Transparent line across the top of the web view

[a-m-s]

Blocked by tiliado/valacef#11

There is a transparent line across the top of every web view that does not appear in other browsers. It's typically rendered in white, and is particularly noticeable when watching full-screen videos (e.g. YouTube or BBC).

It's been bugging me for a while, but I've just noticed that it shows up in snapshots taken with the new sidebar too:

You'll probably have to download that image and view it in an external tool to see the problem (Gnome Image Viewer works).

[jiri-janousek]

Yeah, it looks as if the top 1 px line was erased. Playing with the offset of the web view X window does not help.

[jiri-janousek]

It's pixel-perfect in ValaCEF so the issue is in Nuvola Runtime.

[jiri-janousek]

• I've added a 2px red line at y=0 and a shorter 1px green line at y=1. Initially, the top part of the red line was not visible, confirming this issue.
• Then I set margin-top to 1px and the line became visible, i.e. the web view is not crippled anymore. I suppose that whatever painted over the web view now paints over the 1px margin (light grey color).
  
• The snapshot of the web views also looks good, so I suppose the fullscreen mode will work well as well. I'll rebuild Nuvola ADK for you to check that.
• I think it is a pretty good workaround until I find out which GTK+ widgetry is responsible for the issue and how to fix that for good.

[jiri-janousek]

The snapshot of the web views also looks good, so I suppose the fullscreen mode will work well as well. I'll rebuild Nuvola ADK for you to check that.

Hello @ams, could you confirm that with the latest ADK or any app flatpak (stable or master)?

I think it is a pretty good workaround until I find out which GTK+ widgetry is responsible for the issue and how to fix that for good.

I'm afraid it is necessary to switch to windowless/off-screen rendering as the current windowed rendering doesn't work well with GTK+ 3 drawing model and it will get even worse with GTK+ 4. CEF supports OSR, but it is not accelerated yet (tiliado/valacef#11).

[a-m-s]

The screen shot tool seems fixed, but I still see the line on my screen, in both windowed and fullscreen mode.

You can see the white line between title bar and content.

[jiri-janousek]

Sure, the line is expected in the windowed mode - as I said I added only a workaround with a 1px top margin. But I didn't expect it in the fullscreen mode. Now I remember how the fullscreen is implemented and it makes sense - I thought only the CEF window goes to fullscreen, but the fullscreen applies to the whole Nuvola window including the 1px top margin.

[jiri-janousek]

@a-m-s, could you test with Nuvola/master and VALACEF_DEFAULT_RENDERING_MODE=offscreen? E.g. VALACEF_DEFAULT_RENDERING_MODE=offscreen flatpak run eu.tiliado.NuvolaAdk//master?

[a-m-s]

The first time I ran it I got a Segmentation Fault.

