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# Qt Motif Extension

## Introduction

The Qt Motif Extension assists the migration of old Xt and Motif based applications to the more comfortable Qt toolkit. This extension replaces the older Xt/Motif Support Extension included with earlier versions of Qt.

The Qt Motif Extension consists of the following classes:

- QMotif - Provides the basis of the Qt Motif Extension.
- QMotifWidget - Provides the QWidget API for Motif widgets.
- QMotifDialog - Provides the QDialog API for Motif dialogs.
- QXtWidget - The Xt/Motif integration widget from the previous Xt/Motif extension. This class is unsupported and has many known problems and limitations. It is provided only to keep existing source working; it should not be used in new code.

### Additional Documentation

- Examples
- Migration Walkthrough - A complete migration of a Motif based program to the Qt toolkit.

## Common Problems

### Incorrect CDE Color Scheme

QMotifWidget and QMotifDialog will use the same Visual, Colormap and color depth that QApplication uses. When using CDE, the color scheme may be incorrect when using a Visual, Colormap and color depth that is not the default. To work around this problem, add the following resource string to your startup files (for example, `$HOME/.dt/sessions/current/dt.resources`):

        *userColorObj: false

### X11 Header Conflicts

The X11 headers define some constants that conflict with the Qt headers. The solution is to include all Qt headers first, followed by headers from this extension, and all Xt/Motif and X11 headers last. For example:

        // Qt headers first
        #include <qapplication.h>
        #include <qpushbutton.h>
        #include <qsocket.h>
        ...

        // QMotif* headers next
        #include <qmotif.h>
        #include <qmotifdialog.h>
        #include <qmotifwidget.h>

        // Xt/Motif and X11 headers last
        #include <X11/Xlib.h>
        #include <Xt/Intrinsic.h>
        #include <Xm/Xm.h>
        ...

### Multiple Screen Support

QMotifWidget can be used together with QDesktopWidget to create top-level windows on multiple screens. A common mistake is to create a QMotifWidget on a non-default screen while the Xt/Motif widgets are created on the default screen. The solution is to specify the screen to both QMotifWidget and the Xt/Motif child. For example:

        Display *dpy = QApplication::desktop()->x11Display();
        Arg args[1];

        // make sure both QMotifWidget and the XmMainWindow are on screen 1
        XtSetArg(args[0], XtNscreen, ScreenOfDisplay(dpy, 1));
        QMotifWidget *toplevel =
            new QMotifWidget(QApplication::desktop()->screen(1),
                             xmMainWindowWidgetClass, args, 1, "mainwindow");

## Known Problems and Limitations

### Clipboard Transfers between Motif and Qt

In some situations, clipboard transfers between Motif and Qt widgets will fail, and neither Motif nor Qt seem to recover. This will occur when Motif and Qt are using the same X11 display connection. This typically happens in 2 situations:

1. QApplication was created with a foreign display, or
2. QMotifWidget is used in the widget heirarchy.

The only way to work around this problem is to ensure that Motif and Qt use a different X11 connection. However, this solution will not work when using QMotifWidget in the widget heirarchy (since QMotifWidget uses the same X11 display connection that Qt does).

This problem will be fixed in a future release.