[host] app: allow the capture interface to select async or sync mode

While it's correct for DXGI to use a asyncronous waitFrame model, other
capture interfaces such as NvFBC it is not correct. This change allows
the capture interface to specify which is more correct for it and moves
the waitFrame/post into the main thread if async is not desired.

host/include/interface/capture.h

@@ -91,9 +91,10 @@ typedef void (*CapturePostPointerBuffer)(CapturePointer pointer);
 
 typedef struct CaptureInterface
 {
-  const char     *shortName;
+  const char * shortName;
-  const char *  (*getName        )();
+  const bool   asyncCapture;
-  void          (*initOptions    )();
+  const char * (*getName        )();
+  void         (*initOptions    )();
 
   bool(*create)(
     CaptureGetPointerBuffer  getPointerBufferFn,

host/platform/Linux/capture/XCB/src/xcb.c

@@ -236,6 +236,7 @@ static CaptureResult xcb_getFrame(FrameBuffer * frame, const unsigned int height
 struct CaptureInterface Capture_XCB =
 {
   .shortName       = "XCB",
+  .asyncCapture    = true,
   .getName         = xcb_getName,
   .create          = xcb_create,
   .init            = xcb_init,

host/platform/Windows/capture/DXGI/src/dxgi.c

@@ -996,6 +996,7 @@ static CaptureResult dxgi_releaseFrame(void)
 struct CaptureInterface Capture_DXGI =
 {
   .shortName       = "DXGI",
+  .asyncCapture    = true,
   .getName         = dxgi_getName,
   .initOptions     = dxgi_initOptions,
   .create          = dxgi_create,

host/platform/Windows/capture/NVFBC/src/nvfbc.c

@@ -424,6 +424,7 @@ static int pointerThread(void * unused)
 struct CaptureInterface Capture_NVFBC =
 {
   .shortName       = "NvFBC",
+  .asyncCapture    = false,
   .getName         = nvfbc_getName,
   .initOptions     = nvfbc_initOptions,
 

host/src/app.c

@@ -88,10 +88,12 @@ struct app
   unsigned int   pointerIndex;
   unsigned int   pointerShapeIndex;
 
+  long           pageSize;
   size_t         maxFrameSize;
   PLGMPHostQueue frameQueue;
   PLGMPMemory    frameMemory[LGMP_Q_FRAME_LEN];
   unsigned int   frameIndex;
+  bool           frameValid;
 
   CaptureInterface * iface;
 
@@ -140,15 +142,111 @@ static bool lgmpTimer(void * opaque)
   return true;
 }
 
+static bool sendFrame(void)
+{
+  CaptureFrame frame = { 0 };
+  bool repeatFrame = false;
+  switch(app.iface->waitFrame(&frame, app.maxFrameSize))
+  {
+    case CAPTURE_RESULT_OK:
+      break;
+
+    case CAPTURE_RESULT_REINIT:
+    {
+      app.state = APP_STATE_RESTART;
+      DEBUG_INFO("Frame thread reinit");
+      return false;
+    }
+
+    case CAPTURE_RESULT_ERROR:
+    {
+      DEBUG_ERROR("Failed to get the frame");
+      return false;
+    }
+
+    case CAPTURE_RESULT_TIMEOUT:
+    {
+      if (app.frameValid && lgmpHostQueueNewSubs(app.frameQueue) > 0)
+      {
+        // resend the last frame
+        repeatFrame = true;
+        break;
+      }
+
+      return true;
+    }
+  }
+
+  LGMP_STATUS status;
+
+  // if we are repeating a frame just send the last frame again
+  if (repeatFrame)
+  {
+    if ((status = lgmpHostQueuePost(app.frameQueue, 0, app.frameMemory[app.frameIndex])) != LGMP_OK)
+      DEBUG_ERROR("%s", lgmpStatusString(status));
+    return true;
+  }
+
+  // we increment the index first so that if we need to repeat a frame
+  // the index still points to the latest valid frame
+  if (++app.frameIndex == LGMP_Q_FRAME_LEN)
+    app.frameIndex = 0;
+
+  KVMFRFrame * fi = lgmpHostMemPtr(app.frameMemory[app.frameIndex]);
+  switch(frame.format)
+  {
+    case CAPTURE_FMT_BGRA   : fi->type = FRAME_TYPE_BGRA   ; break;
+    case CAPTURE_FMT_RGBA   : fi->type = FRAME_TYPE_RGBA   ; break;
+    case CAPTURE_FMT_RGBA10 : fi->type = FRAME_TYPE_RGBA10 ; break;
+    case CAPTURE_FMT_RGBA16F: fi->type = FRAME_TYPE_RGBA16F; break;
+    default:
+      DEBUG_ERROR("Unsupported frame format %d, skipping frame", frame.format);
+      return true;
+  }
+
+  switch(frame.rotation)
+  {
+    case CAPTURE_ROT_0  : fi->rotation = FRAME_ROT_0  ; break;
+    case CAPTURE_ROT_90 : fi->rotation = FRAME_ROT_90 ; break;
+    case CAPTURE_ROT_180: fi->rotation = FRAME_ROT_180; break;
+    case CAPTURE_ROT_270: fi->rotation = FRAME_ROT_270; break;
+    default:
+      DEBUG_WARN("Unsupported frame rotation %d", frame.rotation);
+      fi->rotation = FRAME_ROT_0;
+      break;
+  }
+
+  fi->formatVer         = frame.formatVer;
+  fi->width             = frame.width;
+  fi->height            = frame.height;
+  fi->realHeight        = frame.realHeight;
+  fi->stride            = frame.stride;
+  fi->pitch             = frame.pitch;
+  fi->offset            = app.pageSize - FrameBufferStructSize;
+  fi->mouseScalePercent = app.iface->getMouseScale();
+  fi->blockScreensaver  = os_blockScreensaver();
+  app.frameValid        = true;
+
+  // put the framebuffer on the border of the next page
+  // this is to allow for aligned DMA transfers by the receiver
+  FrameBuffer * fb = (FrameBuffer *)(((uint8_t*)fi) + fi->offset);
+  framebuffer_prepare(fb);
+
+  /* we post and then get the frame, this is intentional! */
+  if ((status = lgmpHostQueuePost(app.frameQueue, 0, app.frameMemory[app.frameIndex])) != LGMP_OK)
+  {
+    DEBUG_ERROR("%s", lgmpStatusString(status));
+    return true;
+  }
+
+  app.iface->getFrame(fb, frame.height);
+  return true;
+}
+
 static int frameThread(void * opaque)
 {
   DEBUG_INFO("Frame thread started");
 
