Add space atom.

iosMath/lib/MTMathList.h

@@ -9,7 +9,8 @@
 //  MIT license. See the LICENSE file for details.
 //
 
-#import <Foundation/Foundation.h>
+@import Foundation;
+@import CoreGraphics;
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -62,6 +63,13 @@ typedef NS_ENUM(NSUInteger, MTMathAtomType)
 
     /// A left atom - Left & Right in TeX. We don't need two since we track boundaries separately.
     kMTMathAtomBoundary = 101,
+
+    // Atoms after this are non-math TeX nodes that are still useful in math mode. They do not have
+    // the usual structure.
+
+    /// Spacing between math atoms. This denotes both glue and kern for TeX. We do not
+    /// distinguish between glue and kern.
+    kMTMathAtomSpace = 201,
 };
 
 /** A `MTMathAtom` is the basic unit of a math list. Each atom represents a single character
@@ -222,6 +230,22 @@ typedef NS_ENUM(NSUInteger, MTMathAtomType)
 
 @end
 
+/** An atom representing space.
+ @note None of the usual fields of the `MTMathAtom` apply even though this
+ class inherits from `MTMathAtom`. i.e. it is meaningless to have a value
+ in the nucleus, subscript or superscript fields. */
+@interface MTMathSpace : MTMathAtom
+
+/** Creates a new `MTMathSpace` with the given spacing.
+ @param space The amount of space in mu units.
+ */
+- (instancetype) initWithSpace:(CGFloat) space NS_DESIGNATED_INITIALIZER;
+
+/** The amount of space represented by this object in mu units. */
+@property (nonatomic, readonly) CGFloat space;
+
+@end
+
 /** A representation of a list of math objects.
 
     This list can be constructed directly or built with

iosMath/lib/MTMathList.m

@@ -62,6 +62,8 @@ static BOOL isNotBinaryOperator(MTMathAtom* prevNode)
             return @"Accent";
         case kMTMathAtomBoundary:
             return @"Boundary";
+        case kMTMathAtomSpace:
+            return @"Space";
     }
 }
 
@@ -105,6 +107,12 @@ + (instancetype)atomWithType:(MTMathAtomType)type value:(NSString *)value
         case kMTMathAtomUnderline:
             return [[MTUnderLine alloc] init];
 
+        case kMTMathAtomAccent:
+            return [[MTAccent alloc] initWithValue:value];
+
+        case kMTMathAtomSpace:
+            return [[MTMathSpace alloc] initWithSpace:0];
+
         default:
             return [[MTMathAtom alloc] initWithType:type value:value];
     }
@@ -512,13 +520,45 @@ - (instancetype)initWithType:(MTMathAtomType)type value:(NSString *)value
 
 - (id)copyWithZone:(NSZone *)zone
 {
-    MTUnderLine* op = [super copyWithZone:zone];
+    MTAccent* op = [super copyWithZone:zone];
     op.innerList = [self.innerList copyWithZone:zone];
     return op;
 }
 
 @end
 
+#pragma mark - MTMathSpace
+
+@implementation MTMathSpace
+
+- (instancetype)initWithSpace:(CGFloat)space
+{
+    self = [super initWithType:kMTMathAtomSpace value:@""];
+    if (self) {
+        _space = space;
+    }
+    return self;
+}
+
+- (instancetype)initWithType:(MTMathAtomType)type value:(NSString *)value
+{
+    if (type == kMTMathAtomSpace) {
+        return [self initWithSpace:0];
+    }
+    @throw [NSException exceptionWithName:@"InvalidMethod"
+                                   reason:@"[MTMathSpace initWithType:value:] cannot be called. Use [MTMathSpace initWithSpace:] instead."
+                                 userInfo:nil];
+}
+
+- (id)copyWithZone:(NSZone *)zone
+{
+    MTMathSpace* op = [super copyWithZone:zone];
+    op->_space = self.space;
+    return op;
+}
+
+@end
+
 #pragma mark - MTMathList
 
 @implementation MTMathList {

iosMath/render/internal/MTTypesetter.m

@@ -285,6 +285,7 @@ - (void) createDisplayAtoms:(NSArray*) preprocessed
                 NSAssert(NO, @"These types should never show here as they are removed by preprocessing.");
                 break;
 
+            case kMTMathAtomSpace:
             case kMTMathAtomAccent:
                 NSAssert(NO, @"These math atom types are not yet implemented.");
                 break;

iosMathTests/MTMathListTest.m

@@ -507,7 +507,7 @@ - (void) testCopyUnderline
     XCTAssertEqual(under.type, kMTMathAtomUnderline);
     under.innerList = list;
 
-    MTOverLine* copy = [under copy];
+    MTUnderLine* copy = [under copy];
     [MTMathListTest checkAtomCopy:copy original:under forTest:self];
     [MTMathListTest checkListCopy:copy.innerList original:under.innerList forTest:self];
 }
@@ -526,8 +526,18 @@ - (void) testCopyAcccent
     XCTAssertEqual(accent.type, kMTMathAtomAccent);
     accent.innerList = list;
 
-    MTOverLine* copy = [accent copy];
+    MTAccent* copy = [accent copy];
     [MTMathListTest checkAtomCopy:copy original:accent forTest:self];
     [MTMathListTest checkListCopy:copy.innerList original:accent.innerList forTest:self];
 }
+
+- (void) testCopySpace
+{
+    MTMathSpace* space = [[MTMathSpace alloc] initWithSpace:3];
+    XCTAssertEqual(space.type, kMTMathAtomSpace);
+
+    MTMathSpace* copy = [space copy];
+    [MTMathListTest checkAtomCopy:copy original:space forTest:self];
+    XCTAssertEqual(space.space, copy.space);
+}
 @end