Use a set to track pointer button state.

In addition to `button_count`, we keep track of the current buttons
pressed just as in `wlr_keyboard`.

Add `set_add` and `set_remove` to assist with this. These functions can
only be used with values greater than 0 (such as the button/key masks
for keyboards and pointers).

Partially addresses:
- https://github.com/swaywm/wlroots/issues/1716
- https://github.com/swaywm/wlroots/issues/1593

include/util/array.h

@@ -3,7 +3,22 @@
 
 #include <stdint.h>
 #include <stdlib.h>
+#include <stdbool.h>
 
 size_t push_zeroes_to_end(uint32_t arr[], size_t n);
 
+/**
+ * Add `target` to `values` if it doesn't exist
+ * "set"s should only be modified with set_* functions
+ * Values MUST be greater than 0
+ */
+bool set_add(uint32_t values[], size_t *len, size_t cap, uint32_t target);
+
+/**
+ * Remove `target` from `values` if it exists
+ * "set"s should only be modified with set_* functions
+ * Values MUST be greater than 0
+ */
+bool set_remove(uint32_t values[], size_t *len, size_t cap, uint32_t target);
+
 #endif

include/wlr/types/wlr_seat.h

@@ -131,6 +131,8 @@ struct wlr_seat_pointer_grab {
 	void *data;
 };
 
+#define WLR_POINTER_BUTTONS_CAP 16
+
 struct wlr_seat_pointer_state {
 	struct wlr_seat *seat;
 	struct wlr_seat_client *focused_client;
@@ -140,7 +142,8 @@ struct wlr_seat_pointer_state {
 	struct wlr_seat_pointer_grab *grab;
 	struct wlr_seat_pointer_grab *default_grab;
 
-	uint32_t button_count;
+	uint32_t buttons[WLR_POINTER_BUTTONS_CAP];
+	size_t button_count;
 	uint32_t grab_button;
 	uint32_t grab_serial;
 	uint32_t grab_time;

types/seat/wlr_seat_pointer.c

@@ -8,6 +8,7 @@
 #include <wlr/util/log.h>
 #include "types/wlr_seat.h"
 #include "util/signal.h"
+#include "util/array.h"
 
 static void default_pointer_enter(struct wlr_seat_pointer_grab *grab,
 		struct wlr_surface *surface, double sx, double sy) {
@@ -339,26 +340,32 @@ void wlr_seat_pointer_notify_motion(struct wlr_seat *wlr_seat, uint32_t time,
 uint32_t wlr_seat_pointer_notify_button(struct wlr_seat *wlr_seat,
 		uint32_t time, uint32_t button, enum wlr_button_state state) {
 	clock_gettime(CLOCK_MONOTONIC, &wlr_seat->last_event);
+
+	struct wlr_seat_pointer_state* pointer_state = &wlr_seat->pointer_state;
+
 	if (state == WLR_BUTTON_PRESSED) {
-		if (wlr_seat->pointer_state.button_count == 0) {
-			wlr_seat->pointer_state.grab_button = button;
-			wlr_seat->pointer_state.grab_time = time;
+		if (pointer_state->button_count == 0) {
+			pointer_state->grab_button = button;
+			pointer_state->grab_time = time;
 		}
-		wlr_seat->pointer_state.button_count++;
+		set_add(pointer_state->buttons, &pointer_state->button_count,
+			WLR_POINTER_BUTTONS_CAP, button);
 	} else {
-		if (wlr_seat->pointer_state.button_count == 0) {
-			wlr_log(WLR_ERROR, "Corrupted seat button count");
-		} else {
-			wlr_seat->pointer_state.button_count--;
-		}
+		set_remove(pointer_state->buttons, &pointer_state->button_count,
+			WLR_POINTER_BUTTONS_CAP, button);
 	}
 
-	struct wlr_seat_pointer_grab *grab = wlr_seat->pointer_state.grab;
+
+	struct wlr_seat_pointer_grab *grab = pointer_state->grab;
 	uint32_t serial = grab->interface->button(grab, time, button, state);
 