-  bool         frameValid     = false;
-  bool         repeatFrame    = false;
-  CaptureFrame frame          = { 0 };
-  const long   pageSize       = sysinfo_getPageSize();
-
   while(app.state == APP_STATE_RUNNING)
   {
     //wait until there is room in the queue
@@ -158,100 +256,8 @@ static int frameThread(void * opaque)
       continue;
     }
 
-    switch(app.iface->waitFrame(&frame, app.maxFrameSize))
+    if (!sendFrame())
-    {
+      break;
-      case CAPTURE_RESULT_OK:
-        repeatFrame = false;
-        break;
-
-      case CAPTURE_RESULT_REINIT:
-      {
-        app.state = APP_STATE_RESTART;
-        DEBUG_INFO("Frame thread reinit");
-        return 0;
-      }
-
-      case CAPTURE_RESULT_ERROR:
-      {
-        DEBUG_ERROR("Failed to get the frame");
-        return 0;
-      }
-
-      case CAPTURE_RESULT_TIMEOUT:
-      {
-        if (frameValid && lgmpHostQueueNewSubs(app.frameQueue) > 0)
-        {
-          // resend the last frame
-          repeatFrame = true;
-          break;
-        }
-
-        continue;
-      }
-    }
-
-    LGMP_STATUS status;
-
-    // if we are repeating a frame just send the last frame again
-    if (repeatFrame)
-    {
-      if ((status = lgmpHostQueuePost(app.frameQueue, 0, app.frameMemory[app.frameIndex])) != LGMP_OK)
-        DEBUG_ERROR("%s", lgmpStatusString(status));
-      continue;
-    }
-
-    // we increment the index first so that if we need to repeat a frame
-    // the index still points to the latest valid frame
-    if (++app.frameIndex == LGMP_Q_FRAME_LEN)
-      app.frameIndex = 0;
-
-    KVMFRFrame * fi = lgmpHostMemPtr(app.frameMemory[app.frameIndex]);
-    switch(frame.format)
-    {
-      case CAPTURE_FMT_BGRA   : fi->type = FRAME_TYPE_BGRA   ; break;
-      case CAPTURE_FMT_RGBA   : fi->type = FRAME_TYPE_RGBA   ; break;
-      case CAPTURE_FMT_RGBA10 : fi->type = FRAME_TYPE_RGBA10 ; break;
-      case CAPTURE_FMT_RGBA16F: fi->type = FRAME_TYPE_RGBA16F; break;
-      default:
-        DEBUG_ERROR("Unsupported frame format %d, skipping frame", frame.format);
-        continue;
-    }
-
-    switch(frame.rotation)
-    {
-      case CAPTURE_ROT_0  : fi->rotation = FRAME_ROT_0  ; break;
-      case CAPTURE_ROT_90 : fi->rotation = FRAME_ROT_90 ; break;
-      case CAPTURE_ROT_180: fi->rotation = FRAME_ROT_180; break;
-      case CAPTURE_ROT_270: fi->rotation = FRAME_ROT_270; break;
-      default:
-        DEBUG_WARN("Unsupported frame rotation %d", frame.rotation);
-        fi->rotation = FRAME_ROT_0;
-        break;
-    }
-
-    fi->formatVer         = frame.formatVer;
-    fi->width             = frame.width;
-    fi->height            = frame.height;
-    fi->realHeight        = frame.realHeight;
-    fi->stride            = frame.stride;
-    fi->pitch             = frame.pitch;
-    fi->offset            = pageSize - FrameBufferStructSize;
-    fi->mouseScalePercent = app.iface->getMouseScale();
-    fi->blockScreensaver  = os_blockScreensaver();
-    frameValid            = true;
-
-    // put the framebuffer on the border of the next page
-    // this is to allow for aligned DMA transfers by the receiver
-    FrameBuffer * fb = (FrameBuffer *)(((uint8_t*)fi) + fi->offset);
-    framebuffer_prepare(fb);
-
-    /* we post and then get the frame, this is intentional! */
-    if ((status = lgmpHostQueuePost(app.frameQueue, 0, app.frameMemory[app.frameIndex])) != LGMP_OK)
-    {
-      DEBUG_ERROR("%s", lgmpStatusString(status));
-      continue;
-    }
-    app.iface->getFrame(fb, frame.height);
   }
   DEBUG_INFO("Frame thread stopped");
   return 0;
@@ -260,6 +266,9 @@ static int frameThread(void * opaque)
 bool startThreads(void)
 {
   app.state = APP_STATE_RUNNING;
+  if (!app.iface->asyncCapture)
+    return true;
+
   if (!lgCreateThread("FrameThread", frameThread, NULL, &app.frameThread))
   {
     DEBUG_ERROR("Failed to create the frame thread");
@@ -271,20 +280,25 @@ bool startThreads(void)
 
