nanogui: [nannogui] fast updating of (background) images
Subject:
[nannogui] fast updating of (background) images
From:
Ib ####@####.####
Date:
9 Aug 2001 15:07:26 -0000
Message-Id: <510819110362D211ABFD00A0C9A2BE4A012D4472@mail.visionik.dk>
Hi all
We want to develop a kind of slideshow using nano-x. This slideshow must
refresh large background images a number of times, and we have problems
getting this done at a reasonable speed.
At present we use GrLoadImageFromFile() to load an image into a GR_IMAGE_ID.
When updates are neded we use a call
GrDrawImageToFit() to put the image onto the screen. The updating gets to be
very slow - line by line - and we don't have the possibility of just
updating the relevant part of the screen.
We have tried using GrCopyArea to move the image onto the screen from the
GR_IMAGE_ID. This call seems like it should do exactly what we want: copy a
rectangular piece of an image onto the appropriate place in an other window.
Howeever, it seems that we can only copy images from a mapped window on the
screen i.e. we can not copy from an off screen imagebuffer onto the screen
using GrCopyArea.
Does anybody have experience with this problem - should GRCopyAre be able to
move images from offscreen locations to the screen - or is there an other
way to do the job of fast updating the screen.
It also seems that the basic drawing onto the screen using GrDrawImageToFit
clips around sibling windows. This may be nice - giving flicker free updates
when windows overlap. Since we are using windows that do not fill their
background color we need to draw images without clipping around the siblings
how can this be done?
Our slideshow must also display animations - we would like to use animated
GIFs is that possible? - if not, we expect to do the animations by ourselves
- but then we need fast updating.
Finally a related problem. We are using several windows displaying texts,
again with no background drawn. We want to unmap some of these textwindows
and at the same time map other textwindows (displaying changes with mouse
over) We can manage to get this to function against a general background -
but when we unmap one window and map an other window and the two windows
intersect then the intersection of the two windows doesn´t get updated the
way we would like. It seems that the windows engine looks ahead and ony
updates the intersection once - can this look ahead function be controlled
in any way?
> Ib Jørgensen Lead Technical Consultant
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