Map wxDF_TEXT to text in UTF-8 encoding in wxOSX

Don't use legacy encoding for it, this was unexpected and resulted in
e.g. wxClipboard::IsSupported(wxDF_TEXT) returning false when there was
text on the clipboard and IsSupported(wxDF_UNICODETEXT) returned true.

On current systems text and Unicode text are the same thing, so make
behaviour of wxDF_TEXT consistent with wxDF_UNICODETEXT.

See #26552.

Closes #26565.

docs/changes.txt

@@ -140,6 +140,11 @@ Changes in behaviour not resulting in compilation errors
   already didn't do it in wxMSW. Call Show() explicitly before Raise() if
   necessary.
 
+- wxDF_TEXT on macOS now corresponds to the text in UTF-8 encoding instead of
+  previously used MacRoman. No changes are necessary for the programs using
+  wxTextDataObject, but for the code working with the raw bytes in this format
+  you may need to change it to use wxConvUTF8 instead of wxConvLocal.
+
 
 Changes in behaviour which may result in build errors
 -----------------------------------------------------

interface/wx/dataobj.h

@@ -751,8 +751,8 @@ public:
 
     /**
         Returns 2 under wxMac and wxGTK, where text data coming from the
-        clipboard may be provided as ANSI (@c wxDF_TEXT) or as Unicode text
-        (@c wxDF_UNICODETEXT).
+        clipboard may be provided as (@c wxDF_TEXT), in ANSI (wxGTK) or UTF8 (wxMac),
+        or as Unicode text (@c wxDF_UNICODETEXT).
 
         Returns 1 under other platforms (e.g. wxMSW).
     */

src/common/dobjcmn.cpp

@@ -345,7 +345,11 @@ inline wxMBConv& GetConv(const wxDataFormat& format)
     static wxMBConvUTF16 s_UTF16Converter;
 
     return format == wxDF_UNICODETEXT ? static_cast<wxMBConv&>(s_UTF16Converter)
+#ifdef __WXOSX__
+                                      : static_cast<wxMBConv&>(wxConvUTF8);
+#else
                                       : static_cast<wxMBConv&>(wxConvLocal);
+#endif
 }
 
 } // anonymous namespace

src/osx/carbon/dataobj.cpp

@@ -33,8 +33,6 @@
 
 #include <memory>
 
-static CFStringRef kUTTypeTraditionalMacText = CFSTR("com.apple.traditional-mac-plain-text");
-
 static wxString privateUTIPrefix = "org.wxwidgets.private.";
 
 // ----------------------------------------------------------------------------
@@ -94,7 +92,7 @@ wxDataFormat::NativeFormat wxDataFormat::GetFormatForType(wxDataFormatId type)
     switch (type)
     {
         case wxDF_TEXT:
-            f = kUTTypeTraditionalMacText;
+            f = kUTTypeUTF8PlainText;
             break;
 
         case wxDF_UNICODETEXT: