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<p class="MsoNormal"><span lang="EN-US">Some debugs show, after a shell surface is created, the future registry_handle_global (of wl_registry_listener) doesn’t receive any interface.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">There are some wl_registry_listener in the stack, if I skip wl_shell_get_shell_surface from the previous bind, it will be ok.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">It seems: after one shell surface is created, wayland server will not broadcast its interface again. – even for the interfaces has nothing to do with wl_shell.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The background is:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">In multimedia stack, wl_registry_listener is used in different layer:
<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:21.0pt"><span lang="EN-US">app may use the shell surface to handle window stack.<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:21.0pt"><span lang="EN-US">Middleware (gst-vaapi) may use wl_shell (in case create wl_surface of its own), wl_output to get screen resolution for full-screen support, even wl_compositor to handle region_opaque<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:21.0pt"><span lang="EN-US">Video driver uses wl_drm interface to manage wl_buffer.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Usually it is ok (by gst-launch), because decoder runs first, which load video driver to setup wl_drm interface, then video render (vaapisink) create a wl_surface (and its shell surface) to display video frames.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">However, that’s not typical usage.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">In real case, media player (app) connects to Weston, creates a wl_surface, then app set wl_display/wl_surface to middleware (vaapisink), vaapi sink will try to create shell_surface from the wl_surface.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Next, media pipeline starts to run, decoder loads video driver, driver doesn’t receive any interface(wl_registry_listener) from Weston. Then fail.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">(by the way, in this case, it’s better app creates the shell surface, not vaapisink. Anyway, It doesn’t impact the result)<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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