# The XTrestle interface

`XTrestle` checks for X-style ```-display`'' and ```-geometry`'' command-line switches and installs a top-level window accordingly. If your application install more than one top-level window, you may find the routines in the `XParam` interface helpful.

    INTERFACE XTrestle;

    IMPORT TrestleComm, VBT;

    EXCEPTION Error;

    PROCEDURE Install (v          : VBT.T;
                       applName   : TEXT    := NIL;
                       inst       : TEXT    := NIL;
                       windowTitle: TEXT    := NIL;
                       iconTitle  : TEXT    := NIL;
                       bgColorR   : REAL    := -1.0;
                       bgColorG   : REAL    := -1.0;
                       bgColorB   : REAL    := -1.0;
                       iconWindow : VBT.T   := NIL   )
      RAISES {TrestleComm.Failure, Error};
    <* LL.sup = VBT.mu *>

This is like `Trestle.Install` except that the locking level is different and the command line is parsed for X-style `-display` and `-geometry` options.

    END XTrestle.

The syntax of these switches is described in the X manpage and in The X Window System [XWindowSystem] .

If there is a `-display` argument, it will be made the default Trestle connection for those procedures in the `Trestle` interface that take a `Trestle.T` as a parameter.

The `TrestleComm.Failure` exception is raised if a call to `Trestle` raises that exception. The `Error` exception is raised if the parameter following `-display` or `-geometry` contains any syntax errors (or is missing).