Display Screen Settings

Help index


Visible Screen Area

The values specified here are used to compute the screens actual resolution This information is by some of ST/X's drawing windows to scale the output to the printed papers size.
You should enter the size of the visible area (i.e. excluding any black frame of the screen).

If your display simulates a bigger virtual screen (i.e. an XFree server with a bigger virtual screen), the size of the overall screen area must to be entered (i.e. including the invisible part).
This is because ST/X computes the resolution from the given screenSize and the display extent (in pixels). However, there is usually no way to get information about the physical dimensions.

The exact resolution is required if you want 1:1 display of graphics; for example, the DrawTool demo program adjusts its scaling to draw its figure in the actual (paper) size.
Also, the PostscriptGraphicsContext class needs those values, to adjust the printing scale and to compute font sizes for systems which do not provide postscript font metrics.
Finally, some popup dialogs compute their default extent to be sized a certain number of millimeters or inches.

If the common-sizes list does not include a valid dimension for your actual monitor, you should specify the size by entering the numeric values.

Notice, that ST/X asks the display (i.e. the Xserver) about the screen dimensions. However, in practice the values as returned are not realistic on most - especially PC based - systems.

To have the screens size be set automatically at startup time, add a line such as:

    Screen default widthInMillimeter:xxx; heightInMillimeter:yyy.
to your "display.rc" file (or to a display-specific "d_xxx.rc" file).

Color Monitor

Clear this checkBoxes mark, if you have a black & white monitor attached to a color graphics card (or color X server).
(Although ST/X asks the display about its color capabilities, this question cannot be answered correctly in the above situation.)
As specified in the styleSheet files, Smalltalk/X chooses different colors for cursors, selection highlighting etc. to assert use of contrasting colors.

Especially clear this, if you are running on a black & white laptop with a color VGA Xserver.

Fix Color Palette

This flag only affects graphic displays which use a limited (256-) color palette.

If enabled, Smalltalk/X preallocates 6x6x4 colors and only uses those when bitmap images are displayed. If disabled, colors are allocated as required.
Enabling the fix colorMap, usually results in suboptimal image quality, but the system will never run out of colors - also, some colors remain to be used by other applications.

If disabled, your display may run out of available colors when images are displayed; this might affect both smalltalk itself and other graphical applications.

Since no colors have to be allocated from the display, image rendering is much faster if the fixColor option is enabled.
Especially, when viewing many images (for example: with the HTML browser).

On trueColor displays (i.e. 5x5x6 or even 8x8x8 available colors), the above situation cannot happen - there, this setting is disabled.
Therefore, if you have a choice when setting up your display hardware, we recommend using the trueColor mode, if possible.

Fix Gray Color Palette

The same as above, for gray colors.
If enabled, grayscale images can be rendered faster and ST/X will not run out of gray colors when images are rendered.

Image Display

Selects the algorithm used to approximate colors in an image, which are not available in the displays colormap.
Typically, you can choose between nearest paint, which will choose the nearest available color and error diffusion which also takes the nearest color, but spreads the resulting error over surrounding pixels.
The error diffusion algorithm usually results in higher quality image display, but is slightly slower.

A good compromise between speed and image display quality is obtained by using a fix color palette combined with the error diffusion algorithm.
This will not run out of colors AND provides reasonably good image quality.

Owners of trueColor (i.e. 24bit/pixel) systems are lucky: they do not suffer from the limited color problem and do not have to care for those settings.

Allow Color/Grayscale Icons

If disabled, grayscale or color icons are automatically converted to b&w dithered images, when used as window icon.
This automatism was added for Xservers/window-managers which crash, when a non-monochrome icon bitmap is installed.

Typically, this error does not exist in newer (X11R5 and later) Xservers.

Clipboard Encoding

This setting is only needed, when 16-bit strings are pasted from the clipboard on systems which do not pass the clipBoards encoding (i.e. some applications on the XWindow system).
Since each 16-bit character application may encode its clipBoard strings in different ways, ST/X is prepared to convert it according to the value defined here.

For example, when pasting japanese text which was selected in a netscape browser, use "EUC" clipboard encoding.

For 'normal' ascii and iso8859 strings, this should be left as "untranslated" (this is the default).

Clipboard Buffer Size Limit

Whenever text is deleted or copied in a textView, ST/X copies the affected text to the displays clipBoard. Some XServers are known crash, if the size of this text exceeds a certain limit or if the XServer runs out of memory due to swap space limitations.
This setting sets a maximum on the clipBoard size - text longer than this amount are NOT copied to the displays clipBoard.

Further Reading

For more information, read "Configuration & Customization".


Copyright © Claus Gittinger Development & Consulting, all rights reserved


Doc $Revision: 1.13 $ $Date: 2003/08/29 12:51:45 $