diff --git a/commands.c b/commands.c
index 6fb25fc..2688c09 100644
--- a/commands.c
+++ b/commands.c
@@ -53,7 +53,7 @@ bool it_quit(arg_t a) {
 
 bool it_switch_mode(arg_t a) {
 	if (mode == MODE_IMAGE) {
-		if (!tns.thumbs)
+		if (tns.thumbs == NULL)
 			tns_init(&tns, filecnt, &win);
 		img_close(&img, false);
 		reset_timeout(reset_cursor);
@@ -273,21 +273,19 @@ bool i_zoom(arg_t a) {
 }
 
 bool i_fit_to_win(arg_t a) {
-	bool ret;
+	bool ret = false;
 
 	if (mode == MODE_IMAGE) {
 		if ((ret = img_fit_win(&img)))
 			img_center(&img);
-		return ret;
-	} else {
-		return false;
 	}
+	return ret;
 }
 
 bool i_fit_to_img(arg_t a) {
 	int x, y;
 	unsigned int w, h;
-	bool ret;
+	bool ret = false;
 
 	if (mode == MODE_IMAGE) {
 		x = MAX(0, win.x + img.x);
@@ -298,10 +296,8 @@ bool i_fit_to_img(arg_t a) {
 			img.x = x - win.x;
 			img.y = y - win.y;
 		}
-		return ret;
-	} else {
-		return false;
 	}
+	return ret;
 }
 
 bool i_rotate(arg_t a) {
@@ -381,7 +377,7 @@ bool it_open_with(arg_t a) {
 	const char *prog = (const char*) a;
 	pid_t pid;
 
-	if (!prog || !*prog)
+	if (prog == NULL || *prog == '\0')
 		return false;
 
 	if ((pid = fork()) == 0) {
@@ -392,7 +388,6 @@ bool it_open_with(arg_t a) {
 	} else if (pid < 0) {
 		warn("could not fork. program was: %s", prog);
 	}
-	
 	return false;
 }
 
@@ -401,8 +396,8 @@ bool it_shell_cmd(arg_t a) {
 	const char *cmdline = (const char*) a;
 	pid_t pid;
 
-	if (!cmdline || !*cmdline)
-		return 0;
+	if (cmdline == NULL || *cmdline == '\0')
+		return false;
 
 	n = mode == MODE_IMAGE ? fileidx : tns.sel;
 
@@ -424,7 +419,7 @@ bool it_shell_cmd(arg_t a) {
 	win_set_cursor(&win, CURSOR_WATCH);
 
 	waitpid(pid, &status, 0);
-	if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
+	if (WIFEXITED(status) == 0 || WEXITSTATUS(status) != 0)
 		warn("child exited with non-zero return value: %d. command line was: %s",
 		     WEXITSTATUS(status), cmdline);
 	
@@ -440,6 +435,5 @@ bool it_shell_cmd(arg_t a) {
 		if (tns.sel >= tns.cnt)
 			tns.sel = tns.cnt - 1;
 	}
-
 	return true;
 }
diff --git a/config.c b/config.c
index c5987a9..d040b94 100644
--- a/config.c
+++ b/config.c
@@ -14,10 +14,11 @@ inline int puts_if(const char *s, int c) {
 }
 
 int main(int argc, char **argv) {
-	int i, n = 0;
+	int i;
+	unsigned int n = 0;
 
 	for (i = 1; i < argc; i++) {
-		switch (argv[i][0] != '-' || argv[i][2] ? -1 : argv[i][1]) {
+		switch ((argv[i][0] != '-' || argv[i][2] != '\0') ? -1 : argv[i][1]) {
 			case 'D':
 				n += PUT_MACRO(EXIF_SUPPORT);
 				n += PUT_MACRO(GIF_SUPPORT);
@@ -31,7 +32,7 @@ int main(int argc, char **argv) {
 				return 1;
 		}
 	}
-	if (n)
+	if (n > 0)
 		printf("\n");
 	return 0;
 }
diff --git a/image.c b/image.c
index cb867b5..4ea9b8d 100644
--- a/image.c
+++ b/image.c
@@ -49,7 +49,7 @@ void img_init(img_t *img, win_t *win) {
 	zoom_min = zoom_levels[0] / 100.0;
 	zoom_max = zoom_levels[ARRLEN(zoom_levels) - 1] / 100.0;
 
-	if (!img || !win)
+	if (img == NULL || win == NULL)
 		return;
 
 	imlib_context_set_display(win->env.dpy);
@@ -77,15 +77,15 @@ void exif_auto_orientate(const fileinfo_t *file) {
 	ExifEntry *entry;
 	int byte_order, orientation;
 
-	if (!(ed = exif_data_new_from_file(file->path)))
+	if ((ed = exif_data_new_from_file(file->path)) == NULL)
 		return;
 	entry = exif_content_get_entry(ed->ifd[EXIF_IFD_0], EXIF_TAG_ORIENTATION);
-	if (entry) {
+	if (entry != NULL) {
 		byte_order = exif_data_get_byte_order(ed);
 		orientation = exif_get_short(entry->data, byte_order);
 	}
 	exif_data_unref(ed);
-	if (!entry)
+	if (entry == NULL)
 		return;
 
 	switch (orientation) {
@@ -145,7 +145,7 @@ bool img_load_gif(img_t *img, const fileinfo_t *file) {
 	img->multi.sel = 0;
 
 	gif = DGifOpenFileName(file->path);
-	if (!gif) {
+	if (gif == NULL) {
 		warn("could not open gif file: %s", file->name);
 		return false;
 	}
@@ -215,7 +215,7 @@ bool img_load_gif(img_t *img, const fileinfo_t *file) {
 					if (i < y || i >= y + h || j < x || j >= x + w ||
 					    rows[i-y][j-x] == transp)
 					{
-						if (prev_frame)
+						if (prev_frame != NULL)
 							*ptr = prev_frame[i * sw + j];
 						else
 							*ptr = bgpixel;
@@ -236,7 +236,7 @@ bool img_load_gif(img_t *img, const fileinfo_t *file) {
 			free(rows);
 			free(data);
 
-			if (!im) {
+			if (im == NULL) {
 				err = true;
 				break;
 			}
@@ -286,10 +286,12 @@ bool img_load_gif(img_t *img, const fileinfo_t *file) {
 bool img_load(img_t *img, const fileinfo_t *file) {
 	const char *fmt;
 
-	if (!img || !file || !file->name || !file->path)
+	if (img == NULL || file == NULL || file->name == NULL || file->path == NULL)
 		return false;
 
