-The exceptions are {\it width} and {\it height}, which are set to wxAsIs to
-ensure that if the user does not specify a constraint, the existing
-width and height will be used, to be compatible with panel items which often
-have take a default size. If the constraint is wxAsIs, the dimension will
-not be changed.
-
-To call the \helpref{wxWindow::Layout}{wxwindowlayout} function which evaluates
-constraints, you can either call wxWindow::SetAutoLayout to tell
-default OnSize handlers to call Layout, or override OnSize and call Layout yourself.
-
-\subsection{Constraint layout: more detail}
+To calculate the position and size of the control, the layout algorithm needs to
+know exactly 4 constraints (as it has 4 numbers to calculate from them), so you
+should always set exactly 4 of the constraints from the above table.
+
+If you want the controls height or width to have the default value, you may use
+a special value for the constraint: wxAsIs. If the constraint is wxAsIs, the
+dimension will not be changed which is useful for the dialog controls which
+often have the default size (e.g. the buttons whose size is determined by their
+label).
+
+The constrains calculation is done in \helpref{wxWindow::Layout}{wxwindowlayout}
+function which evaluates constraints. To call it you can either call
+\helpref{wxWindow::SetAutoLayout}{wxwindowsetautolayout} if the parent window
+is a frame, panel or a dialog to tell default OnSize handlers to call Layout
+automatically whenever the window size changes, or override OnSize and call
+Layout yourself (note that you do have to call
+\helpref{Layout}{wxwindowlayout} yourself if the parent window is not a
+frame, panel or dialog).
+
+\subsection{Constraint layout: more details}\label{constraintlayoutdetails}