
 - (void)selectAll:(id)sender
 {
     NSIndexPath *location = [NSIndexPath indexPathWithIndex:0];
@@ -579,13 +667,42 @@
 
 - (void)deleteBackward:(id)sender
 {
-    MPExpression *targetExpression = [self.expressionStorage elementAtIndexPath:[self.selection.location indexPathByRemovingLastIndex]];
     if (self.selection.length > 0) {
-        [targetExpression replaceSymbolsInRange:self.selection.rangeAtLastIndex withElements:@[]];
+        [self.expressionStorage replaceSymbolsInRangePath:self.selection withElements:@[]];
         self.selection = MPMakeRangePath(self.selection.location, 0);
     } else if (self.selection.location.lastIndex > 0) {
-        [targetExpression replaceSymbolsInRange:NSMakeRange(self.selection.location.lastIndex-1, 1) withElements:@[]];
+        MPExpression *targetExpression = [self.expressionStorage elementAtIndexPath:[self.selection.location indexPathByRemovingLastIndex]];
-        self.selection = MPMakeRangePath([self.selection.location indexPathByDecrementingLastIndex], 0);
+        id <MPExpressionElement> elementToDelete = [targetExpression elementAtIndex:[targetExpression indexOfElementAtLocation:self.selection.location.lastIndex-1
+                                                                                                                        offset:NULL]];
+        if ([elementToDelete isFunction]) {
+            self.selection = MPMakeRangePath(self.selection.location.indexPathByDecrementingLastIndex, 1);
+        } else {
+            [targetExpression replaceSymbolsInRange:NSMakeRange(self.selection.location.lastIndex-1, 1) withElements:@[]];
+            self.selection = MPMakeRangePath([self.selection.location indexPathByDecrementingLastIndex], 0);
+        }
+    } else {
+        NSIndexPath *targetExpressionPath = [self.selection.location indexPathByRemovingLastIndex];
+        MPExpression *targetExpression = [self.expressionStorage elementAtIndexPath:targetExpressionPath];
+        if (targetExpression.parent != nil) {
+            NSIndexPath *functionPath = [targetExpressionPath indexPathByRemovingLastIndex];
+            MPFunction *function = [self.expressionStorage elementAtIndexPath:functionPath];
+            MPFunctionLayout *functionLayout = (MPFunctionLayout *)[self.expressionStorage.rootLayout childLayoutAtIndexPath:functionPath];
+            NSIndexSet *remainingIndexes = [functionLayout indexesOfRemainingChildren];
+            
+            NSMutableArray *remainder = [[NSMutableArray alloc] init];
+            for (NSUInteger index = remainingIndexes.firstIndex;
+                 index <= remainingIndexes.lastIndex;
+                 index = [remainingIndexes indexGreaterThanIndex:index]) {
+                [remainder addObjectsFromArray:[function childAtIndex:index].elements];
+            }
+            
+            NSIndexPath *newTargetExpressionPath = [functionPath indexPathByRemovingLastIndex];
+            MPExpression *newTargetExpression = [self.expressionStorage elementAtIndexPath:newTargetExpressionPath];
+            NSIndexPath *newSelectionLocation = [functionPath indexPathByReplacingLastIndexWithIndex:[newTargetExpression locationOfElementAtIndex:functionPath.lastIndex]];
+            
+            [self.expressionStorage replaceSymbolsInRangePath:MPMakeRangePath(functionPath, 1) withElements:remainder];
+            self.selection = MPMakeRangePath(newSelectionLocation, 0);
+        }
     }
 }
 
@@ -626,6 +743,11 @@
     // Calculate the position of the expression (probably also forces layout of the expression the first time)
     NSPoint expressionOrigin = self.expressionOrigin;
     
+    NSAffineTransform *transform = [NSAffineTransform transform];
+    [transform translateXBy:expressionOrigin.x
+                        yBy:expressionOrigin.y];
+    [transform concat];
+    
     // Draw the selection
     if (self.caretVisible || self.selection.length > 0) {
         if (self.selection.length == 0) {
@@ -633,15 +755,12 @@
         } else {
             [[NSColor selectedTextBackgroundColor] set];
         }
-        NSAffineTransform *transform = [NSAffineTransform transform];
-        [transform translateXBy:expressionOrigin.x
-                            yBy:expressionOrigin.y];
-        [transform concat];
         NSRectFill([self selectionRect]);
-        [transform invert];
-        [transform concat];
     }
     
