Sets the selection.
<p>
The new selection may not be visible. Call showSelection to scroll
the selection into view.
</p>
@param start offset of the first selected character, start >= 0 must be true.
@param length number of characters to select, 0 <= start + length
<= getCharCount() must be true.
A negative length places the caret at the selection start.
@param sendEvent a Selection event is sent when set to true and when
the selection is reset.
Sets the selection. <p> The new selection may not be visible. Call showSelection to scroll the selection into view. </p>
@param start offset of the first selected character, start >= 0 must be true. @param length number of characters to select, 0 <= start + length <= getCharCount() must be true. A negative length places the caret at the selection start. @param sendEvent a Selection event is sent when set to true and when the selection is reset.