Re: [osg-users] set proper size to window manager at startup

[Robert Osfield]

Hi Gianni.

On 18 April 2016 at 13:48, Gianni Ambrosio  wrote:

> I can understand you don't have time and you are not the author of
> osgWidgets. Anyway the case can be reproduced with osgviewerQt example.
> Putting one breakpoint on GLWidget::event(QEvent*) and another breakpoint
> on ViewerWidget::paintevent() method (the one that calls frame()) you can
> easily see that QEvent::Resize, QEvent::Show, QEvent::WindowActivate events
> fall into GLWidget::event() "before" the first frame() is called. So, from
> my point of view, this is not strictly a problem of osgWidgets: resize,
> show and activate evets are cleared from the event queue in every case and
> I dont' think this is correct.
>

Events before the viewer frame loop have begun should be moot for what
happens in the frame loop, these events may affect state but these should
all be accounted from by the appropriate viewer code prior to the frame
loop.  What happens prior to the frame loop is completely arbitrary and out
of the viewer's directly so it's not something it should be passing on as
events.

The problem here with osgWidget is that it's trying to use events prior to
the frame loop starting as a means of getting state about the windowing
side.  Rather than trying to second guess what the values are for a window
based on events it really should be going directly to the windows
themselves if it wants to account for their state.

Robert.
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Re: [osg-users] set proper size to window manager at startup

[Gianni Ambrosio]

I can understand you don't have time and you are not the author of osgWidgets. 
Anyway the case can be reproduced with osgviewerQt example. Putting one 
breakpoint on GLWidget::event(QEvent*) and another breakpoint on 
ViewerWidget::paintevent() method (the one that calls frame()) you can easily 
see that QEvent::Resize, QEvent::Show, QEvent::WindowActivate events fall into 
GLWidget::event() "before" the first frame() is called. So, from my point of 
view, this is not strictly a problem of osgWidgets: resize, show and activate 
evets are cleared from the event queue in every case and I dont' think this is 
correct.

Regards,
Gianni

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Re: [osg-users] set proper size to window manager at startup

[Robert Osfield]

Hi Gianni,

It is appropriate for osgGA::EventQueue::setStartClick() to call clear() as
otherwise the queue would end up with inconsistent time stamps, as existing
events would have the wrong relative time.

The only alternative to this would be to reset all the event in the queue
so that their time was reset relative to the previous and new start ticks.
However, the setStartClick is something done at initialization of the
viewer, before event handling is meant to kick off, it's not something that
is meant for after start up.

Personally I think the problem you are seeing is in osgWidget relying upon
resize events at the start of the application, it really shouldn't rely
upon this.  I'm not the author though so pinpointing what it should do
would require sifting through the design and implementation to see a better
approach.  Unfortunately I don't have the time to do this right now.

Robert.

On 18 April 2016 at 11:19, Gianni Ambrosio  wrote:

> OK, thanks Robert for the informations.
> So, just tio summarize the case for Cedric.
> When a Qt Application starts, most of Qt events (like resize, show,
> activate, ...) are sent to GLWidget before the OSG code handles them.
> GLWidget handles those events and queue them into OSG Eventqueue to be
> processed on the next frame() call. The problem in that the first call of
> ViewerBase::frame(double) calls
> setStartTick(osg::Timer::instance()->getStartTick()) (in realize() method)
> which clears the queued events. So this causes all events already queues
> not correctly handled.
>
> I found that setStartTick() call is used somewhere in OSG code. I can
> suggest to call eventQueue.clear() before setStartTick() separatedly when
> needed instead of calling it directly inside setStartTick() but I'm not
> aware of the overall OSG code and possible consequences.
>
> Hope this helps.
> Gianni
>
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>
>
>
>
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Re: [osg-users] set proper size to window manager at startup

[Gianni Ambrosio]

OK, thanks Robert for the informations.
So, just tio summarize the case for Cedric.
When a Qt Application starts, most of Qt events (like resize, show, activate, 
...) are sent to GLWidget before the OSG code handles them. GLWidget handles 
those events and queue them into OSG Eventqueue to be processed on the next 
frame() call. The problem in that the first call of ViewerBase::frame(double) 
calls setStartTick(osg::Timer::instance()->getStartTick()) (in realize() 
method) which clears the queued events. So this causes all events already 
queues not correctly handled.

I found that setStartTick() call is used somewhere in OSG code. I can suggest 
to call eventQueue.clear() before setStartTick() separatedly when needed 
instead of calling it directly inside setStartTick() but I'm not aware of the 
overall OSG code and possible consequences.

