Usage

Gamma/Photon: Using Gamma™ with the Photon microGUIŽ, Version 4.0
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# `Usage`

`Usage` -- gives a QNX 4-style usage message during run-time.

## Syntax

    Usage(usemsg?, program?)

## Arguments

`usemsg`

  An optional message name. The default is __USAGE.

`program`

  An optional program name. The default is the current program.

## Returns

A usage message on success, or -1 on failure.

## Description

This function prints a QNX 4 `use` message while a program is running. The default message name is __USAGE, and the default program is the program that is currently running. Generally the defaults are used.

The usage message must be entered in the exact same format as a QNX 4 `use` message, where each line starts with `#`. The line immediately before the first QNX 4 `use` message line (#ifdef...) must be the name of the message, followed by `"`(double quote). The #endif line at the end of the QNX 4 `use` message must end with another `"` (double quote), followed by `;` (semicolon). See the example below. For an entry of `%C` at the beginning of any line, QNX will insert the name of the program.

To use this method, you must load the Usage.lsp library with a call to `require_lisp("Usage.lsp")`.

## Example

This example, `ex_Usage.g`, is included in the `gamma_ph_`#`_examples_1_QNX4.tgz` file available on the Cogent Web Site.

    #!/usr/cogent/bin/phgamma

    /*
    The following example puts up a window with an exit button, and prints
    a usage message.
    */

    PtInit(nil);
    require_lisp("Usage.lsp");
    require_lisp("PhotonWidgets.lsp");

    win = new(PtWindow);
    win.SetDim(200,130);
    win.fill_color = PgRGB(140,200,250);

    but = new(PtButton);
    but.SetPos(80,50);
    but.text_string = "Exit";
    PtAttachCallback(but,Pt_CB_ACTIVATE,#exit_program(3));

    __USAGE="
    #ifdef __USAGE
    #The usage message appears here.
    #For example:
    #%C
    #Push the exit button to exit.
    #endif";

    Usage();

    PtRealizeWidget(win);
    PtMainLoop();

## See Also

In Photon documentation: use.

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