Created attachment 112093 [details] taskmgr see screenshot
Fredik, looks like your changes it in some configurations? Also got some reports on IRC yesterday. Can you run the following command and observe its console output? plasmawindowed org.kde.plasma.taskmanager Then hover a task and see if something unusual happens when the preview should show, something like "shader program did not compile" or something. Also, please provide the output of qdbus org.kde.KWin /KWin org.kde.KWin.supportInformation When you have done this, please reset status back to Unconfirmed. Thanks!
Please provide the output from glxinfo as well.
It seems that https://cgit.kde.org/plasma-framework.git/commit/?id=612494e2b2e9265d33ce148332d5f490b024a3bd is the culprit, reverting that (and https://cgit.kde.org/plasma-framework.git/commit/?id=42d3fde1eef6866640cee8671b07dc81fa2df28c because depending on it, but only reverting that did not fix it) resolves the issue for me. Was able to reproduce on gentoo with Qt 5.10 and 5.9, both the nvidia and nouveau driver, on a Thinkpad T430 with a NVIDIA Corporation GF108M [NVS 5400M] had no thumbnails, downgrading plasma-frameworks to 5.44 or reverting the above brought thumbnails back.
Created attachment 112152 [details] Support information of KWin
Having the same issue on Arch with plasma 5.12.4, frameworks 5.45.0, Qt 5.10.1, nvidia 390.48-9. The issue does not appear with nouveu by the way. (In reply to Kai Uwe Broulik from comment #1) I've attached the output from qdbus org.kde.KWin /KWin org.kde.KWin.supportInformation. When I run plasmawindowed org.kde.plasma.taskmanager, it first shows: org.kde.plasmaquick: Applet preload policy set to 1 org.kde.plasma: requesting config for "Task Manager" without a containment! Connecting to deprecated signal QDBusConnectionInterface::serviceOwnerChanged(QString,QString,QString) qml: 0 Failed to register unity service Then, every time I enter the windowed task manager with the cursor, it shows an error like "QXcbConnection: XCB error: 2 (BadValue), sequence: 1282, resource id: 60817413, major code: 142 (Unknown), minor code: 3". This error only appears if a hover-preview has not been shown. I.e. when I move the cursor quickly over the icons/buttons, the error is spammed to the terminal. When I close the windowed task manager, it shows: <Unknown File>:1: TypeError: Cannot read property 'Layout' of null Xlib: extension "NV-GLX" missing on display ":0". Note that the NV-GLX line is only printed if I tried to get the hover-preview. This line is missing for example when I immediately close the window again. Hope this info helps.
Just to have it documented: On nvidia hardware, it throws a 1286 OpenGL error, thrown around if (prevScissorTest) glDisable(GL_SCISSOR_TEST); extraFuncs->glBlitFramebuffer(0, 0, size.width(), size.height(), 0, 0, size.width(), size.height(), GL_COLOR_BUFFER_BIT, GL_NEAREST) and qDebug() << "Read FBO status:" << funcs->glCheckFramebufferStatus(GL_READ_FRAMEBUFFER); qDebug() << "Draw FBO status:" << funcs->glCheckFramebufferStatus(GL_DRAW_FRAMEBUFFER); gives Read FBO status: 36061 Draw FBO status: 36053 and with the OpenGL context hack by frederikh we get QXcbConnection: XCB error: 2 (BadValue), sequence: 1680, resource id: 92274704, major code: 141 (Unknown), minor code: 3 0x506: GL_INVALID_FRAMEBUFFER_OPERATION error generated. Framebuffer bindings are not framebuffer complete. 0x20071: Buffer detailed info: Buffer object 3 (bound to GL_ARRAY_BUFFER_ARB, usage hint is GL_STATIC_DRAW) will use VIDEO memory as the source for buffer object operations. 0x20071: Buffer detailed info: Buffer object 4 (bound to GL_ELEMENT_ARRAY_BUFFER_ARB, usage hint is GL_STATIC_DRAW) will use VIDEO memory as the source for buffer object operations. 0x20071: Buffer detailed info: Buffer object 5 (bound to GL_ARRAY_BUFFER_ARB, usage hint is GL_STATIC_DRAW) will use VIDEO memory as the source for buffer object operations. 0x20071: Buffer detailed info: Buffer object 6 (bound to GL_ELEMENT_ARRAY_BUFFER_ARB, usage hint is GL_STATIC_DRAW) will use VIDEO memory as the source for buffer object operations. 0x20071: Buffer detailed info: Buffer object 7 (bound to GL_ARRAY_BUFFER_ARB, usage hint is GL_STATIC_DRAW) will use VIDEO memory as the source for buffer object operations. with an nvidia card and nvidia driver. I was able to get also no previews on nouveau, but due to limited time was not able to reproduce all of it on nouveau with the above debugging enabled. For nvidia users: reverting https://cgit.kde.org/plasma-framework.git/commit/?id=612494e2b2e9265d33ce148332d5f490b024a3bd and https://cgit.kde.org/plasma-framework.git/commit/?id=42d3fde1eef6866640cee8671b07dc81fa2df28c is a workaround so you can have the previews back whilst waiting for a proper solution.
Also this should potentially move product, since it is not in plasmashell, but rather the plasma frameworks integration.
Triaged to frameworks-plasma
reopening based on fuchs' comments
Reverted earlier today (but forgot the BUG syntax). We can retry the fancy filtering thing for the frameworks after.