+    [transform invert];
+    [transform concat];
+    
     // Draw the expression
     [[NSColor textColor] set];
     [self.expressionStorage.rootLayout drawAtPoint:expressionOrigin];

MathPad/MPFunctionLayout.h

@@ -26,6 +26,8 @@
 #pragma mark Cache Methods
 - (CTLineRef)lineForPrivateCacheIndex:(NSUInteger)index
                             generator:(CTLineRef (^)())generator;
+- (id)objectForPrivateCacheIndex:(NSUInteger)index
+                       generator:(id (^)())generator;
 
 // Should also implement accessor method for special function type:
 // - (MPCustomFunction *)customFunction
@@ -34,10 +36,12 @@
 // }
 
 #pragma mark Size and Drawing Methods
+- (BOOL)childAtIndexUsesSmallSize:(NSUInteger)index; // May be implemented
 - (NSPoint)offsetOfChildLayoutAtIndex:(NSUInteger)index; // To be implemented
-- (NSIndexPath *)indexPathForMousePoint:(NSPoint)point; // To be implemented
+- (NSIndexPath *)indexPathForMousePoint:(NSPoint)point;
+- (NSIndexPath *)indexPathForLocalMousePoint:(NSPoint)point; // To be implemented
 - (NSRect)generateBounds; // To be implemented
-- (void)drawAtPoint:(NSPoint)point; // To be implemented
+- (void)draw; // To be implemented
 
 // Specify the child that is used when the cursor enters the function from the left or right respectively
 - (NSUInteger)indexOfLeadingChild; // To be implemented
@@ -46,5 +50,8 @@
 // The index of the child before (left) or after (right) the child at @c index. return NSNotFound if there is no child before or after @c index.
 - (NSUInteger)indexOfChildBeforeChildAtIndex:(NSUInteger)index; // May be implemented
 - (NSUInteger)indexOfChildAfterChildAtIndex:(NSUInteger)index; // May be implemented
+- (NSUInteger)indexOfChildBelowChildAtIndex:(NSUInteger)index; // May be implemented
+- (NSUInteger)indexOfChildAboveChildAtIndex:(NSUInteger)index; // May be implemented
+- (NSIndexSet *)indexesOfRemainingChildren; // May be implemented
 
 @end

MathPad/MPFunctionLayout.m

@@ -12,6 +12,10 @@
 
 #import "MPSumFunction.h"
 #import "MPSumFunctionLayout.h"
+#import "MPParenthesisFunction.h"
+#import "MPParenthesisFunctionLayout.h"
+
+#import "NSIndexPath+MPAdditions.h"
 
 @implementation MPFunctionLayout
 
@@ -22,6 +26,8 @@
     Class class = [function class];
     if (class == [MPSumFunction class]) {
         return [[MPSumFunctionLayout alloc] initWithFunction:function parent:parent];
+    } else if (class == [MPParenthesisFunction class]) {
+        return [[MPParenthesisFunctionLayout alloc] initWithFunction:function parent:parent];
     }
     return [[self alloc] initWithFunction:function
                                    parent:parent];
@@ -51,6 +57,13 @@
     return (__bridge CTLineRef)(lineObject);
 }
 
+- (id)objectForPrivateCacheIndex:(NSUInteger)index
+                       generator:(id (^)())generator
+{
+    NSUInteger actualIndex = self.function.numberOfChildren + index;
+    return [self cachableObjectForIndex:actualIndex generator:generator];
+}
+
 - (MPLayout *)childLayoutAtIndex:(NSUInteger)index
 {
     return [self cachableObjectForIndex:index generator:^id{
@@ -58,11 +71,36 @@
         MPExpressionLayout *layout = [[MPExpressionLayout alloc] initWithExpression:child
                                                                              parent:self];
         layout.flipped = self.flipped;
-        layout.usesSmallSize = (index == 0 || index == 1) ? YES : self.usesSmallSize;
+        layout.usesSmallSize = self.usesSmallSize ? YES : [self childAtIndexUsesSmallSize:index];
         return layout;
     }];
 }
 