-	if (serial && wlr_seat->pointer_state.button_count == 1 &&
+	wlr_log(WLR_DEBUG, "button_count=%zu grab_serial=%"PRIu32" serial=%"PRIu32"",
+		pointer_state->button_count,
+		pointer_state->grab_serial, serial);
+
+	if (serial && pointer_state->button_count == 1 &&
 			state == WLR_BUTTON_PRESSED) {
-		wlr_seat->pointer_state.grab_serial = serial;
+		pointer_state->grab_serial = serial;
 	}
 
 	return serial;
@@ -413,7 +420,7 @@ bool wlr_seat_validate_pointer_grab_serial(struct wlr_seat *seat,
 	if (seat->pointer_state.button_count != 1 ||
 			seat->pointer_state.grab_serial != serial) {
 		wlr_log(WLR_DEBUG, "Pointer grab serial validation failed: "
-			"button_count=%"PRIu32" grab_serial=%"PRIu32" (got %"PRIu32")",
+			"button_count=%zu grab_serial=%"PRIu32" (got %"PRIu32")",
 			seat->pointer_state.button_count,
 			seat->pointer_state.grab_serial, serial);
 		return false;

types/wlr_keyboard.c

@@ -57,22 +57,13 @@ static bool keyboard_modifier_update(struct wlr_keyboard *keyboard) {
 
 static void keyboard_key_update(struct wlr_keyboard *keyboard,
 		struct wlr_event_keyboard_key *event) {
-	bool found = false;
-	size_t i = 0;
-	for (; i < keyboard->num_keycodes; ++i) {
-		if (keyboard->keycodes[i] == event->keycode) {
-			found = true;
-			break;
-		}
+	if (event->state == WLR_KEY_PRESSED) {
+		set_add(keyboard->keycodes, &keyboard->num_keycodes,
+			WLR_KEYBOARD_KEYS_CAP, event->keycode);
 	}
-
-	if (event->state == WLR_KEY_PRESSED && !found &&
-			keyboard->num_keycodes < WLR_KEYBOARD_KEYS_CAP) {
-		keyboard->keycodes[keyboard->num_keycodes++] = event->keycode;
-	}
-	if (event->state == WLR_KEY_RELEASED && found) {
-		keyboard->keycodes[i] = 0;
-		keyboard->num_keycodes = push_zeroes_to_end(keyboard->keycodes, WLR_KEYBOARD_KEYS_CAP);
+	if (event->state == WLR_KEY_RELEASED) {
+		set_remove(keyboard->keycodes, &keyboard->num_keycodes,
+			WLR_KEYBOARD_KEYS_CAP, event->keycode);
 	}
 
 	assert(keyboard->num_keycodes <= WLR_KEYBOARD_KEYS_CAP);

util/array.c

@@ -1,5 +1,5 @@
-#include <stdlib.h>
-#include <stdint.h>
+#include "util/array.h"
+#include <assert.h>
 
 // https://www.geeksforgeeks.org/move-zeroes-end-array/
 size_t push_zeroes_to_end(uint32_t arr[], size_t n) {
@@ -19,3 +19,31 @@ size_t push_zeroes_to_end(uint32_t arr[], size_t n) {
 
 	return ret;
 }
+
+bool set_add(uint32_t values[], size_t *len, size_t cap, uint32_t target) {
+	if (*len == cap) {
+		return false;
+	}
+	assert(target > 0);
+	for (uint32_t i = 0; i < *len; ++i) {
+		if (values[i] == target) {
+			return false;
+		}
+	}
+	values[(*len)++] = target;
+	return false;
+}
+
+bool set_remove(uint32_t values[], size_t *len, size_t cap, uint32_t target) {
+	for (uint32_t i = 0; i < *len; ++i) {
+		if (values[i] == target) {
+			// Set to 0 and swap with the end element so that
+			// zeroes exist only after all the values.
+			size_t last_elem_pos = --(*len);
+			values[i] = values[last_elem_pos];
+			values[last_elem_pos] = 0;
+			return true;
+		}
+	}
+	return false;
+}