Fix hang on stream termination if no frames can be captured (#709)

src/platform/common.h

@@ -216,7 +216,8 @@ enum class capture_e : int {
 class display_t {
 public:
   /**
-   * When display has a new image ready, this callback will be called with the new image.
+   * When display has a new image ready or a timeout occurs, this callback will be called with the image.
+   * If a frame was captured, frame_captured will be true. If a timeout occurred, it will be false.
    * 
    * On Break Request -->
    *    Returns nullptr
@@ -225,7 +226,7 @@ public:
    *    Returns the image object that should be filled next.
    *    This may or may not be the image send with the callback
    */
-  using snapshot_cb_t = std::function<std::shared_ptr<img_t>(std::shared_ptr<img_t> &img)>;
+  using snapshot_cb_t = std::function<std::shared_ptr<img_t>(std::shared_ptr<img_t> &img, bool frame_captured)>;
 
   display_t() noexcept : offset_x { 0 }, offset_y { 0 } {}
 

src/platform/linux/cuda.cpp

@@ -505,10 +505,10 @@ public:
       case platf::capture_e::error:
         return status;
       case platf::capture_e::timeout:
-        std::this_thread::sleep_for(1ms);
+        img = snapshot_cb(img, false);
-        continue;
+        break;
       case platf::capture_e::ok:
-        img = snapshot_cb(img);
+        img = snapshot_cb(img, true);
         break;
       default:
         BOOST_LOG(error) << "Unrecognized capture status ["sv << (int)status << ']';

src/platform/linux/kmsgrab.cpp

@@ -684,10 +684,10 @@ public:
       case platf::capture_e::error:
         return status;
       case platf::capture_e::timeout:
-        std::this_thread::sleep_for(1ms);
+        img = snapshot_cb(img, false);
-        continue;
+        break;
       case platf::capture_e::ok:
-        img = snapshot_cb(img);
+        img = snapshot_cb(img, true);
         break;
       default:
         BOOST_LOG(error) << "Unrecognized capture status ["sv << (int)status << ']';
@@ -805,10 +805,10 @@ public:
       case platf::capture_e::error:
         return status;
       case platf::capture_e::timeout:
-        std::this_thread::sleep_for(1ms);
+        img = snapshot_cb(img, false);
-        continue;
+        break;
       case platf::capture_e::ok:
-        img = snapshot_cb(img);
+        img = snapshot_cb(img, true);
         break;
       default:
         BOOST_LOG(error) << "Unrecognized capture status ["sv << (int)status << ']';

src/platform/linux/wlgrab.cpp

@@ -134,9 +134,10 @@ public:
       case platf::capture_e::error:
         return status;
       case platf::capture_e::timeout:
-        continue;
+        img = snapshot_cb(img, false);
+        break;
       case platf::capture_e::ok:
-        img = snapshot_cb(img);
+        img = snapshot_cb(img, true);
         break;
       default:
         BOOST_LOG(error) << "Unrecognized capture status ["sv << (int)status << ']';
@@ -239,9 +240,10 @@ public:
       case platf::capture_e::error:
         return status;
       case platf::capture_e::timeout:
-        continue;
+        img = snapshot_cb(img, false);
+        break;
       case platf::capture_e::ok:
-        img = snapshot_cb(img);
+        img = snapshot_cb(img, true);
         break;
       default:
         BOOST_LOG(error) << "Unrecognized capture status ["sv << (int)status << ']';

src/platform/linux/x11grab.cpp

@@ -476,10 +476,10 @@ struct x11_attr_t : public display_t {
       case platf::capture_e::error:
         return status;
       case platf::capture_e::timeout:
-        std::this_thread::sleep_for(1ms);
+        img = snapshot_cb(img, false);
-        continue;
+        break;
       case platf::capture_e::ok:
-        img = snapshot_cb(img);
+        img = snapshot_cb(img, true);
         break;
       default:
         BOOST_LOG(error) << "Unrecognized capture status ["sv << (int)status << ']';
@@ -587,10 +587,10 @@ struct shm_attr_t : public x11_attr_t {
       case platf::capture_e::error:
         return status;
       case platf::capture_e::timeout:
-        std::this_thread::sleep_for(1ms);
+        img = snapshot_cb(img, false);
-        continue;
+        break;
       case platf::capture_e::ok:
-        img = snapshot_cb(img);
+        img = snapshot_cb(img, true);
         break;
       default:
         BOOST_LOG(error) << "Unrecognized capture status ["sv << (int)status << ']';

src/platform/macos/display.mm

@@ -60,11 +60,12 @@ struct av_display_t : public display_t {
       img_next->row_pitch   = CVPixelBufferGetBytesPerRow(pixelBuffer);
       img_next->pixel_pitch = img_next->row_pitch / img_next->width;
 
-      img_next = snapshot_cb(img_next);
+      img_next = snapshot_cb(img_next, true);
 
       return img_next != nullptr;
     }];
 
+    // FIXME: We should time out if an image isn't returned for a while
     dispatch_semaphore_wait(signal, DISPATCH_TIME_FOREVER);
 
     return capture_e::ok;

src/platform/windows/display_ram.cpp

@@ -181,10 +181,11 @@ capture_e display_ram_t::capture(snapshot_cb_t &&snapshot_cb, std::shared_ptr<::
     case platf::capture_e::error:
       return status;
     case platf::capture_e::timeout:
+      img = snapshot_cb(img, false);
       std::this_thread::sleep_for(1ms);
-      continue;
+      break;
     case platf::capture_e::ok:
-      img = snapshot_cb(img);
+      img = snapshot_cb(img, true);
       break;
     default:
       BOOST_LOG(error) << "Unrecognized capture status ["sv << (int)status << ']';

src/platform/windows/display_vram.cpp

@@ -652,10 +652,11 @@ capture_e display_vram_t::capture(snapshot_cb_t &&snapshot_cb, std::shared_ptr<:
     case platf::capture_e::error:
       return status;
     case platf::capture_e::timeout:
+      img = snapshot_cb(img, false);
       std::this_thread::sleep_for(1ms);
-      continue;
+      break;
     case platf::capture_e::ok:
-      img = snapshot_cb(img);
+      img = snapshot_cb(img, true);
       break;
     default:
       BOOST_LOG(error) << "Unrecognized capture status ["sv << (int)status << ']';

src/video.cpp

@@ -707,7 +707,7 @@ void captureThread(
   while(capture_ctx_queue->running()) {
     bool artificial_reinit = false;
 
-    auto status = disp->capture([&](std::shared_ptr<platf::img_t> &img) -> std::shared_ptr<platf::img_t> {
+    auto status = disp->capture([&](std::shared_ptr<platf::img_t> &img, bool frame_captured) -> std::shared_ptr<platf::img_t> {
       KITTY_WHILE_LOOP(auto capture_ctx = std::begin(capture_ctxs), capture_ctx != std::end(capture_ctxs), {
         if(!capture_ctx->images->running()) {
           capture_ctx = capture_ctxs.erase(capture_ctx);
@@ -715,7 +715,10 @@ void captureThread(
           continue;
         }
 
-        capture_ctx->images->raise(img);
+        if(frame_captured) {
+          capture_ctx->images->raise(img);
+        }
+
         ++capture_ctx;
       })
 
@@ -1274,7 +1277,7 @@ encode_e encode_run_sync(
 
   auto ec = platf::capture_e::ok;
   while(encode_session_ctx_queue.running()) {
-    auto snapshot_cb = [&](std::shared_ptr<platf::img_t> &img) -> std::shared_ptr<platf::img_t> {
+    auto snapshot_cb = [&](std::shared_ptr<platf::img_t> &img, bool frame_captured) -> std::shared_ptr<platf::img_t> {
       while(encode_session_ctx_queue.peek()) {
         auto encode_session_ctx = encode_session_ctx_queue.pop();
         if(!encode_session_ctx) {
@@ -1318,7 +1321,7 @@ encode_e encode_run_sync(
           ctx->idr_events->pop();
         }
 
-        if(pos->session.device->convert(*img)) {
+        if(frame_captured && pos->session.device->convert(*img)) {
           BOOST_LOG(error) << "Could not convert image"sv;
           ctx->shutdown_event->raise(true);