Fix some CoreText perf low-hanging fruit

 - Remove NSLayoutManager __lineHasGlyphsAfterIndex(), which is called multiple times per line
    - Instead, directly search for the index of the last visible glyph once, compare against this

 - DWriteWrapper_CoreText
    - Skip first range of attributes in __DWriteTextLayoutCreate()
        - was redundant due to the underlaying Format already taking it into account
    - reserve() ahead of time for glyphRunDescriptionInfo._clusterMap, CTRun->_glyphOrigins, ->_glyphAdvances
        - A lot of time was being spent in reallocation, resizing

 - Remove DWriteWrapper _GetUserDefaultLocaleName(), don't wrap in a wstring, directly use a wchar_t buffer
 - Reduce the number of character buffer copies in _CFStringFromLocalizedString() by 1
 - Remove unused/not useful _characters member from CTTypesetter

 - Misc

Related to microsoft#1374

Frameworks/CoreGraphics/DWriteWrapper.mm

@@ -96,19 +96,6 @@ HRESULT UpdateCollection(const ComPtr<IDWriteFactory>& dwriteFactory, const ComP
     return s_userFontCollection;
 }
 
-/**
- * Helper method to return the user set default locale string.
- *
- * @return use set locale string as wstring.
- */
-std::wstring _GetUserDefaultLocaleName() {
-    wchar_t localeName[LOCALE_NAME_MAX_LENGTH];
-    int defaultLocaleSuccess = GetUserDefaultLocaleName(localeName, LOCALE_NAME_MAX_LENGTH);
-
-    // If the default locale is returned, find that locale name, otherwise use "en-us".
-    return std::wstring(defaultLocaleSuccess ? localeName : c_defaultUserLanguage);
-}
-
 /**
  * Helper method to convert IDWriteLocalizedStrings object to CFString object.
  *
@@ -123,13 +110,15 @@ CFStringRef _CFStringFromLocalizedString(IDWriteLocalizedStrings* localizedStrin
     }
 
     // Get the default locale for this user.
-    std::wstring localeName = _GetUserDefaultLocaleName();
+    // If the default locale is returned, find that locale name, otherwise use "en-us".
+    wchar_t localeNameBuf[LOCALE_NAME_MAX_LENGTH];
+    int defaultLocaleSuccess = GetUserDefaultLocaleName(localeNameBuf, LOCALE_NAME_MAX_LENGTH);
+    const wchar_t* localeName = defaultLocaleSuccess ? localeNameBuf : c_defaultUserLanguage;
 
     uint32_t index = 0;
     BOOL exists = FALSE;
 
-    // If the default locale is returned, find that locale name, otherwise use "en-us".
-    RETURN_NULL_IF_FAILED(localizedString->FindLocaleName(localeName.c_str(), &index, &exists));
+    RETURN_NULL_IF_FAILED(localizedString->FindLocaleName(localeName, &index, &exists));
     if (!exists) {
         RETURN_NULL_IF_FAILED(localizedString->FindLocaleName(c_defaultUserLanguage, &index, &exists));
     }
@@ -143,13 +132,15 @@ CFStringRef _CFStringFromLocalizedString(IDWriteLocalizedStrings* localizedStrin
     uint32_t length = 0;
     RETURN_NULL_IF_FAILED(localizedString->GetStringLength(index, &length));
 
-    // Get the string.
-    std::vector<wchar_t> wcharString = std::vector<wchar_t>(length + 1, 0);
-    RETURN_NULL_IF_FAILED(localizedString->GetString(index, wcharString.data(), length + 1));
+    // Get the string. Use length + 1 here as GetString requires room for the null terminator.
+    woc::unique_iw<wchar_t> wcharString(static_cast<wchar_t*>(IwMalloc(sizeof(wchar_t) * (length + 1))));
+    RETURN_NULL_IF_FAILED(localizedString->GetString(index, wcharString.get(), length + 1));
 
     // Strip out unnecessary null terminator
-    return (CFStringRef)CFAutorelease(
-        CFStringCreateWithCharacters(kCFAllocatorDefault, reinterpret_cast<UniChar*>(wcharString.data()), length));
+    return (CFStringRef)CFAutorelease(CFStringCreateWithCharactersNoCopy(kCFAllocatorDefault,
+                                                                         reinterpret_cast<UniChar*>(wcharString.release()),
+                                                                         length,
+                                                                         kCFAllocatorDefault));
 }
 
