Hi Manfred,
not what you asked but: Are you sure you need a second QMainWindow or
maybe a non-modal QDialog or a QDockWidget would be sufficient? Those
might be easier to use. Or maybe even just using the window that
plt.show() creates?
Cheers, Hannes
Am 14.02.23 um 22:11 schrieb Manfred Strahlhofer via QGIS-User:
Hello!
There is a problem when using "matplotlib.backends" and drawing plots
when called from a QGIS processing plugin. I am using the following
test code:
# sample code below draws a canvas with a plot
# however closing this plot canvas crashes the plugin (cannot be
restarted)
# and further qgis can't be closed with the X button
# originates from:
https://matplotlib.org/stable/gallery/user_interfaces/embedding_in_qt_sgskip.html#sphx-glr-gallery-user-interfaces-embedding-in-qt-sgskip-py
importsys
importtime
importnumpyasnp
frommatplotlib.backends.qt_compatimportQtWidgets
frommatplotlib.backends.backend_qtaggimport(
FigureCanvas, NavigationToolbar2QT asNavigationToolbar)
frommatplotlib.figureimportFigure
classApplicationWindow(QtWidgets.QMainWindow):
def__init__(self):
super().__init__()
self._main= QtWidgets.QWidget()
self.setCentralWidget(self._main)
layout= QtWidgets.QVBoxLayout(self._main)
static_canvas= FigureCanvas(Figure(figsize=(5, 3)))
# Ideally one would use self.addToolBar here, but it is slightly
# incompatible between PyQt6 and other bindings, so we just add the
# toolbar as a plain widget instead.
layout.addWidget(NavigationToolbar(static_canvas, self))
layout.addWidget(static_canvas)
dynamic_canvas= FigureCanvas(Figure(figsize=(5, 3)))
layout.addWidget(dynamic_canvas)
layout.addWidget(NavigationToolbar(dynamic_canvas, self))
self._static_ax= static_canvas.figure.subplots()
t= np.linspace(0, 10, 501)
self._static_ax.plot(t, np.tan(t), ".")
self._dynamic_ax= dynamic_canvas.figure.subplots()
t= np.linspace(0, 10, 101)
# Set up a Line2D.
self._line, = self._dynamic_ax.plot(t, np.sin(t+ time.time()))
self._timer= dynamic_canvas.new_timer(50)
self._timer.add_callback(self._update_canvas)
self._timer.start()
def_update_canvas(self):
t= np.linspace(0, 10, 101)
# Shift the sinusoid as a function of time.
self._line.set_data(t, np.sin(t+ time.time()))
self._line.figure.canvas.draw()
deftest_plot():
# Check whether there is already a running QApplication (e.g., if running
# from an IDE).
#qapp = QtWidgets.QApplication.instance() this stucks QGIS!
#if not qapp:
qapp= QtWidgets.QApplication(sys.argv) # this stucks QGIS main window
when the dialog's close button is pressed
app= ApplicationWindow()
app.show()
app.activateWindow()
app.raise_()
qapp.exec()
#app.exit()
When using "qapp = QtWidgets.QApplication.instance()", QGIS stucks
completely and no plot is shown ever.
When using "qapp = QtWidgets.QApplication(sys.argv)", the plot is
shown and updated correctly. But when pressing the "close button" of
the plot window, there are some strange effects (cannot start a plugin
again) and the "close button" of the QGIS main window is disabled.
Have to shut down qgis-bin.exe from the windows task-manager.
I am using:
QGIS Version 3.24.1 Tisler
matplotlib 3.5.1
Windows 10
Anybody have a solution for this problem?
Thanks a lot.
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