+- (BOOL)childAtIndexUsesSmallSize:(NSUInteger)index
+{
+    return NO;
+}
+
+- (NSIndexPath *)indexPathForMousePoint:(NSPoint)point
+{
+    // A single index is used to communicate back wether the
+    // selection should be before or after the function.
+    // A 0 means before, a 1 means after.
+    for (NSUInteger index = 0; index < self.function.numberOfChildren; index++) {
+        MPLayout *childLayout = [self childLayoutAtIndex:index];
+        NSRect childBounds = childLayout.bounds;
+        NSPoint childOffset = [self offsetOfChildLayoutAtIndex:index];
+        childBounds.origin.x += childOffset.x;
+        childBounds.origin.y += childOffset.y;
+        if (NSMouseInRect(point, childBounds, self.flipped)) {
+            NSPoint pointInChild = NSMakePoint(point.x - childOffset.x, point.y - childOffset.y);
+            NSIndexPath *subPath = [childLayout indexPathForMousePoint:pointInChild];
+            return [subPath indexPathByPreceedingIndex:index];
+        }
+    }
+    return [self indexPathForLocalMousePoint:point];
+}
+
 - (NSUInteger)indexOfChildBeforeChildAtIndex:(NSUInteger)index
 {
     return NSNotFound;
@@ -73,4 +111,19 @@
     return NSNotFound;
 }
 
+- (NSUInteger)indexOfChildBelowChildAtIndex:(NSUInteger)index
+{
+    return index;
+}
+
+- (NSUInteger)indexOfChildAboveChildAtIndex:(NSUInteger)index
+{
+    return index;
+}
+
+- (NSIndexSet *)indexesOfRemainingChildren
+{
+    return [NSIndexSet indexSet];
+}
+
 @end

MathPad/MPFunctionsViewController.h

@@ -0,0 +1,24 @@
+//
+//  MPFunctionsViewController.h
+//  MathPad
+//
+//  Created by Kim Wittenburg on 28.09.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import <Cocoa/Cocoa.h>
+
+@class MPFunctionsCollectionView;
+
+@interface MPFunctionsViewController : NSViewController
+
+- (id)init;
+
+@property (weak) IBOutlet MPFunctionsCollectionView *collectionView;
+@property (nonatomic, strong) NSArray *functionPrototypes;
+@property (nonatomic, strong) NSString *currentDescription;
+
+@property (nonatomic, weak) id target;
+@property (nonatomic) SEL action; // 1 argument: The function to insert
+
+@end