 /**
@@ -280,6 +271,12 @@ HRESULT _DWriteCreateTextFormatWithFontNameAndSize(CFStringRef optionalFontName,
         userFontInfo = __GetUserFontCollectionHelper()->GetFontPropertiesFromUppercaseFontName(upperFontName);
     }
 
+    // Get the default locale for this user.
+    // If the default locale is returned, find that locale name, otherwise use "en-us".
+    wchar_t localeNameBuf[LOCALE_NAME_MAX_LENGTH];
+    int defaultLocaleSuccess = GetUserDefaultLocaleName(localeNameBuf, LOCALE_NAME_MAX_LENGTH);
+    const wchar_t* localeName = defaultLocaleSuccess ? localeNameBuf : c_defaultUserLanguage;
+
     if (info) {
         RETURN_IF_FAILED(
             dwriteFactory->CreateTextFormat(reinterpret_cast<wchar_t*>(Strings::VectorFromCFString(info->familyName.get()).data()),
@@ -288,7 +285,7 @@ HRESULT _DWriteCreateTextFormatWithFontNameAndSize(CFStringRef optionalFontName,
                                             info->style,
                                             info->stretch,
                                             fontSize,
-                                            _GetUserDefaultLocaleName().data(),
+                                            localeName,
                                             &textFormat));
     }
 
@@ -301,7 +298,7 @@ HRESULT _DWriteCreateTextFormatWithFontNameAndSize(CFStringRef optionalFontName,
                                             userFontInfo->style,
                                             userFontInfo->stretch,
                                             fontSize,
-                                            _GetUserDefaultLocaleName().data(),
+                                            localeName,
                                             &textFormat));
     }
 

Frameworks/CoreText/CTFramesetter.mm

@@ -32,7 +32,7 @@ @implementation _CTFramesetter : NSObject
     // Call _DWriteWrapper to get _CTLine object list that makes up this frame
     _CTTypesetter* typesetter = static_cast<_CTTypesetter*>(framesetter->_typesetter);
     if (range.length == 0L) {
-        range.length = typesetter->_characters.size() - range.location;
+        range.length = [typesetter->_string length] - range.location;
     }
 
     StrongId<_CTFrame> ret = _DWriteGetFrame(static_cast<CFAttributedStringRef>(typesetter->_attributedString.get()), range, frameRect);

Frameworks/CoreText/CTTypesetter.mm

@@ -33,10 +33,6 @@ - (instancetype)initWithAttributedString:(NSAttributedString*)str {
     _attributedString = str;
     _string = [str string];
 
-    //  Measure the string
-    _characters.resize(str.length);
-    [_string getCharacters:_characters.data()];
-
     return self;
 }
 
@@ -109,7 +105,7 @@ CFIndex CTTypesetterSuggestLineBreak(CTTypesetterRef typesetter, CFIndex startIn
 CFIndex CTTypesetterSuggestLineBreakWithOffset(CTTypesetterRef ts, CFIndex index, double width, double offset) {
     _CTTypesetter* typesetter = static_cast<_CTTypesetter*>(ts);
     _CTFrame* frame = _DWriteGetFrame(static_cast<CFAttributedStringRef>(typesetter->_attributedString.get()),
-                                      CFRangeMake(index, typesetter->_characters.size() - index),
+                                      CFRangeMake(index, [typesetter->_string length] - index),
                                       CGRectMake(offset, 0, width, FLT_MAX));
     return ([frame->_lines count] > 0) ? static_cast<_CTLine*>([frame->_lines firstObject])->_strRange.length : 0;
 }

Frameworks/CoreText/DWriteWrapper_CoreText.mm

@@ -265,11 +265,15 @@ static HRESULT __DWriteTextLayoutCreate(CFAttributedStringRef string, CFRange ra
     uint32_t incompatibleAttributeFlag = 0;
     CFRange attributeRange;
 
-    for (CFIndex currentIndex = range.location; currentIndex < rangeEnd; currentIndex += attributeRange.length) {
-        CTFontRef font =
-            static_cast<CTFontRef>(CFAttributedStringGetAttribute(string, currentIndex, kCTFontAttributeName, &attributeRange));
+    // Find the range of the first set of attributes and skip it, since the underlying DWriteTextFormat has already internalized it
+    // If this first set of attributes lasts the entire range, the below for loop is not executed at all
+    // attributeRange is populated even if this attribute is not found
+    CFAttributedStringGetAttribute(string, range.location, kCTFontAttributeName, &attributeRange);
 
