[Uml-devel] Big umbrello project causes X11 to take too much memory - current CVS

Achim Spangler Achim.Spangler at mnet-online.de
Thu Jun 24 06:30:04 UTC 2004

Hi again,
I digged some time in the Qt-Doc and in the uml.h/cpp, umldoc.h/cpp and 
umlview.h/cpp source.

Well, obviously my assumption on the parallel creation of a "hidden" graphical 
representation for all diagrams seems to be right.
The QWidgetStack class in UMLApp is used to store instances of QCanvasView.

The documentation of Qt is not very clear in regard to memory efficiency of 
the several methods to have

several QCanvas ( not QCanvasView ) instances

with everytime just one of them ( i.e. diagram )

visible on main display.

As far as I understand the relation between QCanvas and QCanvasView correct, 
the diagram contents could be drawn into a QCanvas instance independend from 
their display.
If a diagram shall be displayed, the corresponding QCanvas must be connected 
to a visible QCanvasView.

If my reasoning is correct, then umbrello could reduce the memory usage ( in 
X11!!! ) by changing
UMLApp 1 <---->n QCanvasView 1 <--> 1 QCanvas 1 <----> m QCanvasItem
                                                   ( single graphic elements )
UMLApp 1 <---->1 QCanvasView 1 <--> n QCanvas 1 <----> m QCanvasItem

Therefore the code for control of visible and invisible diagrams would need a 
change. As there are already several comments like "Obsolete??" or some 
functions like UMLDoc::activateView() - ( just set m_bLoading = false; and 
return constant true ), there is already some need for change.

Is anybody on the list ( or at least knows somebody ) a Qt expert, who can 
tell the best way to manage several diagrams in a memory efficient way?


Am Donnerstag 24 Juni 2004 12:23 schrieb Achim Spangler:
> Hi,
> I'm not shure, if this effect was introduced previously into umbrello, or
> if this is only triggered by my growing project.
> My project ( xmi file ) is around 2 MB in size.
> If I load the project into umbrello, "top" tells me the following memory
> usage:
> 98452  46m  28m S 56.7  9.3   0:43.84 umbrello
> 615m 337m  46m S  2.9 67.0   3:32.83 X
> ^^^^^^^^^^^^
> So while umbrellos memory usage is quite fine - in sum less than 80MB, the
> X server takes too much memory. As the memory usage is normal, as soon as I
> stop umbrello, this must be caused directly or indirectly by umbrello and
> my project. A smaller project ( with less diagrams ) doesn't cause such
> memory usage.
> This could be caused, if all diagrams are created in parallel drawing areas
> ( canvas ), and the event "Display diagram Foo" does only set the
> visibility flag of "Foo" to true, and false of all other diagrams.
> I thought until now, that only the currently  displayed diagram is created
> within the X11 memory space.
> Can somebody explain this effect?
> Bye,
> Achim
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