[cairo] Help required with redraw problems

[Charles Tuckey]

Hi David,

We are proceeding with integrating the OpenGL backend with our project. 
However, we have run into a problem(s). Note that we are running this on 
a Redhat Enteprise Linux 2.1 machine (XFree 4.1.0).

For our purpsoses, we cannot use the method 
'cairo_glx_surface_create_for_window' because we want to draw on to a 
gtk window's backbuffer which is a pixmap. So we created a clone of 
cairo_glx_surface_create_for_window called 
cairo_glx_surface_create_for_pixmap and then 
glc_glx_surface_create_for_pixmap and created a GLXPixmap using a 
glXCreateGLXPixmap() call. On one machine that is running on a VMWare 
virtual machine we can draw on to the pixmap and everything works fine. 
Another machine (a real one) that has NVIDIA card running NVIDIA X 
server and GL implementaion, we get an X error that says:

The program '<unknown>' received an X Window System error.
This probably reflects a bug in the program.
The error was 'BadMatch (invalid parameter attributes)'.
   (Details: serial 588 error_code 8 request_code 129 minor_code 5)
   (Note to programmers: normally, X errors are reported asynchronously;
    that is, you will receive the error a while after causing it.
    To debug your program, run it with the --sync command line
    option to change this behavior. You can then get a meaningful
    backtrace from your debugger if you break on the gdk_x_error() 
function.)

We tracked down the error to a line that calls glXMakeCurrent().

Do you have any idea what may be causing this error? Or any suggestions 
as to what we should be looking at?

Thanks David.

Soorya & Charlie

David Reveman wrote:
> On Thu, 2004-03-25 at 18:02 -0700, Soorya Kuloor wrote:
> 
> 
>>Hi Carl,
>>
>>We are using cairo on a real-time schematic display application. We have run 
>>into some serious problems during redraws. The schematic displays have 
>>animated parts that flash with alternating colors when there are problems 
>>with the monitored system. When the flashing happens cairo consumes more CPU 
>>cycles than is acceptable. We think the only choice for us is to speed up 
>>Cairo. We need speed up of atleast by a factor of 2 and we have until Monday 
>>to do this :-((.
>>
>>We are using cairo version 0.1.17. We are using the pixman backend and we 
>>cannot use Render backend. Would there be any benefits to moving to a newer 
>>version? May be the OpenGL backend? Is there any particular part of Cairo or 
>>the libpixman, that we can speed up? We do not use any sophisticated 
>>capabilities such as transparency or pattern based fills. We use text (a 
>>lot).
> 
> 
> hmm, the OpenGL backend might do it, but text will be the bottleneck
> with the current GL backend patches, especially if you use a lot of it.
> This is because cairo render each glyph using freetype and then transfer
> it to the backend every time a glyph is drawn. A few weeks ago I hacked
> cairo_ft_font.c a little so that it cached glyphs. The results were
> great, text rendering went from the bottleneck to insignificant compared
> to the other drawing operations.
> 
> I've put my hacked version of cairo_ft_font.c in
> http://www.cs.umu.se/~c99drn/
> if you like to have a look at it. It's a bit old so I'm not sure it will
> work with the current version of cairo.
> 
> The OpenGL backend together with some kind of text hack like mine, would
> give you some great speed improvements. Maybe just a font hack would do
> it for you.
> 
> - David
> 

-- 
Charles Tuckey, MSc.
Software Developer
Verano, Inc.
403.299.4765

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