-        // attributeRange is properly populated even if this attribute is not found
+    for (CFIndex index = attributeRange.location + attributeRange.length; index < rangeEnd; index += attributeRange.length) {
+        CTFontRef font = static_cast<CTFontRef>(CFAttributedStringGetAttribute(string, index, kCTFontAttributeName, &attributeRange));
+
+        // attributeRange is populated even if this attribute is not found
         const DWRITE_TEXT_RANGE dwriteRange = { attributeRange.location, attributeRange.length };
         if (font) {
             RETURN_IF_FAILED(__DWriteTextLayoutApplyFont(textLayout, font, dwriteRange));
@@ -282,7 +286,7 @@ static HRESULT __DWriteTextLayoutCreate(CFAttributedStringRef string, CFRange ra
         }
 
         CFNumberRef extraKerningRef =
-            static_cast<CFNumberRef>(CFAttributedStringGetAttribute(string, currentIndex, kCTKernAttributeName, nullptr));
+            static_cast<CFNumberRef>(CFAttributedStringGetAttribute(string, index, kCTKernAttributeName, nullptr));
         if (extraKerningRef) {
             RETURN_IF_FAILED(__DWriteTextLayoutApplyExtraKerning(textLayout, typography, extraKerningRef, dwriteRange));
         } else {
@@ -329,6 +333,7 @@ HRESULT STDMETHODCALLTYPE DrawGlyphRun(_In_ void* clientDrawingContext,
         _DWriteGlyphRunDescription glyphRunDescriptionInfo;
         glyphRunDescriptionInfo._stringLength = glyphRunDescription->stringLength;
         glyphRunDescriptionInfo._textPosition = glyphRunDescription->textPosition;
+        glyphRunDescriptionInfo._clusterMap.reserve(glyphRun->glyphCount);
         std::transform(glyphRunDescription->clusterMap,
                        glyphRunDescription->clusterMap + glyphRun->glyphCount,
                        std::back_inserter(glyphRunDescriptionInfo._clusterMap),
@@ -479,6 +484,8 @@ HRESULT STDMETHODCALLTYPE GetPixelsPerDip(_In_opt_ void* clientDrawingContext, _
 
             // TODO::
             // This is a temp workaround until we can have actual glyph origins
+            run->_glyphOrigins.reserve(glyphRunDetails._dwriteGlyphRun[j].glyphCount);
+            run->_glyphAdvances.reserve(glyphRunDetails._dwriteGlyphRun[j].glyphCount);
             for (int index = 0; index < glyphRunDetails._dwriteGlyphRun[j].glyphCount; index++) {
                 run->_glyphOrigins.emplace_back(CGPoint{ xPos, yPos });
                 run->_glyphAdvances.emplace_back(CGSize{ glyphRunDetails._dwriteGlyphRun[j].glyphAdvances[index], 0.0f });

Frameworks/UIKit/NSLayoutManager.mm

@@ -34,22 +34,38 @@ @implementation NSLayoutManager {
     woc::unique_cf<CTFrameRef> _frame;
 }
 
-// Returns true if any of the characters in line after index have visible glyphs, false otherwise
-// Used to determine if a given index is past the visible part of a line for linebreaking
-static bool __lineHasGlyphsAfterIndex(CTLineRef line, CFIndex index) {
-    for (id runRef in static_cast<NSArray*>(CTLineGetGlyphRuns(line))) {
-        CTRunRef run = static_cast<CTRunRef>(runRef);
-        CFRange runRange = CTRunGetStringRange(run);
-        if (runRange.location <= index && index <= runRange.location + runRange.length) {
-            const CFIndex* indices = CTRunGetStringIndicesPtr(run);
-            if (std::any_of(indices,
-                            indices + CTRunGetGlyphCount(run),
-                            std::bind(std::greater_equal<CFIndex>(), std::placeholders::_1, index))) {
-                return true;
+// Private helper:
+// Given a CTLineRef, returns the index of the character in the original string, that maps to the last visible glyph in the line
+static CFIndex __CTLineGetStringIndexOfLastVisibleGlyph(CTLineRef line) {
+    CFArrayRef runs = CTLineGetGlyphRuns(line);
+
+    CFIndex ret = -1;
+    for (CFIndex i = CFArrayGetCount(runs) - 1; i >= 0; --i) {
+        CTRunRef run = static_cast<CTRunRef>(CFArrayGetValueAtIndex(runs, i));
+        CFIndex glyphCount = CTRunGetGlyphCount(run);
+
+        // Open question: Can runs ever be non-monotonic with respect to the original string?
+        // If not, can do an early return here
+        if (glyphCount > 0) {
+            const CFIndex* stringIndices = CTRunGetStringIndicesPtr(run);
+
+            // Glyphs within a run can be non-monotonic with respect to the original string
+            // Find the greatest index within the run's string indices
+            const CFIndex* maxIndexInRun = std::max_element(stringIndices, stringIndices + glyphCount);
+
+            if (*maxIndexInRun > ret) {
+                ret = *maxIndexInRun;
             }
         }
     }
-    return false;
+
+    return ret;
+}
+
+// Private helper for getting the width and height of a line in DIPs
+static inline CGSize __CTLineGetBounds(CTLineRef line) {
+    CGFloat ascent, descent, leading;
+    return { CTLineGetTypographicBounds(line, &ascent, &descent, &leading), ascent + descent + leading };
 }
 
