Fix determining the length of the text in wxTextEntry/wxTextCtrl (wxGTK)

Several functions of wxTextEntry and wxTextCtrl call to
gtk_entry_get_text_length() API to determine the length of the text in
GTKEntry. This API is available since GTK+ 2.14 so we have to implement
a fallback method for older GTK+ versions.
Dedicated function GTKGetEntryTextLength() is implemented in wxTextEntry
and exposed through its interface because it is also used in wxTextCtrl.

include/wx/gtk/textentry.h

@@ -80,6 +80,8 @@ protected:
     // Override the base class method to use GtkEntry IM context.
     virtual int GTKIMFilterKeypress(GdkEventKey* event) const;
 
+    static unsigned int GTKGetEntryTextLength(GtkEntry* entry);
+
 private:
     // implement this to return the associated GtkEntry or another widget
     // implementing GtkEditable

src/gtk/textctrl.cpp

@@ -1204,7 +1204,7 @@ bool wxTextCtrl::PositionToXY(long pos, long *x, long *y ) const
     }
     else // single line control
     {
-        if (pos <= gtk_entry_get_text_length(GTK_ENTRY(m_text)))
+        if (pos <= GTKGetEntryTextLength(GTK_ENTRY(m_text)))
         {
             if ( y )
                 *y = 0;
@@ -1225,7 +1225,8 @@ long wxTextCtrl::XYToPosition(long x, long y ) const
 {
     if ( IsSingleLine() )
     {
-        if ( y != 0 || x >= gtk_entry_get_text_length(GTK_ENTRY(m_text)) )
+
+        if ( y != 0 || x >= GTKGetEntryTextLength(GTK_ENTRY(m_text)) )
             return -1;
 
         return x;

src/gtk/textentry.cpp

@@ -35,6 +35,22 @@
 #include "wx/gtk/private/gtk2-compat.h"
 #include "wx/gtk/private/string.h"
 
+//-----------------------------------------------------------------------------
+//  helper function to get the length of the text
+//-----------------------------------------------------------------------------
+
+static unsigned int GetEntryTextLength(GtkEntry* entry)
+{
+#if GTK_CHECK_VERSION(2, 14, 0)
+    if ( gtk_check_version(2, 14, 0) == NULL )
+    {
+        return gtk_entry_get_text_length(entry);
+    }
+#endif // GTK+ 2.14+
+
+    return strlen(gtk_entry_get_text(entry));
+}
+
 // ============================================================================
 // signal handlers implementation
 // ============================================================================
@@ -61,7 +77,7 @@ wx_gtk_insert_text_callback(GtkEditable *editable,
     // check that we don't overflow the max length limit if we have it
     if ( text_max_length )
     {
-        const int text_length = gtk_entry_get_text_length(entry);
+        const int text_length = GetEntryTextLength(entry);
 
         // We can't use new_text_length as it is in bytes while we want to count
         // characters (in first approximation, anyhow...).
@@ -243,6 +259,12 @@ void wxTextEntry::Remove(long from, long to)
     gtk_editable_delete_text(GetEditable(), from, to);
 }
 
+// static
+unsigned int wxTextEntry::GTKGetEntryTextLength(GtkEntry* entry)
+{
+    return GetEntryTextLength(entry);
+}
+
 // ----------------------------------------------------------------------------
 // clipboard operations
 // ----------------------------------------------------------------------------
@@ -320,7 +342,7 @@ long wxTextEntry::GetLastPosition() const
     long pos = -1;
     GtkEntry* entry = (GtkEntry*)GetEditable();
     if (GTK_IS_ENTRY(entry))
-        pos = gtk_entry_get_text_length(entry);
+        pos = GetEntryTextLength(entry);
 
     return pos;
 }