Blank window on libhybris with Xwayland

[fredldotme]

Hello! I'm trying to get GL4ES working on Ubuntu Touch, but came across some hurdles.

Ubuntu Touch on Android devices uses libhybris to access the Android driver blobs, which means full GLESv2 using proprietary drivers. To query visuals I had to add the Termux patch to GL4ES in order for it not to bail out with LIBGL_FB=3. Xwayland is set up to use shm mode.

My goal is to get GLX apps running, but right now Xwayland only displays blank surfaces, which seem to be RGBA, resulting in transparent window buffers in our Wayland compositor. To build GL4ES I used -DNOEGL=OFF -DGBM=OFF as CMake arguments.

What could be missing?

Thank you.

[ptitSeb]

What GKX app are you running? simple ones like glxgears?

[fredldotme]

What GKX app are you running? simple ones like glxgears?

Yes, glxgears to be specific. glxinfo prints out information as expected.

[ptitSeb]

All the shaders are building correctly? no error in the logs?

If there is no issue, there is probably a misconfiguration between the context created with LIBGL_FB=3 and what the compositor expect? Do you have any details of the framebuffer created?

[fredldotme]

No problems are printed on screen, but Android's libEGL reports an error when querying surface width and height. Check the bottom of this log.

egl.log

[ptitSeb]

Yeah, the surface is not correct. It's blank because the EGL Surface isn't created correctly. I'm not familliar with the inner working of Termux, so there is little I can do here.

I would suggest you trace, or put extensive log, at the egl surface create to understand where it goes wrong.

[fredldotme]

Please enlighten me, since this is with LIBGL_FB=3 I should check for eglCreatePbufferSurface, right?

EDIT: For clarification, this is not using Termux, just it's patch.

[ptitSeb]

Yep

I know it's just a patch, but that doesn't change the fact I don't know what that patch would do and why...

[fredldotme]

I've reduced the Termux patch down to what is really needed:

diff --git a/src/glx/glx.c b/src/glx/glx.c
index 06dce281..c55bf7ef 100644
--- a/src/glx/glx.c
+++ b/src/glx/glx.c
@@ -1841,7 +1841,7 @@ GLXFBConfig *gl4es_glXChooseFBConfig(Display *display, int screen,
         attr[cur++] = EGL_STENCIL_SIZE;
         attr[cur++] = 8;
     }
-    attr[1] |= (globals4es.usepbuffer)?(/*EGL_PBUFFER_BIT|*/EGL_PIXMAP_BIT):EGL_WINDOW_BIT;
+    attr[1] |= (globals4es.usepbuffer)?(EGL_PBUFFER_BIT/*|EGL_PIXMAP_BIT*/):EGL_WINDOW_BIT;
 
     attr[cur++] = EGL_RENDERABLE_TYPE;
     attr[cur++] = (hardext.esversion==1)?EGL_OPENGL_ES_BIT:EGL_OPENGL_ES2_BIT;
@@ -1944,7 +1944,7 @@ GLXFBConfig *gl4es_glXGetFBConfigs(Display *display, int screen, int *count) {
     int cur = 0;
     int tmp;
     attr[cur++] = EGL_SURFACE_TYPE;
-    attr[cur++] = (globals4es.usepbuffer)?(EGL_PBUFFER_BIT|EGL_PIXMAP_BIT):EGL_WINDOW_BIT;
+    attr[cur++] = (globals4es.usepbuffer)?(EGL_PBUFFER_BIT/*|EGL_PIXMAP_BIT*/):EGL_WINDOW_BIT;
     attr[cur++] = EGL_RENDERABLE_TYPE;
     attr[cur++] = (hardext.esversion==1)?EGL_OPENGL_ES_BIT:EGL_OPENGL_ES2_BIT;
     attr[cur++] = EGL_NONE; // end list

This is because Android drivers don't support EGL_PIXMAP_BIT, so choosing and getting the GLX FBConfig needed adaptation.

Breaking at createPBuffer shows no sign of a mismatch, the PBuffer gets created correctly and EGLContext and EGLSurface are assigned correctly. The EGL_BAD_SURFACE error stems from a different call, namely refreshMainFBO().

[fredldotme]

@ptitSeb would you be willing to help if you either installed Ubuntu Touch on an existing device (https://devices.ubuntu-touch.io), or we send a preinstalled device your way?

[ptitSeb]

I can try, but I checked the list of supported devices and I have none of them.

[fredldotme]

I'll send you a mail after getting the green light.