QFontMetrics::tightBoundingRect acting strange

SafaAlfulaij

Hello all.
I was trying hard to know why I’m getting larger rects for the text I’m using (mostly Arabic). Issue is that QFontMetrics::tightBoundingRect returns strange width sometimes.

Check the width of these functions and you’ll see that they it is different, even though there is no change in the layout at all. I am using Noto Sans font.

QFontMetrics::tightBoundingRect("ab")
QFontMetrics::tightBoundingRect("a\u200Cb") // \u200C is ZWNJ character

SGaist

Hi,

What version of Qt are you using ?
On what OS ?
What results are you getting ?

SafaAlfulaij

Hi!
I’m using Qt 5.11.1 on ArchLinux and getting these results:

PyQt5.QtCore.QRectF(3.0, -64.0, 91.0, 65.0) \\ "ab"
PyQt5.QtCore.QRectF(3.0, -64.0, 113.0, 65.0) \\ "a\u200Cb"

Yes I’m using PyQt, but I believe it has nothing to do with the binding.

Edit: I'm using Noto Sans, point size 62.

SGaist

Can you show the complete code with font setup ?

SafaAlfulaij

Sure thing.

# minimal code
from PyQt5.QtGui import QGuiApplication, QFont, QFontMetricsF

app = QGuiApplication(["myApp"])

notoFont = QFont("Noto Sans", 62)
notoMetrics = QFontMetricsF(notoFont)

print(notoMetrics.tightBoundingRect("ab"))
print(notoMetrics.tightBoundingRect("a\u200Cb"))

Output:

PyQt5.QtCore.QRectF(3.0, -64.0, 91.0, 65.0)
PyQt5.QtCore.QRectF(3.0, -64.0, 113.0, 65.0)

SGaist

Which variation of the Note Sans font ? There's a lot of possibilities.

SafaAlfulaij

Well, I think that the font doesn’t really matter here. Whatever font I use I get the same problem.
Reported bug: https://bugreports.qt.io/browse/QTBUG-70184