Qt for Embedded Linux Virtual Framebuffer

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The virtual frame buffer allows a Qt for Embedded Linux program to be developed

on your desktop machine, without switching between consoles and X11.  The virtual

framebuffer consists of a shared memory region (the virtual frame buffer)

and a utility to display the framebuffer in a window.  The display is updated

periodically, so you will see discrete snapshots of the framebuffer rather

than each individual drawing operation.  For this reason drawing problems

such as flickering may not be apparent until the program is run using a real

framebuffer.

To use the virtual framebuffer:

1. Ensure QT_NO_QWS_VFB is not set in qconfig.h (when you configure Qt,

    add the -qvfb option).

2. Start qvfb (qvfb should be compiled as a normal Qt for X11 application,

    NOT as a Qt for Embedded Linux application!).

3. Start a Qt for Embedded Linux server (i.e. construct QApplication with

   QApplication::GuiServer flag, or run a client with the -qws option).

qvfb supports the following command line options:

[-width width]   the width of the virtual framebuffer (default: 240).

[-height height] the height of the virtual framebuffer (default: 320).

[-depth depth]   the depth of the virtual framebuffer (1,4,8 or 32, default: 8).

[-nocursor]      do not display the X11 cursor in the framebuffer window.

[-qwsdisplay]    the Qt for Embedded Linux display ID, e.g. -qwsdisplay :1 (default :0).

[-skin skinfile] tells qvfb to load a skin file, e.g. -skin pda.skin

Please refer to the file "pda.skin" as an example of what a skin file looks like.

The format for skin files is:

    Image filename of skin with buttons in their up positions

    Image filename of skin with buttons in their down positions

    X offset of top left corner of the virtual screen on the skin image

    Y offset of top left corner of the virtual screen on the skin image

    Width of the virtual screen on the skin image

    Height of the virtual screen on the skin image

    Number of defined button regions

Then for each button region the format is:

    Button identifier

    Qt scan codes to generate for the button

    Top left X coordinate of the button region

    Top left Y coordinate of the button region

    Bottom right X coordinate of the button region

    Bottom right Y coordinate of the button region

The virtual framebuffer is a development tool only.  No security issues have

been considered in the virtual framebuffer design.  It should not be used

in a production environment and QT_NO_QWS_VFB should always be in force

in production libraries.