options: add a no-frame-pacing option

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

man/picom.1.asciidoc

@@ -109,6 +109,9 @@ OPTIONS
 *--rounded-corners-exclude* 'CONDITION'::
 	Exclude conditions for rounded corners.
 
+*--no-frame-pacing*::
+	Disable vsync-aware frame pacing. By default, the compositor tries to make sure it only renders once per vblank interval, and also the render happens as late as possible to minimize the latency from updates to the screen. However this can sometimes cause stuttering, or even lowered frame rate. This option can be used to disable frame pacing.
+
 *--mark-wmwin-focused*::
 	Try to detect WM windows (a non-override-redirect window with no child that has 'WM_STATE') and mark them as active.
 

src/config.c

@@ -742,6 +742,7 @@ char *parse_config(options_t *opt, const char *config_file, bool *shadow_enable,
 	    .logpath = NULL,
 
 	    .use_damage = true,
+	    .no_frame_pacing = false,
 
 	    .shadow_red = 0.0,
 	    .shadow_green = 0.0,

src/config.h

@@ -140,6 +140,8 @@ typedef struct options {
 	bool vsync_use_glfinish;
 	/// Whether use damage information to help limit the area to paint
 	bool use_damage;
+	/// Disable frame pacing
+	bool no_frame_pacing;
 
 	// === Shadow ===
 	/// Red, green and blue tone of the shadow.

src/config_libconfig.c

@@ -363,6 +363,9 @@ char *parse_config_libconfig(options_t *opt, const char *config_file, bool *shad
 	// --corner-radius-rules
 	parse_cfg_condlst_corner(opt, &cfg, "corner-radius-rules");
 
+	// --no-frame-pacing
+	lcfg_lookup_bool(&cfg, "no-frame-pacing", &opt->no_frame_pacing);
+
 	// -e (frame_opacity)
 	config_lookup_float(&cfg, "frame-opacity", &opt->frame_opacity);
 	// -c (shadow_enable)

src/options.c

@@ -176,6 +176,7 @@ static const struct picom_option picom_options[] = {
                                                                              "rendered screen. Reduces banding artifacts, but might cause performance "
                                                                              "degradation. Only works with OpenGL."},
     // 340 is corner-radius-rules
+    {"no-frame-pacing"             , no_argument      , 341, NULL          , "Disable frame pacing. This might increase the latency."},
     {"legacy-backends"             , no_argument      , 733, NULL          , "Use deprecated version of the backends."},
     {"monitor-repaint"             , no_argument      , 800, NULL          , "Highlight the updated area of the screen. For debugging."},
     {"diagnostics"                 , no_argument      , 801, NULL          , "Print diagnostic information"},
@@ -738,6 +739,7 @@ bool get_cfg(options_t *opt, int argc, char *const *argv, bool shadow_enable,
 			// --dithered-present
 			opt->dithered_present = true;
 			break;
+		P_CASEBOOL(341, no_frame_pacing);
 		P_CASEBOOL(733, legacy_backends);
 		P_CASEBOOL(800, monitor_repaint);
 		case 801:

src/picom.c

@@ -1445,9 +1445,9 @@ static bool redirect_start(session_t *ps) {
 		pixman_region32_init(&ps->damage_ring[i]);
 	}
 
-	ps->frame_pacing = true;
-	if (ps->o.legacy_backends || ps->o.benchmark ||
-	    !ps->backend_data->ops->last_render_time) {
+	ps->frame_pacing = !ps->o.no_frame_pacing;
+	if ((ps->o.legacy_backends || ps->o.benchmark || !ps->backend_data->ops->last_render_time) &&
+	    ps->frame_pacing) {
 		// Disable frame pacing if we are using a legacy backend or if we are in
 		// benchmark mode, or if the backend doesn't report render time
 		log_info("Disabling frame pacing.");