-	if (access(file->path, R_OK) || !(img->im = imlib_load_image(file->path))) {
+	if (access(file->path, R_OK) < 0 ||
+	    (img->im = imlib_load_image(file->path)) == NULL)
+	{
 		warn("could not open image: %s", file->name);
 		return false;
 	}
@@ -324,17 +326,17 @@ bool img_load(img_t *img, const fileinfo_t *file) {
 void img_close(img_t *img, bool decache) {
 	int i;
 
-	if (!img)
+	if (img == NULL)
 		return;
 
-	if (img->multi.cnt) {
+	if (img->multi.cnt > 0) {
 		for (i = 0; i < img->multi.cnt; i++) {
 			imlib_context_set_image(img->multi.frames[i].im);
 			imlib_free_image();
 		}
 		img->multi.cnt = 0;
 		img->im = NULL;
-	} else if (img->im) {
+	} else if (img->im != NULL) {
 		imlib_context_set_image(img->im);
 		if (decache)
 			imlib_free_image_and_decache();
@@ -348,7 +350,7 @@ void img_check_pan(img_t *img, bool moved) {
 	win_t *win;
 	int ox, oy;
 
-	if (!img || !img->im || !img->win)
+	if (img == NULL || img->im == NULL || img->win == NULL)
 		return;
 
 	win = img->win;
@@ -379,7 +381,7 @@ void img_check_pan(img_t *img, bool moved) {
 bool img_fit(img_t *img) {
 	float z, zmax, zw, zh;
 
-	if (!img || !img->im || !img->win)
+	if (img == NULL || img->im == NULL || img->win == NULL)
 		return false;
 	if (img->scalemode == SCALE_ZOOM)
 		return false;
@@ -406,7 +408,7 @@ void img_render(img_t *img) {
 	int sx, sy, sw, sh;
 	int dx, dy, dw, dh;
 
-	if (!img || !img->im || !img->win)
+	if (img == NULL || img->im == NULL || img->win == NULL)
 		return;
 
 	win = img->win;
@@ -461,7 +463,7 @@ void img_render(img_t *img) {
 
 	imlib_context_set_image(img->im);
 
-	if (imlib_image_has_alpha() && !img->alpha)
+	if (!img->alpha && imlib_image_has_alpha())
 		win_draw_rect(win, win->pm, dx, dy, dw, dh, True, 0, win->white);
 	
 	imlib_context_set_drawable(win->pm);
@@ -473,7 +475,7 @@ void img_render(img_t *img) {
 }
 
 bool img_fit_win(img_t *img) {
-	if (!img || !img->im)
+	if (img == NULL || img->im == NULL)
 		return false;
 
 	img->scalemode = SCALE_FIT;
@@ -483,7 +485,7 @@ bool img_fit_win(img_t *img) {
 bool img_center(img_t *img) {
 	int ox, oy;
 
-	if (!img || !img->im || !img->win)
+	if (img == NULL || img->im == NULL || img->win == NULL)
 		return false;
 	
 	ox = img->x;
@@ -501,7 +503,7 @@ bool img_center(img_t *img) {
 }
 
 bool img_zoom(img_t *img, float z) {
-	if (!img || !img->im || !img->win)
+	if (img == NULL || img->im == NULL || img->win == NULL)
 		return false;
 
 	z = MAX(z, zoom_min);
@@ -524,7 +526,7 @@ bool img_zoom(img_t *img, float z) {
 bool img_zoom_in(img_t *img) {
 	int i;
 
-	if (!img || !img->im)
+	if (img == NULL || img->im == NULL)
 		return false;
 
 	for (i = 1; i < ARRLEN(zoom_levels); i++) {
@@ -537,7 +539,7 @@ bool img_zoom_in(img_t *img) {
 bool img_zoom_out(img_t *img) {
 	int i;
 
-	if (!img || !img->im)
+	if (img == NULL || img->im == NULL)
 		return false;
 
 	for (i = ARRLEN(zoom_levels) - 2; i >= 0; i--) {
@@ -550,7 +552,7 @@ bool img_zoom_out(img_t *img) {
 bool img_move(img_t *img, int dx, int dy) {
 	int ox, oy;
 
-	if (!img || !img->im)
+	if (img == NULL || img->im == NULL)
 		return false;
 
 	ox = img->x;
@@ -570,7 +572,7 @@ bool img_move(img_t *img, int dx, int dy) {
 }
 
 bool img_pan(img_t *img, direction_t dir, bool screen) {
-	if (!img || !img->im || !img->win)
+	if (img == NULL || img->im == NULL || img->win == NULL)
 		return false;
 
 	switch (dir) {
@@ -589,7 +591,7 @@ bool img_pan(img_t *img, direction_t dir, bool screen) {
 bool img_pan_edge(img_t *img, direction_t dir) {
 	int ox, oy;
 
-	if (!img || !img->im || !img->win)
+	if (img == NULL || img->im == NULL || img->win == NULL)
 		return false;
 
 	ox = img->x;
@@ -624,7 +626,7 @@ void img_rotate(img_t *img, int d) {
 	win_t *win;
 	int ox, oy, tmp;
 
-	if (!img || !img->im || !img->win)
+	if (img == NULL || img->im == NULL || img->win == NULL)
 		return;
 
 	win = img->win;
@@ -654,7 +656,7 @@ void img_rotate_right(img_t *img) {
 }
 
 void img_toggle_antialias(img_t *img) {
-	if (!img || !img->im)
+	if (img == NULL || img->im == NULL)
 		return;
 
 	img->aa = !img->aa;
@@ -664,7 +666,7 @@ void img_toggle_antialias(img_t *img) {
 }
 
 bool img_frame_goto(img_t *img, int n) {
-	if (!img || !img->im)
+	if (img == NULL || img->im == NULL)
 		return false;
 	if (n < 0 || n >= img->multi.cnt || n == img->multi.sel)
 		return false;
@@ -682,7 +684,7 @@ bool img_frame_goto(img_t *img, int n) {
 }
 
 bool img_frame_navigate(img_t *img, int d) {
-	if (!img || !img->im || !img->multi.cnt || !d)
+	if (img == NULL|| img->im == NULL || img->multi.cnt == 0 || d == 0)
 		return false;
 
 	d += img->multi.sel;
@@ -695,7 +697,7 @@ bool img_frame_navigate(img_t *img, int d) {
 }
 
 bool img_frame_animate(img_t *img, bool restart) {
-	if (!img || !img->im || !img->multi.cnt)
+	if (img == NULL || img->im == NULL || img->multi.cnt == 0)
 		return false;
 
 	if (img->multi.sel + 1 >= img->multi.cnt) {
diff --git a/main.c b/main.c
index 18db413..876ab4e 100644
--- a/main.c
+++ b/main.c
@@ -73,9 +73,10 @@ timeout_t timeouts[] = {
 };
 
 void cleanup() {
-	static int in = 0;
+	static bool in = false;
 