MathPad/MPFunctionsViewController.m

@@ -0,0 +1,252 @@
+//
+//  MPFunctionsViewController.m
+//  MathPad
+//
+//  Created by Kim Wittenburg on 28.09.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import "MPFunctionsViewController.h"
+#import "MPFunction.h"
+#import "MPFunctionLayout.h"
+
+#import "MPSumFunction.h"
+#import "MPParenthesisFunction.h"
+
+
+@class MPFunctionTemplatePrototype;
+
+@interface MPFunctionsCollectionView : NSCollectionView
+
+@property (nonatomic, weak) MPFunctionTemplatePrototype *hoverItem;
+
+@property (nonatomic, weak) id target;
+@property (nonatomic) SEL action;
+
+@end
+
+
+@interface MPFunctionTemplateView : NSView
+
+@property (nonatomic, strong) MPFunction *functionTemplate;
+@property (readonly, nonatomic, strong) MPFunctionLayout *functionTemplateLayout;
+@property (nonatomic, strong) NSTrackingArea *trackingArea;
+@property (nonatomic) BOOL mouseOver;
+
+@end
+
+
+
+@interface MPFunctionTemplatePrototype : NSCollectionViewItem
+@end
+
+
+@implementation MPFunctionsCollectionView
+
+- (void)mouseDown:(NSEvent *)theEvent
+{
+}
+
+- (void)mouseUp:(NSEvent *)theEvent
+{
+    NSPoint pointInView = [self convertPoint:theEvent.locationInWindow
+                                    fromView:nil];
+    for (NSUInteger index = 0; index < self.content.count; index++) {
+        NSCollectionViewItem *viewItem = [self itemAtIndex:index];
+        if (NSMouseInRect(pointInView, viewItem.view.frame, self.isFlipped)) {
+            if (self.target && self.action) {
+                [self.target performSelector:self.action
+                                  withObject:[viewItem.representedObject copy]
+                                  afterDelay:0.0];
+            }
+            break;
+        }
+    }
+}
+
+@end
+
+
+
+@implementation MPFunctionTemplateView
+
+- (void)updateTrackingAreas
+{
+    if (!self.trackingArea) {
+        self.trackingArea = [[NSTrackingArea alloc] initWithRect:self.bounds
+                                                         options:NSTrackingMouseEnteredAndExited|NSTrackingActiveInKeyWindow|NSTrackingInVisibleRect
+                                                           owner:self
+                                                        userInfo:nil];
+        [self addTrackingArea:self.trackingArea];
+    }
+    [super updateTrackingAreas];
+}
+
+- (void)mouseEntered:(NSEvent *)theEvent
+{
+    self.mouseOver = YES;
+    self.needsDisplay = YES;
+}
+
+- (void)mouseExited:(NSEvent *)theEvent
+{
+    self.mouseOver = NO;
+    self.needsDisplay = YES;
+}
+
+- (void)setFunctionTemplate:(MPFunction *)functionTemplate
+{
+    _functionTemplate = functionTemplate;
+    _functionTemplateLayout = nil;
+}
+
+@synthesize functionTemplateLayout = _functionTemplateLayout;
+- (MPFunctionLayout *)functionTemplateLayout
+{
+    if (!_functionTemplateLayout) {
+        _functionTemplateLayout = [MPFunctionLayout functionLayoutForFunction:self.functionTemplate
+                                                                       parent:nil];
+        _functionTemplateLayout.usesSmallSize = YES;
+    }
+    return _functionTemplateLayout;
+}
+
+- (NSSize)intrinsicContentSize
+{
+    return [self.functionTemplateLayout bounds].size;
+}
+
+- (BOOL)isOpaque
+{
+    return NO;
+}
+
+- (void)drawRect:(NSRect)dirtyRect
+{
+    if (self.mouseOver) {
+        [[NSColor selectedTextBackgroundColor] set];
+        NSBezierPath *background = [NSBezierPath bezierPathWithRoundedRect:self.bounds
+                                                                   xRadius:10
+                                                                   yRadius:10];
+        [background fill];
+    }
