Fix bug 3759 for qt < 4.2

[lyx.git] / src / support / qstring_helpers.cpp

diff --git a/src/support/qstring_helpers.cpp b/src/support/qstring_helpers.cpp
index 724e58b066f35a70109597f48046b8af7abb6cd9..01c5de4b97ecdaa1b08624c30c68b1603658235d 100644 (file)
--- a/src/support/qstring_helpers.cpp
+++ b/src/support/qstring_helpers.cpp
@@ -12,6 +12,7 @@
 #include <config.h>
 
 #include "qstring_helpers.h"
+#include "unicode.h"
 
 #include <QVector>
 
@@ -24,12 +25,25 @@ using std::string;
 // We use QString::fromUcs4 in Qt 4.2 and higher
 QString const toqstr(docstring const & str)
 {
-       // This does not properly convert surrogate pairs
        QString s;
        int i = static_cast<int>(str.size());
        s.resize(i);
-       for (; --i >= 0;)
-               s[i] = ucs4_to_qchar(str[i]);
+       for (; --i >= 0;) {
+               char_type const c = str[i];
+               if (is_utf16(c))
+                       // Use a simple cast in the common case for speed
+                       // reasons
+                       s[i] = static_cast<unsigned short>(c);
+               else {
+                       // A simple cast is not possible, so we need to use
+                       // the full blown conversion.
+                       std::vector<unsigned short> const utf16 =
+                               ucs4_to_utf16(str.data(), str.size());
+                       // Enable the compiler to do NRVO
+                       s = QString::fromUtf16(&utf16[0], utf16.size());
+                       break;
+               }
+       }
        return s;
 }
 #endif
@@ -41,11 +55,25 @@ docstring const qstring_to_ucs4(QString const & qstr)
        QVector<uint> const ucs4 = qstr.toUcs4();
        return docstring(ucs4.begin(), ucs4.end());
 #else
-       // This does not properly convert surrogate pairs
        int const ls = qstr.size();
        docstring ucs4;
-       for (int i = 0; i < ls; ++i)
-               ucs4 += qchar_to_ucs4(qstr[i].unicode());
+       for (int i = 0; i < ls; ++i) {
+               char_type const c = static_cast<char_type>(qstr[i].unicode());
+               if (is_utf16(c))
+                       // Use a simple cast in the common case for speed
+                       // reasons
+                       ucs4 += c;
+               else {
+                       // A simple cast is not possible, so we need to use
+                       // the full blown conversion.
+                       std::vector<char_type> const v = utf16_to_ucs4(
+                               reinterpret_cast<unsigned short const *>(qstr.utf16()),
+                               qstr.size());
+                       // Enable the compiler to do NRVO
+                       ucs4 = docstring(v.begin(), v.end());
+                       break;
+               }
+       }
        return ucs4;
 #endif
 }