Add HarfBuzz Text Shaping and Font Fallback Support (#3611)

Co-authored-by: alan wei chen <alanchenboy@gmail.com>

include/mbgl/util/convert.hpp

@@ -7,6 +7,9 @@
 #include <cstddef>
 #include <tuple>
 #include <type_traits>
+#include <string_view>
+#include <optional>
+#include <string>
 
 namespace mbgl {
 namespace util {
@@ -36,5 +39,53 @@ inline constexpr auto to_array(std::tuple<Ts...>&& tuple) {
                       std::forward<std::tuple<Ts...>>(tuple));
 }
 
+/// Convert string to integral types
+template <typename T>
+std::enable_if_t<std::is_integral_v<T>, std::optional<T>> parse(std::string_view str, int base = 10) noexcept {
+    static_assert(std::is_same_v<T, int32_t> || std::is_same_v<T, uint32_t> || std::is_same_v<T, int64_t> ||
+                      std::is_same_v<T, uint64_t>,
+                  "Unsupported integral type in mbgl::util::parse<T>.");
+    char* end = nullptr;
+    errno = 0;
+
+    if constexpr (std::is_same_v<T, int32_t>) {
+        long val = std::strtol(str.data(), &end, base);
+        if (errno == 0 && end == str.data() + str.size()) return static_cast<T>(val);
+    } else if constexpr (std::is_same_v<T, uint32_t>) {
+        unsigned long val = std::strtoul(str.data(), &end, base);
+        if (errno == 0 && end == str.data() + str.size()) return static_cast<T>(val);
+    } else if constexpr (std::is_same_v<T, int64_t>) {
+        long long val = std::strtoll(str.data(), &end, base);
+        if (errno == 0 && end == str.data() + str.size()) return static_cast<T>(val);
+    } else if constexpr (std::is_same_v<T, uint64_t>) {
+        unsigned long long val = std::strtoull(str.data(), &end, base);
+        if (errno == 0 && end == str.data() + str.size()) return static_cast<T>(val);
+    }
+
+    return std::nullopt;
+}
+
+/// Convert string to floating point types
+template <typename T>
+std::enable_if_t<std::is_floating_point_v<T>, std::optional<T>> parse(std::string_view str) noexcept {
+    static_assert(std::is_same_v<T, float> || std::is_same_v<T, double> || std::is_same_v<T, long double>,
+                  "Unsupported floating point type in mbgl::util::parse<T>.");
+    char* end = nullptr;
+    errno = 0;
+
+    if constexpr (std::is_same_v<T, float>) {
+        float val = std::strtof(str.data(), &end);
+        if (errno == 0 && end == str.data() + str.size()) return val;
+    } else if constexpr (std::is_same_v<T, double>) {
+        double val = std::strtod(str.data(), &end);
+        if (errno == 0 && end == str.data() + str.size()) return val;
+    } else if constexpr (std::is_same_v<T, long double>) {
+        long double val = std::strtold(str.data(), &end);
+        if (errno == 0 && end == str.data() + str.size()) return val;
+    }
+
+    return std::nullopt;
+}
+
 } // namespace util
 } // namespace mbgl