database: support $XDG_CONFIG_HOME/libwacom as additional path

This completes the traditional triplet of $XDG_CONFIG_HOME, /etc, and
/usr/share for configuration files.

Having custom .tablet files in $XDG_CONFIG_HOME makes it easier for
immutable systems and also for backups that only back up the user home
directory.

.github/workflows/main.yml

@@ -115,6 +115,9 @@ jobs:
           - sudo mv /usr/share/libwacom/wacom-intuos*.tablet /etc/libwacom
           - sudo mv /usr/share/libwacom/*.tablet /etc/libwacom
           - sudo mv /usr/share/libwacom/*.stylus /etc/libwacom
+          - sudo mv /usr/share/libwacom/*.tablet $HOME/.config/libwacom
+          - sudo mv /usr/share/libwacom/*.stylus $HOME/.config/libwacom
+          - sudo mv /usr/share/libwacom/wacom-*.tablet $HOME/.config/libwacom && sudo mv /usr/share/libwacom/huion-*.tablet /etc/libwacom
           # split the wacom.stylus file into to two files to check for
           # accumlated loading
           - sudo csplit data/wacom.stylus '/^\[0x822\]/' && sudo mv xx00 /etc/libwacom/first.stylus && sudo mv xx01 /usr/share/libwacom/wacom.stylus
@@ -141,6 +144,7 @@ jobs:
       - name: list devices with database in /usr
         run: libwacom-list-devices --format=datafile > devicelist.default.txt
       - run: sudo mkdir /etc/libwacom
+      - run: sudo mkdir $HOME/.config/libwacom
       - name: split the databases between /usr/share and /etc
         run: ${{matrix.command}}
       - name: list devices with database in /etc and /usr

libwacom/libwacom-database.c

@@ -1192,13 +1192,28 @@ libwacom_database_new_for_path (const char *datadir)
 LIBWACOM_EXPORT WacomDeviceDatabase *
 libwacom_database_new (void)
 {
+	WacomDeviceDatabase *db;
+	char *xdgdir = NULL;
+	char *xdg_config_home = g_strdup(g_getenv("XDG_CONFIG_HOME"));
+
+	if (!xdg_config_home)
+		xdg_config_home = g_strdup_printf("%s/.config/", g_get_home_dir());
+
+	xdgdir = g_strdup_printf("%s/libwacom", xdg_config_home);
+
 	char *datadir[] = {
+		xdgdir,
 		ETCDIR,
 		DATADIR,
 		NULL,
 	};
 
-	return database_new_for_paths(datadir);
+	db = database_new_for_paths(datadir);
+
+	free(xdgdir);
+	free(xdg_config_home);
+
+	return db;
 }
 
 LIBWACOM_EXPORT void

test/test_libwacom.py

@@ -600,3 +600,24 @@ def test_nonwacom_stylus_ids(tmp_path):
     assert sum(s.vendor_id == 0x1234 and s.tool_id == 0x9876 for s in styli) == 1
     assert sum(s.vendor_id == 0 and s.tool_id == 0xFFFFE for s in styli) == 1
     assert sum(s.vendor_id == 0 and s.tool_id == 0xFFFFF for s in styli) == 1
+
+
+def test_load_xdg_config_home(monkeypatch, tmp_path, custom_datadir):
+    monkeypatch.setenv("XDG_CONFIG_HOME", str(tmp_path.absolute()))
+
+    xdg = tmp_path / "libwacom"
+    xdg.mkdir()
+
+    usbid = (0x1234, 0x5678)
+    matches = [f"usb|{usbid[0]:04x}|{usbid[1]:04x}"]
+    TabletFile(name="XDGTablet", matches=matches).write_to(xdg / "uniq.tablet")
+
+    StylusFile.default().write_to_dir(xdg)
+
+    # This should load from system *and* XDG. system files could
+    # interfere with our test or may not exist but unfortunately we can't
+    # chroot for the test. it should be good enough this way anyway.
+    db = WacomDatabase()
+    builder = WacomBuilder.create(usbid=usbid)
+    device = db.new_from_builder(builder)
+    assert device is not None and device.name == "XDGTablet"

tools/libwacom-update-db.py

@@ -23,11 +23,17 @@
 
 import argparse
 import configparser
+import os
 import sys
 import subprocess
+import tempfile
 from pathlib import Path
 
 
+def xdg_dir():
+    return Path(os.getenv("XDG_CONFIG_HOME", Path.home() / ".config")) / "libwacom"
+
+
 class Tablet(object):
     def __init__(self, name, bus, vid, pid):
         self.name = name
@@ -154,19 +160,20 @@ def _load(self, path):
 