 - (void)__layoutAllText {
@@ -60,9 +76,6 @@ - (void)__layoutAllText {
 
     woc::unique_cf<CTFramesetterRef> framesetter{ CTFramesetterCreateWithAttributedString(
         static_cast<CFAttributedStringRef>(_textStorage.get())) };
-    NSTextContainer* container = (NSTextContainer*)_textContainers[0];
-    CGSize containerSize = container.size;
-    CGPoint origin = { 0, 0 };
 
     // Creates frame containing all of the text, which allows us to measure the line heights for measuring rectangles and breaks the text
     // into CTLineRefs for hard line breaks (e.g. '\n') which allows the assumption that once we run out of glyphs in a line to draw we must
@@ -72,105 +85,107 @@ - (void)__layoutAllText {
         _frame.reset(CTFramesetterCreateFrame(framesetter.get(), {}, path.get(), nullptr));
     }
 
+    NSTextContainer* container = (NSTextContainer*)_textContainers[0];
+    const CGSize containerSize = container.size;
+    CGPoint origin{ 0, 0 };
+
     for (id lineRef in static_cast<NSArray*>(CTFrameGetLines(_frame.get()))) {
         CTLineRef line = static_cast<CTLineRef>(lineRef);
 
-        // Width of line already drawn, saves us from having to redraw line twice
-        double drawnWidth = 0.0;
+        // Maximum height of lines on current horizontal, needed to get next yPos
+        const CGFloat lineHeight = __CTLineGetBounds(line).height;
 
-        CGFloat ascent, descent, leading;
+        const CFRange lineRange = CTLineGetStringRange(line);
+        const CFIndex lineEnd = lineRange.location + lineRange.length; // String index of last glyph in line
 
-        // Width of entire line
-        double width = CTLineGetTypographicBounds(line, &ascent, &descent, &leading);
+        const CFIndex indexOfLastVisibleChar = __CTLineGetStringIndexOfLastVisibleGlyph(line); // Alternate termination point
 
-        // Maximum height of lines on current horizontal, needed to get next yPos
-        CGFloat lineHeight = leading + ascent + descent;
+        CGRect proposedRect{}; // Proposes a drawing rectangle to [NSTextContainer lineFragmentRectForProposedRect]
+        proposedRect.size.width = containerSize.width;
+        proposedRect.size.height = lineHeight;
 
-        CFRange lineRange = CTLineGetStringRange(line);
+        CGRect frameDrawRect{}; // Drawing rectangle actually used in CTFramesetterCreateFrame to layout the text
+        frameDrawRect.size.height = lineHeight;
 
-        // Index of first glyph in line to be drawn
-        CFIndex stringIndex = lineRange.location;
-        CFIndex lineEnd = stringIndex + lineRange.length;
+        double drawnWidth = 0.0; // Width of line already drawn, saves us from having to redraw line twice
 
+        CFIndex stringIndex = lineRange.location; // String index of first glyph in line to be drawn
         while (stringIndex < lineEnd) {
             if (origin.y > containerSize.height) {
                 // Added as much text as can fit in the frame, can end here
                 return;
             }
 
-            if (!__lineHasGlyphsAfterIndex(line, stringIndex)) {
-                // Ended up without any visible glyphs to draw
-                // Caused by a line of only whitespace
+            if (stringIndex > indexOfLastVisibleChar) {
+                // Ended up without any visible glyphs to draw, caused by a line of only whitespace
                 origin = { 0.0f, origin.y + lineHeight };
-                _totalSize.height += lineHeight;
                 break;
             }
 
