Revisit the motion recorder approach to FFP

Fixes #485.

src/bspwm.c

@@ -195,6 +195,7 @@ int main(int argc, char *argv[])
 	ungrab_buttons();
 	xcb_ewmh_connection_wipe(ewmh);
 	xcb_destroy_window(dpy, meta_window);
+	xcb_destroy_window(dpy, motion_recorder.id);
 	free(ewmh);
 	xcb_flush(dpy);
 	xcb_disconnect(dpy);
@@ -237,6 +238,14 @@ void setup(void)
 	xcb_create_window(dpy, XCB_COPY_FROM_PARENT, meta_window, root, -1, -1, 1, 1, 0, XCB_WINDOW_CLASS_INPUT_ONLY, XCB_COPY_FROM_PARENT, XCB_NONE, NULL);
 	xcb_icccm_set_wm_class(dpy, meta_window, sizeof(META_WINDOW_IC), META_WINDOW_IC);
 
+	motion_recorder.id = xcb_generate_id(dpy);
+	motion_recorder.sequence = 0;
+	motion_recorder.enabled = false;
+	uint32_t values[] = {XCB_EVENT_MASK_STRUCTURE_NOTIFY | XCB_EVENT_MASK_POINTER_MOTION};
+	xcb_create_window(dpy, XCB_COPY_FROM_PARENT, motion_recorder.id, root, 0, 0, 1, 1, 0,
+	                  XCB_WINDOW_CLASS_INPUT_ONLY, XCB_COPY_FROM_PARENT, XCB_CW_EVENT_MASK, values);
+	xcb_icccm_set_wm_class(dpy, motion_recorder.id, sizeof(MOTION_RECORDER_IC), MOTION_RECORDER_IC);
+
 	xcb_atom_t net_atoms[] = {ewmh->_NET_SUPPORTED,
 	                          ewmh->_NET_SUPPORTING_WM_CHECK,
 	                          ewmh->_NET_DESKTOP_NAMES,

src/bspwm.h

@@ -34,6 +34,8 @@
 #define ROOT_WINDOW_IC      "root\0" BSPWM_CLASS_NAME
 #define PRESEL_FEEDBACK_I   "presel_feedback"
 #define PRESEL_FEEDBACK_IC  PRESEL_FEEDBACK_I "\0" BSPWM_CLASS_NAME
+#define MOTION_RECORDER_I   "motion_recorder"
+#define MOTION_RECORDER_IC  MOTION_RECORDER_I "\0" BSPWM_CLASS_NAME
 
 xcb_connection_t *dpy;
 int default_screen, screen_width, screen_height;
@@ -59,6 +61,11 @@ pending_rule_t *pending_rule_head;
 pending_rule_t *pending_rule_tail;
 
 xcb_window_t meta_window;
+struct {
+	xcb_window_t id;
+	uint16_t sequence;
+	bool enabled;
+} motion_recorder;
 xcb_atom_t WM_STATE;
 xcb_atom_t WM_TAKE_FOCUS;
 xcb_atom_t WM_DELETE_WINDOW;

src/desktop.c

@@ -43,14 +43,8 @@ void focus_desktop(monitor_t *m, desktop_t *d)
 	focus_monitor(m);
 
 	if (m->desk != d) {
-		if (focus_follows_pointer) {
-			listen_enter_notify(d->root, false);
-		}
 		show_desktop(d);
 		hide_desktop(m->desk);
-		if (focus_follows_pointer) {
-			listen_enter_notify(d->root, true);
-		}
 		m->desk = d;
 	}
 
