From 3ec632dd3c1292ce138274abe58f6a796a322008 Mon Sep 17 00:00:00 2001
From: Geoffrey McRae <geoff@hostfission.com>
Date: Mon, 7 Nov 2022 19:46:18 +1100
Subject: [PATCH] [host] initial changes to implement frame rate control

---
 common/include/common/KVMFR.h | 23 ++++++++++++++++++++---
 host/src/app.c                |  8 ++++++++
 repos/LGMP                    |  2 +-
 3 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/common/include/common/KVMFR.h b/common/include/common/KVMFR.h
index c208487e..b6c06b85 100644
--- a/common/include/common/KVMFR.h
+++ b/common/include/common/KVMFR.h
@@ -28,7 +28,7 @@
 #include "types.h"
 
 #define KVMFR_MAGIC   "KVMFR---"
-#define KVMFR_VERSION 19
+#define KVMFR_VERSION 20
 
 #define KVMFR_MAX_DAMAGE_RECTS 64
 
@@ -56,7 +56,8 @@ typedef uint32_t KVMFRFeatureFlags;
 
 enum
 {
-  KVMFR_MESSAGE_SETCURSORPOS
+  KVMFR_MESSAGE_SETCURSORPOS,
+  KVMFR_MESSAGE_FRAME_TIME
 };
 
 typedef uint32_t KVMFRMessageType;
@@ -137,6 +138,8 @@ typedef struct KVMFRFrame
 {
   uint32_t        formatVer;          // the frame format version number
   uint32_t        frameSerial;        // the unique frame number
+  uint64_t        frameTimeUs;        // when the capture was started
+  uint64_t        frameElapsedUs;     // total time elapsed to capture the frame
   FrameType       type;               // the frame data type
   uint32_t        screenWidth;        // the client's screen width
   uint32_t        screenHeight;       // the client's screen height
@@ -155,14 +158,28 @@ KVMFRFrame;
 typedef struct KVMFRMessage
 {
   KVMFRMessageType type;
+  uint32_t         clientID;
 }
 KVMFRMessage;
 
-typedef struct KVMFRSetCursorPos
+typedef struct KVMFRMessage_SetCursorPos
 {
   KVMFRMessage msg;
   int32_t x, y;
 }
 KVMFRSetCursorPos;
 
+typedef struct KVMFRMessage_FrameTime
+{
+  KVMFRMessage msg;
+  /* this is the desired time to start the next capture operation where zero is
+   * immediate. This is only a hint to the host application and may not be
+   * honored. The value provided should be offset from the latest frame's
+   * frameTimeUs. When multiple clients are sending this message, the one with
+   * the lowest value will be used.
+   */
+  uint64_t frameTimeUs;
+}
+KVMFRMessage_FrameTime;
+
 #endif
diff --git a/host/src/app.c b/host/src/app.c
index a52fb53e..449a8a09 100644
--- a/host/src/app.c
+++ b/host/src/app.c
@@ -96,6 +96,7 @@ struct app
   unsigned int   frameIndex;
   bool           frameValid;
   uint32_t       frameSerial;
+  uint64_t       frameTimeUs;
 
   CaptureInterface * iface;
 
@@ -268,6 +269,7 @@ static bool sendFrame(void)
   }
 
   fi->formatVer         = frame.formatVer;
+  fi->frameTimeUs       = app.frameTimeUs;
   fi->frameSerial       = app.frameSerial++;
   fi->screenWidth       = frame.screenWidth;
   fi->screenHeight      = frame.screenHeight;
@@ -295,6 +297,11 @@ static bool sendFrame(void)
   FrameBuffer * fb = (FrameBuffer *)(((uint8_t*)fi) + fi->offset);
   framebuffer_prepare(fb);
 
+  // calculate the elapsed time as late as possible, note that this does not
+  // take into account the memory copy time and the client's that care about
+  // this value will need to take this into account
+  fi->frameElapsedUs = microtime() - app.frameTimeUs;
+
   /* we post and then get the frame, this is intentional! */
   if ((status = lgmpHostQueuePost(app.frameQueue, 0,
     app.frameMemory[app.frameIndex])) != LGMP_OK)
@@ -911,6 +918,7 @@ int app_main(int argc, char * argv[])
       else
         previousFrameTime = now;
 
+      app.frameTimeUs = microtime();
       switch(iface->capture())
       {
         case CAPTURE_RESULT_OK:
diff --git a/repos/LGMP b/repos/LGMP
index 66ac3bae..18a96cd9 160000
--- a/repos/LGMP
+++ b/repos/LGMP
@@ -1 +1 @@
-Subproject commit 66ac3bae0b4136f0a4e817b3d0892db4dc153759
+Subproject commit 18a96cd95ed71fae782d306a5a0dd231c800ea44