-	if (!in++) {
+	if (!in) {
+		in = true;
 		img_close(&img, false);
 		tns_free(&tns);
 		win_close(&win);
@@ -83,10 +84,10 @@ void cleanup() {
 }
 
 void check_add_file(char *filename) {
-	if (!filename || !*filename)
+	if (filename == NULL || *filename == '\0')
 		return;
 
-	if (access(filename, R_OK)) {
+	if (access(filename, R_OK) < 0) {
 		warn("could not open file: %s", filename);
 		return;
 	}
@@ -97,7 +98,7 @@ void check_add_file(char *filename) {
 	}
 	if (*filename != '/') {
 		files[fileidx].path = absolute_path(filename);
-		if (!files[fileidx].path) {
+		if (files[fileidx].path == NULL) {
 			warn("could not get absolute path of file: %s\n", filename);
 			return;
 		}
@@ -173,7 +174,7 @@ bool check_timeouts(struct timeval *t) {
 			tdiff = tv_diff(&timeouts[i].when, &now);
 			if (tdiff <= 0) {
 				timeouts[i].active = false;
-				if (timeouts[i].handler)
+				if (timeouts[i].handler != NULL)
 					timeouts[i].handler();
 				i = tmin = -1;
 			} else if (tmin < 0 || tdiff < tmin) {
@@ -182,7 +183,7 @@ bool check_timeouts(struct timeval *t) {
 		}
 		i++;
 	}
-	if (tmin > 0 && t)
+	if (tmin > 0 && t != NULL)
 		tv_set_msec(t, tmin);
 	return tmin > 0;
 }
@@ -204,12 +205,12 @@ void load_image(int new) {
 
 	files[new].loaded = true;
 	fileidx = new;
-	if (!stat(files[new].path, &fstats))
+	if (stat(files[new].path, &fstats) == 0)
 		filesize = fstats.st_size;
 	else
 		filesize = 0;
 
-	if (img.multi.cnt && img.multi.animate)
+	if (img.multi.cnt > 0 && img.multi.animate)
 		set_timeout(animate, img.multi.frames[img.multi.sel].delay, true);
 	else
 		reset_timeout(animate);
@@ -238,7 +239,7 @@ void update_title() {
 		} else {
 			sshow_info[0] = '\0';
 		}
-		if (img.multi.cnt)
+		if (img.multi.cnt > 0)
 			snprintf(frame_info, sizeof(frame_info), "{%d/%d} ",
 			         img.multi.sel + 1, img.multi.cnt);
 		else
@@ -329,14 +330,14 @@ void on_keypress(XKeyEvent *kev) {
 	KeySym ksym;
 	char key;
 
-	if (!kev)
+	if (kev == NULL)
 		return;
 
 	XLookupString(kev, &key, 1, &ksym, NULL);
 
 	for (i = 0; i < ARRLEN(keys); i++) {
 		if (keys[i].ksym == ksym && keymask(&keys[i], kev->state)) {
-			if (keys[i].cmd && keys[i].cmd(keys[i].arg))
+			if (keys[i].cmd != NULL && keys[i].cmd(keys[i].arg))
 				redraw();
 			return;
 		}
@@ -346,7 +347,7 @@ void on_keypress(XKeyEvent *kev) {
 void on_buttonpress(XButtonEvent *bev) {
 	int i, sel;
 
-	if (!bev)
+	if (bev == NULL)
 		return;
 
 	if (mode == MODE_IMAGE) {
@@ -357,7 +358,7 @@ void on_buttonpress(XButtonEvent *bev) {
 			if (buttons[i].button == bev->button &&
 			    buttonmask(&buttons[i], bev->state))
 			{
-				if (buttons[i].cmd && buttons[i].cmd(buttons[i].arg))
+				if (buttons[i].cmd != NULL && buttons[i].cmd(buttons[i].arg))
 					redraw();
 				return;
 			}
@@ -397,9 +398,9 @@ void run() {
 
 	redraw();
 
-	while (1) {
+	while (true) {
 		while (mode == MODE_THUMB && tns.cnt < filecnt &&
-		       !XPending(win.env.dpy))
+		       XPending(win.env.dpy) == 0)
 		{
 			/* load thumbnails */
 			set_timeout(redraw, TO_REDRAW_THUMBS, false);
@@ -413,7 +414,7 @@ void run() {
 				check_timeouts(NULL);
 		}
 
-		while (!XPending(win.env.dpy) && check_timeouts(&timeout)) {
+		while (XPending(win.env.dpy) == 0 && check_timeouts(&timeout)) {
 			/* wait for timeouts */
 			xfd = ConnectionNumber(win.env.dpy);
 			FD_ZERO(&fds);
@@ -421,35 +422,34 @@ void run() {
 			select(xfd + 1, &fds, 0, 0, &timeout);
 		}
 
-		if (!XNextEvent(win.env.dpy, &ev)) {
+		XNextEvent(win.env.dpy, &ev);
+		switch (ev.type) {
 			/* handle events */
-			switch (ev.type) {
-				case ButtonPress:
-					on_buttonpress(&ev.xbutton);
-					break;
-				case ClientMessage:
-					if ((Atom) ev.xclient.data.l[0] == wm_delete_win)
-						return;
-					break;
-				case ConfigureNotify:
-					if (win_configure(&win, &ev.xconfigure)) {
-						set_timeout(redraw, TO_REDRAW_RESIZE, false);
-						if (mode == MODE_IMAGE)
-							img.checkpan = true;
-						else
-							tns.dirty = true;
-					}
-					break;
-				case KeyPress:
-					on_keypress(&ev.xkey);
-					break;
-				case MotionNotify:
-					if (mode == MODE_IMAGE) {
-						win_set_cursor(&win, CURSOR_ARROW);
-						set_timeout(reset_cursor, TO_CURSOR_HIDE, true);
-					}
-					break;
-			}
+			case ButtonPress:
+				on_buttonpress(&ev.xbutton);
+				break;
+			case ClientMessage:
+				if ((Atom) ev.xclient.data.l[0] == wm_delete_win)
+					return;
+				break;
+			case ConfigureNotify:
+				if (win_configure(&win, &ev.xconfigure)) {
+					set_timeout(redraw, TO_REDRAW_RESIZE, false);
+					if (mode == MODE_IMAGE)
+						img.checkpan = true;
+					else
+						tns.dirty = true;
+				}
+				break;
+			case KeyPress:
+				on_keypress(&ev.xkey);
+				break;
+			case MotionNotify:
+				if (mode == MODE_IMAGE) {
+					win_set_cursor(&win, CURSOR_ARROW);
+					set_timeout(reset_cursor, TO_CURSOR_HIDE, true);
+				}
+				break;
 		}
 	}
 }
@@ -474,7 +474,7 @@ int main(int argc, char **argv) {
 		exit(EXIT_SUCCESS);
 	}
 