@@ -139,17 +133,11 @@ void handle_presel_feedbacks(monitor_t *m, desktop_t *d)
 	if (m->desk != d) {
 		return;
 	}
-	if (focus_follows_pointer) {
-		listen_enter_notify(d->root, false);
-	}
 	if (d->layout == LAYOUT_MONOCLE) {
 		hide_presel_feedbacks(m, d, d->root);
 	} else {
 		show_presel_feedbacks(m, d, d->root);
 	}
-	if (focus_follows_pointer) {
-		listen_enter_notify(d->root, true);
-	}
 }
 
 bool transfer_desktop(monitor_t *ms, monitor_t *md, desktop_t *d)

src/events.c

@@ -62,6 +62,9 @@ void handle_event(xcb_generic_event_t *evt)
 		case XCB_ENTER_NOTIFY:
 			enter_notify(evt);
 			break;
+		case XCB_MOTION_NOTIFY:
+			motion_notify(evt);
+			break;
 		case XCB_BUTTON_PRESS:
 			button_press(evt);
 			break;
@@ -162,16 +165,8 @@ void configure_request(xcb_generic_event_t *evt)
 		c->floating_rectangle.height = height;
 		xcb_rectangle_t r = c->floating_rectangle;
 
-		if (focus_follows_pointer) {
-			listen_enter_notify(loc.desktop->root, false);
-		}
-
 		window_move_resize(e->window, r.x, r.y, r.width, r.height);
 
-		if (focus_follows_pointer) {
-			listen_enter_notify(loc.desktop->root, true);
-		}
-
 		put_status(SBSC_MASK_NODE_GEOMETRY, "node_geometry 0x%08X 0x%08X 0x%08X %ux%u+%i+%i\n", loc.monitor->id, loc.desktop->id, e->window, r.width, r.height, r.x, r.y);
 
 		monitor_t *m = monitor_from_client(c);
@@ -238,6 +233,15 @@ void unmap_notify(xcb_generic_event_t *evt)
 {
 	xcb_unmap_notify_event_t *e = (xcb_unmap_notify_event_t *) evt;
 
+	if (e->window == motion_recorder.id) {
+		/* Unmapping the motion recorder in `query_pointer` will produce
+		 * unwanted enter notify events. We can filter those events because
+		 * their sequence number is the same as the sequence number of the
+		 * related unmap notify event. This is a technique used by i3-wm to
+		 * filter enter notify events. */
+		motion_recorder.sequence = e->sequence;
+	}
+
 	unmanage_window(e->window);
 }
 
@@ -370,30 +374,64 @@ void enter_notify(xcb_generic_event_t *evt)
 		return;
 	}
 
-	xcb_point_t pt = {e->root_x, e->root_y};
-	monitor_t *m = monitor_from_point(pt);
-
-	if (m == NULL) {
+	/* Ignore the enter notify events that we generated by unmapping the motion
+	 * recorder window in `query_pointer`. */
+	if (motion_recorder.enabled && motion_recorder.sequence == e->sequence) {
 		return;
 	}
 
+	if (win == mon->root || (mon->desk->focus != NULL &&
+	                         (win == mon->desk->focus->id ||
+	                          (mon->desk->focus->presel != NULL &&
+	                           win == mon->desk->focus->presel->feedback)))) {
+		return;
+	}
+
+	update_motion_recorder();
+}
+
+void motion_notify(xcb_generic_event_t *evt)
+{
+	xcb_motion_notify_event_t *e = (xcb_motion_notify_event_t *) evt;
+
+	static uint16_t last_motion_x = 0, last_motion_y = 0;
+	static xcb_timestamp_t last_motion_time = 0;
+
+	int64_t dtime = e->time - last_motion_time;
+
+	/* Ignore unintentional pointer motions. */
+	if (dtime > 1000) {
+		last_motion_time = e->time;
+		last_motion_x = e->event_x;
+		last_motion_y = e->event_y;
+		return;
+	}
+	int mdist = abs(e->event_x - last_motion_x) + abs(e->event_y - last_motion_y);
+	if (mdist < 10) {
+		return;
+	}
+
+	disable_motion_recorder();
+
+	xcb_window_t win = XCB_NONE;
+	query_pointer(&win, NULL);
+	coordinates_t loc;
 	bool pff = pointer_follows_focus;
 	bool pfm = pointer_follows_monitor;
 	pointer_follows_focus = false;
 	pointer_follows_monitor = false;
 	auto_raise = false;
 
