I can provide a bit of history, at least. Originally the Qt support was
meant to support embedding the plotting widget in external GUIs
(meshbuilder, Dolfin GUI applications for teaching, etc.). However, it
turned out that the VTK built-in window-manager interaction is (or was, at
the time) really primitive, and it was impossible to get simple things like
closing windows to work reliably across platforms. Hence, Qt was used also
for the "simple" plot window. Since Qt is commonly installed already on
workstations, and cluster-installations don't need a plotting window
anyway, I considered it a reasonable dependency. (Rightly or wrongly.)
Now, as Anders pointed out, these GUIs haven't materialized yet. One
under-communicated aspect (because it wasn't considered back then) is that
this can be done in Python, too, using PySide or PyQt. Just for fun I've
attached a small demo that creates a Python GUI application for the Poisson
demo, using PySide. Note: This is not meant to be included as a Dolfin
demo, it is just thrown together to show that it can be done.
Benjamin: It is probably as easy as you suggest. The reason it is like it
is now, it that we (or I) ended up using Qt for the simple plot window
anyway, for stability reasons; and then it's even easier to embed the
window in another application.
Regards,
Joachim.
On 17 January 2015 at 09:12, Garth N. Wells <[email protected]> wrote:
>
> On Fri, 16 Jan, 2015 at 11:06 PM, Benjamin Kehlet <[email protected]>
> wrote:
>
>> 2015-01-16 16:00 GMT+01:00 Jan Blechta <[email protected]>:
>>
>>> On Fri, 16 Jan 2015 12:55:35 +0100
>>> Benjamin Kehlet <[email protected]> wrote:
>>>
>>> I agree with Garth and Jan that Qt should be removed. The Qt
>>>>
>>>
>>> I didn't say whether Qt should be removed.
>>>
>>
>> Ah, I see that now. Sorry.
>>
>> I don't think that there's a
>>> strong need to remove it unless it requires in a future any maintenance
>>> which nobody wants to do.
>>>
>>> With a removal, VTK plots will loose a capability of closing a window.
>>>
>>
>> I didn't know that. What functionality is it that the Qt-based
>> plotting provides? Closing plotting windows programmatically?
>>
>>
>>> functionality was added to make it possible to reuse the plotting
>>>> functionality in third party Qt applications, but this is (apparently)
>>>> not used at all. The plotting code should really be kept as minimal as
>>>> possible.
>>>>
>>>> If someone wants to embed the plots in Qt (or another GUI framework),
>>>> it is better to expose the what is needed to do that outside of
>>>> Dolfin. (I haven't looked into this, but it may be possible already by
>>>> using VTKWindowOutputStage).
>>>>
>>>
>>> This is exactly what is done. There are few #ifdef HAS_QVTK switching
>>> between vtkRenderWindowInteractor implementation and QVTKWidget
>>> implementation. If we remove Qt, QVTK (I'm not sure how coupled are
>>> these two dependencies; anyway DOLFIN requires both or none) then this
>>> interface will be gone.
>>>
>>> Code in plot-qt demo is just application using this interface.
>>>
>>
>> My point was that I imagine it would be pretty simple to adjust the
>> interface so that applications can do this outside Dolfin. An
>> application could maybe do somethin like this:
>> * Create a dolfin::VTKPlotter object.
>> * Grab a reference to the vtkRenderWindow object from the
>> dolfin::VTKPlotter object an connect it to whatever GUI framework it
>> uses.
>> * Plot the dolfin object to the dolfin::VTKPlotter.
>>
>> or (a bit more low level)
>> * Create a dolfin::GenericVTKPlottable object from the dolfin object
>> it would like to plot.
>> * Grab a reference to the vtkActor object from the GenericVTKPlottable.
>>
>> In both cases the plotting code in Dolfin is reused, but Dolfin is
>> unaware of the GUI framework and linking, find_package() etc. is done
>> (and maintained) on the application side.
>>
>> Joachim: Shout if I'm missing anything essential here!
>>
>>
>>> Finally, the apparent confusion of new users by enormous number of
>>> useless dependencies is rather problem of documentation. There should
>>> be clearly stated:
>>>
>>> 1. What is dependency for.
>>> 2. Which dependencies are recommended to have useful DOLFIN.
>>>
>>
>> Good point, but maintaining documentation also requires work. This is
>> maintenance that no one is eager to do and should be minimized.
>>
>
> I don't think documentation is the solution. It helps, but if someone
> needs to make a decision at that level before they can get started it's
> already too late. A new user is unlikely to understand the full
> implications of having or not having an optional dependency, and err on the
> side of caution and enable it. I know I do.
>
> Cutting dependencies that offer little reduces maintenance, simplifies
> testing (fewer combinations to consider) and simplifies installation
> approaches like Hashdist and containers/VMs that have fewer dependencies to
> worry about supporting.
>
> Garth
>
>
>
>> Benjamin
>>
>>
>>> Jan
>>>
>>>
>>>> Regards
>>>>
>>>> Benjamin
>>>>
>>>> 2015-01-15 21:33 GMT+01:00 Anders Logg <[email protected]>:
>>>> > I would vote for keeping the Qt functionality for a while longer.
