Detect if the X server is XWayland and report an error. (#342)

* Detect if the X server is XWayland and report an error.

Also: Detect if $DISPLAY env is not set and report a more informative
error message.

For the purposes of libxdo/xdotool, XWayland does not work, so it's best
to notify the user accordingly if detected.

This adds a dependency on XInput `libxi` because the only[1] way I have
found to detect XWayland is through this extension

[1] There is another detection method which uses
  XFree86-VidModeExtension, but I don't know how common that extension is
  compared to XInput2.

Fixes #341.
Related to #337.

* xdo_version.h update when VERSION updates

* Fix typo in version.sh which leaves an extra plus '+' character in the date

* Run help or version commands without trying to connect to the X11 display

* Free when detecting

Author: jordansissel

Makefile

@@ -36,8 +36,8 @@ DEFAULT_LIBS=-L/usr/X11R6/lib -L/usr/local/lib -lX11 -lXtst -lXinerama -lxkbcomm
 DEFAULT_INC=-I/usr/X11R6/include -I/usr/local/include
 
 XDOTOOL_LIBS=$(shell pkg-config --libs x11 2> /dev/null || echo "$(DEFAULT_LIBS)")  $(shell sh platform.sh extralibs)
-LIBXDO_LIBS=$(shell pkg-config --libs x11 xtst xinerama xkbcommon 2> /dev/null || echo "$(DEFAULT_LIBS)")
-INC=$(shell pkg-config --cflags x11 xtst xinerama xkbcommon 2> /dev/null || echo "$(DEFAULT_INC)")
+LIBXDO_LIBS=$(shell pkg-config --libs xi x11 xtst xinerama xkbcommon 2> /dev/null || echo "$(DEFAULT_LIBS)")
+INC=$(shell pkg-config --cflags xi x11 xtst xinerama xkbcommon 2> /dev/null || echo "$(DEFAULT_INC)")
 CFLAGS+=-std=c99 $(INC)
 
 CMDOBJS= cmd_click.o cmd_mousemove.o cmd_mousemove_relative.o cmd_mousedown.o \
@@ -195,7 +195,7 @@ test: xdotool libxdo.$(VERLIBSUFFIX)
 	fi
 	SHELL=$(WITH_SHELL) $(MAKE) -C t
 
-xdo_version.h:
+xdo_version.h: VERSION
 	sh version.sh --header > $@
 
 VERSION:

version.sh

@@ -7,7 +7,7 @@ fi
 if [ -z "$MAJOR" -o -z "$RELEASE" -o -z "$REVISION" ] ; then
   MAJOR="3"
   SOURCE_DATE_EPOCH="${SOURCE_DATE_EPOCH:-$(date +%s)}"
-  DATE_FMT="+%Y%m%d"
+  DATE_FMT="%Y%m%d"
   RELEASE="$(date -u -d "@$SOURCE_DATE_EPOCH" "+$DATE_FMT" 2>/dev/null || date -u -r "$SOURCE_DATE_EPOCH" "+$DATE_FMT" 2>/dev/null || date -u "+$DATE_FMT")"
   REVISION=1
   #$([ -d .svn ] && svn info . | awk '/Revision:/ {print $2}')

xdo.c

@@ -28,6 +28,7 @@
 #include <X11/Xutil.h>
 #include <X11/extensions/XTest.h>
 #include <X11/extensions/Xinerama.h>
+#include <X11/extensions/XInput2.h>
 #include <X11/keysym.h>
 #include <X11/cursorfont.h>
 
@@ -83,14 +84,23 @@ static Atom atom_UTF8_STRING = -1;
 xdo_t* xdo_new(const char *display_name) {
   Display *xdpy;
 
-  if ((xdpy = XOpenDisplay(display_name)) == NULL) {
-    /* Can't use _xdo_eprintf yet ... */
-    fprintf(stderr, "Error: Can't open display: %s\n", display_name);
-    return NULL;
+  if (display_name == NULL) {
+    display_name = XDisplayName(display_name);
   }
 
+#define DISPLAY_HINT "Is there an Xorg or other X server running? You can try setting 'export DISPLAY=:0' and trying again."
   if (display_name == NULL) {
-    display_name = getenv("DISPLAY");
+    fprintf(stderr, "Error: No DISPLAY environment variable is set. " DISPLAY_HINT "\n");
+    return NULL;
+  }
+
+  if (*display_name == '\0') {
+    fprintf(stderr, "Error: DISPLAY environment variable is empty. " DISPLAY_HINT "\n");
+    return NULL;
+  }
+
+  if ((xdpy = XOpenDisplay(display_name)) == NULL) {
+    return NULL;
   }
 
   return xdo_new_with_opened_display(xdpy, display_name, 1);
@@ -106,6 +116,14 @@ xdo_t* xdo_new_with_opened_display(Display *xdpy, const char *display,
     return NULL;
   }
 
+  // This library and xdotool do not work correctly on Wayland/XWayland.
+  // Try to detect XWayland and warn the user about problems.
+  if (appears_to_be_wayland(xdpy)) {
+    fprintf(stderr, "The X server at %s appears to be XWayland. Unfortunately, XWayland does not correctly support the features used by libxdo and xdotool.\n", display);
+    return NULL;
+  }
+
+
   /* XXX: Check for NULL here */
   xdo = malloc(sizeof(xdo_t));
   memset(xdo, 0, sizeof(xdo_t));
@@ -2017,3 +2035,24 @@ int xdo_get_viewport_dimensions(xdo_t *xdo, unsigned int *width,
     return xdo_get_window_size(xdo, root, width, height);
   }
 }
+
+int appears_to_be_wayland(Display *xdpy) {
+  // XWayland leaks its presence in two extensions (at time of writing, August 2021)
+  // First: the name of input devices "xwayland-pointer"
+  // Second: in the Vendor string of XFree86-VidModeExtension
+
+  int count;
+  XDeviceInfo *devices = XListInputDevices(xdpy, &count);
+  for (int i = 0; i < count; i++) {
+    // fprintf(stderr, "Device %d: %s\n", i, devices[i].name);
+    // If the input device name starts with "xwayland-", 
+    // there's a good chance we're running on XWayland.
+    if (strstr(devices[i].name, "xwayland-") == devices[i].name) {
+      XFreeDeviceList(devices);
+      return 1; // Running on wayland
+    }
+  }
+  XFreeDeviceList(devices);
+
+  return 0;
+}

xdotool.c

@@ -521,6 +521,14 @@ int args_main(int argc, char **argv) {
     exit(1);
   }
 
+  if (!strcasecmp(argv[1], "help")) {
+    cmd_help(NULL);
+    exit(EXIT_SUCCESS);
+  } else if (!strcasecmp(argv[1], "version")) {
+    cmd_version(NULL);
+    exit(EXIT_SUCCESS);
+  }
+
   while ((opt = getopt_long_only(argc, argv, "++hv", long_options, &option_index)) != -1) {
     switch (opt) {
       case 'h':
@@ -547,7 +555,7 @@ int args_main(int argc, char **argv) {
   context.debug = (getenv("DEBUG") != NULL);
 
   if (context.xdo == NULL) {
-    fprintf(stderr, "Failed creating new xdo instance\n");
+    fprintf(stderr, "Failed creating new xdo instance.\n");
     return 1;
   }
   context.xdo->debug = context.debug;