Prepared to implement improved keyboard navigation

MathPad/MPFunctionLayout.h

@@ -37,4 +37,12 @@
 - (NSRect)generateBounds; // To be implemented
 - (void)drawAtPoint:(NSPoint)point; // 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
+- (NSUInteger)indexOfTrailingChild; // To be implemented
+
+// 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
+
 @end

MathPad/MPFunctionLayout.m

@@ -72,15 +72,14 @@
     }];
 }
 
-#pragma mark Size and Drawing Methods
-- (NSRect)generateBounds
+- (NSUInteger)indexOfChildBeforeChildAtIndex:(NSUInteger)index
 {
-    return NSZeroRect;
+    return NSNotFound;
 }
 
-- (void)draw
+- (NSUInteger)indexOfChildAfterChildAtIndex:(NSUInteger)index
 {
-    
+    return NSNotFound;
 }
 
 @end

MathPad/MPSumFunctionLayout.m

@@ -23,6 +23,16 @@
     return (MPSumFunction *)self.function;
 }
 
+- (NSUInteger)indexOfLeadingChild
+{
+    return 2;
+}
+
+- (NSUInteger)indexOfTrailingChild
+{
+    return 2;
+}
+
 - (CTLineRef)line
 {
     CTLineRef line = [self lineForPrivateCacheIndex:0 generator:^CTLineRef{
@@ -75,7 +85,7 @@
         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);
+            NSPoint pointInChild = NSMakePoint(point.x - childOffset.x, point.y - childOffset.y);
             NSIndexPath *subPath = [childLayout indexPathForMousePoint:pointInChild];
             return [subPath indexPathByPreceedingIndex:index];
         }