allow disabling anti-aliasing via cli flag

simply running nsxiv with `--anti-alias` will enable anti-aliasing, and
running it with `--anti-alias=no` will disable it.

the cli flag will overwrite the config.h default.

Closes: https://codeberg.org/nsxiv/nsxiv/issues/349

config.def.h

@@ -42,11 +42,6 @@ static const int    GAMMA_RANGE = 32;
 /* command i_scroll pans image 1/PAN_FRACTION of screen width/height */
 static const int PAN_FRACTION = 5;
 
-/* if false, pixelate images at zoom level != 100%,
- * toggled with 'a' key binding
- */
-static const bool ANTI_ALIAS = true;
-
 /* if true, use a checkerboard background for alpha layer,
  * toggled with 'A' key binding
  */
@@ -64,6 +59,14 @@ static const int CACHE_SIZE_MEM_PERCENTAGE = 3;          /* use 3% of total memo
 static const int CACHE_SIZE_LIMIT = 256 * 1024 * 1024;   /* but not above 256MiB */
 static const int CACHE_SIZE_FALLBACK = 32 * 1024 * 1024; /* fallback to 32MiB if we can't determine total memory */
 
+#endif
+#ifdef INCLUDE_OPTIONS_CONFIG
+
+/* if false, pixelate images at zoom level != 100%,
+ * toggled with 'a' key binding (overwritten via `--anti-alias` option)
+ */
+static const bool ANTI_ALIAS = true;
+
 #endif
 #ifdef INCLUDE_THUMBS_CONFIG
 

etc/nsxiv.1

@@ -114,6 +114,11 @@ Set zoom level to ZOOM percent.
 .B "\-0, \-\-null"
 Use NULL-separator. With this option, output of \-o and file-list sent to the
 key-handler and the input of \-i will be separated by a NULL character.
+.TP
+.BI "\-\-anti\-alias" [=no]
+Enables anti-aliasing, when given
+.I no
+as an argument, disables it instead.
 .SH KEYBOARD COMMANDS
 .SS General
 The following keyboard commands are available in both image and thumbnail modes:

image.c

@@ -80,7 +80,7 @@ void img_init(img_t *img, win_t *win)
 	img->zoom = MIN(img->zoom, ZOOM_MAX);
 	img->checkpan = false;
 	img->dirty = false;
-	img->aa = ANTI_ALIAS;
+	img->aa = options->aa;
 	img->alpha = ALPHA_LAYER;
 	img->multi.cap = img->multi.cnt = 0;
 	img->multi.animate = options->animate;

nsxiv.h

@@ -237,6 +237,7 @@ struct opt {
 	scalemode_t scalemode;
 	float zoom;
 	bool animate;
+	bool aa;
 	int gamma;
 	int slideshow;
 	int framerate;

options.c

@@ -19,8 +19,11 @@
 
 #include "nsxiv.h"
 #include "version.h"
+#define INCLUDE_OPTIONS_CONFIG
+#include "config.h"
 
 #include <assert.h>
+#include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -63,6 +66,9 @@ static void print_version(void)
 
 void parse_options(int argc, char **argv)
 {
+	enum { /* ensure these can't be represented in a single byte */
+		OPT_AA = UCHAR_MAX + 1
+	};
 	static const struct optparse_long longopts[] = {
 		{ "framerate",      'A',     OPTPARSE_REQUIRED },
 		{ "animate",        'a',     OPTPARSE_NONE },
@@ -88,6 +94,7 @@ void parse_options(int argc, char **argv)
 		{ "zoom-100",       'Z',     OPTPARSE_NONE },
 		{ "zoom",           'z',     OPTPARSE_REQUIRED },
 		{ "null",           '0',     OPTPARSE_NONE },
+		{ "anti-alias",    OPT_AA,   OPTPARSE_OPTIONAL },
 		{ 0 }, /* end */
 	};
 
@@ -106,6 +113,7 @@ void parse_options(int argc, char **argv)
 
 	_options.scalemode = SCALE_DOWN;
 	_options.zoom = 1.0;
+	_options.aa = ANTI_ALIAS;
 	_options.animate = false;
 	_options.gamma = 0;
 	_options.slideshow = 0;
@@ -233,6 +241,11 @@ void parse_options(int argc, char **argv)
 		case '0':
 			_options.using_null = true;
 			break;
+		case OPT_AA:
+			if (op.optarg != NULL && !STREQ(op.optarg, "no"))
+				error(EXIT_FAILURE, 0, "Invalid argument for option --anti-alias: %s", op.optarg);
+			_options.aa = op.optarg == NULL;
+			break;
 		}
 	}