Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!lll-winken!elroy.jpl.nasa.gov!sdd.hp.com!samsung!munnari.oz.au!metro!ipso!runxtsa!timm
From: timm@runx.oz.au (Tim Menzies)
Newsgroups: comp.lang.smalltalk
Subject: optimising redraws of graphic panes in  ST/V 286
Message-ID: <1991Feb8.102528.10392@runx.oz.au>
Date: 8 Feb 91 10:25:28 GMT
Sender: timm@runx.oz.au (Tim Menzies)
Organization: RUNX Un*x Timeshare.  Sydney, Australia.
Lines: 130

Dear netland,

I've got a graphics application written in Smalltalk V/286. One 
problem with it is that the screen redraws are a slow. I've
got a display of a X-Y plot with lots of  lines/ text labels on it. 
I've tried various ways to speed up the redraws. The manuals isn't exactly 
helpful and so I include below a sample listing and ask the following
questions...

- would you expect that writing to a virtual form, then copying
  this to the display, would speed up the redraw? If yes, then
  how is this done? I've tried every variant I can think of on
  setting drawLine's pen's dest/sourceForm to Display/form etc.,
  etc.
- any other ideas on how to speed up the redraws on the following
  sample system?
 
There must be a way. The standard Smalltalk window redraws are 
FASTTTT. What am I doing wrong?

Tanks in advance,

--
 _--_|\  Tim Menzies (timm@runxtsa.oz)        "A degree proves that you can do 
/      \ HiSoft Expert Systems Group,	       something you don't enjoy for 3
\_.--._/ 2-6 Orion Rd, Lane Cove, NSW, 2066    years. And if you get good marks,
      v  61 2 9297729(voice),61 2 4280200(fax) it shows you can do it well."

--- cut here ----  

Object subclass: #UNSDrawTest
  instanceVariableNames: 
    'view form '
  classVariableNames: ''
  poolDictionaries: '' !


!UNSDrawTest class methods !

demo
    "Give it a whirl and see what happens."
    self new open! !


!UNSDrawTest methods !

comment
"
This class is a test of various methods
of speeding up a graphic redraw."!

drawLines
    "Draw a line from position to position."
    |pen|
    pen := Pen new  defaultNib: 1;
                    frame: view frame.  
    self positions pairsDo: [:last :next|
        pen place: last.
        pen goto:  next]!

graph: rect
    "Return a new graph-form for the
    display."
    form := Display compatibleForm
                width:  rect width
                height: rect  height.
    form displayAt: rect origin.
    self drawLines.
    ^form!

open
    "open the display."
    |topPane|
    topPane  := TopPane new label: 'redraw test';
                        minimumSize: (200 @ 100);
                        yourself.
    topPane addSubpane:
        (view := GraphPane new
            model:  self;
            name:   #graph:;
            framingBlock: [ :box | box]).
    topPane reframe: (10 @ 10 extent: 350 @ 200).
    topPane dispatcher open scheduleWindow!

positions
    "Return a long list of points that are
    the corners of a complicated line that will
    take some time to draw on the screen."
    |topLeft topRight bottomLeft bottomRight
    x0 y0 x1 y1 n  deltax deltay positions|  
    positions := OrderedCollection new.
    n := 20.
    topLeft  := view frame origin.
    topRight := view frame origin +
                (view frame width @ 0).
    bottomLeft := view frame origin +
                (0 @ view frame height).
    bottomRight := view frame corner.
    y0 := topLeft y.
    y1 := bottomLeft y.
    x0 := topLeft x.
    x1 := bottomRight x.
    deltax := x1 - x0  / n.
    deltay := y1 - y0 / n.
    x0 to: x1 by: deltax do:  [:x|
        y1 to: y0 by: deltay negated do: [:y|
             positions add:  x rounded @ y rounded]].
   x0 to: x1 by: deltax  do:  [:x|
        y0 to: y1 by: deltay  do: [:y|
             positions add:  x rounded @ y rounded]].
    ^positions  ! !

! Collection methods !
pairsDo: aBlock
    "Message the block with all adjacent
    items in  the receiver, working left to
    right."
    |last|
    self indexDo: [:next :index|
           index > 1
                ifTrue: [aBlock value: last
                                value: next].
            last := next] ! !

! GraphDispatcher methods !
processControlKey: aCharacter
        "Private - Cr = update."
    aCharacter == Cr
        ifTrue: [^pane  update].
    super processControlKey: aCharacter ! !