Use UTF-8 for saving wxTextCtrl contents now.

This ensures that the files created by wxTextCtrl::SaveFile() can be read back
by wxTextCtrl::LoadFile() as previously the files were saved using the current
locale encoding but read back using Latin1 (after first trying, and failing,
to read them as UTF-8).

This is a backwards incompatible change but it ensures that wxTextCtrl can
load its own files and is also consistent with the use of UTF-8 by default in
other places. Finally, and perhaps most importantly, this ensures that the
file contents can always be saved, i.e. there is no risk of conversion errors
any more.

Closes #15611.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75073 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -493,6 +493,13 @@ Deprecated methods and their replacements
 Changes in behaviour visible to end users
 -----------------------------------------
 
+- wxTextCtrl::SaveFile() now creates UTF-8-encoded files instead of using the
+  default locale encoding. This ensures that the entire text control contents
+  can be saved and is consistent with the use of UTF-8 by default in the other
+  places, notably DoLoadFile(), but is a change since the previous versions.
+  If you need the old behaviour, consider calling wxFFile::Write() explicitly
+  with wxConvCurrent conversion parameter.
+
 - In wxMSW wxSpinCtrl used to prevent the user from entering more digits than
   could fit in its visible area. This was inconsistent with the other ports and
   now the control scrolls if too much text is added.
@@ -565,6 +572,7 @@ Major new features in this release
 
 All:
 
+- wxTextFile::SaveFile() uses UTF-8 now.
 - Add possibility to validate the input files against a schema to wxrc.
 - Fix recently broken compilation with Intel compiler.
 - Fix reading of files with Mac EOLs in wxTextFile.

src/common/textcmn.cpp

@@ -927,7 +927,7 @@ bool wxTextAreaBase::DoSaveFile(const wxString& filename, int WXUNUSED(fileType)
 {
 #if wxUSE_FFILE
     wxFFile file(filename, wxT("w"));
-    if ( file.IsOpened() && file.Write(GetValue(), *wxConvCurrent) )
+    if ( file.IsOpened() && file.Write(GetValue()) )
     {
         // if it worked, save for future calls
         m_filename = filename;