From 6d2cb3073c42b74c0f28c372f71ac158378fe616 Mon Sep 17 00:00:00 2001
From: Joshua Ashton <joshua@froggi.es>
Date: Mon, 31 Jan 2022 23:05:22 +0000
Subject: [PATCH] steamcompmgr: Implement dynamic refresh rate based on FPS
 limit

Adds a mode to dynamically change the refresh rate based on the existing FPS limit.
---
 src/drm.cpp          | 16 ++++++++++++++++
 src/drm.hpp          |  1 +
 src/steamcompmgr.cpp | 21 +++++++++++++++++++++
 src/xwayland_ctx.hpp |  1 +
 4 files changed, 39 insertions(+)

diff --git a/src/drm.cpp b/src/drm.cpp
index 9da45eb..1e805df 100644
--- a/src/drm.cpp
+++ b/src/drm.cpp
@@ -1533,3 +1533,19 @@ bool drm_set_resolution( struct drm_t *drm, int width, int height )
 
 	return drm_set_mode(drm, mode);
 }
+
+int drm_get_default_refresh(struct drm_t *drm)
+{
+	if ( drm->preferred_refresh )
+		return drm->preferred_refresh;
+
+	if ( drm->connector && drm->connector->connector )
+	{
+		drmModeConnector *connector = drm->connector->connector;
+		const drmModeModeInfo *mode = find_mode( connector, g_nOutputWidth, g_nOutputHeight, 0);
+		if ( mode )
+			return mode->vrefresh;
+	}
+
+	return 60;
+}
\ No newline at end of file
diff --git a/src/drm.hpp b/src/drm.hpp
index d73e5c9..77841f0 100644
--- a/src/drm.hpp
+++ b/src/drm.hpp
@@ -162,3 +162,4 @@ bool drm_set_color_gain_blend(struct drm_t *drm, float blend);
 bool drm_update_gamma_lut(struct drm_t *drm);
 
 char *find_drm_node_by_devid(dev_t devid);
+int drm_get_default_refresh(struct drm_t *drm);
\ No newline at end of file
diff --git a/src/steamcompmgr.cpp b/src/steamcompmgr.cpp
index a8b51dd..b1a22b4 100644
--- a/src/steamcompmgr.cpp
+++ b/src/steamcompmgr.cpp
@@ -229,6 +229,10 @@ std::mutex g_FrameLimitCommitsMutex;
 std::queue< std::shared_ptr<commit_t> > g_FrameLimitCommits;
 
 static int g_nSteamCompMgrTargetFPS = 0;
+static uint64_t g_uDynamicRefreshEqualityTime = 0;
+static bool g_bDynamicRefreshEnabled = false;
+// Delay to stop modes flickering back and forth.
+static const uint64_t g_uDynamicRefreshDelay = 600'000'000; // 600ms
 
 bool steamcompmgr_window_should_limit_fps( win *w )
 {
@@ -1714,6 +1718,18 @@ paint_all()
 	const bool bOverrideCompositeHack = false;
 #endif
 
+	int nTargetRefresh = g_nSteamCompMgrTargetFPS && g_bDynamicRefreshEnabled && steamcompmgr_window_should_limit_fps( global_focus.focusWindow ) && !global_focus.overlayWindow
+		? g_nSteamCompMgrTargetFPS
+		: drm_get_default_refresh( &g_DRM );
+
+	uint64_t now = get_time_in_nanos();
+
+	if ( g_nOutputRefresh == nTargetRefresh )
+		g_uDynamicRefreshEqualityTime = now;
+
+	if ( !BIsNested() && g_nOutputRefresh != nTargetRefresh && g_uDynamicRefreshEqualityTime + g_uDynamicRefreshDelay < now )
+		drm_set_refresh( &g_DRM, nTargetRefresh );
+
 	bool bNeedsNearest = !g_bFilterGameWindow && composite.data.vScale[0].x != 1.0f && composite.data.vScale[0].y != 1.0f;
 
 	bool bNeedsComposite = BIsNested();
@@ -3719,6 +3735,10 @@ handle_property_notify(xwayland_ctx_t *ctx, XPropertyEvent *ev)
 	{
 		steamcompmgr_set_target_fps( get_prop( ctx, ctx->root, ctx->atoms.gamescopeFPSLimit, 0 ) );
 	}
+	if ( ev->atom == ctx->atoms.gamescopeDynamicRefresh )
+	{
+		g_bDynamicRefreshEnabled = !!get_prop( ctx, ctx->root, ctx->atoms.gamescopeDynamicRefresh, 0 );
+	}
 }
 
 static int
@@ -4576,6 +4596,7 @@ void init_xwayland_ctx(gamescope_xwayland_server_t *xwayland_server)
 	ctx->atoms.gamescopeColorLinearGainBlend = XInternAtom( ctx->dpy, "GAMESCOPE_COLOR_LINEARGAIN_BLEND", false );
 	ctx->atoms.gamescopeXWaylandModeControl = XInternAtom( ctx->dpy, "GAMESCOPE_XWAYLAND_MODE_CONTROL", false );
 	ctx->atoms.gamescopeFPSLimit = XInternAtom( ctx->dpy, "GAMESCOPE_FPS_LIMIT", false );
+	ctx->atoms.gamescopeDynamicRefresh = XInternAtom( ctx->dpy, "GAMESCOPE_DYNAMIC_REFRESH", false );
 
 	ctx->root_width = DisplayWidth(ctx->dpy, ctx->scr);
 	ctx->root_height = DisplayHeight(ctx->dpy, ctx->scr);
diff --git a/src/xwayland_ctx.hpp b/src/xwayland_ctx.hpp
index d99461a..06c6672 100644
--- a/src/xwayland_ctx.hpp
+++ b/src/xwayland_ctx.hpp
@@ -123,5 +123,6 @@ struct xwayland_ctx_t
 		Atom gamescopeXWaylandModeControl;
 
 		Atom gamescopeFPSLimit;
+		Atom gamescopeDynamicRefresh;
 	} atoms;
 };