1 files changed, 53 insertions, 0 deletions
diff --git a/src/mbgl/text/bidi.cpp b/src/mbgl/text/bidi.cpp
new file mode 100644
index 0000000000..2b6967110c
--- /dev/null
+++ b/src/mbgl/text/bidi.cpp
@@ -0,0 +1,53 @@
+#include <memory>
+
+#include <mbgl/text/bidi.hpp>
+#include <unicode/ubidi.h>
+#include <unicode/ushape.h>
+
+namespace mbgl {
+
+BiDi::BiDi() {
+    UErrorCode errorCode = U_ZERO_ERROR;
+    transform = ubiditransform_open(&errorCode); // Only error is failure to allocate memory, in
+                                                 // that case ubidi_transform would fall back to
+                                                 // creating transform object on the fly
+}
+
+BiDi::~BiDi() {
+    if (transform)
+        ubiditransform_close(transform);
+}
+
+std::u16string BiDi::bidiTransform(const std::u16string& input) {
+    UErrorCode errorCode = U_ZERO_ERROR;
+
+    std::unique_ptr<UChar[]> outputText =
+        std::make_unique<UChar[]>(input.size() * 2); // Maximum output of ubidi_transform is twice
+                                                     // the size of input according to
+                                                     // ubidi_transform.h
+    uint32_t outputLength = ubiditransform_transform(
+        transform, input.c_str(), static_cast<int32_t>(input.size()), outputText.get(),
+        static_cast<int32_t>(input.size()) * 2,
+        UBIDI_DEFAULT_LTR,     // Assume input is LTR unless strong RTL characters are found
+        UBIDI_LOGICAL,         // Input is in logical order
+        UBIDI_LTR,             // Output is in "visual LTR" order
+        UBIDI_VISUAL,          //  ''
+        UBIDI_MIRRORING_ON,    // Use mirroring lookups for things like parentheses that need mirroring
+                               // in RTL text
+        U_SHAPE_LETTERS_SHAPE, // Add options here for handling numbers in bidirectional text
+        &errorCode);
+
+    // If the algorithm fails for any reason, fall back to non-transformed text
+    if (U_FAILURE(errorCode))
+        return input;
+
+    return std::u16string(outputText.get(), outputLength);
+}
+
+bool BiDi::baseDirectionRightToLeft(const std::u16string& input) {
+    // This just looks for the first character with a strong direction property, it does not perform
+    // the BiDi algorithm
+    return ubidi_getBaseDirection(input.c_str(), static_cast<int32_t>(input.size())) == UBIDI_RTL;
+}
+
+} // end namespace mbgl