-	if (!options->filecnt) {
+	if (options->filecnt == 0) {
 		print_usage();
 		exit(EXIT_FAILURE);
 	}
@@ -495,25 +495,29 @@ int main(int argc, char **argv) {
 				filename[len-1] = '\0';
 			check_add_file(filename);
 		}
-		if (filename)
+		if (filename != NULL)
 			free(filename);
 	} else {
 		for (i = 0; i < options->filecnt; i++) {
 			filename = options->filenames[i];
 
-			if (stat(filename, &fstats) || !S_ISDIR(fstats.st_mode)) {
+			if (stat(filename, &fstats) < 0) {
+				warn("could not stat file: %s", filename);
+				continue;
+			}
+			if (!S_ISDIR(fstats.st_mode)) {
 				check_add_file(filename);
 			} else {
 				if (!options->recursive) {
 					warn("ignoring directory: %s", filename);
 					continue;
 				}
-				if (r_opendir(&dir, filename)) {
+				if (r_opendir(&dir, filename) < 0) {
 					warn("could not open directory: %s", filename);
 					continue;
 				}
 				start = fileidx;
-				while ((filename = r_readdir(&dir))) {
+				while ((filename = r_readdir(&dir)) != NULL) {
 					check_add_file(filename);
 					free((void*) filename);
 				}
@@ -524,7 +528,7 @@ int main(int argc, char **argv) {
 		}
 	}
 
-	if (!fileidx) {
+	if (fileidx == 0) {
 		fprintf(stderr, "sxiv: no valid image file given, aborting\n");
 		exit(EXIT_FAILURE);
 	}
@@ -548,7 +552,7 @@ int main(int argc, char **argv) {
 	}
 
 	win_open(&win);
-	
+
 	run();
 	cleanup();
 
diff --git a/options.c b/options.c
index 1405dc4..2226040 100644
--- a/options.c
+++ b/options.c
@@ -95,7 +95,7 @@ void parse_options(int argc, char **argv) {
 				print_usage();
 				exit(EXIT_SUCCESS);
 			case 'n':
-				if (!sscanf(optarg, "%d", &t) || t < 1) {
+				if (sscanf(optarg, "%d", &t) <= 0 || t < 1) {
 					fprintf(stderr, "sxiv: invalid argument for option -n: %s\n",
 					        optarg);
 					exit(EXIT_FAILURE);
@@ -127,7 +127,7 @@ void parse_options(int argc, char **argv) {
 				break;
 			case 'z':
 				_options.scalemode = SCALE_ZOOM;
-				if (!sscanf(optarg, "%d", &t) || t <= 0) {
+				if (sscanf(optarg, "%d", &t) <= 0 || t <= 0) {
 					fprintf(stderr, "sxiv: invalid argument for option -z: %s\n",
 					        optarg);
 					exit(EXIT_FAILURE);
diff --git a/thumbs.c b/thumbs.c
index 4a7c0db..b2c9e0e 100644
--- a/thumbs.c
+++ b/thumbs.c
@@ -41,23 +41,23 @@ char *cache_dir = NULL;
 bool tns_cache_enabled() {
 	struct stat stats;
 
-	return cache_dir && !stat(cache_dir, &stats) && S_ISDIR(stats.st_mode) &&
-	       !access(cache_dir, W_OK);
+	return cache_dir != NULL && stat(cache_dir, &stats) == 0 &&
+	       S_ISDIR(stats.st_mode) && access(cache_dir, W_OK) == 0;
 }
 
 char* tns_cache_filepath(const char *filepath) {
 	size_t len;
 	char *cfile = NULL;
 
-	if (!cache_dir || !filepath || *filepath != '/')
+	if (cache_dir == NULL || filepath == NULL || *filepath != '/')
 		return NULL;
 	
-	if (strncmp(filepath, cache_dir, strlen(cache_dir))) {
+	if (strncmp(filepath, cache_dir, strlen(cache_dir)) != 0) {
+		/* don't cache images inside the cache directory! */
 		len = strlen(cache_dir) + strlen(filepath) + 6;
 		cfile = (char*) s_malloc(len);
 		snprintf(cfile, len, "%s/%s.png", cache_dir, filepath + 1);
 	}
-	
 	return cfile;
 }
 
@@ -66,18 +66,16 @@ Imlib_Image* tns_cache_load(const char *filepath) {
 	struct stat cstats, fstats;
 	Imlib_Image *im = NULL;
 
-	if (!filepath)
+	if (filepath == NULL)
+		return NULL;
+	if (stat(filepath, &fstats) < 0)
 		return NULL;
 
-	if (stat(filepath, &fstats))
-		return NULL;
-
-	if ((cfile = tns_cache_filepath(filepath))) {
-		if (!stat(cfile, &cstats) && cstats.st_mtime == fstats.st_mtime)
+	if ((cfile = tns_cache_filepath(filepath)) != NULL) {
+		if (stat(cfile, &cstats) == 0 && cstats.st_mtime == fstats.st_mtime)
 			im = imlib_load_image(cfile);
 		free(cfile);
 	}
-
 	return im;
 }
 
@@ -87,32 +85,35 @@ void tns_cache_write(thumb_t *t, bool force) {
 	struct utimbuf times;
 	Imlib_Load_Error err = 0;
 
-	if (!t || !t->im || !t->file || !t->file->name || !t->file->path)
+	if (t == NULL || t->im == NULL)
+		return;
+	if (t->file == NULL || t->file->name == NULL || t->file->path == NULL)
+		return;
+	if (stat(t->file->path, &fstats) < 0)
 		return;
 
