Atari ST series Technical Reference Manual page 168

used to remove the sprite and restore the background. The
only parameter it requires is a pointer to the save block,
which is passed in register A2.
The mouse pointer is a special type of sprite that the op­
erating system automatically moves in response to movement
of the mouse. Line A routines allow you to hide the mouse
pointer (terminate its display), show the mouse pointer (dis­
play it), or transform the pointer (change its shape). The
Hide Mouse function ($A00A) requires no inputs. When you
call Hide Mouse, the mouse pointer is turned off. To make it
reappear, you must call Show Mouse ($A009). If Hide Mouse
has been called more than once, you must call Show Mouse
an equal number of times before the mouse pointer is dis­
played. The depth at which the mouse pointer is hidden is
stored in the line A variable HIDE__CNT (offset -598). This
variable holds the number of times the mouse has been hid­
den, or a 0 if the mouse is currently being displayed. If you
wish to display the pointer regardless of how many times it
has been hidden, you may set a pointer to a 16-bit 0 value in
the INTIN variable (offset 8) before calling Show Mouse.
The final line A mouse function is Transform Mouse
($A00B). This function allows you to change the shape of the
mouse pointer. As input, it requires that the address of a
mouse pointer definition block be placed in INTIN. This
mouse pointer definition block is almost exactly the same as
the sprite definition block used for Draw Spite, above. The
mouse pointer must be drawn using VDI mode, however. In
addition, the image data and mask data are handled differ­
ently. Instead of being interleaved as in the case of sprites,
these data planes are kept separate for the mouse pointer.
Bytes 10-41 of the data block contain 16 consecutive words of
mask data, while bytes 42-73 contain 16 consecutive words
of image data.
There are several line A variable locations which may as­
sist in dealing with the mouse pointer. The current mouse
pointer definition is stored in sprite format starting at M__
POS__HX (offset -856). You may save this data before
changing the mouse shape, so you can restore it later. The
variable MOUSE__FLAG (offset —153) determines whether
the mouse interrupt processing is enabled. By changing this
value to 0, you may disable mouse cursor updates while
changing its shape (though you should restore it to its origi-
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CHAPTER 7