-	desktop_t *d = m->desk;
-	node_t *n = NULL;
-
-	for (n = first_extrema(d->root); n != NULL; n = next_leaf(n, d->root)) {
-		if (n->id == win || (n->presel != NULL && n->presel->feedback == win)) {
-			break;
+	if (locate_window(win, &loc)) {
+		if (loc.monitor->desk == loc.desktop && loc.node != mon->desk->focus) {
+			focus_node(loc.monitor, loc.desktop, loc.node);
+		}
+	} else {
+		xcb_point_t pt = {e->root_x, e->root_y};
+		monitor_t *m = monitor_from_point(pt);
+		if (m != NULL && m != mon) {
+			focus_node(m, m->desk, m->desk->focus);
 		}
-	}
-
-	if (n != mon->desk->focus || mon->desk->focus == NULL) {
-		focus_node(m, d, n == NULL ? d->focus : n);
 	}
 
 	pointer_follows_focus = pff;

src/events.h

@@ -41,6 +41,7 @@ void client_message(xcb_generic_event_t *evt);
 void focus_in(xcb_generic_event_t *evt);
 void button_press(xcb_generic_event_t *evt);
 void enter_notify(xcb_generic_event_t *evt);
+void motion_notify(xcb_generic_event_t *evt);
 void handle_state(monitor_t *m, desktop_t *d, node_t *n, xcb_atom_t state, unsigned int action);
 void process_error(xcb_generic_event_t *evt);
 

src/messages.c

@@ -1475,15 +1475,20 @@ void set_setting(coordinates_t loc, char *name, char *value, FILE *rsp)
 			}
 			focus_follows_pointer = b;
 			for (monitor_t *m = mon_head; m != NULL; m = m->next) {
-				if (b) {
+				if (focus_follows_pointer) {
 					window_show(m->root);
 				} else {
 					window_hide(m->root);
 				}
 				for (desktop_t *d = m->desk_head; d != NULL; d = d->next) {
-					listen_enter_notify(d->root, b);
+					listen_enter_notify(d->root, focus_follows_pointer);
 				}
 			}
+			if (focus_follows_pointer) {
+				update_motion_recorder();
+			} else {
+				disable_motion_recorder();
+			}
 			return;
 		} else {
 			fail(rsp, "config: %s: Invalid value: '%s'.\n", name, value);

src/query.c

@@ -454,7 +454,7 @@ int node_from_desc(char *desc, coordinates_t *ref, coordinates_t *dst)
 	} else if (streq("biggest", desc)) {
 		find_biggest(ref, dst, sel);
 	} else if (streq("pointed", desc)) {
-		xcb_window_t win;
+		xcb_window_t win = XCB_NONE;
 		query_pointer(&win, NULL);
 		if (locate_window(win, dst) && node_matches(dst, ref, sel)) {
 			return SELECTOR_OK;

src/tree.c

@@ -67,15 +67,7 @@ void arrange(monitor_t *m, desktop_t *d)
 		rect.height -= d->window_gap;
 	}
 
-	if (focus_follows_pointer) {
-		listen_enter_notify(d->root, false);
-	}
-
 	apply_layout(m, d, d->root, l, rect, rect);
-
-	if (focus_follows_pointer) {
-		listen_enter_notify(d->root, true);
-	}
 }
 
 void apply_layout(monitor_t *m, desktop_t *d, node_t *n, layout_t l, xcb_rectangle_t rect, xcb_rectangle_t root_rect)
@@ -224,18 +216,10 @@ void cancel_presel(monitor_t *m, desktop_t *d, node_t *n)
 		return;
 	}
 
