screencast: have our streams provide SPA_META_Header

It can be useful for clients to know what's going on in a specific
stream.

src/plugins/screencast/outputscreencastsource.cpp

@@ -11,6 +11,7 @@
 #include "composite.h"
 #include "kwingltexture.h"
 #include "kwinglutils.h"
+#include "renderloop.h"
 #include "scene.h"
 
 namespace KWin
@@ -62,4 +63,9 @@ void OutputScreenCastSource::render(GLRenderTarget *target)
     GLRenderTarget::popRenderTarget();
 }
 
+std::chrono::nanoseconds OutputScreenCastSource::clock() const
+{
+    return m_output->renderLoop()->lastPresentationTimestamp();
+}
+
 } // namespace KWin

src/plugins/screencast/outputscreencastsource.h

@@ -27,6 +27,7 @@ public:
 
     void render(GLRenderTarget *target) override;
     void render(QImage *image) override;
+    std::chrono::nanoseconds clock() const override;
 
 private:
     QPointer<AbstractOutput> m_output;

src/plugins/screencast/screencastsource.h

@@ -25,6 +25,7 @@ public:
 
     virtual void render(GLRenderTarget *target) = 0;
     virtual void render(QImage *image) = 0;
+    virtual std::chrono::nanoseconds clock() const = 0;
 
 Q_SIGNALS:
     void closed();

src/plugins/screencast/screencaststream.cpp

@@ -108,9 +108,13 @@ void ScreenCastStream::newStreamParams()
                                                             sizeof(struct spa_meta_region) * videoDamageRegionCount,
                                                             sizeof(struct spa_meta_region) * 1,
                                                             sizeof(struct spa_meta_region) * videoDamageRegionCount)),
+        (spa_pod*) spa_pod_builder_add_object(&pod_builder,
+                                                SPA_TYPE_OBJECT_ParamMeta, SPA_PARAM_Meta,
+                                                SPA_PARAM_META_type, SPA_POD_Id(SPA_META_Header),
+                                                SPA_PARAM_META_size, SPA_POD_Int(sizeof(struct spa_meta_header))),
     };
 
-    pw_stream_update_params(pwStream, params, 3);
+    pw_stream_update_params(pwStream, params, 4);
 }
 
 void ScreenCastStream::onStreamParamChanged(void *data, uint32_t id, const struct spa_pod *format)
@@ -456,6 +460,19 @@ void ScreenCastStream::recordFrame(const QRegion &damagedRegion)
         }
     }
 
+    spa_meta_header *spaHeader = (spa_meta_header *) spa_buffer_find_meta_data(spa_buffer, SPA_META_Header, sizeof(spaHeader));
+    if (spaHeader) {
+        spaHeader->flags = 0;
+        spaHeader->dts_offset = 0;
+        spaHeader->seq = m_sequential++;
+
+        const auto timestamp = m_source->clock();
+        if (!m_start) {
+            m_start = timestamp;
+        }
+        spaHeader->pts = (timestamp - m_start.value()).count();
+    }
+
     tryEnqueue(buffer);
 }
 

src/plugins/screencast/screencaststream.h

@@ -18,6 +18,8 @@
 #include <QSharedPointer>
 #include <QSize>
 #include <QSocketNotifier>
+#include <chrono>
+#include <optional>
 
 #include <pipewire/pipewire.h>
 #include <spa/param/format-utils.h>
@@ -50,7 +52,10 @@ public:
 
     void stop();
 
-    /** Renders @p frame into the current framebuffer into the stream */
+    /**
+     * Renders @p frame into the current framebuffer into the stream
+     * @p timestamp
+     */
     void recordFrame(const QRegion &damagedRegion);
 
     void setCursorMode(KWaylandServer::ScreencastV1Interface::CursorMode mode, qreal scale, const QRect &viewport);
@@ -111,6 +116,8 @@ private:
     pw_buffer *m_pendingBuffer = nullptr;
     QSocketNotifier *m_pendingNotifier = nullptr;
     EGLNativeFence *m_pendingFence = nullptr;
+    std::optional<std::chrono::nanoseconds> m_start;
+    quint64 m_sequential = 0;
 };
 
 } // namespace KWin

src/plugins/screencast/windowscreencastsource.cpp

@@ -7,11 +7,13 @@
 #include "windowscreencastsource.h"
 #include "screencastutils.h"
 
+#include "abstract_output.h"
 #include "deleted.h"
 #include "effects.h"
 #include "kwineffects.h"
 #include "kwingltexture.h"
 #include "kwinglutils.h"
+#include "renderloop.h"
 #include "scene.h"
 #include "toplevel.h"
 
@@ -62,4 +64,9 @@ void WindowScreenCastSource::render(GLRenderTarget *target)
     GLRenderTarget::popRenderTarget();
 }
 
+std::chrono::nanoseconds WindowScreenCastSource::clock() const
+{
+    return m_window->output()->renderLoop()->lastPresentationTimestamp();
+}
+
 } // namespace KWin

src/plugins/screencast/windowscreencastsource.h

@@ -27,6 +27,7 @@ public:
 
     void render(GLRenderTarget *target) override;
     void render(QImage *image) override;
+    std::chrono::nanoseconds clock() const override;
 
 private:
     QPointer<Toplevel> m_window;