Default to automatic ARGB use

[luebking]

Preserves -t behavior, -t0 or -t1 to control the ARGB use and the default behavior just looks for a compositor and selects the proper mode. This even works when toggling the compositor while find-cursor is running.

diff --git a/find-cursor.c b/find-cursor.c
index 3931964..bbbeef6 100644
--- a/find-cursor.c
+++ b/find-cursor.c
@@ -21,6 +21,7 @@
 #include <X11/extensions/shape.h>
 
 void usage(char *name);
+int has_compositor(Display *dpy, int screen);
 int parse_num(int ch, char *opt, char *name);
 int pointer_screen(char *name, Display *display);
 void draw(char *name, Display *display, int screen,
@@ -35,7 +36,7 @@ static struct option longopts[] = {
 	{"line-width",    required_argument, NULL, 'l'},
 	{"color",         required_argument, NULL, 'c'},
 	{"follow",        no_argument,       NULL, 'f'},
-	{"transparent",   no_argument,       NULL, 't'},
+	{"transparent",   optional_argument, NULL, 't'}, // Optional for compat, as previously it was hard-coded to 1
 	{"grow",          no_argument,       NULL, 'g'},
 	{"outline",       optional_argument, NULL, 'o'}, // Optional for compat, as previously it was hard-coded to 2px.
 	{"repeat",        required_argument, NULL, 'r'},
@@ -62,10 +63,9 @@ void usage(char *name) {
 	"\n"
 	"Extra options:\n"
 	"  -f, --follow        Follow the cursor position as the cursor is moving.\n"
-	"  -t, --transparent   Make the window truly 'transparent'. This helps with\n"
-	"                      some display issues when following the cursor position,\n"
-	"                      but it doesn't work well with all WMs, which is why\n"
-	"                      it's disabled by default.\n"
+	"  -t, --transparent   Make the window truly 'transparent'. [-1,0,1]\n"
+    "                      Defaults to -1 (auto) if unset, -t is equivalent to -t1\n"
+	"                      Use -t0 to explicitly disable it\n"
 	"  -o, --outline       Width in pixels of outline; uses 2px if no value is given.\n"
 	"                      Helps visibility on all backgrounds.\n"
 	"  -O, --outline-color Color of outline; if omitted it will automatically use\n"
@@ -108,6 +108,13 @@ int parse_num(int ch, char *opt, char *name) {
 	return result;
 }
 
+int has_compositor(Display *dpy, int screen) {
+    char prop_name[20];
+    snprintf(prop_name, 20, "_NET_WM_CM_S%d", screen);
+    Atom prop_atom = XInternAtom(dpy, prop_name, False);
+    return XGetSelectionOwner(dpy, prop_atom) != None;
+}
+
 int main(int argc, char* argv[]) {
 	// Parse options
 	int size = 320;
@@ -117,14 +124,14 @@ int main(int argc, char* argv[]) {
 	char color_name[64] = "black";
 	char ocolor_name[64];
 	int follow = 0;
-	int transparent = 0;
+	int transparent = -1;
 	int grow = 0;
 	int outline = 0;
 	int repeat = 0;
 
 	extern int optopt;
 	int ch;
-	while ((ch = getopt_long(argc, argv, ":hs:d:w:l:c:r:ftgo:O:", longopts, NULL)) != -1)
+	while ((ch = getopt_long(argc, argv, ":hs:d:w:l:c:r:ft:go:O:", longopts, NULL)) != -1)
 		switch (ch) {
 		case 's':
 			size = parse_num(ch, optarg, argv[0]);
@@ -148,7 +155,7 @@ int main(int argc, char* argv[]) {
 			follow = 1;
 			break;
 		case 't':
-			transparent = 1;
+			transparent = parse_num(ch, optarg, argv[0]);
 			break;
 		case 'g':
 			grow = 1;
@@ -169,6 +176,9 @@ int main(int argc, char* argv[]) {
 			case 'o':
 				outline = 2;
 				break;
+            case 't':
+                transparent = 1;
+				break;
 			default:
 			    fprintf(stderr, "%s: missing required argument for -%c\n\n", argv[0], optopt);
 			    usage(argv[0]);
@@ -260,7 +270,7 @@ void draw(char *name, Display *display, int screen,
 	window_attr.override_redirect = 1;
 
     Colormap colormap = DefaultColormap(display, screen);
-	if (transparent) {
+	if (transparent > 0 || (transparent < 0 && has_compositor(display, screen))) {
 		XVisualInfo vinfo;
 		XMatchVisualInfo(display, screen, 32, TrueColor, &vinfo);
 		colormap = window_attr.colormap = XCreateColormap(display, DefaultRootWindow(display), vinfo.visual, AllocNone);

[arp242]

I think using --transparent {always,never,auto} would be nicer, maybe with some aliases for always and never (yes/no, on/off, true/false). I had to read your modified help text a few times to understand what it does.

Other than that, seems okay – just need to set the transparent variable from a string instead of a number.

