Scrollbars in wkgtk are rendered by the gtk theme using cairo directly. In order to do this, the cairo cr of the current GraphicsContext is gotten through the PlatformContext. But when using threaded rendering, the GraphicsContext used for recording the commands doesn't have a PlatformContext, so when trying to draw the scrollbars there's a crash.
Created attachment 343143 [details] Patch
Comment on attachment 343143 [details] Patch Does this mean scrollbars will not be rendered at all when using the threaded painting? What about other places where graphicsContext.platformContext()->cr() is used, like RenderThemeGtk?
(In reply to Carlos Garcia Campos from comment #2) > Comment on attachment 343143 [details] > Patch > > Does this mean scrollbars will not be rendered at all when using the > threaded painting? What about other places where > graphicsContext.platformContext()->cr() is used, like RenderThemeGtk? I was just doing more testing and I realized that,as you say, not only the scrollbars but everything that's rendered by the theme has the same problem. This is a wrong fix then. We need to be able to exclude layers with themed elements from the threaded rendering or completely disable threaded rendering in wkgtk.
As theme integration is not a priority at this point, and we need to finish the threaded rendering path in wpe, we are going to keep it disabled on wkgtk for the moment.
Created attachment 343146 [details] Patch
Comment on attachment 343146 [details] Patch Clearing flags on attachment: 343146 Committed r233009: <https://trac.webkit.org/changeset/233009>
All reviewed patches have been landed. Closing bug.