 # Guess the udev directory based on path. For the case of /usr/share, the
 # udev directory is probably in /usr/lib so let's fallback to that.
-def find_udev_base_dir(path):
-    for parent in path.parents:
-        d = Path(parent / "udev" / "rules.d")
-        if d.exists():
-            return d.parent
+def find_udev_base_dir(paths):
+    for path in paths:
+        for parent in path.parents:
+            d = Path(parent / "udev" / "rules.d")
+            if d.exists():
+                return d.parent
 
-    # /usr/share but also any custom prefixes
-    for parent in path.parents:
-        d = Path(parent / "lib" / "udev" / "rules.d")
-        if d.exists():
-            return d.parent
+        # /usr/share but also any custom prefixes
+        for parent in path.parents:
+            d = Path(parent / "lib" / "udev" / "rules.d")
+            if d.exists():
+                return d.parent
 
-    raise FileNotFoundError(path)
+    raise FileNotFoundError(paths)
 
 
 # udev's behaviour is that where a file X exists in two locations,
@@ -190,8 +197,8 @@ def guess_hwdb_filename(basedir):
         "path",
         nargs="?",
         type=Path,
-        default="/etc/libwacom",
-        help="Directory to load .tablet files from",
+        default=None,
+        help="Directory to load .tablet files from. Default: $XDG_CONFIG_HOME/libwacom and /etc/libwacom",
     )
     # buildsystem-mode is what we use from meson, it changes the
     # the behavior to just generate the file and print it
@@ -215,7 +222,14 @@ def guess_hwdb_filename(basedir):
     )
     ns = parser.parse_args()
 
-    db = TabletDatabase(ns.path)
+    if ns.path is None:
+        paths = [xdg_dir(), Path("/etc/libwacom")]
+    else:
+        paths = [ns.path]
+
+    # Reverse the list so the most important one is last and takes precedence
+    paths.reverse()
+    dbs = [TabletDatabase(p) for p in paths]
 
     hwdb = HWDBFile()
     # Bamboo and Intuos devices connected to the system via Wacom's
@@ -230,20 +244,32 @@ def guess_hwdb_filename(basedir):
         wwak.has_touch = True
         hwdb.tablets.append(wwak)
 
-    hwdb.tablets.extend(db.tablets)
+    for db in dbs:
+        hwdb.tablets.extend(db.tablets)
+
     if ns.buildsystem_mode:
         hwdb.print()
     else:
+        if os.geteuid() == 0:
+            print(
+                "WARNING: Running this command as root will not pick up .tablet files in $XDG_CONFIG_HOME/libwacom"
+            )
+
         try:
-            udevdir = ns.udev_base_dir or find_udev_base_dir(ns.path)
+            udevdir = ns.udev_base_dir or find_udev_base_dir(paths)
             hwdbfile = guess_hwdb_filename(udevdir)
-            with open(hwdbfile, "w") as fd:
+
+            with tempfile.NamedTemporaryFile(
+                mode="w+", prefix=f"{hwdbfile.name}-XXXXXX", encoding="utf-8"
+            ) as fd:
                 hwdb.print(fd)
-            print(f"New hwdb file: {hwdbfile}")
+                print(f"Using sudo to copy hwdb file to {hwdbfile}")
+                subprocess.run(["sudo", "cp", f"{fd.name}", hwdbfile.absolute()])
 
             if not ns.skip_systemd_hwdb_update:
+                print("Using sudo to run systemd-hwdb update")
                 subprocess.run(
-                    ["systemd-hwdb", "update"],
+                    ["sudo", "systemd-hwdb", "update"],
                     capture_output=True,
                     check=True,
                     text=True,
@@ -255,3 +281,5 @@ def guess_hwdb_filename(basedir):
             print(f"Unable to find udev base directory: {e}")
         except subprocess.CalledProcessError as e:
             print(f"hwdb update failed: {e.stderr}")
+        except KeyboardInterrupt:
+            pass

tools/show-stylus.py

@@ -22,6 +22,7 @@
 
 import argparse
 import configparser
+import os
 import sys
 from pathlib import Path
 
@@ -37,6 +38,10 @@
     sys.exit(1)
 
 
+def xdg_dir():
+    return Path(os.getenv("XDG_CONFIG_HOME", Path.home() / ".config")) / "libwacom"
+
+
 class Ansi:
     clearline = "\x1b[K"
 
@@ -133,7 +138,7 @@ def record_events(ns):
 def load_data_files():
     lookup_paths = (
         ("./data/",),
-        ("@DATADIR@", "@ETCDIR@"),
+        ("@DATADIR@", "@ETCDIR@", xdg_dir()),
         ("/usr/share/libwacom/", "/etc/libwacom/"),
     )
     stylusfiles = []