Don't set maximum text length for non-text wxPG properties

Setting the limit for the length of the text the user can enter in the text editor makes sense only for properties having text editors so in wxPGProperty::SetMaxLength() should be done a check whether to actually set a limit or not depending on the kind of editor used.
wxPropertyGridInterface::SetPropertyMaxLength() should be implemented on top of wxPGProperty::SetMaxLength() to proceed only if maximum length was actually set.

include/wx/propgrid/property.h

@@ -1490,10 +1490,11 @@ public:
     // this function usually returns Null variant.
     wxVariant GetDefaultValue() const;
 
-    // Returns maximum allowed length of property's text value.
+    // Returns maximum allowed length of the text the user can enter in
+    // the property text editor.
     int GetMaxLength() const
     {
-        return (int) m_maxLen;
+        return m_maxLen;
     }
 
     // Determines, recursively, if all children are not unspecified.
@@ -2038,11 +2039,10 @@ protected:
 
     FlagType                    m_flags;
 
-    // Maximum length (mainly for string properties). Could be in some sort of
+    // Maximum length (for string properties). Could be in some sort of
     // wxBaseStringProperty, but currently, for maximum flexibility and
-    // compatibility, we'll stick it here. Anyway, we had 3 excess bytes to use
-    // so short int will fit in just fine.
-    short                       m_maxLen;
+    // compatibility, we'll stick it here.
+    int                         m_maxLen;
 
     // Root has 0, categories etc. at that level 1, etc.
     unsigned char               m_depth;

include/wx/propgrid/propgrid.h

@@ -2001,7 +2001,13 @@ inline void wxPGProperty::SetEditor( const wxString& editorName )
 
 inline bool wxPGProperty::SetMaxLength( int maxLen )
 {
-    return GetGrid()->SetPropertyMaxLength(this,maxLen);
+    const wxPGEditor* editorClass = GetEditorClass();
+    if ( editorClass != wxPGEditor_TextCtrl &&
+         editorClass != wxPGEditor_TextCtrlAndButton )
+        return false;
+
+    m_maxLen = wxMax(maxLen, 0); // shouldn't be a nagative value
+    return true;
 }
 
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