SUMMARY When the screen dimensions change while an effect is open, the effect goes black. This is easily triggered from Plasma Mobile by opening the task switcher and rotating the phone. STEPS TO REPRODUCE 1. Open Plasma in a window (KWin windowed mode) 2. Open an effect (ex. Overview) 3. Resize the window Video: https://invent.kde.org/teams/plasma-mobile/issues/uploads/67f94e91afee245c39a51ba140f8140b/Screencast_20231113_203755.webm OBSERVED RESULT The screen goes black EXPECTED RESULT The screen doesn't go black SOFTWARE/OS VERSIONS Linux/KDE Plasma: Fedora (available in About System) KDE Plasma Version: git master KDE Frameworks Version: git master Qt Version: 6.6 ADDITIONAL INFORMATION https://invent.kde.org/teams/plasma-mobile/issues/-/issues/229
Can confirm. The log spams > kwin_scene_opengl: 0x3: GL_INVALID_OPERATION in glBindBuffer(non-gen name) on every rendered frame, so presumably something's wrong with the code blitting the effect results to the screen
A possibly relevant merge request was started @ https://invent.kde.org/plasma/kwin/-/merge_requests/4681
Git commit 6a997b41ae9acccaba8169eb69c354774085fd00 by Vlad Zahorodnii. Committed on 21/11/2023 at 20:11. Pushed by vladz into branch 'master'. Fix screen becoming black when its geometry changes while overview is active Offscreen quick views are repainted in the pre paint step because that requires a QOpenGLContext and we don't want it to mess with kwin's opengl context. After a view is updated, its QOpenGLContext is going to be unbound. During normal operation mode, it works as expected: - the view gets updated in the pre paint stage - kwin opengl context is made current when starting the paint stage - the offscreen view is painted on the screen However, effects->renderScreen() has no such separation. The OpenGL context changes from the pre paint stage will leak to the paint stage. So we have - the workspace notifies that the screens have changed - the screen transform effect sees that, makes opengl context current and renders the screen - the offscreen quick view is updated and after OffscreenQuickView is done, it's going to call QOpenGLContext::doneCurrent() - effects->renderScreen() calls m_scene->paint() - since there's no current opengl context, vbo allocation in GLTexture::render() will fail and nothing will be rendered on the screen As a way around it, this change adds a makeOpenGLContextCurrent() call before the paint stage. It doesn't quite belong there, the opengl context has to be made current in the paint stage, e.g. by the ItemRenderer or something. But atm we have no good place where we could stick it in. M +5 -1 src/effect/effecthandler.cpp https://invent.kde.org/plasma/kwin/-/commit/6a997b41ae9acccaba8169eb69c354774085fd00