renderer: Explicit sync fixes (#7151)

Enables explicit sync by default for most platforms

`misc:no_direct_scanout` -> `render:direct_scanout`

src/helpers/sync/SyncReleaser.cpp

@@ -0,0 +1,25 @@
+#include "SyncReleaser.hpp"
+#include "SyncTimeline.hpp"
+#include "../../render/OpenGL.hpp"
+
+CSyncReleaser::CSyncReleaser(WP<CSyncTimeline> timeline_, uint64_t point_) : timeline(timeline_), point(point_) {
+    ;
+}
+
+CSyncReleaser::~CSyncReleaser() {
+    if (timeline.expired())
+        return;
+
+    if (sync)
+        timeline->importFromSyncFileFD(point, sync->fd());
+    else
+        timeline->signal(point);
+}
+
+void CSyncReleaser::addReleaseSync(SP<CEGLSync> sync_) {
+    sync = sync_;
+}
+
+void CSyncReleaser::drop() {
+    timeline.reset();
+}

src/helpers/sync/SyncReleaser.hpp

@@ -0,0 +1,31 @@
+#pragma once
+
+#include <cstdint>
+#include <optional>
+#include <vector>
+#include <functional>
+#include "../memory/Memory.hpp"
+
+/*
+    A helper (inspired by KDE's KWin) that will release the timeline point in the dtor
+*/
+
+class CSyncTimeline;
+class CEGLSync;
+
+class CSyncReleaser {
+  public:
+    CSyncReleaser(WP<CSyncTimeline> timeline_, uint64_t point_);
+    ~CSyncReleaser();
+
+    // drops the releaser, will never signal anymore
+    void drop();
+
+    // wait for this gpu job to finish before releasing
+    void addReleaseSync(SP<CEGLSync> sync);
+
+  private:
+    WP<CSyncTimeline> timeline;
+    uint64_t          point = 0;
+    SP<CEGLSync>      sync;
+};

src/helpers/sync/SyncTimeline.cpp

@@ -188,3 +188,8 @@ bool CSyncTimeline::transfer(SP<CSyncTimeline> from, uint64_t fromPoint, uint64_
 
     return true;
 }
+
+void CSyncTimeline::signal(uint64_t point) {
+    if (drmSyncobjTimelineSignal(drmFD, &handle, &point, 1))
+        Debug::log(ERR, "CSyncTimeline::signal: drmSyncobjTimelineSignal failed");
+}

src/helpers/sync/SyncTimeline.hpp

@@ -35,6 +35,7 @@ class CSyncTimeline {
     int                 exportAsSyncFileFD(uint64_t src);
     bool                importFromSyncFileFD(uint64_t dst, int fd);
     bool                transfer(SP<CSyncTimeline> from, uint64_t fromPoint, uint64_t toPoint);
+    void                signal(uint64_t point);
 
     int                 drmFD  = -1;
     uint32_t            handle = 0;