Incorrect character width calculation

Hi,

In console_widget.py#L491 the character width is calculated using boundingRect. In my system (Windows 10, python 3.8.5, pyqt5 5.15.0) the result of boundingRect width() is not consistent (even though the font is monospaced).

print(' ', font_metrics.boundingRect(' ').width(), font_metrics.horizontalAdvance(' '), file=f)
for c in range(ord('a'), ord('z') + 1):
  print(chr(c), font_metrics.boundingRect(chr(c)).width(), font_metrics.horizontalAdvance(chr(c)), file=f)

  1 6 <- ' ' character
a 5 6
b 6 6
c 5 6
d 5 6
e 5 6
f 5 6
g 5 6
h 5 6
i 5 6
j 4 6
k 6 6
l 5 6
m 6 6
n 5 6
o 6 6
p 6 6
q 5 6
r 5 6
s 5 6
t 5 6
u 5 6
v 6 6
w 6 6
x 5 6
y 6 6
z 5 6

This results in the wrong window width. What works is to use horizontalAdvance which is the alternative to the deprecated width method (https://doc.qt.io/qt-5/qfontmetricsf-obsolete.html#width-1).

[char101]

@yannick1974 Thanks, I have updated the pull request.

[yannick1974]

Hi,

I think it’s worth replacing the other boundingRect. On my system, for a reason I don’t understand, boundingRect(' ').width() returns 0 (I tried with different fonts). This leads to a ZeroDivisionError at completion_html.py:313 that makes qtconsole crash when using pyqt5 (but not with pyside). Also, another effect is the qtconsole does not honour c.JupyterWidget.console_width .

I replaced all the boundingRect(' ').width() by horizontalAdvance(' ') and now everything works as expected.