TC 9.5ß7 / ß8 Darkmode: Behaviour of scrollbars is strange

[Dennis_Stevens]

Maybe this has been reported or is due to Windows functionalities but it is strange anyway.

Tested on TCß7 and ß8 under Win 10 1709 and Win 10 1803:

Navigate to a folder with a bunch of files (vertical scrollbars must be visible).
Scroll down to the end of the list with the mouse-wheel and keep on turning the wheel although the end of the list has been reached. During scrolling the scrollbars remain in dark mode.
By hitting the end of the list, the inner fields of the scrollbars are switched to bright (the arrows for up and down remain dark) and remain like this until either mouse-cursor is moved a bit or mouse-wheel is pushed to top.
If you do the same procedure in the other direction and hit the top of the list, the scrollbars remain completely dark.
If you do the scrolling with ctrl-button pushed down, the color of the scrollbars is not changed at any position.

Now scroll the list by moving the scrollbar with the mouse-cursor.
As soon as the bar is moved, the inner field of the bar is switched to bright, the arrows for up and down remain dark. Now release the mouse-button, but do not move the cursor. The arrows for up and down will switch to bright. Hold position for 2 or 3 seconds and scrollbars will switch to dark.
If you do this scrolling with ctrl-button pushed down, the behaviour is the same (scrollbars will not stay dark like by scrolling with the wheel).

I know that scrollbars in dark mode are kind of special, but anyway the dark mode does not seem to work properly since the behaviour is quite different during each scrolling direction.
Bug or feature?

[ghisler(Author)]

This happens because Windows 10 1803 and older do NOT support dark scrollbars. Onl Windows 10 1809 and newer do.

Therefore TC is overdrawing the existing scrollbars with its own when it receives WM_PAINT or WM_NCPAINT messages. Unfortunately Windows sometimes redraws the scrollbars internally within the control, bypassing these messages, so I cannot overdraw them. They are then redrawn after a short delay when a change is noticed in the control.

There is no fix except for updating to a newer Windows 10 version.