Displaying large graphics

I seem to be having a lot of trouble solving this one. I have a typical  view/model/controller set-up. The view is part of an application window and has scroll bars. It needs to display (the visible part of) a large map (up to 3200 pixels square)  and scroll around to reveal the invisible parts.

I assemble the map by drawing shapes on a Pixmap's GraphicsContext. I then display that on the View's GraphicsContext. Unfortunately, the GC is never any larger than my screen resolution, so I can only scroll around the area 1024x768 top left.

I can display the pixmap at a negative offset, so revealing a different rectangle, but it will still only scroll around a 1024x768 area. Also, that messes up the coordinates for point-and-click placement of objects.

How would I obtain a display surface larger than the default screen GC? Or do I have to combine multiple sections?

VWNC7.4.1 Windows Vista.

Just a resend for the list. In the meantime, I published a new version
of GHFractalExplorer, which no longer tries to load old MacOS 9 stuff. I
tested it on VW7.6, and unfortunately, the fast Mandelbrot
implementation in C does not work on Intel-MacOSX :-(


Hi Trium,

Please have a look at the GHFractalExplorer in the public repository.
The oal of the application is to draw Mandelbrod-Sets and alike with
VisualWorks. One side of the app is to create very large pictures of
such sets, and so there is an MVC-hierarchy of controllers and views in
there, which do what you desire: display a large Pixmap, and scroll arround.
Look at:
     IterativeGraphicsPart openExtraLarge

The solution may not fit completely for your application, but feel free
to take a deep look;-)

Good Luck

Roland Wagener
--
Roland Wagener * Senior Consultant * [hidden email]
Tel: x49-231-9 75 99-26   Fax: x49-231-9 75 99-20
Georg Heeg eK Dortmund
Handelsregister: Amtsgericht Dortmund  A 12812


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Am 02.07.2008 um 19:13 schrieb Trium:

> I assemble the map by drawing shapes on a Pixmap's GraphicsContext.

Unless you need to use a Pixmap for a special purpose, you could as  
well do without it. Just draw your shapes to the window GC in your  
#displayOn: method and have your window use the double-buffer display  
policy. It will do the buffering for you.

I'm using very populated graphics with a couple thousand objects on a  
timeline spanning up to 100,000 pixels of width. Querying the GC's  
clipping bounds helps to avoid drawing the invisible parts (skip  
everything outside bounds plus a little padding for scroll updates).  
After all, it's fast enough even for thumb scrolling.

Andre

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Try to implement something like this in your View


preferredBounds
    "Answer the preferred bounds of the receiver."

    ^0@0 extent: 4000@6000

@+Maarten,



Andre Schnoor a écrit :

Am 02.07.2008 um 19:13 schrieb Trium:

  

I assemble the map by drawing shapes on a Pixmap's GraphicsContext.
    

Unless you need to use a Pixmap for a special purpose, you could as  
well do without it. Just draw your shapes to the window GC in your  
#displayOn: method and have your window use the double-buffer display  
policy. It will do the buffering for you.

I'm using very populated graphics with a couple thousand objects on a  
timeline spanning up to 100,000 pixels of width. Querying the GC's  
clipping bounds helps to avoid drawing the invisible parts (skip  
everything outside bounds plus a little padding for scroll updates).  
After all, it's fast enough even for thumb scrolling.

Andre

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Many thanks all - following Maarten's tip I just get my file-opening routine to let the view know how big the map is and override the 'preferredBounds' method accordingly. No problems with view-to-model coordinate translation either. Works a treat. Now I just have to weed out all those places I was using translation!

---

Date: Thu, 3 Jul 2008 23:16:00 +0200
From: [hidden email]
CC: [hidden email]
Subject: Re: [vwnc] Displaying large graphics

Try to implement something like this in your View


preferredBounds
    "Answer the preferred bounds of the receiver."

    ^0@0 extent: 4000@6000

@+Maarten,



Andre Schnoor a écrit :

Am 02.07.2008 um 19:13 schrieb Trium:

  

I assemble the map by drawing shapes on a Pixmap's GraphicsContext.
    

Unless you need to use a Pixmap for a special purpose, you could as  
well do without it. Just draw your shapes to the window GC in your  
#displayOn: method and have your window use the double-buffer display  
policy. It will do the buffering for you.

I'm using very populated graphics with a couple thousand objects on a  
timeline spanning up to 100,000 pixels of width. Querying the GC's  
clipping bounds helps to avoid drawing the invisible parts (skip  
everything outside bounds plus a little padding for scroll updates).  
After all, it's fast enough even for thumb scrolling.

Andre

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