fix(egfx): respect client frame acknowledgement limits

crates/ironrdp-egfx/src/client.rs

@@ -1201,10 +1201,10 @@ impl GraphicsPipelineClient {
         self.handler.on_frame_complete(frame_id);
 
         // Per [3.3.5.12]: client MUST send FrameAcknowledge after EndFrame.
-        // We send the actual queue depth (not Unavailable / 0xFFFFFFFF as FreeRDP does);
-        // the real value gives the server backpressure information for frame pacing.
+        // QueueDepth counts queued bytes, not decoded/queued frames. This client
+        // does not measure queued bytes, so report Unavailable (not Suspend).
         let ack = GfxPdu::FrameAcknowledge(FrameAcknowledgePdu {
-            queue_depth: QueueDepth::from_u32(self.frames_queued),
+            queue_depth: QueueDepth::Unavailable,
             frame_id,
             total_frames_decoded: self.total_frames_decoded,
         });
@@ -2683,4 +2683,17 @@ mod tests {
              a destRect-relative reading would take (28, 32) instead (issue #2042)"
         );
     }
+    #[test]
+    fn frame_ack_queue_depth_is_not_a_frame_count() {
+        let mut handler = GraphicsPipelineClient::new(Box::new(TestHandler), None);
+        handler.total_frames_decoded = 3;
+        let responses = handler.handle_end_frame(7).unwrap();
+        let bytes = ironrdp_core::encode_vec(responses[0].as_ref()).unwrap();
+        let GfxPdu::FrameAcknowledge(ack) = ironrdp_core::decode::<GfxPdu>(&bytes).unwrap() else {
+            panic!("expected frame ack")
+        };
+        assert_eq!(ack.frame_id, 7);
+        assert_eq!(ack.total_frames_decoded, 4);
+        assert_eq!(ack.queue_depth, QueueDepth::Unavailable);
+    }
 }