-	if (stat(t->file->path, &fstats))
-		return;
-
-	if ((cfile = tns_cache_filepath(t->file->path))) {
-		if (force || stat(cfile, &cstats) || cstats.st_mtime != fstats.st_mtime) {
-			if ((dirend = strrchr(cfile, '/'))) {
+	if ((cfile = tns_cache_filepath(t->file->path)) != NULL) {
+		if (force || stat(cfile, &cstats) < 0 ||
+		    cstats.st_mtime != fstats.st_mtime)
+		{
+			if ((dirend = strrchr(cfile, '/')) != NULL) {
 				*dirend = '\0';
 				err = r_mkdir(cfile);
 				*dirend = '/';
 			}
 
-			if (!err) {
+			if (err == 0) {
 				imlib_context_set_image(t->im);
 				imlib_image_set_format("png");
 				imlib_save_image_with_error_return(cfile, &err);
 			}
 
-			if (err) {
-				warn("could not cache thumbnail: %s", t->file->name);
-			} else {
+			if (err == 0) {
 				times.actime = fstats.st_atime;
 				times.modtime = fstats.st_mtime;
 				utime(cfile, &times);
+			} else {
+				warn("could not cache thumbnail: %s", t->file->name);
 			}
 		}
 		free(cfile);
@@ -125,33 +126,32 @@ void tns_clean_cache(tns_t *tns) {
 	char *cfile, *filename, *tpos;
 	r_dir_t dir;
 
-	if (!cache_dir)
+	if (cache_dir == NULL)
 		return;
 	
-	if (r_opendir(&dir, cache_dir)) {
+	if (r_opendir(&dir, cache_dir) < 0) {
 		warn("could not open thumbnail cache directory: %s", cache_dir);
 		return;
 	}
 
 	dirlen = strlen(cache_dir);
 
-	while ((cfile = r_readdir(&dir))) {
+	while ((cfile = r_readdir(&dir)) != NULL) {
 		filename = cfile + dirlen;
 		delete = false;
 
-		if ((tpos = strrchr(filename, '.'))) {
+		if ((tpos = strrchr(filename, '.')) != NULL) {
 			*tpos = '\0';
-			if (access(filename, F_OK))
+			if (access(filename, F_OK) < 0)
 				delete = true;
 			*tpos = '.';
 		}
-
-		if (delete && unlink(cfile))
-			warn("could not delete cache file: %s", cfile);
-
+		if (delete) {
+			if (unlink(cfile) < 0)
+				warn("could not delete cache file: %s", cfile);
+		}
 		free(cfile);
 	}
-
 	r_closedir(&dir);
 }
 
@@ -160,10 +160,10 @@ void tns_init(tns_t *tns, int cnt, win_t *win) {
 	int len;
 	char *homedir;
 
-	if (!tns)
+	if (tns == NULL)
 		return;
 
-	if (cnt) {
+	if (cnt > 0) {
 		tns->thumbs = (thumb_t*) s_malloc(cnt * sizeof(thumb_t));
 		memset(tns->thumbs, 0, cnt * sizeof(thumb_t));
 	} else {
@@ -176,8 +176,8 @@ void tns_init(tns_t *tns, int cnt, win_t *win) {
 	tns->alpha = true;
 	tns->dirty = false;
 
-	if ((homedir = getenv("HOME"))) {
-		if (cache_dir)
+	if ((homedir = getenv("HOME")) != NULL) {
+		if (cache_dir != NULL)
 			free(cache_dir);
 		len = strlen(homedir) + 10;
 		cache_dir = (char*) s_malloc(len * sizeof(char));
@@ -190,12 +190,12 @@ void tns_init(tns_t *tns, int cnt, win_t *win) {
 void tns_free(tns_t *tns) {
 	int i;
 
-	if (!tns)
+	if (tns != NULL)
 		return;
 
-	if (tns->thumbs) {
+	if (tns->thumbs != NULL) {
 		for (i = 0; i < tns->cnt; i++) {
-			if (tns->thumbs[i].im) {
+			if (tns->thumbs[i].im != NULL) {
 				imlib_context_set_image(tns->thumbs[i].im);
 				imlib_free_image();
 			}
@@ -204,7 +204,7 @@ void tns_free(tns_t *tns) {
 		tns->thumbs = NULL;
 	}
 
-	if (cache_dir) {
+	if (cache_dir != NULL) {
 		free(cache_dir);
 		cache_dir = NULL;
 	}
@@ -220,31 +220,34 @@ bool tns_load(tns_t *tns, int n, const fileinfo_t *file,
 	Imlib_Image *im;
 	const char *fmt;
 
-	if (!tns || !tns->thumbs || !file || !file->name || !file->path)
+	if (tns == NULL || tns->thumbs == NULL)
+		return false;
+	if (file == NULL || file->name == NULL || file->path == NULL)
 		return false;
-
 	if (n < 0 || n >= tns->cap)
 		return false;
 
 	t = &tns->thumbs[n];
 	t->file = file;
 
-	if (t->im) {
+	if (t->im != NULL) {
 		imlib_context_set_image(t->im);
 		imlib_free_image();
 	}
 
 	if ((use_cache = tns_cache_enabled())) {
-		if (!force && (im = tns_cache_load(file->path)))
+		if (!force && (im = tns_cache_load(file->path)) != NULL)
 			cache_hit = true;
 	}
 
-	if (!cache_hit &&
-	    (access(file->path, R_OK) || !(im = imlib_load_image(file->path))))
-	{
-		if (!silent)
-			warn("could not open image: %s", file->name);
-		return false;
+	if (!cache_hit) {
+		if (access(file->path, R_OK) < 0 ||
+		    (im = imlib_load_image(file->path)) == NULL)
+		{
+			if (!silent)
+				warn("could not open image: %s", file->name);
+			return false;
+		}
 	}
 
 	imlib_context_set_image(im);
@@ -267,7 +270,8 @@ bool tns_load(tns_t *tns, int n, const fileinfo_t *file,
 	t->w = z * w;
 	t->h = z * h;
 
-	if (!(t->im = imlib_create_cropped_scaled_image(0, 0, w, h, t->w, t->h)))
+	t->im = imlib_create_cropped_scaled_image(0, 0, w, h, t->w, t->h);
+	if (t->im == NULL)
 		die("could not allocate memory");
 
 	imlib_free_image_and_decache();
@@ -282,7 +286,7 @@ bool tns_load(tns_t *tns, int n, const fileinfo_t *file,
 void tns_check_view(tns_t *tns, bool scrolled) {
 	int r;
 