-	if (focus_follows_pointer) {
-		listen_enter_notify(n, false);
-	}
-
 	if (n->presel->feedback != XCB_NONE) {
 		xcb_destroy_window(dpy, n->presel->feedback);
 	}
 
-	if (focus_follows_pointer) {
-		listen_enter_notify(n, true);
-	}
-
 	free(n->presel);
 	n->presel = NULL;
 
@@ -594,6 +578,9 @@ bool focus_node(monitor_t *m, desktop_t *d, node_t *n)
 	put_status(SBSC_MASK_REPORT);
 
 	if (n == NULL) {
+		if (focus_follows_pointer) {
+			update_motion_recorder();
+		}
 		return true;
 	}
 
@@ -604,6 +591,8 @@ bool focus_node(monitor_t *m, desktop_t *d, node_t *n)
 
 	if (pointer_follows_focus) {
 		center_pointer(get_rectangle(d, n));
+	} else if (focus_follows_pointer) {
+		update_motion_recorder();
 	}
 
 	return true;
@@ -1725,11 +1714,6 @@ void set_hidden(monitor_t *m, desktop_t *d, node_t *n, bool value)
 		return;
 	}
 
-
-	if (focus_follows_pointer) {
-		listen_enter_notify(d->root, false);
-	}
-
 	bool held_focus = is_descendant(d->focus, n);
 
 	propagate_hidden_downward(m, d, n, value);
@@ -1748,10 +1732,6 @@ void set_hidden(monitor_t *m, desktop_t *d, node_t *n, bool value)
 			activate_node(m, d, d->focus);
 		}
 	}
-
-	if (focus_follows_pointer) {
-		listen_enter_notify(d->root, true);
-	}
 }
 
 void set_hidden_local(monitor_t *m, desktop_t *d, node_t *n, bool value)

src/window.c

@@ -274,10 +274,6 @@ void draw_presel_feedback(monitor_t *m, desktop_t *d, node_t *n)
 		return;
 	}
 
-	if (focus_follows_pointer) {
-		listen_enter_notify(d->root, false);
-	}
-
 	bool exists = (n->presel->feedback != XCB_NONE);
 	if (!exists) {
 		initialize_presel_feedback(n);
@@ -314,10 +310,6 @@ void draw_presel_feedback(monitor_t *m, desktop_t *d, node_t *n)
 	if (!exists && m->desk == d) {
 		window_show(p->feedback);
 	}
-
-	if (focus_follows_pointer) {
-		listen_enter_notify(d->root, true);
-	}
 }
 
 void refresh_presel_feedbacks(monitor_t *m, desktop_t *d, node_t *n)
@@ -510,16 +502,8 @@ bool move_client(coordinates_t *loc, int dx, int dy)
 		int16_t x = rect.x + dx;
 		int16_t y = rect.y + dy;
 
-		if (focus_follows_pointer) {
-			listen_enter_notify(loc->desktop->root, false);
-		}
-
 		window_move(n->id, x, y);
 
-		if (focus_follows_pointer) {
-			listen_enter_notify(loc->desktop->root, true);
-		}
-
 		c->floating_rectangle.x = x;
 		c->floating_rectangle.y = y;
 		if (!grabbing) {
@@ -594,16 +578,8 @@ bool resize_client(coordinates_t *loc, resize_handle_t rh, int dx, int dy)
 		}
 		n->client->floating_rectangle = (xcb_rectangle_t) {x, y, width, height};
 		if (n->client->state == STATE_FLOATING) {
-			if (focus_follows_pointer) {
-				listen_enter_notify(loc->desktop->root, false);
-			}
-
 			window_move_resize(n->id, x, y, width, height);
 