Hope this helps.
Gianni

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Re: [osg-users] set proper size to window manager at startup

[Robert Osfield]

Hi Gianni,

As a general note, I'm not the author of osgWidget so not in great position
to answer specific questions about this.  Unfortuantely, the author Cedric
Pinson is now busy with the javascript version of the OSG and Sketchfab so
not pitching in my on the osgWidget side these days.

On 18 April 2016 at 09:49, Gianni Ambrosio  wrote:

> I verified the clear() call has been added to EventQueue::setStartTick()
> method in OSG 3.1.1. Who did that can explain me please why it was
> required? Is there a way to move a clear() call outside the method to
> prevent the regression from OSG 3.1.1 onwards?
>

It's quite a while back, but I have recall having to address bugs with
event time stamps getting out of sync in certain circumstances.  As whether
you are seeing a regression in osgOGA or a fix to osgGA exposing a bug in
osgWidget I can't say.

Robert.
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Re: [osg-users] set proper size to window manager at startup

[Gianni Ambrosio]

I verified the clear() call has been added to EventQueue::setStartTick() method 
in OSG 3.1.1. Who did that can explain me please why it was required? Is there 
a way to move a clear() call outside the method to prevent the regression from 
OSG 3.1.1 onwards?

Cheers,
Gianni

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Re: [osg-users] set proper size to window manager at startup

[Gianni Ambrosio]

I recently moved from OSG 3.0.1 to 3.4.0 and I'm getting this unexpected 
behaviour only with OSG 3.4.0. In fact comparing the code of 3.0.1 and 3.4.0 I 
realized the clear() call in EventQueue::setStartTick() is only present in 
3.4.0 code. I don't know the reason of that but from my point of view in 3.4.0 
setStartTick() does more that it says: setStartTick just have to set the tick 
non more than that. Moreover that modification (clear()) has broken the scenaio 
I described.

Gianni

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Re: [osg-users] set proper size to window manager at startup

[Gianni Ambrosio]

The problem seems to be here:

osg130-osgGAd.dll!osgGA::EventQueue::clear()  Line 37   C++
osg130-osgGAd.dll!osgGA::EventQueue::setStartTick(__int64 tick)  Line 212 + 
0x25 bytes  C++
osg130-osgViewerd.dll!osgViewer::CompositeViewer::setStartTick(__int64 tick)  
Line 355 + 0x1d bytes C++
osg130-osgViewerd.dll!osgViewer::CompositeViewer::realize()  Line 646 + 0x31 
bytes  C++
osg130-osgViewerd.dll!osgViewer::ViewerBase::frame(double simulationTime)  Line 
678 + 0xf bytes C++
osgWidgetsTest.exe!ViewerWidget::paintEvent(QPaintEvent * event)  Line 154 + 
0x46 bytes C++

The first time a paint event is called, the eventqueue is cleaned up (see 
EventQueue::clear()) and the RESIZE event with correct width and height 
unavoidably lost!

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Re: [osg-users] set proper size to window manager at startup

[Gianni Ambrosio]

I verified that when the application starts the code falls into the following 
method (osgQt\GraphicsWindowQt.cpp),

void GLWidget::resizeEvent( QResizeEvent* event )

where it seems a resize event is insert into the event queue with proper width 
and height:

_gw->getEventQueue()->windowResize( x(), y(), scaled_width, scaled_height );

but a RESIZE event is not passed to the ResizeHandler. Can anybody see a good 
reason or a bug there?

Regards,
Gianni

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[osg-users] set proper size to window manager at startup

[Gianni Ambrosio]

Hi All,
I have a Qt application ad I have to initialize a WindowManager with some 
default width and height like follows:

osg::ref_ptr wm = new osgWidget::WindowManager(view, 
1280.0f, 1024.0f, MASK_2D, osgWidget::WindowManager::WM_USE_RENDERBINS);

When the Qt application starts up then the QWidget containing the OSG view is 
resized properly by the Qt framework but even if I use:

view->addEventHandler(new osgWidget::ResizeHandler(wm, camera));

an osgGA::GUIEventAdapter::RESIZE event is not raised at that point. That 
means, every OSG windows added to the WindowManager are not resized correctly. 
Only when the user interactiverly resizes the window of Qt application, then a 
osgGA::GUIEventAdapter::RESIZE is rised and, falling into 
ResizeHandler::handle() methodm the Window Manager is updated with proper width 
and height.

Now, which is the correct way you see to solve this issue?

Regards,
Gianni

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