Refactor wxGridCellDateRenderer::Parse() to make it reusable

No real changes, just create TryParseDate() helper in order to allow
reusing it from wxGridCellDateEditor too in the upcoming commit.

include/wx/generic/private/grid.h

@@ -1084,5 +1084,20 @@ wxGetContentRect(wxSize contentSize,
                  int hAlign,
                  int vAlign);
 
+namespace wxGridPrivate
+{
+
+#if wxUSE_DATETIME
+
+// Helper function trying to parse the given string using the specified date
+// format and then using ParseDate() as a fallback if it failed. If this still
+// fails, returns false.
+bool
+TryParseDate(wxDateTime& result, const wxString& text, const wxString& format);
+
+#endif // wxUSE_DATETIME
+
+} // namespace wxGridPrivate
+
 #endif // wxUSE_GRID
 #endif // _WX_GENERIC_GRID_PRIVATE_H_

src/generic/gridctrl.cpp

@@ -76,6 +76,23 @@ void wxGridCellRenderer::Draw(wxGrid& grid,
 
 #if wxUSE_DATETIME
 
+bool
+wxGridPrivate::TryParseDate(wxDateTime& result,
+                            const wxString& text,
+                            const wxString& format)
+{
+    wxString::const_iterator end;
+
+    // Try parsing using the same format we use for output first.
+    if ( result.ParseFormat(text, format, &end) && end == text.end() )
+        return true;
+
+    // But fall back to free-form parsing, which notably allows us to parse
+    // strings such as "today" or "tomorrow" which would be never accepted by
+    // ParseFormat().
+    return result.ParseDate(text, &end) && end == text.end();
+}
+
 // Enables a grid cell to display a formatted date
 
 wxGridCellDateRenderer::wxGridCellDateRenderer(const wxString& outformat)
@@ -131,16 +148,7 @@ wxString wxGridCellDateRenderer::GetString(const wxGrid& grid, int row, int col)
 
 bool wxGridCellDateRenderer::Parse(const wxString& text, wxDateTime& result)
 {
-    wxString::const_iterator end;
-
-    // Try parsing using the same format we use for output first.
-    if ( result.ParseFormat(text, m_oformat, &end) && end == text.end() )
-        return true;
-
-    // But fall back to free-form parsing, which notably allows us to parse
-    // strings such as "today" or "tomorrow" which would be never accepted by
-    // ParseFormat().
-    return result.ParseDate(text, &end) && end == text.end();
+    return wxGridPrivate::TryParseDate(result, text, m_oformat);
 }
 
 void wxGridCellDateRenderer::Draw(wxGrid& grid,