flashing scrollbars with Qt 5.12

[kevinushey]

System details

RStudio Edition : Desktop
RStudio Version : v1.2.1322
OS Version      : macOS 10.14.3
R Version       : 3.5.1

Steps to reproduce the problem

Open RStudio, and try navigating within the Files pane.

Describe the problem in detail

Describe the behavior you expected

No flashing scrollbars.

Notes

• Does not reproduce with Qt 5.11.3, but does reproduce with Qt 5.12.1.
• Does not reproduce if we disable this preference (

  rstudio/src/cpp/desktop/DesktopMain.cpp

  Lines 473 to 478 in 0868e5c

  	// don't prefer compositing to LCD text rendering. when enabled, this causes the compositor to
  	// be used too aggressively on Retina displays on macOS, with the side effect that the
  	// scrollbar doesn't auto-hide because a compositor layer is present.
  	// https://github.com/rstudio/rstudio/issues/1953
  	static char disableCompositorPref[] = "--disable-prefer-compositing-to-lcd-text";
  	arguments.push_back(disableCompositorPref);

  ), but then sticky scrollbars return.
• Does not reproduce if mouse is plugged in (only reproduces with trackpad)
• Still reproduces when using software rendering (so evidently, something beyond the GPU is going on?)

See Also

Flashing scrollbars. See #3078, #2808, #4047 for previous run-ins with this render bug.

[ronblum]

@kevinushey It looks like the scrollbar in the Environment pane sticks around when it shouldn't:

[kevinushey]

I don't see a scrollbar in the environment pane. Can you provide more details on your configuration? Do you have a mouse plugged in?

[gtritchie]

Here's an example of what I'm seeing. This is on late 2015 iMac 5K, AMD Radeon R9 M390 2048 MB, macOS 10.14.3. RStudio 1.2.1322-3. (external mouse and keyboard, of course)

[ronblum]

No external mouse. It happens when you mouse over the area at the bottom of the pane, when System Preferences -> General -> Show Scroll Bars is set to "Automatically" or "When scrolling," but not "Always."

1. Close RStudio (so that we start fresh)
2. System Preferences -> General -> Show Scroll Bars -> Automatically (or When Scrolling etc.)
3. Open RStudio
4. Switch to Environment pane
5. Hover mouse over bottom of quadrant, right above the border
   • Horizontal scroll bar should appear
6. Click on another pane in the same quadrant
7. Click on Environment pane
   • Horizontal scroll bar is still gone

Follow that up with:

8. Hover over the bottom of the pane, so that the scrollbar returns
9. System Preferences -> General -> Show Scroll Bars -> Always
   • Horizontal scroll is still there
10. Mouse over the Environment pane
    • Horizontal scroll bar may or may not go away
11. Switch to another pane in the same quadrant
12. Switch to Environment pane
    • Horizontal scroll bar may go away or be replaced by a lighter-gray scrollbar

Next:

13. Close RStudio
14. Reopen RStudio
15. Hover over bottom of Environment pane
    • No horizontal scroll bar

[ronblum]

This is an issue in 1.2.1332.

[ronblum]

Closing and opening #4529 which covers the persistent floating scrollbar, which is a separate issue.