swaybar: Fix scrolling with precise trackpads

include/swaybar/input.h

@@ -2,6 +2,7 @@
 #define _SWAYBAR_INPUT_H
 
 #include <wayland-client.h>
+#include <stdbool.h>
 #include "list.h"
 
 #define SWAY_SCROLL_UP KEY_MAX + 1
@@ -56,6 +57,9 @@ struct swaybar_seat {
 	struct wl_seat *wl_seat;
 	struct swaybar_pointer pointer;
 	struct swaybar_touch touch;
+	uint32_t scroll_time;
+	bool scroll_is_discrete_horizontal;
+	bool scroll_is_discrete_vertical;
 	struct wl_list link; // swaybar_seat:link
 };
 

swaybar/bar.c

@@ -340,7 +340,7 @@ static void handle_global(void *data, struct wl_registry *registry,
 		}
 		seat->bar = bar;
 		seat->wl_name = name;
-		seat->wl_seat = wl_registry_bind(registry, name, &wl_seat_interface, 3);
+		seat->wl_seat = wl_registry_bind(registry, name, &wl_seat_interface, 5);
 		wl_seat_add_listener(seat->wl_seat, &seat_listener, seat);
 		wl_list_insert(&bar->seats, &seat->link);
 	} else if (strcmp(interface, wl_shm_interface.name) == 0) {

swaybar/input.c

@@ -246,7 +246,24 @@ static void wl_pointer_axis(void *data, struct wl_pointer *wl_pointer,
 		return;
 	}
 
-	workspace_next(seat->bar, output, amt < 0.0);
+	// If the scroll device is discrete, we don't need to do anything fancy.
+	// If it's continuous, do our best to emulate discrete scrolling.
+	bool do_scroll =
+		(axis == WL_POINTER_AXIS_VERTICAL_SCROLL && seat->scroll_is_discrete_vertical) ||
+		(axis == WL_POINTER_AXIS_HORIZONTAL_SCROLL && seat->scroll_is_discrete_horizontal) ||
+		fabs(amt) >= 10 ||
+		(fabs(amt) >= 1 && time >= seat->scroll_time + 200);
+
+	// Clear flags in case the next event isn't discrete
+	if (axis == WL_POINTER_AXIS_VERTICAL_SCROLL)
+		seat->scroll_is_discrete_vertical = false;
+	else if (axis == WL_POINTER_AXIS_HORIZONTAL_SCROLL)
+		seat->scroll_is_discrete_horizontal = false;
+
+	if (do_scroll) {
+		seat->scroll_time = time;
+		workspace_next(seat->bar, output, amt < 0.0);
+	}
 
 	// Check button release bindings
 	check_bindings(seat->bar, button, WL_POINTER_BUTTON_STATE_RELEASED);
@@ -268,7 +285,12 @@ static void wl_pointer_axis_stop(void *data, struct wl_pointer *wl_pointer,
 
 static void wl_pointer_axis_discrete(void *data, struct wl_pointer *wl_pointer,
 		uint32_t axis, int32_t discrete) {
-	// Who cares
+	struct swaybar_seat *seat = data;
+	if (axis == WL_POINTER_AXIS_VERTICAL_SCROLL) {
+		seat->scroll_is_discrete_vertical = true;
+	} else if (axis == WL_POINTER_AXIS_HORIZONTAL_SCROLL) {
+		seat->scroll_is_discrete_horizontal = true;
+	}
 }
 
 static struct wl_pointer_listener pointer_listener = {