OS X + SDL_SetEventFilter = Bus Error

Zedr0n · January 4, 2008, 9:31am

I have encapsulated the SDL init/drawing into a separate class and
use it with my console app.

I’m trying to use dynamic resizing by doing this

void Graph::drawGraph()
{
SDL_Init(SDL_INIT_VIDEO); // initialize SDL
SDL_SetEventFilter(eventFilter);
SDL_SetVideoMode(WindowWidth,WindowHeight,0,
SDL_OPENGL | SDL_RESIZABLE);
SDL_WM_SetCaption(WindowName.c_str(),NULL);
bool done = false;
while(!done)
{
current_graph = this;
drawGLScene();
SDL_Event event;
while(SDL_PollEvent(&event))
{
if(event.type == SDL_VIDEORESIZE)
{
WindowWidth = event.resize.w;
WindowHeight = event.resize.h;
SDL_SetVideoMode(event.resize.w,event.resize.h,
0,SDL_OPENGL|SDL_RESIZABLE);
}
}
}
SDL_Quit();
}

The event filter is declared as a static member(so that it can be used as
a callback, i tried just the same with glut and it worked).

static int eventFilter(const SDL_Event *e)
{
if(e->type == SDL_VIDEORESIZE)
{
SDL_SetVideoMode(e->resize.w,e->resize.h,
0,SDL_OPENGL | SDL_RESIZABLE);
current_graph->WindowWidth = e->resize.w;
current_graph->WindowHeight = e->resize.h;
current_graph->drawGLScene();
}
return 1;
}

The problem here is that the app fails with “Bus Error”. I’ve hunted it down to
the SDL_SetVideoMode call i.e. if I remove the call, it resizes successfully
but naturally it doesn’t draw what I need(although
it does draw because I call drawGLScene() from here).

Any idea what the problem is?

And just an additional question - is it normal that when I resize the
window it also gets centered?

slouken · January 4, 2008, 4:22pm

The problem here is that the app fails with “Bus Error”.

Have you tried running it under the debugger?

And just an additional question - is it normal that when I resize the
window it also gets centered?

Nope, are you using SDL 1.2.13?

See ya!
-Sam Lantinga, Lead Software Engineer, Blizzard Entertainment

Christian_Walther · January 4, 2008, 4:49pm

Sam Lantinga wrote:

And just an additional question - is it normal that when I resize the
window it also gets centered?

Nope, are you using SDL 1.2.13?

As far as I know that is indeed normal, also in 1.2.13. IIRC
SDL_SetVideoMode() completely destroys and recreates the window, causing
it to be re-centered.

-Christian

Zedr0n · January 4, 2008, 8:25pm

Sam Lantinga <slouken devolution.com> writes:

The problem here is that the app fails with “Bus Error”.

Have you tried running it under the debugger?

Yes, as I see(I haven’t used SDL sources) it doesn’t crash in
SDL_SetVideoMode but after return 1…

What happens as I see it: when I use SDL_PollEvent then SDL_VIDEORESIZE
gets posted to internal queue only when the button is released - so no
dynamic resizing - is it intended behaviour? By resorting to
event filter I hack the code by catching all the SDL_VideoResize messages
and handling it on my own. Or maybe the eventFilter handler is in another
thread, and the thread with the main loop gets paused when dragging…
If I remove the call to SDL_SetVideoMode from eventFilter handler the
window gets redrawn but I see garbage outside the original window, if
I don’t use eventFilter at all then the window
just blanks during resizing.
What I actually want to do is that the window gets redrawn during
resizing - the way it’s done in glut
for example. Or is it intended that it doesn’t get redrawn?

And just an additional question - is it normal that when I resize the
window it also gets centered?

Nope, are you using SDL 1.2.13?

Yes, 1.2.13… I’ve built it unix way(autogen.sh configure make make install)
with --without-x --disable-x11-video

Yes, I’ve read that setVideoMode recreates the window that’s why it gets
centered so I thought it was default behaviour.

Maybe I should compile from SVN…> See ya!

