ges: framepositioner: Make zorder controllable and expose it

And add a test for it

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5987>

subprojects/gst-editing-services/ges/ges-video-source.c

@@ -116,7 +116,7 @@ ges_video_source_create_filters (GESVideoSource * self, GPtrArray * elements,
   GstElement *positioner, *videoflip, *capsfilter, *videorate;
   const gchar *positioner_props[]
       = { "alpha", "posx", "fposx", "posy", "fposy", "width", "fwidth",
-    "height", "fheight", "operator", NULL
+    "height", "fheight", "operator", "zorder", NULL
   };
   const gchar *videoflip_props[] = { "video-direction", NULL };
   gchar *ename = NULL;

subprojects/gst-editing-services/ges/gstframepositioner.c

@@ -595,8 +595,12 @@ gst_frame_positioner_class_init (GstFramePositionerClass * klass)
    * The desired z order for the stream.
    */
   properties[PROP_ZORDER] =
-      g_param_spec_uint ("zorder", "zorder", "z order of the stream", 0,
-      G_MAXUINT, 0, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS);
+      g_param_spec_uint ("zorder", "zorder",
+      "z order of the stream.\n\n"
+      "**WARNING**: Setting it manually overrides the "
+      "#GESLayer:priority and should be used very carefully", 0,
+      G_MAXUINT, 0,
+      G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS | GST_PARAM_CONTROLLABLE);
 
   /**
    * gesframepositioner:width:

subprojects/gst-editing-services/tests/check/ges/test-utils.h

@@ -287,6 +287,8 @@ G_STMT_START {                                          \
       continue; \
     if (g_strcmp0 (prop->name, "parent") == 0) \
       continue; \
+    if (g_strcmp0 (prop->name, "zorder") == 0) \
+      continue; \
     g_value_init (&val1, prop->value_type); \
     g_value_init (&val2, prop->value_type); \
     ges_timeline_element_get_child_property_by_pspec ( \

subprojects/gst-editing-services/tests/check/meson.build

@@ -102,6 +102,7 @@ if gstvalidate_dep.found() and not get_option('tools').disabled()
     'check_keyframes_in_compositor_two_sources': true,
     'check-clip-positioning': true,
     'set-layer-on-command-line': true,
+    'check-zorder': true,
   }
 
   foreach scenario, is_validatetest: scenarios

subprojects/gst-editing-services/tests/check/scenarios/check-zorder.validatetest

@@ -0,0 +1,61 @@
+meta,
+    tool = "ges-launch-$(gst_api_version)",
+    handles-states=true,
+    args = {
+        --track-types, video,
+        --videosink, "fakevideosink name=videosink sync=true",
+        --video-caps, "video/x-raw,format=I420,width=320,height=240,framerate=10/1",
+    }
+
+remove-feature, name=queue
+
+# Add two overlapping clips on different layers
+add-clip, name=c0, asset-id="pattern=red", layer-priority=0, type=GESTestClip, start=0, duration=2.0
+add-clip, name=c1, asset-id="pattern=blue", layer-priority=1, type=GESTestClip, start=0, duration=2.0
+
+# Set initial properties for both clips
+set-child-properties, element-name=c0, width=200, height=150, posx=0, posy=0, pattern=red
+set-child-properties, element-name=c1, width=200, height=150, posx=120, posy=90, pattern=blue
+
+play
+crank-clock
+wait, on-clock=true
+
+# Now manually set zorder to reverse the stacking
+# Make c0 appear on top by giving it a lower zorder value
+set-child-properties, element-name=c0, zorder=1
+set-child-properties, element-name=c1, zorder=2
+
+# Verify the zorder values were set
+check-child-properties, element-name=c0, zorder=1
+check-child-properties, element-name=c1, zorder=2
+
+# Test controllable aspect - set up keyframes for zorder
+set-control-source, element-name=c0, property-name=zorder, binding-type=direct-absolute
+set-control-source, element-name=c1, property-name=zorder, binding-type=direct-absolute
+
+# At 1 second, swap the zorder values
+add-keyframe, element-name=c0, timestamp=0.0, property-name=zorder, value=1
+add-keyframe, element-name=c0, timestamp=1.0, property-name=zorder, value=2
+add-keyframe, element-name=c1, timestamp=0.0, property-name=zorder, value=2
+add-keyframe, element-name=c1, timestamp=1.0, property-name=zorder, value=1
+
+crank-clock, repeat=8
+wait, on-clock=true
+
+# Should now be at 0.8 seconds
+check-position, expected-position=0.8
+check-properties,
+    gessmartmixer0-compositor.sink_0::zorder=2,
+    gessmartmixer0-compositor.sink_1::zorder=1
+
+# Crank 3 more times to reach 1.1 seconds (past the 1.0s keyframe)
+crank-clock, repeat=3
+wait, on-clock=true
+
+# Should now be at 1.1 seconds, verify the zorder values swapped after 1 second animation
+check-properties,
+    gessmartmixer0-compositor.sink_0::zorder=2,
+    gessmartmixer0-compositor.sink_1::zorder=1
+
+stop