Merge lp:~vanvugt/mir/fix-1686620 into lp:mir

[Daniel van Vugt]

Ensure fullscreen eglapps that request initial state 'fullscreen'
know their actual buffer dimensions in time to set up glViewport
and render their first frame (LP: #1686620)

Since r4134 they were getting 0x0 from mir_eglapp_init and using
that to set a 0x0 viewport. So the window would remain black until
resized.

Providing resize events asynchronously is fine, but apps also need to know a sane size before that first resize callback, when they're already rendering their first frame.

Sadly that first resize callback is not guaranteed to occur before mir_create_window_sync returns. Even if you move the location of the call introduced in r4150 then it's still racy because we don't have the nice ordering of real wait handles any more. The initial resize event can _still_ occur in a background thread after mir_create_window_sync has returned and the app is setting up its first frame.

[Mir CI Bot (mir-ci-bot)]

PASSED: Continuous integration, rev:4162
https://mir-jenkins.ubuntu.com/job/mir-ci/3382/
Executed test runs:
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-mir/4577
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-0-fetch/4704
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=xenial+overlay/4693
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-1-sourcepkg/release=zesty/4693
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=zesty/4609
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=clang,platform=mesa,release=zesty/4609/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/4609
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=xenial+overlay/4609/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=zesty/4609
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=amd64,compiler=gcc,platform=mesa,release=zesty/4609/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=cross-armhf,compiler=gcc,platform=mesa,release=zesty/4609
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=cross-armhf,compiler=gcc,platform=mesa,release=zesty/4609/artifact/output/*zip*/output.zip
    SUCCESS: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/4609
        deb: https://mir-jenkins.ubuntu.com/job/build-2-binpkg-mir/arch=i386,compiler=gcc,platform=mesa,release=xenial+overlay/4609/artifact/output/*zip*/output.zip

Click here to trigger a rebuild:
https://mir-jenkins.ubuntu.com/job/mir-ci/3382/rebuild

review: Approve (continuous-integration)

[Alberto Aguirre (albaguirre)]

OK.

review: Approve

=== modified file 'examples/eglapp.c'
--- examples/eglapp.c	2017-04-05 03:11:28 +0000
+++ examples/eglapp.c	2017-04-28 09:57:23 +0000
@@ -512,6 +512,25 @@
     ok = eglMakeCurrent(egldisplay, eglsurface, eglsurface, eglctx);
     CHECK(ok, "Can't eglMakeCurrent");
 
+    EGLint buf_width, buf_height;
+    if (eglQuerySurface(egldisplay, eglsurface, EGL_WIDTH, &buf_width) &&
+        eglQuerySurface(egldisplay, eglsurface, EGL_HEIGHT, &buf_height))
+    {
+        /*
+         * Mir reserves the right to ignore our initial window dimensions and
+         * resize to whatever it likes. Usually that resize callback has
+         * occurred by now (see r4150), but libmirclient does not provide a
+         * solid guarantee of it. Luckily, we don't care... by querying EGL
+         * buffer dimensions we can get the correct answer without being
+         * victim to the callback race that's going on in the background...
+         * If the server has given us dimensions other than what we requested
+         * then EGL will already know about it, possibly before the initial
+         * resize event (!).
+         */
+        *width = buf_width;
+        *height = buf_height;
+    }
+
     signal(SIGINT, shutdown);
     signal(SIGTERM, shutdown);
     signal(SIGHUP, shutdown);