-	if (!tns)
+	if (tns == NULL)
 		return;
 
 	tns->first -= tns->first % tns->cols;
@@ -311,7 +315,7 @@ void tns_render(tns_t *tns) {
 	win_t *win;
 	int i, cnt, r, x, y;
 
-	if (!tns || !tns->thumbs || !tns->win)
+	if (tns == NULL || tns->thumbs == NULL || tns->win == NULL)
 		return;
 	if (!tns->dirty)
 		return;
@@ -345,7 +349,7 @@ void tns_render(tns_t *tns) {
 		t->y = y + (THUMB_SIZE - t->h) / 2;
 		imlib_context_set_image(t->im);
 
-		if (imlib_image_has_alpha() && !tns->alpha)
+		if (!tns->alpha && imlib_image_has_alpha())
 			win_draw_rect(win, win->pm, t->x, t->y, t->w, t->h, true, 0, win->white);
 
 		imlib_render_image_part_on_drawable_at_size(0, 0, t->w, t->h,
@@ -357,7 +361,6 @@ void tns_render(tns_t *tns) {
 			x += thumb_dim;
 		}
 	}
-
 	tns->dirty = false;
 	tns_highlight(tns, tns->sel, true);
 }
@@ -368,7 +371,7 @@ void tns_highlight(tns_t *tns, int n, bool hl) {
 	int x, y;
 	unsigned long col;
 
-	if (!tns || !tns->thumbs || !tns->win)
+	if (tns == NULL || tns->thumbs == NULL || tns->win == NULL)
 		return;
 
 	win = tns->win;
@@ -388,14 +391,13 @@ void tns_highlight(tns_t *tns, int n, bool hl) {
 		win_draw_rect(win, win->pm, x - 3, y - 3, THUMB_SIZE + 6, THUMB_SIZE + 6,
 		              false, 2, col);
 	}
-
 	win_draw(win);
 }
 
 bool tns_move_selection(tns_t *tns, direction_t dir) {
 	int old;
 
-	if (!tns || !tns->thumbs)
+	if (tns == NULL || tns->thumbs == NULL)
 		return false;
 
 	old = tns->sel;
@@ -425,14 +427,13 @@ bool tns_move_selection(tns_t *tns, direction_t dir) {
 		if (!tns->dirty)
 			tns_highlight(tns, tns->sel, true);
 	}
-
 	return tns->sel != old;
 }
 
 bool tns_scroll(tns_t *tns, direction_t dir) {
 	int old;
 
-	if (!tns)
+	if (tns == NULL)
 		return false;
 
 	old = tns->first;
@@ -446,16 +447,14 @@ bool tns_scroll(tns_t *tns, direction_t dir) {
 		tns_check_view(tns, true);
 		tns->dirty = true;
 	}
-
 	return tns->first != old;
 }
 
 int tns_translate(tns_t *tns, int x, int y) {
 	int n;
 
-	if (!tns || !tns->thumbs)
+	if (tns == NULL || tns->thumbs == NULL)
 		return -1;
-
 	if (x < tns->x || y < tns->y)
 		return -1;
 
diff --git a/util.c b/util.c
index a205312..772908d 100644
--- a/util.c
+++ b/util.c
@@ -39,13 +39,15 @@ void cleanup();
 void* s_malloc(size_t size) {
 	void *ptr;
 	
-	if (!(ptr = malloc(size)))
+	ptr = malloc(size);
+	if (ptr == NULL)
 		die("could not allocate memory");
 	return ptr;
 }
 
 void* s_realloc(void *ptr, size_t size) {
-	if (!(ptr = realloc(ptr, size)))
+	ptr = realloc(ptr, size);
+	if (ptr == NULL)
 		die("could not allocate memory");
 	return ptr;
 }
@@ -53,8 +55,9 @@ void* s_realloc(void *ptr, size_t size) {
 char* s_strdup(char *s) {
 	char *d = NULL;
 
-	if (s) {
-		if (!(d = malloc(strlen(s) + 1)))
+	if (s != NULL) {
+		d = malloc(strlen(s) + 1);
+		if (d == NULL)
 			die("could not allocate memory");
 		strcpy(d, s);
 	}
@@ -64,7 +67,7 @@ char* s_strdup(char *s) {
 void warn(const char* fmt, ...) {
 	va_list args;
 
-	if (!fmt || options->quiet)
+	if (fmt == NULL || options->quiet)
 		return;
 
 	va_start(args, fmt);
@@ -77,7 +80,7 @@ void warn(const char* fmt, ...) {
 void die(const char* fmt, ...) {
 	va_list args;
 
-	if (!fmt)
+	if (fmt == NULL)
 		return;
 
 	va_start(args, fmt);
@@ -94,17 +97,17 @@ ssize_t get_line(char **buf, size_t *n, FILE *stream) {
 	size_t len;
 	char *s;
 
-	if (!stream || feof(stream) || ferror(stream))
+	if (stream == NULL || feof(stream) || ferror(stream))
 		return -1;
 
-	if (!*buf || !*n) {
+	if (*buf == NULL || *n == 0) {
 		*n = BUF_SIZE;
 		*buf = (char*) s_malloc(*n);
 	}
 	s = *buf;
 
-	while (1) {
-		if (!fgets(s, *n - (s - *buf), stream))
+	while (true) {
+		if (fgets(s, *n - (s - *buf), stream) == NULL)
 			return -1;
 		len = strlen(s);
 		if (feof(stream))
@@ -119,7 +122,6 @@ ssize_t get_line(char **buf, size_t *n, FILE *stream) {
 			s += len;
 		}
 	}
-
 	return s - *buf + len;
 }
 
@@ -147,41 +149,41 @@ char* absolute_path(const char *filename) {
 	char *dir, *dirname = NULL, *path = NULL, *s;
 	char *cwd = NULL, *twd = NULL;
 
-	if (!filename || *filename == '\0' || *filename == '/')
+	if (filename == NULL || *filename == '\0' || *filename == '/')
 		return NULL;
 
 	len = FNAME_LEN;
 	cwd = (char*) s_malloc(len);
-	while (!(s = getcwd(cwd, len)) && errno == ERANGE) {
+	while ((s = getcwd(cwd, len)) == NULL && errno == ERANGE) {
 		len *= 2;
 		cwd = (char*) s_realloc(cwd, len);
 	}
-	if (!s)
+	if (s == NULL)
 		goto error;
 
 	s = strrchr(filename, '/');
-	if (s) {
+	if (s != NULL) {
 		len = s - filename;
 		dirname = (char*) s_malloc(len + 1);
 		strncpy(dirname, filename, len);
 		dirname[len] = '\0';
 		basename = s + 1;
 
