Theme visibility issues: ToolBar overflow button (dark theme) #100
Description
From DataLab-Platform/DataLab#297
Dark theme: Toolbar overflow button is invisible
When using the dark theme on a small screen, the toolbar shortcut buttons may not all fit in the available space. A small overflow button with two arrows (») appears to access the hidden buttons. However, this button is rendered as a black icon on a black background, making it completely invisible. The button is only discoverable by hovering over its location by chance.
Expected behavior
The toolbar overflow button should use a visible icon color or a different background that contrasts with the main dark background to make it more visible
Solution Proposal
Use Qt stylesheet in qthelpers.py to apply a more visible style for this button :
"QToolButton#qt_toolbar_ext_button {"
"background-color: gray; border: 1px solid gray;"
"}"