+    [[NSColor textColor] set];
+    NSPoint origin = NSMakePoint((self.bounds.size.width - self.functionTemplateLayout.bounds.size.width) / 2, (self.bounds.size.height - self.functionTemplateLayout.bounds.size.height) / 2);
+    origin.y -= self.functionTemplateLayout.bounds.origin.y;
+    [self.functionTemplateLayout drawAtPoint:origin];
+}
+
+@end
+
+
+
+@implementation MPFunctionTemplatePrototype
+
+static void *MPFunctionTemplateViewMouseOverContext = @"MPFunctionTemplateViewMouseOverContext";
+
+- (id)initWithCoder:(NSCoder *)aDecoder
+{
+    self = [super initWithCoder:aDecoder];
+    if (self) {
+        MPFunctionTemplateView *view = (MPFunctionTemplateView *)self.view;
+        [view addObserver:self
+               forKeyPath:@"mouseOver"
+                  options:0
+                  context:MPFunctionTemplateViewMouseOverContext];
+    }
+    return self;
+}
+
+- (void)observeValueForKeyPath:(NSString *)keyPath
+                      ofObject:(id)object
+                        change:(NSDictionary *)change
+                       context:(void *)context
+{
+    if (context == MPFunctionTemplateViewMouseOverContext) {
+        MPFunctionTemplateView *view = (MPFunctionTemplateView *)self.view;
+        ((MPFunctionsCollectionView *)self.collectionView).hoverItem = view.mouseOver ? self : nil;
+    } else {
+        [super observeValueForKeyPath:keyPath
+                             ofObject:object
+                               change:change
+                              context:context];
+    }
+}
+
+- (void)setRepresentedObject:(id)representedObject
+{
+    [super setRepresentedObject:representedObject];
+    ((MPFunctionTemplateView *)self.view).functionTemplate = representedObject;
+}
+
+@end
+
+
+
+@interface MPFunctionsViewController ()
+
+@end
+
+@implementation MPFunctionsViewController
+
+- (id)init
+{
+    return [self initWithNibName:@"MPFunctionsViewController"
+                          bundle:[NSBundle bundleForClass:[self class]]];
+}
+
+- (id)initWithNibName:(NSString *)nibNameOrNil
+               bundle:(NSBundle *)nibBundleOrNil
+{
+    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
+    if (self) {
+        self.functionPrototypes = @[[[MPSumFunction alloc] init], [[MPParenthesisFunction alloc] init]];
+    }
+    return self;
+}
+
+static void *MPCollectionViewHoverItemChangeContext = @"MPCollectionViewHoverItemChangeContext";
+
+- (void)loadView
+{
+    [super loadView];
+    [self.collectionView addObserver:self
+                          forKeyPath:@"hoverItem"
+                             options:0
+                             context:MPCollectionViewHoverItemChangeContext];
+    self.collectionView.target = self.target;
+    self.collectionView.action = self.action;
+}
+
+- (void)setTarget:(id)target
+{
+    _target = target;
+    if (self.collectionView) {
+        self.collectionView.target = target;
+    }
+}
+
+- (void)setAction:(SEL)action
+{
+    _action = action;
+    if (self.collectionView) {
+        self.collectionView.action = action;
+    }
+}
+
+- (void)observeValueForKeyPath:(NSString *)keyPath
+                      ofObject:(id)object
+                        change:(NSDictionary *)change
+                       context:(void *)context
+{
+    if (context == MPCollectionViewHoverItemChangeContext) {
+        self.currentDescription = [[self.collectionView.hoverItem.representedObject class] performSelector:@selector(localizedFunctionName)];
+    } else {
+        [super observeValueForKeyPath:keyPath
+                             ofObject:object
+                               change:change
+                              context:context];
+    }
+}
+
+@end

MathPad/MPFunctionsViewController.xib

@@ -0,0 +1,83 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="6245" systemVersion="13F34" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES">
+    <dependencies>
+        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="6245"/>
+    </dependencies>
+    <objects>
+        <customObject id="-2" userLabel="File's Owner" customClass="MPFunctionsViewController">
+            <connections>
+                <outlet property="collectionView" destination="QmA-Ge-oq3" id="mYG-bs-5TG"/>
+                <outlet property="view" destination="Hz6-mo-xeY" id="0bl-1N-x8E"/>
+            </connections>
+        </customObject>
+        <customObject id="-1" userLabel="First Responder" customClass="FirstResponder"/>
+        <customObject id="-3" userLabel="Application" customClass="NSObject"/>
+        <customView id="Hz6-mo-xeY" customClass="MPWhiteView">
+            <rect key="frame" x="0.0" y="0.0" width="320" height="185"/>
+            <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
+            <subviews>
+                <scrollView borderType="none" autohidesScrollers="YES" horizontalLineScroll="10" horizontalPageScroll="10" verticalLineScroll="10" verticalPageScroll="10" usesPredominantAxisScrolling="NO" translatesAutoresizingMaskIntoConstraints="NO" id="9w0-UQ-Fqx">
+                    <rect key="frame" x="10" y="25" width="300" height="150"/>
+                    <clipView key="contentView" copiesOnScroll="NO" id="Z8C-m4-8Mb">
+                        <rect key="frame" x="1" y="1" width="248" height="158"/>
+                        <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                        <subviews>
+                            <collectionView selectable="YES" id="QmA-Ge-oq3" customClass="MPFunctionsCollectionView">
+                                <rect key="frame" x="0.0" y="0.0" width="248" height="158"/>
+                                <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+                                <color key="primaryBackgroundColor" name="controlBackgroundColor" catalog="System" colorSpace="catalog"/>
+                                <connections>
+                                    <binding destination="-2" name="content" keyPath="functionPrototypes" id="sPD-4B-zL5"/>
+                                    <outlet property="itemPrototype" destination="4Wf-e2-Nmy" id="v9O-tD-Y7U"/>
+                                </connections>
+                            </collectionView>
+                        </subviews>
+                    </clipView>
+                    <scroller key="horizontalScroller" hidden="YES" verticalHuggingPriority="750" horizontal="YES" id="umr-K7-88h">
+                        <rect key="frame" x="1" y="144" width="233" height="15"/>
+                        <autoresizingMask key="autoresizingMask"/>
+                    </scroller>
+                    <scroller key="verticalScroller" hidden="YES" verticalHuggingPriority="750" doubleValue="1" horizontal="NO" id="MEs-Qt-Wze">
+                        <rect key="frame" x="234" y="1" width="15" height="143"/>
+                        <autoresizingMask key="autoresizingMask"/>
+                    </scroller>
+                </scrollView>
+                <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" translatesAutoresizingMaskIntoConstraints="NO" id="D89-Gi-YJm">
+                    <rect key="frame" x="-2" y="0.0" width="324" height="17"/>
+                    <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" alignment="center" title="Description" id="xrL-Xy-aRm">
+                        <font key="font" metaFont="system"/>
+                        <color key="textColor" name="disabledControlTextColor" catalog="System" colorSpace="catalog"/>
+                        <color key="backgroundColor" name="controlColor" catalog="System" colorSpace="catalog"/>
+                    </textFieldCell>
+                    <connections>
+                        <binding destination="-2" name="value" keyPath="currentDescription" id="0Vx-OA-1Zy">
+                            <dictionary key="options">
+                                <string key="NSNullPlaceholder">Choose an Element</string>
+                            </dictionary>
+                        </binding>
+                    </connections>
+                </textField>
+            </subviews>
+            <constraints>
+                <constraint firstAttribute="bottom" secondItem="D89-Gi-YJm" secondAttribute="bottom" id="6QP-Uy-i2A"/>
+                <constraint firstItem="9w0-UQ-Fqx" firstAttribute="leading" secondItem="Hz6-mo-xeY" secondAttribute="leading" constant="10" id="GOC-rC-AE6"/>
+                <constraint firstItem="9w0-UQ-Fqx" firstAttribute="centerX" secondItem="D89-Gi-YJm" secondAttribute="centerX" id="Qk9-hA-Jcj"/>
+                <constraint firstItem="9w0-UQ-Fqx" firstAttribute="top" secondItem="Hz6-mo-xeY" secondAttribute="top" constant="10" id="RFi-H1-0CV"/>
+                <constraint firstItem="D89-Gi-YJm" firstAttribute="leading" secondItem="Hz6-mo-xeY" secondAttribute="leading" id="Rup-Ep-vEV"/>
+                <constraint firstItem="D89-Gi-YJm" firstAttribute="top" secondItem="9w0-UQ-Fqx" secondAttribute="bottom" constant="8" symbolic="YES" id="xGL-ZL-fb1"/>
+                <constraint firstAttribute="trailing" secondItem="9w0-UQ-Fqx" secondAttribute="trailing" constant="10" id="zb3-nc-Iai"/>
+            </constraints>
+            <point key="canvasLocation" x="-101" y="140.5"/>
+        </customView>
+        <collectionViewItem id="4Wf-e2-Nmy" customClass="MPFunctionTemplatePrototype">
+            <connections>
+                <outlet property="view" destination="dE9-Vu-psk" id="hX8-fz-7FR"/>
+            </connections>
+        </collectionViewItem>
+        <view id="dE9-Vu-psk" customClass="MPFunctionTemplateView">
+            <rect key="frame" x="0.0" y="0.0" width="50" height="50"/>
+            <autoresizingMask key="autoresizingMask"/>
+            <point key="canvasLocation" x="119" y="-114.5"/>
+        </view>
+    </objects>
+</document>

MathPad/MPLayout.h

@@ -42,6 +42,7 @@
 
 #pragma mark Calculation and Drawing Methods
 - (CTLineRef)createLineForString:(NSString *)aString;
+- (CTLineRef)createLineForString:(NSString *)aString usingFont:(NSFont *)font;
 
 @property (nonatomic, getter = isFlipped) BOOL flipped;
 @property (nonatomic) BOOL usesSmallSize;

MathPad/MPLayout.m

@@ -136,9 +136,16 @@
 
 #pragma mark Calculation and Drawing Methods
 - (CTLineRef)createLineForString:(NSString *)aString
+{
+    return [self createLineForString:aString
+                           usingFont:self.font];
+}
+
+- (CTLineRef)createLineForString:(NSString *)aString
+                       usingFont:(NSFont *)font
 {
     NSAttributedString *text = [[NSAttributedString alloc] initWithString:aString
-                                                               attributes:@{NSFontAttributeName: self.font}];
+                                                               attributes:@{NSFontAttributeName: font}];
     CFAttributedStringRef attributedString = CFBridgingRetain(text);
     CTLineRef line = CTLineCreateWithAttributedString(attributedString);
     CFRelease(attributedString); // TODO: Is this release appropriate?