-			if (focus_follows_pointer) {
-				listen_enter_notify(loc->desktop->root, true);
-			}
-
 			if (!grabbing) {
 				put_status(SBSC_MASK_NODE_GEOMETRY, "node_geometry 0x%08X 0x%08X 0x%08X %ux%u+%i+%i\n", loc->monitor->id, loc->desktop->id, loc->node->id, width, height, x, y);
 			}
@@ -709,6 +685,10 @@ void apply_size_hints(client_t *c, uint16_t *width, uint16_t *height)
 
 void query_pointer(xcb_window_t *win, xcb_point_t *pt)
 {
+	if (motion_recorder.enabled) {
+		window_hide(motion_recorder.id);
+	}
+
 	xcb_query_pointer_reply_t *qpr = xcb_query_pointer_reply(dpy, xcb_query_pointer(dpy, root), NULL);
 
 	if (qpr != NULL) {
@@ -734,6 +714,59 @@ void query_pointer(xcb_window_t *win, xcb_point_t *pt)
 	}
 
 	free(qpr);
+
+	if (motion_recorder.enabled) {
+		window_show(motion_recorder.id);
+	}
+}
+
+void update_motion_recorder(void)
+{
+	xcb_point_t pt;
+	xcb_window_t win = XCB_NONE;
+	query_pointer(&win, &pt);
+	if (win == XCB_NONE) {
+		return;
+	}
+	monitor_t *m = monitor_from_point(pt);
+	if (m == NULL) {
+		return;
+	}
+	desktop_t *d = m->desk;
+	node_t *n = NULL;
+	for (n = first_extrema(d->root); n != NULL; n = next_leaf(n, d->root)) {
+		if (n->id == win || (n->presel != NULL && n->presel->feedback == win)) {
+			break;
+		}
+	}
+	if ((n != NULL && n != mon->desk->focus) || (n == NULL && m != mon)) {
+		enable_motion_recorder(win);
+	} else {
+		disable_motion_recorder();
+	}
+}
+
+void enable_motion_recorder(xcb_window_t win)
+{
+	xcb_get_geometry_reply_t *geo = xcb_get_geometry_reply(dpy, xcb_get_geometry(dpy, win), NULL);
+	if (geo != NULL) {
+		uint16_t width = geo->width + 2 * geo->border_width;
+		uint16_t height = geo->height + 2 * geo->border_width;
+		window_move_resize(motion_recorder.id, geo->x, geo->y, width, height);
+		window_above(motion_recorder.id, win);
+		window_show(motion_recorder.id);
+		motion_recorder.enabled = true;
+	}
+	free(geo);
+}
+
+void disable_motion_recorder(void)
+{
+	if (!motion_recorder.enabled) {
+		return;
+	}
+	window_hide(motion_recorder.id);
+	motion_recorder.enabled = false;
 }
 
 void window_border_width(xcb_window_t win, uint32_t bw)
@@ -788,11 +821,13 @@ void window_stack(xcb_window_t w1, xcb_window_t w2, uint32_t mode)
 	xcb_configure_window(dpy, w1, mask, values);
 }
 
+/* Stack w1 above w2 */
 void window_above(xcb_window_t w1, xcb_window_t w2)
 {
 	window_stack(w1, w2, XCB_STACK_MODE_ABOVE);
 }
 
+/* Stack w1 below w2 */
 void window_below(xcb_window_t w1, xcb_window_t w2)
 {
 	window_stack(w1, w2, XCB_STACK_MODE_BELOW);

src/window.h

@@ -53,6 +53,9 @@ bool move_client(coordinates_t *loc, int dx, int dy);
 bool resize_client(coordinates_t *loc, resize_handle_t rh, int dx, int dy);
 void apply_size_hints(client_t *c, uint16_t *width, uint16_t *height);
 void query_pointer(xcb_window_t *win, xcb_point_t *pt);
+void update_motion_recorder(void);
+void enable_motion_recorder(xcb_window_t win);
+void disable_motion_recorder(void);
 void window_border_width(xcb_window_t win, uint32_t bw);
 void window_move(xcb_window_t win, int16_t x, int16_t y);
 void window_resize(xcb_window_t win, uint16_t w, uint16_t h);