Fix escaping/unescaping in wxLongStringProperty

wxPropertyGrid::ExpandEscapeSequences() function should convert all valid
escape sequences (\r, \n, \t, \\) to the corresponding single characters
(CR, LF, TAB, backslash, accordingly) and
wxPropertyGrid::CreateEscapeSequences() function should do the reverse
operation and convert these raw characters to the corresponding escape
sequences.

Closes #17896.

docs/changes.txt

@@ -145,6 +145,7 @@ All (GUI):
 - Add support for bitmaps to wxToggleButton XRC handler (tm).
 - Fix wxGCDC::SetDeviceClippingRegion().
 - Never restore size smaller than the best one in wxPersistentTLW.
+- Fix escaping/unescaping characters in wxLongStringProperty in wxPG (mikek).
 
 wxGTK:
 

interface/wx/propgrid/property.h

@@ -543,8 +543,14 @@ wxPG_PROP_CLASS_SPECIFIC_3          = 0x00400000
     @subsection wxLongStringProperty
 
     Like wxStringProperty, but has a button that triggers a small text editor
-    dialog. Note that in long string values, tabs are represented by "\t" and
-    line break by "\n".
+    dialog. Note that in long string values, some control characters are
+    escaped: tab is represented by "\t", line break by "\n", carriage return
+    by "\r" and backslash character by "\\". If another character is preceded
+    by backslash, the backslash is skipped.
+    Note also that depending on the system (port), some sequences of special
+    characters, like e.g. "\r\n", can be interpreted and presented in
+    a different way in the editor and therefore such sequences may not be
+    the same before and after the edition.
 
     To display custom dialog on button press, you can subclass
     wxLongStringProperty and implement OnButtonClick, like this:

src/propgrid/propgrid.cpp

@@ -1744,9 +1744,8 @@ wxString& wxPropertyGrid::ExpandEscapeSequences( wxString& dst_str, const wxStri
 
     bool prev_is_slash = false;
 
-    wxString::const_iterator i = src_str.begin();
-
-    for ( ; i != src_str.end(); ++i )
+    wxString::const_iterator i;
+    for ( i = src_str.begin(); i != src_str.end(); ++i )
     {
         wxUniChar a = *i;
 
@@ -1759,13 +1758,9 @@ wxString& wxPropertyGrid::ExpandEscapeSequences( wxString& dst_str, const wxStri
             else
             {
                 if ( a == wxS('n') )
-                {
-            #ifdef __WXMSW__
                     dst_str << wxS('\n');
-            #else
-                    dst_str << wxS('\n');
-            #endif
-                }
+                else if ( a == wxS('r') )
+                    dst_str << wxS('\r');
                 else if ( a == wxS('t') )
                     dst_str << wxS('\t');
                 else
@@ -1801,40 +1796,25 @@ wxString& wxPropertyGrid::CreateEscapeSequences( wxString& dst_str, const wxStri
     }
 
     wxString::const_iterator i;
-    wxUniChar prev_a = wxS('\0');
-
     for ( i = src_str.begin(); i != src_str.end(); ++i )
     {
         wxUniChar a = *i;
 
-        if ( a >= wxS(' ') )
-        {
-            // This surely is not something that requires an escape sequence.
-            dst_str << a;
-        }
-        else
-        {
-            // This might need...
         if ( a == wxS('\r') )
-            {
-                // DOS style line end.
-                // Already taken care below
-            }
+            // Carriage Return.
+            dst_str << wxS("\\r");
         else if ( a == wxS('\n') )
-                // UNIX style line end.
+            // Line Feed.
             dst_str << wxS("\\n");
         else if ( a == wxS('\t') )
             // Tab.
-                dst_str << wxS('\t');
+            dst_str << wxS("\\t");
+        else if ( a == wxS('\\') )
+            // Escape character (backslash).
+            dst_str << wxS("\\\\");
         else
-            {
-                //wxLogDebug(wxS("WARNING: Could not create escape sequence for character #%i"),(int)a);
             dst_str << a;
     }
-        }
-
-        prev_a = a;
-    }
     return dst_str;
 }