Hackers’ Corner: Reshaping your Mouse

by Adrian Smith

Transcribed from the printed issue; not yet reviewed. Read it in the PDF of the issue, page 112

There are times when a simple reverse-video block is not the kind of mouse pointer you need. To save you the (not inconsiderable) effort of decoding the appropriate page of Ray Duncan's book, here is a simple extension to MSΔINIT which does the trick:

    ∇ CH MSΔINIT CU;RC

[1]    ⍝ Initialize mouse ... sets global ⍙mouse←1 if OK ... else 0
[2]    ⍝ CU is the cursor type ... 0=mouse cursor; 1=hardware cursor
[3]    ⍝ (CH) is the character and colour to be used for the mouse block.

[4]     RC←0 ⎕INT 51 ⋄ ⍙mouse←0≠1↑RC ⋄ →⍙mouse↓0
[5]     →CU↑Hw ⋄ →(⎕NC 'CH')↓0

[6]    ⍝ Use left arg as mouse character, possibly with colour ...

[7]     ⍎(0≠1↑0⍴CH)/'CH←¯1+⎕AV⍳CH'

[8]    ⍝ Colour defaults to bright white ...

[9]     CH←2↑CH,15

[10]   ⍝ CX is set to 'F000' Hex to retain background only;
[11]   ⍝ DX is the encoded character and foreground ...

[12]    RC←(10 0 ,¯4096,CH[1]+256×CH[2])⎕INT 51 ⋄ →0
[13] Hw:RC← 10 1 ⎕INT 51
    ∇

This defaults to the normal mouse block, unless you provide a left argument. This may specify the mouse character (as a character scalar or ⎕AV index), and optionally a colour. APL*PLUS II users should note that the ¯4096 is really Hex(F000), but that in APL*PLUS/PC you trip over the 2-byte integer line, and have to pretend that you mean Hex(-F + FFF).

'⌹' MSΔINIT 0     ⍝ Mouse pointer is a white Domino ...
4 14 MSΔINIT 0    ⍝ ... or a yellow diamond!
MSΔSHOW           ⍝ Let's see it!

That's it folks. Next issue, the .EPS format exposed, or how to get your fancy PostScript graphs into MS Word, Aldus PageMaker and so on. Watch this space.