drm: allow commit/page_flip calls to *not* trigger an event

src/backend/drm/surface/atomic.rs

@@ -350,7 +350,7 @@ impl<A: AsRawFd + 'static> AtomicDrmSurface<A> {
         *self.pending.read().unwrap() != *self.state.read().unwrap()
     }
 
-    pub fn commit(&self, framebuffer: framebuffer::Handle) -> Result<(), Error> {
+    pub fn commit(&self, framebuffer: framebuffer::Handle, event: bool) -> Result<(), Error> {
         if !self.active.load(Ordering::SeqCst) {
             return Err(Error::DeviceInactive);
         }
@@ -430,6 +430,7 @@ impl<A: AsRawFd + 'static> AtomicDrmSurface<A> {
         debug!(self.logger, "Setting screen: {:?}", req);
         let result = self.fd
             .atomic_commit(
+                if event {
                     &[
                         // on the atomic api we can modeset and trigger a page_flip event on the same call!
                         AtomicCommitFlags::PageFlipEvent,
@@ -437,7 +438,13 @@ impl<A: AsRawFd + 'static> AtomicDrmSurface<A> {
                         // we also do not need to wait for completion, like with `set_crtc`.
                         // and have tested this already, so we do not expect any errors later down the line.
                         AtomicCommitFlags::Nonblock,
-                ],
+                    ]
+                } else {
+                    &[
+                        AtomicCommitFlags::AllowModeset,
+                        AtomicCommitFlags::Nonblock,
+                    ]
+                },
                 req,
             )
             .map_err(|source| Error::Access {
@@ -453,7 +460,7 @@ impl<A: AsRawFd + 'static> AtomicDrmSurface<A> {
         result
     }
 
-    pub fn page_flip(&self, framebuffer: framebuffer::Handle) -> Result<(), Error> {
+    pub fn page_flip(&self, framebuffer: framebuffer::Handle, event: bool) -> Result<(), Error> {
         if !self.active.load(Ordering::SeqCst) {
             return Err(Error::DeviceInactive);
         }
@@ -473,7 +480,11 @@ impl<A: AsRawFd + 'static> AtomicDrmSurface<A> {
         // indicating a problem in our assumptions.
         trace!(self.logger, "Queueing page flip: {:?}", req);
         self.fd.atomic_commit(
-            &[AtomicCommitFlags::PageFlipEvent, AtomicCommitFlags::Nonblock],
+            if event {
+                &[AtomicCommitFlags::PageFlipEvent, AtomicCommitFlags::Nonblock]
+            } else {
+                &[AtomicCommitFlags::Nonblock]
+            },
             req,
         )
         .map_err(|source| Error::Access {

src/backend/drm/surface/legacy.rs

@@ -202,7 +202,7 @@ impl<A: AsRawFd + 'static> LegacyDrmSurface<A> {
         *self.pending.read().unwrap() != *self.state.read().unwrap()
     }
 
-    pub fn commit(&self, framebuffer: framebuffer::Handle) -> Result<(), Error> {
+    pub fn commit(&self, framebuffer: framebuffer::Handle, event: bool) -> Result<(), Error> {
         if !self.active.load(Ordering::SeqCst) {
             return Err(Error::DeviceInactive);
         }
@@ -272,6 +272,7 @@ impl<A: AsRawFd + 'static> LegacyDrmSurface<A> {
 
         *current = pending.clone();
 
+        if event {
             // set crtc does not trigger page_flip events, so we immediately queue a flip
             // with the same framebuffer.
             // this will result in wasting a frame, because this flip will need to wait
@@ -288,10 +289,13 @@ impl<A: AsRawFd + 'static> LegacyDrmSurface<A> {
                 errmsg: "Failed to queue page flip",
                 dev: self.fd.dev_path(),
                 source,
-        })
+            })?;
         }
 
-    pub fn page_flip(&self, framebuffer: framebuffer::Handle) -> Result<(), Error> {
+        Ok(())
+    }
+
+    pub fn page_flip(&self, framebuffer: framebuffer::Handle, event: bool) -> Result<(), Error> {
         trace!(self.logger, "Queueing Page flip");
 
         if !self.active.load(Ordering::SeqCst) {
@@ -302,7 +306,7 @@ impl<A: AsRawFd + 'static> LegacyDrmSurface<A> {
             &*self.fd,
             self.crtc,
             framebuffer,
-            &[PageFlipFlags::PageFlipEvent],
+            if event { &[PageFlipFlags::PageFlipEvent] } else { &[] },
             None,
         )
         .map_err(|source| Error::Access {

src/backend/drm/surface/mod.rs

@@ -159,10 +159,10 @@ impl<A: AsRawFd + 'static> DrmSurface<A> {
     /// but will trigger a `vblank` event once done.
     /// Make sure to [set a `DeviceHandler`](Device::set_handler) and
     /// [register the belonging `Device`](device_bind) before to receive the event in time.
-    pub fn commit(&self, framebuffer: framebuffer::Handle) -> Result<(), Error> {
+    pub fn commit(&self, framebuffer: framebuffer::Handle, event: bool) -> Result<(), Error> {
         match &*self.internal {
-            DrmSurfaceInternal::Atomic(surf) => surf.commit(framebuffer),
-            DrmSurfaceInternal::Legacy(surf) => surf.commit(framebuffer),
+            DrmSurfaceInternal::Atomic(surf) => surf.commit(framebuffer, event),
+            DrmSurfaceInternal::Legacy(surf) => surf.commit(framebuffer, event),
         }
     }
 
@@ -174,10 +174,10 @@ impl<A: AsRawFd + 'static> DrmSurface<A> {
     /// This operation is not blocking and will produce a `vblank` event once swapping is done.
     /// Make sure to [set a `DeviceHandler`](Device::set_handler) and
     /// [register the belonging `Device`](device_bind) before to receive the event in time.
-    pub fn page_flip(&self, framebuffer: framebuffer::Handle) -> Result<(), Error> {
+    pub fn page_flip(&self, framebuffer: framebuffer::Handle, event: bool) -> Result<(), Error> {
         match &*self.internal {
-            DrmSurfaceInternal::Atomic(surf) => surf.page_flip(framebuffer),
-            DrmSurfaceInternal::Legacy(surf) => surf.page_flip(framebuffer)
+            DrmSurfaceInternal::Atomic(surf) => surf.page_flip(framebuffer, event),
+            DrmSurfaceInternal::Legacy(surf) => surf.page_flip(framebuffer, event),
         }
     }