MathPad/MPParenthesisFunction.h

@@ -0,0 +1,15 @@
+//
+//  MPParenthesisFunction.h
+//  MathPad
+//
+//  Created by Kim Wittenburg on 17.09.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import <MathKit/MathKit.h>
+
+@interface MPParenthesisFunction : MPFunction
+
+@property (nonatomic, strong) MPExpression *expression;
+
+@end

MathPad/MPParenthesisFunction.m

@@ -0,0 +1,90 @@
+
+//
+//  MPParenthesisFunction.m
+//  MathPad
+//
+//  Created by Kim Wittenburg on 17.09.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import "MPParenthesisFunction.h"
+#import "MPExpressionEvaluator.h"
+
+@implementation MPParenthesisFunction
+
++ (NSString *)localizedFunctionName
+{
+    return NSLocalizedString(@"Parenthesis", @"Name of Parenthesis Function");
+}
+
+- (instancetype)init
+{
+    self = [super init];
+    if (self) {
+        _expression = [[MPExpression alloc] init];
+        _expression.parent = self;
+    }
+    return self;
+}
+
+- (void)setExpression:(MPExpression *)expression
+{
+    _expression.parent = nil;
+    _expression = expression;
+    _expression.parent = self;
+}
+
+- (NSUInteger)numberOfChildren
+{
+    return 1;
+}
+
+- (MPExpression *)childAtIndex:(NSUInteger)index
+{
+    return index == 0 ? self.expression : nil;
+}
+
+- (void)setChild:(MPExpression *)child
+         atIndex:(NSUInteger)index
+{
+    if (index == 0) {
+        self.expression = child;
+    }
+}
+
+- (NSArray *)children
+{
+    return @[self.expression];
+}
+
+- (MPTerm *)parseWithError:(MPParseError *__autoreleasing *)error
+{
+    MPExpressionEvaluator *evaluator = self.expression.evaluator;
+    return [evaluator parseExpectingVariable:NO
+                                       error:error];
+}
+
+- (NSDecimalNumber *)evaluateWithError:(MPParseError *__autoreleasing *)error
+{
+    return [self.expression evaluateWithError:error];
+}
+
+- (NSString *)description
+{
+    return [NSString stringWithFormat:@"(%@)", self.expression.description];
+}
+
+- (NSUInteger)hash
+{
+#warning Unimplemented Method
+    return [super hash] * self.expression.hash;
+}
+
+- (id)copyWithZone:(NSZone *)zone
+{
+    MPParenthesisFunction *copy = [[MPParenthesisFunction allocWithZone:zone] init];
+    copy.expression = self.expression.copy;
+    return copy;
+}
+
+@end

MathPad/MPWhiteView.h

@@ -0,0 +1,13 @@
+//
+//  MPWhiteView.h
+//  MathPad
+//
+//  Created by Kim Wittenburg on 28.09.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import <Cocoa/Cocoa.h>
+
+@interface MPWhiteView : NSView
+
+@end

MathPad/MPWhiteView.m

@@ -0,0 +1,20 @@
+//
+//  MPWhiteView.m
+//  MathPad
+//
+//  Created by Kim Wittenburg on 28.09.14.
+//  Copyright (c) 2014 Kim Wittenburg. All rights reserved.
+//
+
+#import "MPWhiteView.h"
+
+@implementation MPWhiteView
+
+- (void)drawRect:(NSRect)dirtyRect {
+    [super drawRect:dirtyRect];
+    
+    [[NSColor whiteColor] set];
+    NSRectFill(dirtyRect);
+}
+
+@end

MathPad/NSString+MPExpressionElement.m

@@ -7,7 +7,6 @@
 //
 
 #import "NSString+MPExpressionElement.h"
-#import "MPElementParser.h"
 
 @implementation NSString (MPExpressionElement)