ManyMouse fix.

CHANGELOG

@@ -986,6 +986,15 @@ API Changes
 Fixes
 -----
 
+- A machine with no enumerable mouse keeps its pointer.  ManyMouse reads
+  /dev/input/event* directly where there is no X server, and those nodes
+  are root:input, so an account that was never added to the "input" group
+  enumerated nothing -- and Singe then switched off all mouse input,
+  including SDL's own pointer, which single-mouse mode is the only user
+  of.  On a KMSDRM cabinet or handheld that left the mouse and the light
+  gun dead with only "No mice detected" to explain it.  Only --manymouse
+  needs those devices now, and the message names the group.
+
 - A lone .m2v played with --framefile now finds the .ogg beside it, as a
   framefile's segments always have.  A Daphne era elementary stream
   carries no audio of its own, so lair.m2v played silently unless it was

src/singe.c

@@ -15567,9 +15567,18 @@ void singe(SDL_Window *window, SDL_Renderer *renderer, SDL_GPUDevice *device, Co
 	if (_global.mouseCount > MAX_MICE) {
 		_global.mouseCount = MAX_MICE;
 	}
+	// ManyMouse enumerates /dev/input itself, which needs membership of the "input" group;  SDL's
+	// own pointer needs nothing.  Only many-mouse mode reads ManyMouse's events -- the poll in the
+	// event loop discards them in single-mouse mode -- so enumerating nothing must not cost a
+	// machine its pointer, or Singe has no mouse at all on a stock Debian or Ubuntu install, in a
+	// container, or under any account that was never added to that group.
 	if ((_global.mouseCount < 1) && _global.mouseEnabled) {
+		if (_global.conf->manyMouse) {
 			utilSay("Warning:  No mice detected.  Mouse input disabled.");
 			_global.mouseEnabled = false;
+		} else {
+			utilSay("Warning:  No mice could be enumerated;  using the system pointer.  Light guns and --manymouse need this user in the \"input\" group.");
+		}
 	}
 	for (x = 0; x < _global.mouseCount; x++) {
 		strncpy(_global.mice[x].name, ManyMouse_DeviceName((unsigned)x), sizeof(_global.mice[x].name) - 1);