Add: [Win32] Text layout using the native Windows Uniscribe library.

Uniscribe is sometimes producing different results compared to ICU, especially
when RTL and LTR content is mixed. Comparing the results to other programs
(like editors or web browsers) leads me to believe that the result are at least
not worse than ICU and possibly better.

src/os/windows/string_uniscribe.h

@@ -0,0 +1,70 @@
+/* $Id$ */
+
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file string_uniscribe.h Functions related to laying out text on Win32. */
+
+#ifndef STRING_UNISCRIBE_H
+#define STRING_UNISCRIBE_H
+
+#if defined(WITH_UNISCRIBE)
+
+#include "../../gfx_layout.h"
+
+
+void UniscribeResetScriptCache(FontSize size);
+
+
+/**
+ * Helper class to construct a new #UniscribeParagraphLayout.
+ */
+class UniscribeParagraphLayoutFactory {
+public:
+	/** Helper for GetLayouter, to get the right type. */
+	typedef wchar_t CharType;
+	/** Helper for GetLayouter, to get whether the layouter supports RTL. */
+	static const bool SUPPORTS_RTL = true;
+
+	/**
+	* Get the actual ParagraphLayout for the given buffer.
+	* @param buff The begin of the buffer.
+	* @param buff_end The location after the last element in the buffer.
+	* @param fontMapping THe mapping of the fonts.
+	* @return The ParagraphLayout instance.
+	*/
+	static ParagraphLayouter *GetParagraphLayout(CharType *buff, CharType *buff_end, FontMap &fontMapping);
+
+	/**
+	* Append a wide character to the internal buffer.
+	* @param buff        The buffer to append to.
+	* @param buffer_last The end of the buffer.
+	* @param c           The character to add.
+	* @return The number of buffer spaces that were used.
+	*/
+	static size_t AppendToBuffer(CharType *buff, const CharType *buffer_last, WChar c)
+	{
+		if (c >= 0x010000U) {
+			/* Character is encoded using surrogates in UTF-16. */
+			if (buff + 1 <= buffer_last) {
+				buff[0] = (CharType)(((c - 0x010000U) >> 10) + 0xD800);
+				buff[1] = (CharType)(((c - 0x010000U) & 0x3FF) + 0xDC00);
+			} else {
+				/* Not enough space in buffer. */
+				*buff = 0;
+			}
+			return 2;
+		} else {
+			*buff = (CharType)(c & 0xFFFF);
+			return 1;
+		}
+	}
+};
+
+#endif /* defined(WITH_UNISCRIBE) */
+
+#endif /* STRING_UNISCRIBE_H */