[platform-swt-dev] Actual background color of TabFolder contents

[Stephan Aßmus]

Hi,

it seems there has been quite some effort invested to get controls
inside a TabFolder to draw with the correct background. I've found a
number of bug-reports, many tutorials, but nothing concerning the actual
problem I have:

I want to display a wrapping help message below some controls inside a
TabFolder, and the help message shall contain icons within the text.

Not going into the details of how exactly, I should be able to use a
StyledText-widget for this. In this situation, the StyledText-widget
shall have no border and assume the same background color as the
Composite to which it is added. Which shall be the TabFolder background
color.

This should simply be:

styledText.setBackground(styledText.getParent().getBackground());

However, this does not return the color which is actually seen in the
parent widget. The implementation of getBackground() tries to find the
widget that is actually responsible for the color. And I guess the
TabFolder itself actually /has/ gray as background, which can be seen in
the area outside the tabs. The contents of the TabFolder however has a
different color (Windows: white, macOS: lighter gray), leading to the
situation that getBackround() returns a wrong color. I guess it only
works, because most controls rely on the system to clear the background
before they paint the foreground. Which StyledText specifically avoids
by forcing the NO_BACKGROUND style flag.

Any advice?

Best regards,
-Stephan