bash-4.3$ VALACEF_DEFAULT_RENDERING_MODE=offscreen nuvolaruntime -D
Runner: [DEBUG Δ058137us DioriteGtk] DesktopShell.vala:251: Shell: gnome shell 3.28.2, CSD 1, appmenu 1, menubar 0
Runner: [DEBUG Δ000726us Nuvola] Connection.vala:115: Network Proxy: system settings
Runner: [DEBUG Δ000991us Nuvola] WebkitOptions.vala:51: MSE supported: no
Runner: [WARNING Δ014016us Nuvola] StartupWindow.vala:83: Unable to load application icon.
Runner: [DEBUG Δ000223us Nuvola] WebApp.vala:340: Theme icon eu.tiliado.NuvolaAdkAppBbcIplayer 64 not found.
Runner: [DEBUG Δ140647us Nuvola] AppRunnerController.vala:114: Scale factor: 1
Runner: [DEBUG Δ007849us Nuvola] FormatSupport.vala:86: Trying to play /app/share/nuvolaruntime/audio/audiotest.mp3.
Runner: [DEBUG Δ001405us DioriteGtk] Application.vala:276: XFCE session vanished: org.xfce.SessionManager
Runner: [DEBUG Δ000260us Nuvola] FormatSupport.vala:86: Pipeline state changed from NULL to READY.
Runner: [DEBUG Δ000401us Nuvola] Graphics.vala:35: Nvidia 396.24, i915 1, bumblebeed 1 => ignored 1
Runner: [DEBUG Δ010071us Nuvola] FormatSupport.vala:86: Pipeline state changed from READY to PAUSED.
Runner: [DEBUG Δ000224us Nuvola] FormatSupport.vala:86: Pipeline state changed from PAUSED to PLAYING.
Runner: [DEBUG Δ007876us Nuvola] FormatSupport.vala:86: End of stream for file /app/share/nuvolaruntime/audio/audiotest.mp3.
Runner: [DEBUG Δ004109us Nuvola] StartupCheck.vala:216: Checking requirements with WebKitGTK 2.20.2
Runner: [DEBUG Δ000081us Nuvola] Traits.vala:62: Chromium[65] -> DRT_REQUIREMENT_STATE_UNSUPPORTED 
Runner: [DEBUG Δ000039us Nuvola] Traits.vala:62: Codec[H264] -> DRT_REQUIREMENT_STATE_UNSUPPORTED 
Runner: [DEBUG Δ000029us Nuvola] Traits.vala:62: Codec[MP3] -> DRT_REQUIREMENT_STATE_SUPPORTED 
Runner: [DEBUG Δ000030us Nuvola] Traits.vala:62: Feature[MSE] -> DRT_REQUIREMENT_STATE_UNSUPPORTED 
Runner: [DEBUG Δ000029us Nuvola] WebkitOptions.vala:136: Nuvola.WebPlugin: Shockwave Flash (enabled, flash) at /app/lib/flash/libflashplayer.so: Shockwave Flash 28.0 r0
Runner: [DEBUG Δ000020us Nuvola] Traits.vala:62: Feature[Flash] -> DRT_REQUIREMENT_STATE_SUPPORTED 
Runner: [DEBUG Δ000024us Nuvola] StartupCheck.vala:216: Checking requirements with Chromium 67.0.3396.30
Runner: [DEBUG Δ000031us Nuvola] Traits.vala:62: Chromium[65] -> DRT_REQUIREMENT_STATE_SUPPORTED 
Runner: [DEBUG Δ000024us Nuvola] Traits.vala:62: Codec[H264] -> DRT_REQUIREMENT_STATE_SUPPORTED 
Runner: [DEBUG Δ000024us Nuvola] Traits.vala:62: Codec[MP3] -> DRT_REQUIREMENT_STATE_SUPPORTED 
Runner: [DEBUG Δ000024us Nuvola] Traits.vala:62: Feature[MSE] -> DRT_REQUIREMENT_STATE_SUPPORTED 
Runner: [DEBUG Δ000029us Nuvola] Traits.vala:62: Feature[Flash] -> DRT_REQUIREMENT_STATE_UNKNOWN 
Runner: [DEBUG Δ000242us CefGtk] init.vala:84: No widevine plugin dir.
InitLibcLocaltimeFunctions
Your system is broken: dlsym doesn't work! This has been reported to be caused by Nvidia's libGL. You should expect time related functions to misbehave. http://code.google.com/p/chromium/issues/detail?id=16800
InitLibcLocaltimeFunctions
Runner: [DEBUG Δ043812us Nuvola] StartupCheck.vala:247: Checking requirements with Chromium 67.0.3396.30
Runner: [DEBUG Δ000069us Nuvola] Traits.vala:62: Chromium[65] -> DRT_REQUIREMENT_STATE_SUPPORTED 
Runner: [DEBUG Δ000039us Nuvola] Traits.vala:62: Codec[H264] -> DRT_REQUIREMENT_STATE_SUPPORTED 
Runner: [DEBUG Δ000034us Nuvola] Traits.vala:62: Codec[MP3] -> DRT_REQUIREMENT_STATE_SUPPORTED 
Runner: [DEBUG Δ000032us Nuvola] Traits.vala:62: Feature[MSE] -> DRT_REQUIREMENT_STATE_SUPPORTED 
Runner: [DEBUG Δ000033us Nuvola] Traits.vala:62: Feature[Flash] -> DRT_REQUIREMENT_STATE_SUPPORTED 
InitLibcLocaltimeFunctions
Runner: [WARNING Δ256944us Nuvola] WebAppWindow.vala:77: Unable to load application icon.
Runner: [DEBUG Δ003990us Nuvola] WebkitOptions.vala:51: MSE supported: no
Runner: [INFO Δ000250us Nuvola] CefEngine.vala:295: Partially implemented: register_ipc_handlers()
Runner: [INFO Δ000152us CefGtk] WebView.vala:74: CEF rendering mode: CEF_GTK_RENDERING_MODE_OFFSCREEN
Runner: [INFO Δ003435us CefGtk] Client.vala:106: get_life_span_handler
Segmentation fault (core dumped)

However, subsequent runs all worked correctly, and the annoying line across the top is gone. :-)

[jiri-janousek]

Great, so the offscreen rendering seems to be a promising way to go as it solves three bugs. Unfortunately, the memory & CPU usage suffers as Nuvola needs to keep the pixel buffer around (~40 MB for Full HD) and does the final drawing with CPU instead of GPU (Poster circle gives 23 fps instead of 60 fps). That needs to be optimized. More at tiliado/valacef#11

[jiri-janousek]

This should be resolved with #583.

[jiri-janousek]

This will be fixed in the QtWebWengine port of Nuvola in #583. The work-in-progress components Wayland Embedded View Framework Server and Wayland Embedded View Framework Client don't exhibit this issue.

[jiri-janousek]

I'm closing this ticket as Nuvola Player has discontinued active development. We are going to provide only integration bug fixes on a best-effort basis until the final End-of-Life on December 31, 2022. I'm sorry that I haven't managed to resolve this ticket in time.