[core] Render half-width glyphs in upright orientation

This change forces glyphs whose natural orientation in vertical writing
mode is 'sideways' to be rendered in upright orientation (only for non complex
text layouts). This is different compared to W3C / browser behavior that is by
default, renders glyphs in their respective natural orientation.

In the future, there  might need to add a new layout property that would control
glyph orientation separately (e.g., text-glyph-orientation: natural | upright).

1 files changed, 8 insertions, 0 deletions

diff --git a/src/mbgl/util/i18n.cpp b/src/mbgl/util/i18n.cpp
index 716481734e..885c8ec3d1 100644
--- a/src/mbgl/util/i18n.cpp
+++ b/src/mbgl/util/i18n.cpp
@@ -643,6 +643,14 @@ bool isStringInSupportedScript(const std::string& input) {
     return true;
 }
 
+bool isCharInComplexShapingScript(char16_t chr) {
+    return isInArabic(chr) ||
+           isInArabicSupplement(chr) ||
+           isInArabicExtendedA(chr) ||
+           isInArabicPresentationFormsA(chr) ||
+           isInArabicPresentationFormsB(chr);
+}
+
 bool isWhitespace(char16_t chr) {
     return chr == u' ' || chr == u'\t' || chr == u'\n' || chr == u'\v' || chr == u'\f' || chr == u'\r';
 }