[luebking]

I skipped the auto, it's implied by omission and makes the thing just more confusing by being pointed out.
(The objectives here are to maintain the behavior of "-t" while making the default "smart" but also allow to override that in either direction for debugging or corner cases, eg. unredirected windows)

diff --git a/find-cursor.c b/find-cursor.c
index 3931964..2caaf51 100644
--- a/find-cursor.c
+++ b/find-cursor.c
@@ -21,6 +21,7 @@
 #include <X11/extensions/shape.h>
 
 void usage(char *name);
+int has_compositor(Display *dpy, int screen);
 int parse_num(int ch, char *opt, char *name);
 int pointer_screen(char *name, Display *display);
 void draw(char *name, Display *display, int screen,
@@ -35,7 +36,7 @@ static struct option longopts[] = {
 	{"line-width",    required_argument, NULL, 'l'},
 	{"color",         required_argument, NULL, 'c'},
 	{"follow",        no_argument,       NULL, 'f'},
-	{"transparent",   no_argument,       NULL, 't'},
+	{"transparent",   optional_argument, NULL, 't'}, // Optional for compat, as previously it was hard-coded to 1
 	{"grow",          no_argument,       NULL, 'g'},
 	{"outline",       optional_argument, NULL, 'o'}, // Optional for compat, as previously it was hard-coded to 2px.
 	{"repeat",        required_argument, NULL, 'r'},
@@ -62,10 +63,9 @@ void usage(char *name) {
 	"\n"
 	"Extra options:\n"
 	"  -f, --follow        Follow the cursor position as the cursor is moving.\n"
-	"  -t, --transparent   Make the window truly 'transparent'. This helps with\n"
-	"                      some display issues when following the cursor position,\n"
-	"                      but it doesn't work well with all WMs, which is why\n"
-	"                      it's disabled by default.\n"
+	"  -t, --transparent   Make the window truly 'transparent'. [yes|no]\n"
+	"                      If omitted the behavior is determined by the presence of a compositor.\n"
+	"                      If no parameter [yes|no] is given, \"yes\" is implied\n"
 	"  -o, --outline       Width in pixels of outline; uses 2px if no value is given.\n"
 	"                      Helps visibility on all backgrounds.\n"
 	"  -O, --outline-color Color of outline; if omitted it will automatically use\n"
@@ -108,6 +108,39 @@ int parse_num(int ch, char *opt, char *name) {
 	return result;
 }
 
+int strtobool(int ch, char *opt, char *name) {
+	if (opt) {
+		switch (opt[0]) {
+		case 'a': case 'A': case 't': case 'T': case 'y': case 'Y': case '1':
+		case '-': // probably next parameter, so default to true
+			return 1;
+		case 'f': case 'F': case 'n': case 'N': case '0':
+			return 0;
+		case 'o': case 'O':
+			switch (opt[1]) {
+			case 'n': case 'N':
+				return 1;
+			case 'f': case 'F':
+				return 0;
+			default: // includes "\0"
+				break;
+			}
+		default:
+			break;
+		}
+		fprintf(stderr, "%s: value for -%c must be either true/false, on/off, yes/no, always/never or 0/1\n\n", name, ch);
+		exit(1);
+	}
+	return 1; // default to true
+}
+
+int has_compositor(Display *dpy, int screen) {
+	char prop_name[20];
+	snprintf(prop_name, 20, "_NET_WM_CM_S%d", screen);
+	Atom prop_atom = XInternAtom(dpy, prop_name, False);
+	return XGetSelectionOwner(dpy, prop_atom) != None;
+}
+
 int main(int argc, char* argv[]) {
 	// Parse options
 	int size = 320;
@@ -117,14 +150,14 @@ int main(int argc, char* argv[]) {
 	char color_name[64] = "black";
 	char ocolor_name[64];
 	int follow = 0;
-	int transparent = 0;
+	int transparent = -1;
 	int grow = 0;
 	int outline = 0;
 	int repeat = 0;
 
 	extern int optopt;
 	int ch;
-	while ((ch = getopt_long(argc, argv, ":hs:d:w:l:c:r:ftgo:O:", longopts, NULL)) != -1)
+	while ((ch = getopt_long(argc, argv, ":hs:d:w:l:c:r:ft::go:O:", longopts, NULL)) != -1)
 		switch (ch) {
 		case 's':
 			size = parse_num(ch, optarg, argv[0]);
@@ -148,7 +181,7 @@ int main(int argc, char* argv[]) {
 			follow = 1;
 			break;
 		case 't':
-			transparent = 1;
+			transparent = strtobool(ch, optarg, argv[0]);
 			break;
 		case 'g':
 			grow = 1;
@@ -169,6 +202,9 @@ int main(int argc, char* argv[]) {
 			case 'o':
 				outline = 2;
 				break;
+			case 't':
+				transparent = 1;
+				break;
 			default:
 			    fprintf(stderr, "%s: missing required argument for -%c\n\n", argv[0], optopt);
 			    usage(argv[0]);
@@ -260,7 +296,7 @@ void draw(char *name, Display *display, int screen,
 	window_attr.override_redirect = 1;
 
     Colormap colormap = DefaultColormap(display, screen);
-	if (transparent) {
+	if (transparent > 0 || (transparent < 0 && has_compositor(display, screen))) {
 		XVisualInfo vinfo;
 		XMatchVisualInfo(display, screen, 32, TrueColor, &vinfo);
 		colormap = window_attr.colormap = XCreateColormap(display, DefaultRootWindow(display), vinfo.visual, AllocNone);