Fix bug in sizeWithFont (#1917)

NSString+UIKitAdditions sizeWithFont:constrainedToSize: should return the height that the text requires rather than the height of the text that can actually fit in the region that CTFramesetterSuggestFrameSizeWithConstraints returns.
microsoft · Feb 9, 2017 · e6efd44 · e6efd44
1 parent 4527ce3
commit e6efd44
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diff --git a/Frameworks/UIKit/NSString+UIKitAdditions.mm b/Frameworks/UIKit/NSString+UIKitAdditions.mm
@@ -244,6 +244,11 @@ - (CGSize)drawAtPoint:(CGPoint)point
 // Returns the bounding box size this string would occupy when drawn as specified
 // All sizeWith... functions in this file funnel to this
 - (CGSize)_sizeWithAttributes:(NSDictionary<NSString*, id>*)attributes constrainedToSize:(CGSize)size {
+    UIFont* font = attributes[NSFontAttributeName];
+    if (font == nil) {
+        return CGSizeZero;
+    }
+
     if ([attributes objectForKey:NSParagraphStyleAttributeName]) {
         NSMutableDictionary* copied = [NSMutableDictionary dictionaryWithDictionary:attributes];
         woc::unique_cf<CTParagraphStyleRef>
@@ -263,7 +268,13 @@ - (CGSize)_sizeWithAttributes:(NSDictionary<NSString*, id>*)attributes constrain
         size.height = std::numeric_limits<CGFloat>::max();
     }
 
-    return CTFramesetterSuggestFrameSizeWithConstraints(framesetter.get(), CFRangeMake(0, self.length), nullptr, size, nullptr);
+    CGSize ret = CTFramesetterSuggestFrameSizeWithConstraints(framesetter.get(), CFRangeMake(0, self.length), nullptr, size, nullptr);
+
+    // If the constrained height is less than a line height sizeWithFont will increase the returned size to fit at least one line
+    CGFloat lineHeight = [font ascender] - [font descender];
+    ret.height = std::max(ret.height, lineHeight);
+
+    return ret;
 }
 
 // Private helper that converts a UILineBreakMode -> NSParagraphStyle

diff --git a/tests/unittests/UIKit/NSString+UIKitAdditionsTests.mm b/tests/unittests/UIKit/NSString+UIKitAdditionsTests.mm
@@ -16,10 +16,28 @@
 
 #import <TestFramework.h>
 #import <UIKit/UIKit.h>
+#import <CppUtils.h>
 
+static constexpr double c_errorDelta = .0001;
 TEST(NSString_UIKitAdditions, ShouldNotReturnSizeOfZeroWidth) {
     CGSize size =
         [@"TEST" sizeWithFont:[UIFont systemFontOfSize:12.0f] constrainedToSize:CGSizeZero lineBreakMode:NSLineBreakByWordWrapping];
     EXPECT_LT(0.0, size.width);
     EXPECT_LT(0.0, size.height);
+}
+
+TEST(NSString_UIKitAdditions, SizeWithFontShouldReturnLineHeightWhenConstrainedHeightIsTooSmall) {
+    CGSize givenSize = { 0, 15 };
+    UIFont* font = [UIFont systemFontOfSize:144];
+    CGFloat lineHeight = [font ascender] - [font descender];
+    CGSize size = [@"TEST" sizeWithFont:font constrainedToSize:givenSize];
+    EXPECT_NEAR(lineHeight, size.height, c_errorDelta);
+
+    size = [@"TEST\nTEST" sizeWithFont:font constrainedToSize:givenSize];
+    EXPECT_NEAR(lineHeight, size.height, c_errorDelta);
+}
+
+TEST(NSString_UIKitAdditions, SizeWithNoFontShouldReturnCGSizeZero) {
+    CGSize arbitrarySize = { 100, 150 };
+    EXPECT_EQ(CGSizeZero, [@"TEST" sizeWithFont:nil constrainedToSize:arbitrarySize]);
 }