Closed
Description
I am running into issues with Matplotlib 2.0 with the Qt5 backend. The following script:
import matplotlib
matplotlib.use('Qt5Agg')
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_axes([0, 0, 1, 1])
print(ax.transData.transform((0.0, 0.0)))
print(ax.transData.transform((0.5, 0.5)))
print(ax.transData.transform((1.0, 1.0)))
print(fig.canvas.width(), fig.canvas.height())returns
[ 0. 0.]
[ 640. 480.]
[ 1280. 960.]
320 240
with Qt5, and:
[ 0. 0.]
[ 320. 240.]
[ 640. 480.]
(640, 480)
with Qt4. In Qt5 there is a factor of 4x difference between the display coordinates and the size of the widget, where I think there should only be a factor of 2x. A more visual way to see this issue is to run:
from PyQt5 import QtGui, QtWidgets
from matplotlib.figure import Figure
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg as FigureCanvas
class MplCanvas(FigureCanvas):
def __init__(self, fig):
FigureCanvas.__init__(self, fig)
self.renderer = None
self.x = self.y = 0
def paintEvent(self, event):
if self.renderer is None:
self.renderer = self.get_renderer()
super(MplCanvas, self).paintEvent(event)
p = QtGui.QPainter(self)
pen = QtGui.QPen(QtGui.QColor('black'))
pen.setWidth(20)
p.setPen(pen)
p.drawPoint(self.x, self.y)
def mouse_press(self, event):
x, y = ax.transData.transform((event.xdata, event.ydata))
self.x, self.y = x, self.height() - y
self.update()
app = QtWidgets.QApplication([''])
fig = Figure()
canvas = MplCanvas(fig)
ax = fig.add_axes([0, 0, 1, 1])
print(ax.transData.transform((0.0, 0.0)))
print(ax.transData.transform((0.5, 0.5)))
print(ax.transData.transform((1.0, 1.0)))
print(canvas.width(), canvas.height())
canvas.mpl_connect('button_press_event', canvas.mouse_press)
canvas.mpl_connect('motion_notify_event', canvas.mouse_press)
canvas.show()
app.exec_()This shows a window where if you move around the cursor, a black square should follow it. With Qt5, the square is offset by a factor of 2x:
cc @tacaswell