I was able to reproduce similar visual issues on my high dpi Linux system, and put in a fix for it this afternoon. Can you try tomorrow's build (16.0.550) and see if it also fixes the problem for you?

Alexey,

Can you try adding the following method to your Python Panel script:
def dragEnterEvent(self, event):
event.acceptProposedAction()

That block of code was needed to make the example work on my machine. Also, which platform are you currently using? I'm working through some drag and drop bugs on OS X so if you're on the platform drag and drop may not work as expected.

Getting the Houdini stylesheet from the QApplication instance should be safe in both PySide and C++ code. We don't currently have a method for directly querying Houdini's style sheet directly. The stylesheet is generated at runtime based on the current colour settings and a base stylesheet.

If you're working in C++, you can also use QT_Utils::applyWidgetStyleSheets(QWidget*) to apply the Houdini style sheet to a QWidget. Note that this will overwrite any style sheets currently set on the QWidget.

Logged as bug #66344

Calling setStyleSheet in Python Panels should work as expected in tomorrow's build. Since we're using stylesheets, QFont and QPalette values are ignored automatically by Qt.

I'll take look at the QGroupBox and QTextEdit styling issues you mentioned.