[core] Add evaluated images to styled text sections

src/mbgl/layout/symbol_layout.cpp

@@ -146,27 +146,34 @@ SymbolLayout::SymbolLayout(const BucketParameters& parameters,
 
             ft.formattedText = TaggedString();
             for (const auto & section : formatted.sections) {
-                std::string u8string = section.text;
-                if (textTransform == TextTransformType::Uppercase) {
-                    u8string = platform::uppercase(u8string);
-                } else if (textTransform == TextTransformType::Lowercase) {
-                    u8string = platform::lowercase(u8string);
+                if (!section.image) {
+                    std::string u8string = section.text;
+                    if (textTransform == TextTransformType::Uppercase) {
+                        u8string = platform::uppercase(u8string);
+                    } else if (textTransform == TextTransformType::Lowercase) {
+                        u8string = platform::lowercase(u8string);
+                    }
+
+                    ft.formattedText->addTextSection(applyArabicShaping(util::convertUTF8ToUTF16(u8string)),
+                                                     section.fontScale ? *section.fontScale : 1.0,
+                                                     section.fontStack ? *section.fontStack : baseFontStack,
+                                                     section.textColor);
+                } else {
+                    layoutParameters.imageDependencies.emplace(section.image->id(), ImageType::Icon);
+                    ft.formattedText->addImageSection(section.image->id());
                 }
-
-                ft.formattedText->addSection(applyArabicShaping(util::convertUTF8ToUTF16(u8string)),
-                                             section.fontScale ? *section.fontScale : 1.0,
-                                             section.fontStack ? *section.fontStack : baseFontStack,
-                                             section.textColor);
             }
 
-
             const bool canVerticalizeText = layout->get<TextRotationAlignment>() == AlignmentType::Map
                                          && layout->get<SymbolPlacement>() != SymbolPlacementType::Point
                                          && ft.formattedText->allowsVerticalWritingMode();
 
             // Loop through all characters of this text and collect unique codepoints.
             for (std::size_t j = 0; j < ft.formattedText->length(); j++) {
-                const auto& sectionFontStack = formatted.sections[ft.formattedText->getSectionIndex(j)].fontStack;
+                const auto& section = formatted.sections[ft.formattedText->getSectionIndex(j)];
+                if (section.image) continue;
+
+                const auto& sectionFontStack = section.fontStack;
                 GlyphIDs& dependencies =
                     layoutParameters.glyphDependencies[sectionFontStack ? *sectionFontStack : baseFontStack];
                 char16_t codePoint = ft.formattedText->getCharCodeAt(j);

src/mbgl/text/tagged_string.cpp

@@ -1,16 +1,50 @@
-#include <mbgl/text/tagged_string.hpp>
 #include <mbgl/math/minmax.hpp>
+#include <mbgl/text/tagged_string.hpp>
 #include <mbgl/util/i18n.hpp>
+#include <mbgl/util/logging.hpp>
+
+namespace {
+char16_t PUAbegin = u'\uE000';
+char16_t PUAend = u'\uF8FF';
+} // namespace
 
 namespace mbgl {
-    
-void TaggedString::addSection(const std::u16string& sectionText, double scale, FontStack fontStack, optional<Color> textColor) {
+
+void TaggedString::addTextSection(const std::u16string& sectionText,
+                                  double scale,
+                                  FontStack fontStack,
+                                  optional<Color> textColor) {
     styledText.first += sectionText;
     sections.emplace_back(scale, fontStack, std::move(textColor));
     styledText.second.resize(styledText.first.size(), sections.size() - 1);
     supportsVerticalWritingMode = nullopt;
 }
 
+void TaggedString::addImageSection(const std::string& imageID) {
+    const auto& nextImageSectionCharCode = getNextImageSectionCharCode();
+    if (!nextImageSectionCharCode) {
+        Log::Warning(Event::Style, "Exceeded maximum number of images in a label.");
+        return;
+    }
+
+    styledText.first += *nextImageSectionCharCode;
+    sections.emplace_back(imageID);
+    styledText.second.resize(styledText.first.size(), sections.size() - 1);
+}
+
+optional<char16_t> TaggedString::getNextImageSectionCharCode() {
+    if (imageSectionID == 0u) {
+        imageSectionID = PUAbegin;
+        return imageSectionID;
+    }
+
+    if (++imageSectionID > PUAend) {
+        return nullopt;
+    }
+
+    return imageSectionID;
+}
+
 void TaggedString::trim() {
     std::size_t beginningWhitespace = styledText.first.find_first_not_of(u" \t\n\v\f\r");
     if (beginningWhitespace == std::u16string::npos) {

src/mbgl/text/tagged_string.hpp

@@ -13,11 +13,14 @@ struct SectionOptions {
           fontStack(std::move(fontStack_)),
           textColor(std::move(textColor_))
     {}
-    
+
+    explicit SectionOptions(std::string imageID_) : scale(1.0), imageID(std::move(imageID_)) {}
+
     double scale;
     FontStackHash fontStackHash;
     FontStack fontStack;
     optional<Color> textColor;
+    optional<std::string> imageID;
 };
 
 /**
@@ -76,11 +79,13 @@ struct TaggedString {
     const StyledText& getStyledText() const {
         return styledText;
     }
-    
-    void addSection(const std::u16string& text,
-                    double scale,
-                    FontStack fontStack,
-                    optional<Color> textColor_ = nullopt);
+
+    void addTextSection(const std::u16string& text,
+                        double scale,
+                        FontStack fontStack,
+                        optional<Color> textColor_ = nullopt);
+
+    void addImageSection(const std::string& imageID);
 
     const SectionOptions& sectionAt(std::size_t index) const {
         return sections.at(index);
@@ -100,10 +105,16 @@ struct TaggedString {
     void verticalizePunctuation();
     bool allowsVerticalWritingMode();
 
+private:
+    optional<char16_t> getNextImageSectionCharCode();
+
 private:
     StyledText styledText;
     std::vector<SectionOptions> sections;
     optional<bool> supportsVerticalWritingMode;
+    // Max number of images within a text is 6400 U+E000–U+F8FF
+    // that covers Basic Multilingual Plane Unicode Private Use Area (PUA).
+    char16_t imageSectionID = 0u;
 };
 
 } // namespace mbgl

test/text/tagged_string.test.cpp

@@ -11,9 +11,9 @@ TEST(TaggedString, Trim) {
     EXPECT_EQ(basic.rawText(), u"trim that and not this");
     
     TaggedString twoSections;
-    twoSections.addSection(u" \t\ntrim that", 1.5f, {});
-    twoSections.addSection(u" and not this  \n\t", 0.5f, {});
-    
+    twoSections.addTextSection(u" \t\ntrim that", 1.5f, {});
+    twoSections.addTextSection(u" and not this  \n\t", 0.5f, {});
+
     twoSections.trim();
     EXPECT_EQ(twoSections.rawText(), u"trim that and not this");