Repository: spyder-ide/spyder

Issue:
Pane tabs in macOS are center-aligned rather than left-aligned
<!--- **PLEASE READ:** When submitting here, please ensure you've completed the following checklist and checked the boxes to confirm. Issue reports without it may be closed. Thanks! --->

### Issue Report Checklist

* [x] Searched the [issues page](https://github.com/spyder-ide/spyder/issues?q=is%3Aissue) for similar reports
* [x] Read the relevant sections of the [Spyder Troubleshooting Guide](https://github.com/spyder-ide/spyder/wiki/Troubleshooting-Guide-and-FAQ) and followed its advice
* [x] Reproduced the issue after updating with ``conda update spyder`` (or ``pip``, if not using Anaconda)
* [x] Could not reproduce inside ``jupyter qtconsole`` (if console-related)
* [x] Tried basic troubleshooting (if a bug/error)
    * [x] Restarted Spyder
    * [x] Reset preferences with ``spyder --reset``
    * [x] Reinstalled the latest version of [Anaconda](https://www.anaconda.com/download/)
    * [x] Tried the other applicable steps from the Troubleshooting Guide
* [x] Completed the **Problem Description**, **Steps to Reproduce** and **Version** sections below


## Problem Description
Tabs look like this on macOS Monterey after upgrading to Spyder 5.4.2:

![image](https://user-images.githubusercontent.com/1020594/217694995-ad55e95d-afb1-4631-90d4-803d661825b7.png)


### What steps reproduce the problem?

1. Upgrade to Spyder 5.4.2 on mac
2. Open the program

### What is the expected output? What do you see instead?

The expected output is tabs that are aligned correctly. The current output is in the picture above.

### Paste Traceback/Error Below (if applicable)
<!--- Copy from error dialog or View > Panes > Internal Console --->

## Versions
<!--- You can get this information from Help > About Spyder...
or (if Spyder won't launch) the "conda list" command
from the Anaconda Prompt/Terminal/command line. --->

* Spyder version: 5.4.2
* Python version: 3.11.0
* Qt version: 5.15.6
* PyQt version: 5.15.7
* Operating System name/version: macOS Monterey

### Dependencies
<!--- Please go to the menu entry Help > Dependencies,
press the Copy to clipboard button and paste below --->

```
# Mandatory:
applaunchservices >=0.3.0     :  0.3.0 (OK)
atomicwrites >=1.2.0          :  1.4.1 (OK)
chardet >=2.0.0               :  5.1.0 (OK)
cloudpickle >=0.5.0           :  2.2.1 (OK)
cookiecutter >=1.6.0          :  2.1.1 (OK)
diff_match_patch >=20181111   :  20200713 (OK)
intervaltree >=3.0.2          :  3.0.2 (OK)
IPython >=7.31.1;<9.0.0       :  8.9.0 (OK)
jedi >=0.17.2;<0.19.0         :  0.18.2 (OK)
jellyfish >=0.7               :  0.9.0 (OK)
jsonschema >=3.2.0            :  4.17.3 (OK)
keyring >=17.0.0              :  23.13.1 (OK)
nbconvert >=4.0               :  7.2.9 (OK)
numpydoc >=0.6.0              :  1.5.0 (OK)
parso >=0.7.0;<0.9.0          :  0.8.3 (OK)
pexpect >=4.4.0               :  4.8.0 (OK)
pickleshare >=0.4             :  0.7.5 (OK)
psutil >=5.3                  :  5.9.4 (OK)
pygments >=2.0                :  2.14.0 (OK)
pylint >=2.5.0;<3.0           :  2.16.1 (OK)
pylint_venv >=2.1.1           :  2.3.0 (OK)
pyls_spyder >=0.4.0           :  0.4.0 (OK)
pylsp >=1.7.1;<1.8.0          :  1.7.1 (OK)
pylsp_black >=1.2.0           :  1.2.1 (OK)
qdarkstyle >=3.0.2;<3.1.0     :  3.0.3 (OK)
qstylizer >=0.2.2             :  0.2.2 (OK)
qtawesome >=1.2.1             :  1.2.2 (OK)
qtconsole >=5.4.0;<5.5.0      :  5.4.0 (OK)
qtpy >=2.1.0                  :  2.3.0 (OK)
rtree >=0.9.7                 :  1.0.1 (OK)
setuptools >=49.6.0           :  67.1.0 (OK)
sphinx >=0.6.6                :  6.1.3 (OK)
spyder_kernels >=2.4.2;<2.5.0 :  2.4.2 (OK)
textdistance >=4.2.0          :  4.5.0 (OK)
three_merge >=0.1.1           :  0.1.1 (OK)
watchdog >=0.10.3             :  2.2.1 (OK)
zmq >=22.1.0                  :  25.0.0 (OK)

# Optional:
cython >=0.21                 :  0.29.33 (OK)
matplotlib >=3.0.0            :  3.6.3 (OK)
numpy >=1.7                   :  1.24.2 (OK)
pandas >=1.1.1                :  1.5.3 (OK)
scipy >=0.17.0                :  1.10.0 (OK)
sympy >=0.7.3                 :  1.11.1 (OK)
```



Discussion:
See also #9763.
Hey @battaglia01, thanks for opening a new issue about this. We don't know why this is happening, but we'll try to solve it in our next version (5.4.3), to be released next month.

@mrclary, are you seeing this problem on Mac?
Yes, I see center aligned tabs. I assumed it was intentional 😄.
Sorry guys, I think I introduced this error in commit 24d1fdd0dab09df78d115a9407f5d84428ffbe35 by mistake. I'll fix it right away.

Resolving patch:
diff --git a/spyder/utils/stylesheet.py b/spyder/utils/stylesheet.py
--- a/spyder/utils/stylesheet.py
+++ b/spyder/utils/stylesheet.py
@@ -306,7 +306,7 @@ def set_stylesheet(self):
             )
 
             css['QTabWidget::tab-bar'].setValues(
-                alignment='center',
+                alignment='left',
             )
         else:
             # Remove spurious pixel to the left


Test patch: