Repository: spyder-ide/spyder

Issue:
Minimize icon is out of center
### 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

## Problem Description

In outline and profile

![Screenshot Linux 2019-06-19 14 53 06](https://user-images.githubusercontent.com/5084939/59789382-313ec580-92a4-11e9-9dff-d0ca002bd965.png)

![Screenshot Linux 2019-06-19 14 51 32](https://user-images.githubusercontent.com/5084939/59789360-24ba6d00-92a4-11e9-841b-2ac8738e3dfd.png)


### What is the expected output? What do you see instead?

Expected to be at the center.

## Versions

- Spyder 4.0.0.dev0 (Commit: 1a079fc93) 
- Python 3.6.8 64-bit
- Qt 5.12.3
- PyQt5 5.12.2
- Linux 4.15.0-52-generic
- QdarkStyle Develop (Commit: 18ef745e2674) 

### Dependencies

pygments >=2.0     :  2.4.2 (OK)
qdarkstyle >=2.6.4 :  2.8 (OK)
sphinx >=0.6.6     :  2.0.1 (OK)
psutil >=0.3       :  5.6.2 (OK)
pyls >=0.19.0;<0.25:  0.24.0 (OK)
nbconvert >=4.0    :  5.5.0 (OK)
pandas >=0.13.1    :  None (NOK)
numpy >=1.7        :  1.16.4 (OK)
sympy >=0.7.3      :  None (NOK)
cython >=0.21      :  None (NOK)
qtconsole >=4.5.0  :  4.5.1 (OK)
IPython >=4.0      :  7.5.0 (OK)
matplotlib >=2.0.0 :  None (NOK)
pylint >=0.25      :  2.3.1 (OK)


Discussion:
![icons-image-out-off-center](https://user-images.githubusercontent.com/5084939/59791117-ca231000-92a7-11e9-9833-4fa40ce51428.gif)

How can this be fixed? Is this not an issue that should go in QDarkstyle?
Oh, may changing the icon file or something like this issue/PR: #2504. This is not related to QDark because the image is not from there.  Note that only that icon is unaligned. Tks
Ok, thanks for the clarification!
Instead of using the `spyder.inward` icon for this button, maybe using an icon from `fas` or `mdi` could be an option to solve this issue? Here are some options:

![image](https://user-images.githubusercontent.com/10170372/60388470-19272d00-9a80-11e9-8e16-427d84c2160e.png)

Here is my favorite icon selection for this in the light and dark mode. I used the mdi icons for the collapse and expand selection as well to match the icons of the collapse and expand all buttons.

![image](https://user-images.githubusercontent.com/10170372/60388804-71602e00-9a84-11e9-9537-c50255607cba.png)

> I used the mdi icons for the collapse and expand selection as well to match the icons of the collapse and expand all buttons.

I like this solution a lot. Thanks for looking into it!

Resolving patch:
diff --git a/spyder/utils/icon_manager.py b/spyder/utils/icon_manager.py
--- a/spyder/utils/icon_manager.py
+++ b/spyder/utils/icon_manager.py
@@ -194,8 +194,8 @@
     'bug':                     [('fa.bug',), {'color': MAIN_FG_COLOR}],
     'maximize':                [('spyder.maximize-pane',), {'color': MAIN_FG_COLOR}],
     'unmaximize':              [('spyder.minimize-pane',), {'color': MAIN_FG_COLOR}],
-    'window_nofullscreen':     [('spyder.inward',), {'color': MAIN_FG_COLOR}],
-    'window_fullscreen':       [('fa.arrows-alt',), {'color': MAIN_FG_COLOR}],
+    'window_nofullscreen':     [('mdi.arrow-collapse-all',), {'color': MAIN_FG_COLOR}],
+    'window_fullscreen':       [('mdi.arrow-expand-all',), {'color': MAIN_FG_COLOR}],
     'MessageBoxWarning':       [('fa.warning',), {'color': MAIN_FG_COLOR}],
     'arredit':                 [('fa.table',), {'color': MAIN_FG_COLOR}],
     'zoom_out':                [('fa.search-minus',), {'color': MAIN_FG_COLOR}],
@@ -264,8 +264,8 @@
     'project':                 [('fa.folder-open-o',), {'color': MAIN_FG_COLOR}],
     'DriveHDIcon':             [('fa.hdd-o',), {'color': MAIN_FG_COLOR}],
     'arrow':                   [('fa.arrow-right',), {'color': MAIN_FG_COLOR}],
-    'collapse':                [('spyder.inward',), {'color': MAIN_FG_COLOR}],
-    'expand':                  [('fa.arrows-alt',), {'color': MAIN_FG_COLOR}],
+    'collapse':                [('mdi.collapse-all',), {'color': MAIN_FG_COLOR}],
+    'expand':                  [('mdi.expand-all',), {'color': MAIN_FG_COLOR}],
     'restore':                 [('fa.level-up',), {'color': MAIN_FG_COLOR}],
     'collapse_selection':      [('fa.minus-square-o',), {'color': MAIN_FG_COLOR}],
     'expand_selection':        [('fa.plus-square-o',), {'color': MAIN_FG_COLOR}],


Test patch: