From 7f81b16f333b034953c25be7148657552a7da783 Mon Sep 17 00:00:00 2001
From: "B. Watson" <yalhcru@gmail.com>
Date: Tue, 19 May 2020 01:49:22 -0400
Subject: use correct root window

---
 jsmond.c | 50 ++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 38 insertions(+), 12 deletions(-)

diff --git a/jsmond.c b/jsmond.c
index 643287d..a7b8d40 100644
--- a/jsmond.c
+++ b/jsmond.c
@@ -38,12 +38,15 @@
 /* command for -x */
 #define X_COMMAND "xscreensaver-command -deactivate"
 
+/* default "-i 250ms" */
+#define DEFAULT_INTERVAL 250
+
 typedef enum {
 	fm_auto_keycode, fm_keycode, fm_button, fm_motion, fm_cmd
 } fake_mode_t;
 
 /* user options */
-int interval = 250;              /* -i (always in millisec) */
+int interval = DEFAULT_INTERVAL; /* -i (always in millisec) */
 int debug = 0;                   /* -D */
 int keycode = -1;                /* -k */
 int button = -1;                 /* -b */
@@ -287,32 +290,55 @@ int get_joystick_activity(void) {
 	return active;
 }
 
+/* supposedly we could use the X window property _NET_WINDOW_FULLSCREEN
+   to detect a fullscreen window, but not everything actually sets that.
+   so a fullscreen window is defined here as:
+   - visible
+   - is the size of the root window
+   - and has input focus.
+*/
 int have_fullscreen_window(void) {
 	Window w;
 	XWindowAttributes w_attrs, root_attrs;
 	int revert_to;
 
-	/* TODO: error check? */
-	XGetInputFocus(xdisp, &w, &revert_to);
+	/* man page doesn't document the actual
+	   return value, it says "int", is it really a Status? */
+	if(!XGetInputFocus(xdisp, &w, &revert_to)) {
+		if(debug) fprintf(stderr, "XGetInputFocus() failed\n");
+		return 0;
+	}
+
+	/* no window has focus (not an error) */
+	if(w == None)
+		return 0;
+
+	/* TODO: under what conditions does this fail? if it does fail once,
+		will it ever succeed again?
 
-	if(w != None) {
-		XGetWindowAttributes(xdisp, DefaultRootWindow(xdisp), &root_attrs);
-		XGetWindowAttributes(xdisp, w, &w_attrs);
+		Hopefully, using w_attrs.root will do the right thing in multi-screen
+		environments. I can't easily test it though. */
+	if( XGetWindowAttributes(xdisp, w, &w_attrs) &&
+	    XGetWindowAttributes(xdisp, w_attrs.root, &root_attrs) )
+	{
 
-		/*
-		fprintf(stderr, "window id %d has focus, geometry %dx%d\n",
-				(int)w, w_attrs.width, w_attrs.height);
-				*/
+		if(debug)
+			fprintf(stderr,
+					"window id 0x%x (root 0x%x) has focus, map_state %d, geometry %dx%d\n",
+					(int)w, (int)w_attrs.root, w_attrs.map_state, w_attrs.width, w_attrs.height);
 
 		if( (w_attrs.map_state == IsViewable) &&
-			 (root_attrs.width == w_attrs.width) &&
-		    (root_attrs.height == w_attrs.height) )
+				(root_attrs.width == w_attrs.width) &&
+				(root_attrs.height == w_attrs.height) )
 		{
 			if(debug) fprintf(stderr,
 					"window id 0x%x has input focus and looks fullscreen (%dx%d)\n",
 					(int)w, w_attrs.width, w_attrs.height);
 			return 1;
 		}
+	} else if(debug) {
+		if(debug) fprintf(stderr, "XGetWindowAttributes() failed\n");
+		return 0;
 	}
 
 	return 0;
-- 
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