Fonts: Adjust attribute ranges correctly when rendering AttributedStrings

CFAttributedString ranges must be given in terms of 16-bit word offsets,
rather than codepoints.

modules/juce_graphics/fonts/juce_AttributedString.cpp

@@ -54,6 +54,24 @@ namespace
         }
     }
 
+    inline bool areInvariantsMaintained (const String& text, const Array<AttributedString::Attribute>& atts)
+    {
+        if (atts.isEmpty())
+            return true;
+
+        if (atts.getFirst().range.getStart() != 0)
+            return false;
+
+        if (atts.getLast().range.getEnd() != text.length())
+            return false;
+
+        for (auto it = std::next (atts.begin()); it != atts.end(); ++it)
+            if (it->range.getStart() != std::prev (it)->range.getEnd())
+                return false;
+
+        return true;
+    }
+
     Range<int> splitAttributeRanges (Array<AttributedString::Attribute>& atts, Range<int> newRange)
     {
         newRange = newRange.getIntersectionWith ({ 0, getLength (atts) });
@@ -151,30 +169,35 @@ void AttributedString::setText (const String& newText)
         truncate (attributes, newLength);
 
     text = newText;
+    jassert (areInvariantsMaintained (text, attributes));
 }
 
 void AttributedString::append (const String& textToAppend)
 {
     text += textToAppend;
     appendRange (attributes, textToAppend.length(), nullptr, nullptr);
+    jassert (areInvariantsMaintained (text, attributes));
 }
 
 void AttributedString::append (const String& textToAppend, const Font& font)
 {
     text += textToAppend;
     appendRange (attributes, textToAppend.length(), &font, nullptr);
+    jassert (areInvariantsMaintained (text, attributes));
 }
 
 void AttributedString::append (const String& textToAppend, Colour colour)
 {
     text += textToAppend;
     appendRange (attributes, textToAppend.length(), nullptr, &colour);
+    jassert (areInvariantsMaintained (text, attributes));
 }
 
 void AttributedString::append (const String& textToAppend, const Font& font, Colour colour)
 {
     text += textToAppend;
     appendRange (attributes, textToAppend.length(), &font, &colour);
+    jassert (areInvariantsMaintained (text, attributes));
 }
 
 void AttributedString::append (const AttributedString& other)
@@ -188,6 +211,7 @@ void AttributedString::append (const AttributedString& other)
         attributes.getReference (i).range += originalLength;
 
     mergeAdjacentRanges (attributes);
+    jassert (areInvariantsMaintained (text, attributes));
 }
 
 void AttributedString::clear()
@@ -219,21 +243,25 @@ void AttributedString::setLineSpacing (const float newLineSpacing) noexcept
 void AttributedString::setColour (Range<int> range, Colour colour)
 {
     applyFontAndColour (attributes, range, nullptr, &colour);
+    jassert (areInvariantsMaintained (text, attributes));
 }
 
 void AttributedString::setFont (Range<int> range, const Font& font)
 {
     applyFontAndColour (attributes, range, &font, nullptr);
+    jassert (areInvariantsMaintained (text, attributes));
 }
 
 void AttributedString::setColour (Colour colour)
 {
     setColour ({ 0, getLength (attributes) }, colour);
+    jassert (areInvariantsMaintained (text, attributes));
 }
 
 void AttributedString::setFont (const Font& font)
 {
     setFont ({ 0, getLength (attributes) }, font);
+    jassert (areInvariantsMaintained (text, attributes));
 }
 
 void AttributedString::draw (Graphics& g, const Rectangle<float>& area) const

modules/juce_graphics/fonts/juce_AttributedString.h

@@ -34,6 +34,11 @@ namespace juce
     An attributed string lets you create a string with varied fonts, colours, word-wrapping,
     layout, etc., and draw it using AttributedString::draw().
 
+    Invariants:
+    - Every character in the string is a member of exactly one attribute.
+    - Attributes are sorted such that the range-end of attribute 'i' is equal to the
+      range-begin of attribute 'i + 1'.
+
     @see TextLayout
 
     @tags{Graphics}

modules/juce_graphics/native/juce_mac_Fonts.mm

@@ -258,20 +258,24 @@ namespace CoreTextTypeLayout
 
         auto attribString = CFAttributedStringCreateMutable (kCFAllocatorDefault, 0);
         CFUniquePtr<CFStringRef> cfText (text.getText().toCFString());
+
         CFAttributedStringReplaceString (attribString, CFRangeMake (0, 0), cfText.get());
 
-        auto numCharacterAttributes = text.getNumAttributes();
-        auto attribStringLen = CFAttributedStringGetLength (attribString);
+        const auto numCharacterAttributes = text.getNumAttributes();
+        const auto attribStringLen = CFAttributedStringGetLength (attribString);
+        const auto beginPtr = text.getText().toUTF16();
+        auto currentPosition = beginPtr;
 
-        for (int i = 0; i < numCharacterAttributes; ++i)
+        for (int i = 0; i < numCharacterAttributes; currentPosition += text.getAttribute (i).range.getLength(), ++i)
         {
-            auto& attr = text.getAttribute (i);
-            auto rangeStart = attr.range.getStart();
+            const auto& attr = text.getAttribute (i);
+            const auto wordBegin = currentPosition.getAddress() - beginPtr.getAddress();
 
-            if (rangeStart >= attribStringLen)
+            if (attribStringLen <= wordBegin)
                 continue;
 
-            auto range = CFRangeMake (rangeStart, jmin (attr.range.getEnd(), (int) attribStringLen) - rangeStart);
+            const auto wordEnd = jmin (attribStringLen, (currentPosition + attr.range.getLength()).getAddress() - beginPtr.getAddress());
+            const auto range = CFRangeMake (wordBegin, wordEnd - wordBegin);
 
             if (auto ctFontRef = getOrCreateFont (attr.font))
             {

modules/juce_graphics/native/juce_win32_DirectWriteTypeLayout.cpp

@@ -271,12 +271,22 @@ namespace DirectWriteTypeLayout
         format.SetWordWrapping (wrapType);
     }
 
-    void addAttributedRange (const AttributedString::Attribute& attr, IDWriteTextLayout& textLayout,
-                             const int textLen, ID2D1RenderTarget& renderTarget, IDWriteFontCollection& fontCollection)
+    void addAttributedRange (const AttributedString::Attribute& attr,
+                             IDWriteTextLayout& textLayout,
+                             CharPointer_UTF16 begin,
+                             CharPointer_UTF16 textPointer,
+                             const UINT32 textLen,
+                             ID2D1RenderTarget& renderTarget,
+                             IDWriteFontCollection& fontCollection)
     {
         DWRITE_TEXT_RANGE range;
-        range.startPosition = (UINT32) attr.range.getStart();
-        range.length = (UINT32) jmin (attr.range.getLength(), textLen - attr.range.getStart());
+        range.startPosition = (UINT32) (textPointer.getAddress() - begin.getAddress());
+
+        if (textLen <= range.startPosition)
+            return;
+
+        const auto wordEnd = jmin (textLen, (UINT32) ((textPointer + attr.range.getLength()).getAddress() - begin.getAddress()));
+        range.length = wordEnd - range.startPosition;
 
         {
             auto familyName = FontStyleHelpers::getConcreteFamilyName (attr.font);
@@ -367,18 +377,28 @@ namespace DirectWriteTypeLayout
             hr = dwTextFormat->SetTrimming (&trimming, trimmingSign);
         }
 
-        auto textLen = text.getText().length();
+        const auto beginPtr = text.getText().toUTF16();
+        const auto textLen = (UINT32) (beginPtr.findTerminatingNull().getAddress() - beginPtr.getAddress());
 
-        hr = directWriteFactory.CreateTextLayout (text.getText().toWideCharPointer(), (UINT32) textLen, dwTextFormat,
-                                                  maxWidth, maxHeight, textLayout.resetAndGetPointerAddress());
+        hr = directWriteFactory.CreateTextLayout (beginPtr.getAddress(),
+                                                  textLen,
+                                                  dwTextFormat,
+                                                  maxWidth,
+                                                  maxHeight,
+                                                  textLayout.resetAndGetPointerAddress());
 
         if (FAILED (hr) || textLayout == nullptr)
             return false;
 
-        auto numAttributes = text.getNumAttributes();
+        const auto numAttributes = text.getNumAttributes();
+        auto rangePointer = beginPtr;
 
         for (int i = 0; i < numAttributes; ++i)
-            addAttributedRange (text.getAttribute (i), *textLayout, textLen, renderTarget, fontCollection);
+        {
+            const auto attribute = text.getAttribute (i);
+            addAttributedRange (attribute, *textLayout, beginPtr, rangePointer, textLen, renderTarget, fontCollection);
+            rangePointer += attribute.range.getLength();
+        }
 
         return true;
     }