 bool stopThreads(void)
 {
-  bool ok = true;
-
   app.iface->stop();
   if (app.state != APP_STATE_SHUTDOWN)
     app.state = APP_STATE_IDLE;
 
-  if (app.frameThread && !lgJoinThread(app.frameThread, NULL))
+  if (!app.iface->asyncCapture)
-  {
+    return true;
-    DEBUG_WARN("Failed to join the frame thread");
-    ok = false;
-  }
-  app.frameThread = NULL;
 
-  return ok;
+  if (app.frameThread)
+  {
+    if (!lgJoinThread(app.frameThread, NULL))
+    {
+      DEBUG_WARN("Failed to join the frame thread");
+      app.frameThread = NULL;
+      return false;
+    }
+    app.frameThread = NULL;
+  }
+
+  return true;
 }
 
 static bool captureStart(void)
@@ -564,17 +578,19 @@ int app_main(int argc, char * argv[])
     memset(lgmpHostMemPtr(app.pointerShapeMemory[i]), 0, MAX_POINTER_SIZE);
   }
 
+  app.pageSize          = sysinfo_getPageSize();
+  app.frameValid        = false;
   app.pointerShapeValid = false;
 
-  const long sz = sysinfo_getPageSize();
   app.maxFrameSize = lgmpHostMemAvail(app.lgmp);
-  app.maxFrameSize = (app.maxFrameSize - (sz - 1)) & ~(sz - 1);
+  app.maxFrameSize = (app.maxFrameSize - (app.pageSize - 1)) & ~(app.pageSize - 1);
   app.maxFrameSize /= LGMP_Q_FRAME_LEN;
   DEBUG_INFO("Max Frame Size   : %u MiB", (unsigned int)(app.maxFrameSize / 1048576LL));
 
   for(int i = 0; i < LGMP_Q_FRAME_LEN; ++i)
   {
-    if ((status = lgmpHostMemAllocAligned(app.lgmp, app.maxFrameSize, sz, &app.frameMemory[i])) != LGMP_OK)
+    if ((status = lgmpHostMemAllocAligned(app.lgmp, app.maxFrameSize,
+            app.pageSize, &app.frameMemory[i])) != LGMP_OK)
     {
       DEBUG_ERROR("lgmpHostMemAlloc Failed (Frame): %s", lgmpStatusString(status));
       exitcode = LG_HOST_EXIT_FATAL;
@@ -616,6 +632,8 @@ int app_main(int argc, char * argv[])
   }
 
   DEBUG_INFO("Using            : %s", iface->getName());
+  DEBUG_INFO("Capture Method   : %s", iface->asyncCapture ?
+      "Asynchronous" : "Synchronous");
 
   app.state = APP_STATE_RUNNING;
   app.iface = iface;
@@ -710,6 +728,9 @@ int app_main(int argc, char * argv[])
           exitcode = LG_HOST_EXIT_FAILED;
           goto fail_capture;
       }
+
+      if (!iface->asyncCapture)
+        sendFrame();
     }
 
     if (app.state != APP_STATE_SHUTDOWN)