-		if (chdir(cwd))
+		if (chdir(cwd) < 0)
 			/* we're not able to come back afterwards */
 			goto error;
-		if (chdir(dirname))
+		if (chdir(dirname) < 0)
 			goto error;
 
 		len = FNAME_LEN;
 		twd = (char*) s_malloc(len);
-		while (!(s = getcwd(twd, len)) && errno == ERANGE) {
+		while ((s = getcwd(twd, len)) == NULL && errno == ERANGE) {
 			len *= 2;
 			twd = (char*) s_realloc(twd, len);
 		}
-		if (chdir(cwd))
+		if (chdir(cwd) < 0)
 			die("could not revert to prior working directory");
-		if (!s)
+		if (s == NULL)
 			goto error;
 		dir = twd;
 	} else {
@@ -197,27 +199,27 @@ char* absolute_path(const char *filename) {
 	goto end;
 
 error:
-	if (path) {
+	if (path != NULL) {
 		free(path);
 		path = NULL;
 	}
 
 end:
-	if (dirname)
+	if (dirname != NULL)
 		free(dirname);
-	if (cwd)
+	if (cwd != NULL)
 		free(cwd);
-	if (twd)
+	if (twd != NULL)
 		free(twd);
 
 	return path;
 }
 
 int r_opendir(r_dir_t *rdir, const char *dirname) {
-	if (!rdir || !dirname || !*dirname)
+	if (rdir == NULL || dirname == NULL || *dirname == '\0')
 		return -1;
 
-	if (!(rdir->dir = opendir(dirname))) {
+	if ((rdir->dir = opendir(dirname)) == NULL) {
 		rdir->name = NULL;
 		rdir->stack = NULL;
 		return -1;
@@ -236,22 +238,22 @@ int r_opendir(r_dir_t *rdir, const char *dirname) {
 int r_closedir(r_dir_t *rdir) {
 	int ret = 0;
 
-	if (!rdir)
+	if (rdir == NULL)
 		return -1;
 	
-	if (rdir->stack) {
+	if (rdir->stack != NULL) {
 		while (rdir->stlen > 0)
 			free(rdir->stack[--rdir->stlen]);
 		free(rdir->stack);
 		rdir->stack = NULL;
 	}
 
-	if (rdir->dir) {
-		if (!(ret = closedir(rdir->dir)))
+	if (rdir->dir != NULL) {
+		if ((ret = closedir(rdir->dir)) == 0)
 			rdir->dir = NULL;
 	}
 
-	if (rdir->d && rdir->name) {
+	if (rdir->d != 0 && rdir->name != NULL) {
 		free(rdir->name);
 		rdir->name = NULL;
 	}
@@ -265,11 +267,11 @@ char* r_readdir(r_dir_t *rdir) {
 	struct dirent *dentry;
 	struct stat fstats;
 
-	if (!rdir || !rdir->dir || !rdir->name)
+	if (rdir == NULL || rdir->dir == NULL || rdir->name == NULL)
 		return NULL;
 
-	while (1) {
-		if (rdir->dir && (dentry = readdir(rdir->dir))) {
+	while (true) {
+		if (rdir->dir != NULL && (dentry = readdir(rdir->dir)) != NULL) {
 			if (streq(dentry->d_name, ".") || streq(dentry->d_name, ".."))
 				continue;
 
@@ -279,7 +281,9 @@ char* r_readdir(r_dir_t *rdir) {
 			         rdir->name[strlen(rdir->name)-1] == '/' ? "" : "/",
 			         dentry->d_name);
 
-			if (!stat(filename, &fstats) && S_ISDIR(fstats.st_mode)) {
+			if (stat(filename, &fstats) < 0)
+				continue;
+			if (S_ISDIR(fstats.st_mode)) {
 				/* put subdirectory on the stack */
 				if (rdir->stlen == rdir->stcap) {
 					rdir->stcap *= 2;
@@ -295,19 +299,17 @@ char* r_readdir(r_dir_t *rdir) {
 		if (rdir->stlen > 0) {
 			/* open next subdirectory */
 			closedir(rdir->dir);
-			if (rdir->d)
+			if (rdir->d != 0)
 				free(rdir->name);
 			rdir->name = rdir->stack[--rdir->stlen];
 			rdir->d = 1;
-			if (!(rdir->dir = opendir(rdir->name)))
+			if ((rdir->dir = opendir(rdir->name)) == NULL)
 				warn("could not open directory: %s", rdir->name);
 			continue;
 		}
-
 		/* no more entries */
 		break;
 	}
-
 	return NULL;
 }
 
@@ -316,10 +318,10 @@ int r_mkdir(const char *path) {
 	struct stat stats;
 	int err = 0;
 
-	if (!path || !*path)
+	if (path == NULL || *path == '\0')
 		return -1;
 
-	if (!stat(path, &stats)) {
+	if (stat(path, &stats) == 0) {
 		if (S_ISDIR(stats.st_mode)) {
 			return 0;
 		} else {
@@ -331,16 +333,16 @@ int r_mkdir(const char *path) {
 	d = dir = (char*) s_malloc(strlen(path) + 1);
 	strcpy(dir, path);
 
-	while (d != NULL && !err) {
+	while (d != NULL && err == 0) {
 		d = strchr(d + 1, '/');
 		if (d != NULL)
 			*d = '\0';
-		if (access(dir, F_OK) && errno == ENOENT) {
-			if (mkdir(dir, 0755)) {
+		if (access(dir, F_OK) < 0 && errno == ENOENT) {
+			if (mkdir(dir, 0755) < 0) {
 				warn("could not create directory: %s", dir);
 				err = -1;
 			}
-		} else if (stat(dir, &stats) || !S_ISDIR(stats.st_mode)) {
+		} else if (stat(dir, &stats) < 0 || !S_ISDIR(stats.st_mode)) {
 			warn("not a directory: %s", dir);
 			err = -1;
 		}
diff --git a/window.c b/window.c
index fd6229c..e53263a 100644
--- a/window.c
+++ b/window.c
@@ -40,11 +40,11 @@ void win_init(win_t *win) {
 	win_env_t *e;
 	XColor col;
 