-Sam Lantinga, Lead Software Engineer, Blizzard Entertainment

slouken · January 4, 2008, 11:13pm

Sam Lantinga wrote:

And just an additional question - is it normal that when I resize the
window it also gets centered?

Nope, are you using SDL 1.2.13?

As far as I know that is indeed normal, also in 1.2.13. IIRC
SDL_SetVideoMode() completely destroys and recreates the window, causing
it to be re-centered.

I just tested it with testwm -resize and it didn’t recenter the window
during or after resize… ?

-Sam Lantinga, Lead Software Engineer, Blizzard Entertainment

slouken · January 4, 2008, 11:16pm

What happens as I see it: when I use SDL_PollEvent then SDL_VIDEORESIZE
gets posted to internal queue only when the button is released - so no
dynamic resizing - is it intended behaviour? By resorting to
event filter I hack the code by catching all the SDL_VideoResize messages
and handling it on my own. Or maybe the eventFilter handler is in another
thread, and the thread with the main loop gets paused when dragging…

Yes, I believe the documentation states that you should never call SDL
video API functions from the event filter thread. It may be called from
another thread or from a hardware interrupt.

Instead you should either send another SDL event or set a global variable
or use some other messaging system to notify anyone who cares.

See ya,
-Sam Lantinga, Lead Software Engineer, Blizzard Entertainment

Zedr0n · January 4, 2008, 11:38pm

Sam Lantinga <slouken devolution.com> writes:

I just tested it with testwm -resize and it didn’t recenter the window
during or after resize… ?

-Sam Lantinga, Lead Software Engineer, Blizzard Entertainment

I’ve asked around, it doesn’t recenter on win32 and linux it seems.
Have you tested on mac?

Zedr0n · January 4, 2008, 11:50pm

Sam Lantinga <slouken devolution.com> writes:

Yes, I believe the documentation states that you should never call SDL
video API functions from the event filter thread. It may be called from
another thread or from a hardware interrupt.

Instead you should either send another SDL event or set a global variable
or use some other messaging system to notify anyone who cares.

See ya,
-Sam Lantinga, Lead Software Engineer, Blizzard Entertainment

I think that’s what I get from using code hacks

So is there a standard way to do dynamic resizing(redrawing during resize)?

slouken · January 5, 2008, 4:01am

I’ve asked around, it doesn’t recenter on win32 and linux it seems.
Have you tested on mac?

Yes, the testwm test program with the -resize option on Mac OS X 10.5.1

See ya,
-Sam Lantinga, Lead Software Engineer, Blizzard Entertainment

Christian_Walther · January 5, 2008, 10:22am

Sam Lantinga wrote:

As far as I know that is indeed normal, also in 1.2.13. IIRC
SDL_SetVideoMode() completely destroys and recreates the window, causing
it to be re-centered.

I just tested it with testwm -resize and it didn’t recenter the window
during or after resize… ?

You’re right, it only does that in OpenGL mode (and a few other special
cases). See SDL_QuartzVideo.m:666. I missed that because the OpenGL case
is the only one I’m familiar with.

-Christian

Zedr0n · January 5, 2008, 12:23pm

Christian Walther <cwalther gmx.ch> writes:

I just tested it with testwm -resize and it didn’t recenter the window
during or after resize… ?

You’re right, it only does that in OpenGL mode (and a few other special
cases). See SDL_QuartzVideo.m:666. I missed that because the OpenGL case
is the only one I’m familiar with.

-Christian

Hm, but if I don’t change the GL attributes, can I force it not to be destroyed?
Apart from hacking the source code of SDL

Gabriele_Greco · January 9, 2008, 8:48am

Sam Lantinga wrote:

Yes, the testwm test program with the -resize option on Mac OS X 10.5.1

Congratulations for the baby Sam, we all hope she’ll be the SDL 3.0
maintainer, look at where I’ve found this news

Bye,
Gabry

PS: Sorry for the OT

Torsten_Giebl · January 9, 2008, 11:06am

Hello !

Congratulations for the baby Sam, we all hope she’ll be the SDL 3.0
maintainer, look at where I’ve found this news

http://www.wowinsider.com/2008/01/08/congrats-to-blizzards-slouken-on-a-new-baby/

CU