Add: [OSX] Text layout using the native CoreText API.

By default, the native API will be used instead of ICU, but if ICU is
forced in using configure, it will take precedence.

src/gfx_layout.cpp

@@ -25,6 +25,10 @@
 #include "os/windows/string_uniscribe.h"
 #endif /* WITH_UNISCRIBE */
 
+#ifdef WITH_COCOA
+#include "os/macosx/string_osx.h"
+#endif
+
 #include "safeguards.h"
 
 
@@ -670,7 +674,7 @@ Layouter::Layouter(const char *str, int maxw, TextColour colour, FontSize fontsi
 		} else {
 			/* Line is new, layout it */
 			FontState old_state = state;
-#if defined(WITH_ICU_LAYOUT) || defined(WITH_UNISCRIBE)
+#if defined(WITH_ICU_LAYOUT) || defined(WITH_UNISCRIBE) || defined(WITH_COCOA)
 			const char *old_str = str;
 #endif
 
@@ -698,6 +702,16 @@ Layouter::Layouter(const char *str, int maxw, TextColour colour, FontSize fontsi
 			}
 #endif
 
+#ifdef WITH_COCOA
+			if (line.layout == NULL) {
+				GetLayouter<CoreTextParagraphLayoutFactory>(line, str, state);
+				if (line.layout == NULL) {
+					state = old_state;
+					str = old_str;
+				}
+			}
+#endif
+
 			if (line.layout == NULL) {
 				GetLayouter<FallbackParagraphLayoutFactory>(line, str, state);
 			}
@@ -841,6 +855,9 @@ void Layouter::ResetFontCache(FontSize size)
 #if defined(WITH_UNISCRIBE)
 	UniscribeResetScriptCache(size);
 #endif
+#if defined(WITH_COCOA)
+	MacOSResetScriptCache(size);
+#endif
 }
 
 /**