[gtk/wip/otte/build: 1/6] build: Set proper defaults for media backends

[Matthias Clasen <matthiasc src gnome org>]

commit 9f6fb161e2f8dfea0e99abf98d2f39adeb994b56
Author: Benjamin Otte <otte redhat com>
Date:   Thu Apr 1 17:59:18 2021 +0200

    build: Set proper defaults for media backends
    
    GTK supports webm playback, which means a backend should always be
    compiled.
    
    The ffmpeg backend however is incomplete (no audio) and as such, we
    don't want people to end up with it accidentally.
    
    Since we don't want to drag an entire gstreamer build into our ci
    on MacOs or msvc, explicitly disable the gstreame media backend there.

 .gitlab-ci.yml           | 1 +
 .gitlab-ci/test-msvc.bat | 2 +-
 meson_options.txt        | 8 +++++---
 3 files changed, 7 insertions(+), 4 deletions(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index c100755896..8fddbcf284 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -172,6 +172,7 @@ macos:
     - meson -Dx11-backend=false
             -Dbroadway-backend=true
             -Dmacos-backend=true
+            -Dmedia-gstreamer=disabled
             -Dintrospection=disabled
             -Dcpp_std=c++11
             -Dpixman:tests=disabled
diff --git a/.gitlab-ci/test-msvc.bat b/.gitlab-ci/test-msvc.bat
index 294e9480df..c6833f0c0e 100644
--- a/.gitlab-ci/test-msvc.bat
+++ b/.gitlab-ci/test-msvc.bat
@@ -6,7 +6,7 @@ call "C:\Program Files (x86)\Microsoft Visual Studio\2017\BuildTools\VC\Auxiliar
 
 :: FIXME: make warnings fatal
 pip3 install --upgrade --user meson==0.56.2  || goto :error
-meson _build || goto :error
+meson -Dmedia-gstreamer=disabled _build || goto :error
 ninja -C _build || goto :error
 
 goto :EOF
diff --git a/meson_options.txt b/meson_options.txt
index 402caec5fb..2223cb7964 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -26,15 +26,17 @@ option('macos-backend',
        description : 'Enable the macOS gdk backend (only when building on macOS)')
 
 # Media backends
+# For distros: GTK guarantees support for WebM video (VP8 and VP9), so a supported build
+# should provide that.
 
 option('media-ffmpeg',
        type: 'feature',
-       value: 'auto',
-       description : 'Build the ffmpeg media backend')
+       value: 'disabled',
+       description : 'Build the experimental ffmpeg media backend')
 
 option('media-gstreamer',
        type: 'feature',
-       value: 'auto',
+       value: 'enabled',
        description : 'Build the gstreamer media backend')
 
 # Print backends