From 685f16cc39c8d1ae577a774058e4688e1d3ed68a Mon Sep 17 00:00:00 2001
From: Sergey Stepanov <sergystepanov@gmail.com>
Date: Thu, 21 Mar 2024 16:03:52 +0300
Subject: [PATCH] Allow duplicate frames

Some cores for performance reasons may return duplicate frames (i.e. previous frames) instead of rendering them again.
---
 pkg/config/config.yaml                         |  2 ++
 pkg/config/emulator.go                         |  1 +
 pkg/worker/caged/libretro/frontend.go          | 11 ++++++++++-
 pkg/worker/caged/libretro/nanoarch/nanoarch.go | 13 ++++++++-----
 4 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/pkg/config/config.yaml b/pkg/config/config.yaml
index 57cb39de9..60fc6f539 100644
--- a/pkg/config/config.yaml
+++ b/pkg/config/config.yaml
@@ -135,6 +135,8 @@ emulator:
     # Sets a limiter function for some spammy core callbacks.
     # 0 - disabled, otherwise -- time in milliseconds for ignoring repeated calls except the last.
     debounceMs: 0
+    # Allow duplicate frames
+    dup: true
     # Libretro cores logging level: DEBUG = 0, INFO, WARN, ERROR, DUMMY = INT_MAX
     logLevel: 1
     cores:
diff --git a/pkg/config/emulator.go b/pkg/config/emulator.go
index 49bf6713e..24993cbed 100644
--- a/pkg/config/emulator.go
+++ b/pkg/config/emulator.go
@@ -28,6 +28,7 @@ type LibretroConfig struct {
 		List map[string]LibretroCoreConfig
 	}
 	DebounceMs      int
+	Dup             bool
 	SaveCompression bool
 	LogLevel        int
 }
diff --git a/pkg/worker/caged/libretro/frontend.go b/pkg/worker/caged/libretro/frontend.go
index 1b6638e33..935a24f3c 100644
--- a/pkg/worker/caged/libretro/frontend.go
+++ b/pkg/worker/caged/libretro/frontend.go
@@ -93,6 +93,7 @@ var (
 	noData    = func([]byte) {}
 	noVideo   = func(app.Video) {}
 	videoPool sync.Pool
+	lastFrame *app.Video
 )
 
 // NewFrontend implements Emulator interface for a Libretro frontend.
@@ -156,6 +157,7 @@ func (f *Frontend) LoadCore(emu string) {
 	conf := f.conf.GetLibretroCoreConfig(emu)
 	meta := nanoarch.Metadata{
 		AutoGlContext:   conf.AutoGlContext,
+		FrameDup:        f.conf.Libretro.Dup,
 		Hacks:           conf.Hacks,
 		HasVFR:          conf.VFR,
 		Hid:             conf.Hid,
@@ -190,7 +192,6 @@ func (f *Frontend) handleAudio(audio unsafe.Pointer, samples int) {
 }
 
 func (f *Frontend) handleVideo(data []byte, delta int32, fi nanoarch.FrameInfo) {
-	// !to merge both pools
 	fr, _ := videoPool.Get().(*app.Video)
 	if fr == nil {
 		fr = new(app.Video)
@@ -200,10 +201,17 @@ func (f *Frontend) handleVideo(data []byte, delta int32, fi nanoarch.FrameInfo)
 	fr.Frame.H = int(fi.H)
 	fr.Frame.Stride = int(fi.Stride)
 	fr.Duration = delta
+
+	lastFrame = fr
 	f.onVideo(*fr)
+
 	videoPool.Put(fr)
 }
 
+func (f *Frontend) handleDup() {
+	f.onVideo(*lastFrame)
+}
+
 func (f *Frontend) Shutdown() {
 	f.mu.Lock()
 	f.nano.Shutdown()
@@ -224,6 +232,7 @@ func (f *Frontend) linkNano(nano *nanoarch.Nanoarch) {
 	f.nano.OnDpad = f.input.isDpadTouched
 	f.nano.OnVideo = f.handleVideo
 	f.nano.OnAudio = f.handleAudio
+	f.nano.OnDup = f.handleDup
 }
 
 func (f *Frontend) SetVideoChangeCb(fn func()) {
diff --git a/pkg/worker/caged/libretro/nanoarch/nanoarch.go b/pkg/worker/caged/libretro/nanoarch/nanoarch.go
index 95cd24a6f..94ff0b0d7 100644
--- a/pkg/worker/caged/libretro/nanoarch/nanoarch.go
+++ b/pkg/worker/caged/libretro/nanoarch/nanoarch.go
@@ -78,6 +78,7 @@ type Handlers struct {
 	OnKeyPress     func(port uint, key int) int
 	OnAudio        func(ptr unsafe.Pointer, frames int)
 	OnVideo        func(data []byte, delta int32, fi FrameInfo)
+	OnDup          func()
 	OnSystemAvInfo func()
 }
 
@@ -88,6 +89,7 @@ type FrameInfo struct {
 }
 
 type Metadata struct {
+	FrameDup        bool
 	LibPath         string // the full path to some emulator lib
 	IsGlAllowed     bool
 	UsesLibCo       bool
@@ -127,6 +129,7 @@ var Nan0 = Nanoarch{
 		OnKeyPress: func(uint, int) int { return 0 },
 		OnAudio:    func(unsafe.Pointer, int) {},
 		OnVideo:    func([]byte, int32, FrameInfo) {},
+		OnDup:      func() {},
 	},
 }
 
@@ -559,9 +562,9 @@ func coreVideoRefresh(data unsafe.Pointer, width, height uint, packed uint) {
 	}
 	Nan0.LastFrameTime = t
 
-	// some cores can return nothing
-	// !to add duplicate if can dup
+	// when the core returns a duplicate frame
 	if data == nil {
+		Nan0.Handlers.OnDup()
 		return
 	}
 
@@ -694,9 +697,9 @@ func coreEnvironment(cmd C.unsigned, data unsafe.Pointer) C.bool {
 		setRotation((*(*uint)(data) % 4) * 90)
 		return true
 	case C.RETRO_ENVIRONMENT_GET_CAN_DUPE:
-		// !to implement frame dup (nil) some time later
-		*(*C.bool)(data) = C.bool(false)
-		return false
+		dup := C.bool(Nan0.meta.FrameDup)
+		*(*C.bool)(data) = dup
+		return dup
 	case C.RETRO_ENVIRONMENT_GET_USERNAME:
 		*(**C.char)(data) = Nan0.cUserName
 		return true