ID:MD Mouse Droppings in DESQview
Quarterdeck Technical Note #238 Filename: MOUSEDRP.TEC
by Michael Bolton CompuServe: MOUSDR.TEC
Last revised: 5/11/92 Category: DV
Subject: What to do if you encounter unsightly "mouse droppings" -- coloured
text blocks that are left in the wake of the mouse -- under DESQview.
Q. What are those strange trails of oddly-coloured characters that are left on
the screen when I move my mouse in a DESQview window?
Q. What can I do to fix the problem?
A mouse is a seemingly simple thing; roll it around on your desk and the mouse
cursor moves with it. Much more is going on than meets the eye, however. In
order to give the impression of a smooth, dynamic pointer, your mouse driver
and your display have to do quite a bit of work. Your mouse driver must
report any changes in the mouse's position to the system, and the screen must
be updated accordingly. This involves keeping track of the colour of the
character (or, if the screen is in a graphics mode, the range of pixels) to
which the mouse is being moved, changing that colour (or range of pixels) to
that of the mouse pointer, and restoring the area to its original state when
the mouse is moved away. Extra overhead on your system can complicate matters
When some aspect of your mouse's setup is incorrect, or is in conflict with
another piece of hardware or software on your system, a trail of blocks of
odd-coloured characters may appear on your display when you move your mouse in
a DESQview window. These have come to be called "mouse droppings" by
Quarterdeck Technical Support, for reasons so obvious that no-one will
actually admit to authorship of the term.
Mouse droppings are usually seen in program running in a virtualized window --
that is, one in which the following conditions are met:
1) The system is running DESQview 386 (that is, DESQview and QEMM-386 are
running on the same 386 or 486 processor).
2) The program in running in a window whose DESQview Program Information File
(".DVP file") has "Virtualize Text and Graphics" set to "Y" or "T".
(For more information on virtualizing, see Quarterdeck Technical Note #229
(VIRTUALI.TEC), "What is Virtualizing?")
DESQview's default behaviour is to give the mouse to the foreground window,
and virtualize it. There are several things that can interfere with this
behaviour and contribute to the relatively rare problem of mouse droppings,
and thus there are several potential solutions.
Mouse droppings can often happen when you have incorrectly informed DESQview
which port the mouse is using. This is done in the Setup DESQview program in
the Advanced Options / Mouse screen. In general, port 0 (add-on board) is the
best choice; this is appropriate for "bus" or "port" mice -- those which plug
into a special mouse connector, rather than into a 9- or 25-pin serial port.
If DESQview does not find an add-on board with a mouse connected to it,
DESQview will find a mouse attached to any other port; try specifying port 0
as the mouse port. However, if you are certain that you are using a serial
mouse, and if you are certain which serial port the mouse is using, you may
specify 1 for COM1 or 2 for COM2.
Historically, mouse droppings have been seen more often on systems that are
using a mouse driver loaded in CONFIG.SYS than those which are using a mouse
driver loaded in AUTOEXEC.BAT, but they can occur in either case. Try
switching; if you are using MOUSE.SYS in CONFIG.SYS, try MOUSE.COM in
AUTOEXEC.BAT instead, or vice versa.
If you are getting droppings in a non-virtualized window, try turning
Ensure that there are no pieces of hardware contending for the IRQ that your
mouse is using. Be especially aware of modems that are using the same
hardware interrupt as the mouse.
DESQview has historically supported all mouse calls which were valid at the
release time of the DESQview revision in question; undocumented mouse calls
can sometimes result in this phenomenon.
In DESQview 2.40, 2.41, and 2.42, with QEMM-386's Stealth active, and with a
mouse on IRQ 2, mouse droppings can be remedied by the DESQview startup
parameter /HW:71:2. More generally, starting DESQview with the parameter
/HW:nn:FUV can relieve mouse droppings, where nn is the interrupt associated
with your mouse driver.
If your mouse is on the interrupt number is
COM1 (IRQ4) 0C
COM2 (IRQ3) 0B
COM3 (IRQ4) 0C
COM4 (IRQ3) 0B
IRQ12 (PS/2 style mouse) 74
This parameter instructs DESQview to give the mouse to the foreground window,
to unmask it (that is, to let other interrupts of higher priority occur while
the mouse interrupt is being serviced), and to virtualize it.
If none of the above suggestions provide a solution to your mouse dropping
problem, Quarterdeck would like to hear about it.
*This technical note may be copied and distributed freely as long as it*
*is distributed in its entirety and it is not distributed for profit. *
* Copyright (C) 1992 by Quarterdeck Office Systems *
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