-	if (!win)
+	if (win == NULL)
 		return;
 
 	e = &win->env;
-	if (!(e->dpy = XOpenDisplay(NULL)))
+	if ((e->dpy = XOpenDisplay(NULL)) == NULL)
 		die("could not open display");
 
 	e->scr = DefaultScreen(e->dpy);
@@ -58,7 +58,7 @@ void win_init(win_t *win) {
 	win->white = WhitePixel(e->dpy, e->scr);
 
 	if (XAllocNamedColor(e->dpy, DefaultColormap(e->dpy, e->scr), BG_COLOR,
-		                   &col, &col))
+		                   &col, &col) != 0)
 	{
 		win->bgcol = col.pixel;
 	} else {
@@ -66,7 +66,7 @@ void win_init(win_t *win) {
 	}
 
 	if (XAllocNamedColor(e->dpy, DefaultColormap(e->dpy, e->scr), SEL_COLOR,
-		                   &col, &col))
+		                   &col, &col) != 0)
 	{
 		win->selcol = col.pixel;
 	} else {
@@ -81,7 +81,7 @@ void win_init(win_t *win) {
 void win_set_sizehints(win_t *win) {
 	XSizeHints sizehints;
 
-	if (!win || !win->xwin)
+	if (win == NULL || win->xwin == None)
 		return;
 
 	sizehints.flags = PMinSize | PMaxSize;
@@ -100,32 +100,32 @@ void win_open(win_t *win) {
 	Pixmap none;
 	int gmask;
 
-	if (!win)
+	if (win == NULL)
 		return;
 
 	e = &win->env;
 
 	/* determine window offsets, width & height */
-	if (!options->geometry)
+	if (options->geometry == NULL)
 		gmask = 0;
 	else
 		gmask = XParseGeometry(options->geometry, &win->x, &win->y,
 		                       &win->w, &win->h);
-	if (!(gmask & WidthValue))
+	if ((gmask & WidthValue) == 0)
 		win->w = WIN_WIDTH;
 	if (win->w > e->scrw)
 		win->w = e->scrw;
-	if (!(gmask & HeightValue))
+	if ((gmask & HeightValue) == 0)
 		win->h = WIN_HEIGHT;
 	if (win->h > e->scrh)
 		win->h = e->scrh;
-	if (!(gmask & XValue))
+	if ((gmask & XValue) == 0)
 		win->x = (e->scrw - win->w) / 2;
-	else if (gmask & XNegative)
+	else if ((gmask & XNegative) != 0)
 		win->x += e->scrw - win->w;
-	if (!(gmask & YValue))
+	if ((gmask & YValue) == 0)
 		win->y = (e->scrh - win->h) / 2;
-	else if (gmask & YNegative)
+	else if ((gmask & YNegative) != 0)
 		win->y += e->scrh - win->h;
 
 	win->xwin = XCreateWindow(e->dpy, RootWindow(e->dpy, e->scr),
@@ -141,8 +141,8 @@ void win_open(win_t *win) {
 	chand = XCreateFontCursor(e->dpy, XC_fleur);
 	cwatch = XCreateFontCursor(e->dpy, XC_watch);
 
-	if (!XAllocNamedColor(e->dpy, DefaultColormap(e->dpy, e->scr), "black",
-		                    &col, &col))
+	if (XAllocNamedColor(e->dpy, DefaultColormap(e->dpy, e->scr), "black",
+		                    &col, &col) == 0)
 	{
 		die("could not allocate color: black");
 	}
@@ -171,7 +171,7 @@ void win_open(win_t *win) {
 }
 
 void win_close(win_t *win) {
-	if (!win || !win->xwin)
+	if (win == NULL || win->xwin == None)
 		return;
 
 	XFreeCursor(win->env.dpy, carrow);
@@ -188,7 +188,7 @@ void win_close(win_t *win) {
 bool win_configure(win_t *win, XConfigureEvent *c) {
 	bool changed;
 
-	if (!win)
+	if (win == NULL)
 		return false;
 	
 	changed = win->w != c->width || win->h != c->height;
@@ -203,7 +203,7 @@ bool win_configure(win_t *win, XConfigureEvent *c) {
 }
 
 bool win_moveresize(win_t *win, int x, int y, unsigned int w, unsigned int h) {
-	if (!win || !win->xwin)
+	if (win == NULL || win->xwin == None)
 		return false;
 
 	x = MAX(0, x);
@@ -231,7 +231,7 @@ void win_toggle_fullscreen(win_t *win) {
 	XEvent ev;
 	XClientMessageEvent *cm;
 
-	if (!win || !win->xwin)
+	if (win == NULL || win->xwin == None)
 		return;
 
 	win->fullscreen = !win->fullscreen;
@@ -255,13 +255,13 @@ void win_clear(win_t *win) {
 	win_env_t *e;
 	XGCValues gcval;
 
-	if (!win || !win->xwin)
+	if (win == NULL || win->xwin == None)
 		return;
 
 	e = &win->env;
 	gcval.foreground = win->fullscreen ? win->black : win->bgcol;
 
-	if (win->pm)
+	if (win->pm != None)
 		XFreePixmap(e->dpy, win->pm);
 	win->pm = XCreatePixmap(e->dpy, win->xwin, e->scrw, e->scrh, e->depth);
 
@@ -270,7 +270,7 @@ void win_clear(win_t *win) {
 }
 
 void win_draw(win_t *win) {
-	if (!win || !win->xwin)
+	if (win == NULL || win->xwin == None)
 		return;
 
 	XSetWindowBackgroundPixmap(win->env.dpy, win->xwin, win->pm);
@@ -281,7 +281,7 @@ void win_draw_rect(win_t *win, Pixmap pm, int x, int y, int w, int h,
 		bool fill, int lw, unsigned long col) {
 	XGCValues gcval;
 
-	if (!win || !pm)
+	if (win == NULL || pm == None)
 		return;
 
 	gcval.line_width = lw;
@@ -295,10 +295,10 @@ void win_draw_rect(win_t *win, Pixmap pm, int x, int y, int w, int h,
 }
 
 void win_set_title(win_t *win, const char *title) {
-	if (!win || !win->xwin)
+	if (win == NULL || win->xwin == None)
 		return;
 
-	if (!title)
+	if (title == NULL)
 		title = "sxiv";
 
 	XStoreName(win->env.dpy, win->xwin, title);
@@ -315,7 +315,7 @@ void win_set_title(win_t *win, const char *title) {
 }
 
 void win_set_cursor(win_t *win, cursor_t cursor) {
-	if (!win || !win->xwin)
+	if (win == NULL || win->xwin == None)
 		return;
 
 	switch (cursor) {