>>>> > It was added in case we would later needed (for users that want to
>>>> > wrap DOLFIN plots inside applications).
>>>> >
>>>> > But I agree with needing to reduce the number of dependencies.
>>>> >
>>>> > --
>>>> > Anders
>>>> >
>>>> >
>>>> > Thu Jan 15 2015 at 5:28:36 PM skrev Garth N. Wells
>>>> > <[email protected]>:
>>>> >>
>>>> >> It would be nice if we can reduce the number of optional
>>>> >> dependencies in DOLFIN - it's confusing for users to know which
>>>> >> optional dependencies they really should have, e.g. PETSc, and
>>>> >> which they very likely do not need, e.g. QT.
>>>> >>
>>>> >> Garth
>>>> >>
>>>> >> On Thu, 15 Jan, 2015 at 3:18 PM, Jan Blechta
>>>> >> <[email protected]> wrote:
>>>> >> > Garth suggested removing Qt dependency. Here are some facts to be
>>>> >> > considered
>>>> >> >
>>>> >> > 1. DOLFIN links to libQtCore, libQtGui
>>>> >> > - cost:
>>>> >> > - linking problems, recently on support mailing list but
>>>> >> > rather rare
>>>> >> > - size of libdolfin.so, Release build type, with
>>>> >> > everything except PaStiX and slepc4py:
>>>> >> > - with Qt 8M
>>>> >> > - without Qt 8M
>>>> >> > - memory footprint after "from dolfin import *"
>>>> >> > VIRT RES SHR
>>>> >> > - with Qt 751M 101M 39M
>>>> >> > - without Qt 679M 97M 48M
>>>> >> > This is rather negligible.
>>>> >> > - advantages:
>>>> >> > - Plot window can be closed!
>>>> >> >
>>>> >> > 2. there is plot-qt demo demonstrating how interactive widget
>>>> >> > allowing
>>>> >> > - basically what usual VTK plotting does
>>>> >> > - plus reporting some numbers on mouse hover
>>>> >> > - plus marking cells by clicking on them
>>>> >> > for the prize of 252 lines of C++ code (without comments and
>>>> >> > blank lines). According to git log in that directory, it seems
>>>> >> > that the code is not fragile and did not need maintenance nearly
>>>> >> > at all so far.
>>>> >> >
>>>> >> > Similarly, Qt, QVTK related code in dolfin/plot is rather
>>>> >> > minimal and does not require much maintenance. But this isn't so
>>>> >> > straightforward to check.
>>>> >> >
>>>> >> > Jan
>>>> >>
>>>> >> _______________________________________________
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>>>> >> [email protected]
>>>> >> http://fenicsproject.org/mailman/listinfo/fenics
>>>> >
>>>> >
>>>> > _______________________________________________
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>>>>
>>>
>>> _______________________________________________
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>>
>
>
import sys
from dolfin import *
from PySide import QtGui, QtCore
class poisson(QtCore.QObject):
def __init__(self, nx, ny):
# Create mesh and define function space
self.mesh = UnitSquareMesh(nx,ny)
self.set_g("sin(5*x[0])")
def set_g(self, g):
self.g = str(g)
def solve(self):
V = FunctionSpace(self.mesh, "Lagrange", 1)
# Define Dirichlet boundary (x = 0 or x = 1)
def boundary(x):
return x[0] < DOLFIN_EPS or x[0] > 1.0 - DOLFIN_EPS
# Define boundary condition
u0 = Constant(0.0)
bc = DirichletBC(V, u0, boundary)
# Define variational problem
u = TrialFunction(V)
v = TestFunction(V)
f = Expression("10*exp(-(pow(x[0] - 0.5, 2) + pow(x[1] - 0.5, 2)) / 0.02)")
a = inner(grad(u), grad(v))*dx
L = f*v*dx + Expression(self.g)*v*ds
# Compute solution
u = Function(V)
solve(a == L, u, bc)
# Plot solution
plot(u, key='win1')
class window(QtGui.QWidget):
def __init__(self, plotWidget):
super(window, self).__init__()
plotWidget.setParent(self)
plotWidget.setSizePolicy(QtGui.QSizePolicy.Ignored, QtGui.QSizePolicy.Ignored)
self.initUI(plotWidget)
def initUI(self, plotWidget):
self.edit = QtGui.QLineEdit()
self.quit = QtGui.QPushButton("Quit")
hbox = QtGui.QHBoxLayout()
hbox.addWidget(QtGui.QLabel("Expression 'g'"))
hbox.addWidget(self.edit)
hbox.addStretch(1)
hbox.addWidget(self.quit)
vbox = QtGui.QVBoxLayout(self)
vbox.addWidget(plotWidget)
vbox.addLayout(hbox)
self.setGeometry(0,0,800,600)
self.show()
def main():
app = QtGui.QApplication(sys.argv)
ps = poisson(32,32)
ps.solve()
ex = window(app.topLevelWidgets()[0])
ex.edit.setText(ps.g)
ex.edit.textChanged.connect(ps.set_g)
ex.edit.editingFinished.connect(ps.solve)
ex.quit.clicked.connect(app.closeAllWindows)
sys.exit(app.exec_())
if __name__ == '__main__':
main()
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