-            CGRect remainingRect = {};
-            CGRect rect = [container lineFragmentRectForProposedRect:CGRectMake(origin.x, origin.y, containerSize.width, lineHeight)
-                                                             atIndex:stringIndex
-                                                    writingDirection:NSWritingDirectionLeftToRight
-                                                       remainingRect:&remainingRect];
+            CGRect remainingRect{};
+            proposedRect.origin = origin;
+            const CGRect rect = [container lineFragmentRectForProposedRect:proposedRect
+                                                                   atIndex:stringIndex
+                                                          writingDirection:NSWritingDirectionLeftToRight
+                                                             remainingRect:&remainingRect];
 
             // Approximate how many characters can fit to keep from re-rendering large amounts of text
-            CFIndex lastIndex = std::min(CTLineGetStringIndexForPosition(line, { drawnWidth + rect.size.width, 0.0f }) + 1, lineEnd);
+            const CFIndex lastIndex = std::min(CTLineGetStringIndexForPosition(line, { drawnWidth + rect.size.width, 0.0f }) + 1, lineEnd);
 
             if (lastIndex == stringIndex) {
                 // Unable to fit any text in the current rect, continue to next
                 if (remainingRect.size.width > 0.0f && stringIndex < lineEnd) {
                     origin = { remainingRect.origin.x, origin.y };
                 } else {
                     origin = { 0.0f, origin.y + lineHeight };
-                    _totalSize.height += lineHeight;
                 }
 
                 continue;
             }
 
-            woc::unique_cf<CGPathRef> path{ CGPathCreateWithRect(CGRectMake(0, 0, rect.size.width, lineHeight), nullptr) };
+            frameDrawRect.size.width = rect.size.width;
+            woc::unique_cf<CGPathRef> path{ CGPathCreateWithRect(frameDrawRect, nullptr) };
             woc::unique_cf<CTFrameRef> frame{
                 CTFramesetterCreateFrame(framesetter.get(), { stringIndex, lastIndex - stringIndex }, path.get(), nullptr)
             };
 
             // Create line to fit as much text as possible in given rect
             CTLineRef fitLine = static_cast<CTLineRef>(CFArrayGetValueAtIndex(CTFrameGetLines(frame.get()), 0));
 
-            CFIndex fitLength = CTLineGetStringRange(fitLine).length;
+            const CFIndex fitLength = CTLineGetStringRange(fitLine).length;
             if (fitLength == 0L) {
                 // Failed to fit any text in the current rect, continue to next
                 if (remainingRect.size.width > 0.0f && stringIndex < lineEnd) {
                     origin = { remainingRect.origin.x, origin.y };
                 } else {
                     origin = { 0.0f, origin.y + lineHeight };
-                    _totalSize.height += lineHeight;
                 }
 
                 continue;
             }
-
-            // Increase index of next character to layout
             stringIndex += fitLength;
 
             // Save line and origin for when it is drawn
             [_ctLines addObject:(id)fitLine];
             _lineOrigins.emplace_back(CGPoint{ rect.origin.x, rect.origin.y + lineHeight });
 
-            double fitWidth = CTLineGetTypographicBounds(fitLine, nullptr, nullptr, nullptr);
+            const double fitWidth = CTLineGetTypographicBounds(fitLine, nullptr, nullptr, nullptr);
             drawnWidth += fitWidth;
 
             if (remainingRect.size.width > 0 && stringIndex < lineEnd) {
                 origin = { remainingRect.origin.x, origin.y };
             } else {
                 origin = { 0.0f, origin.y + lineHeight };
-                _totalSize.height += lineHeight;
-                _totalSize.width = std::max(_totalSize.width, rect.origin.x + (CGFloat)fitWidth);
-                if (!__lineHasGlyphsAfterIndex(line, stringIndex)) {
+                _totalSize.width = std::max(_totalSize.width, rect.origin.x + fitWidth);
+                if (stringIndex > indexOfLastVisibleChar) {
                     // Ended up with whitespace at end of the line, break to next line
                     break;
                 }
             }
         }
     }
+
+    _totalSize.height = origin.y;
 }
 
 - (void)layoutIfNeeded {

Frameworks/include/CoreGraphics/DWriteWrapper.h

@@ -29,10 +29,6 @@
 #import <memory>
 
 // General DWrite helpers
-#ifdef __cplusplus
-extern "C++" std::wstring _GetUserDefaultLocaleName();
-#endif
-
 static inline CFStringRef _CFStringCreateUppercaseCopy(CFStringRef string) {
     CFMutableStringRef ret = CFStringCreateMutableCopy(nullptr, CFStringGetLength(string), string);
     CFStringUppercase(ret, nullptr);