Add strerror and tests

po/POTFILES.in

@@ -4,6 +4,8 @@ libx52/x52_stringify.c
 
 libx52io/io_strings.c
 
+vkm/vkm_common.c
+
 evtest/ev_test.c
 
 joytest/x52_test.c

po/libx52.pot

@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: libx52 0.3.3\n"
 "Report-Msgid-Bugs-To: https://github.com/nirenjan/libx52/issues\n"
-"POT-Creation-Date: 2026-03-27 08:32-0700\n"
+"POT-Creation-Date: 2026-03-27 20:52-0700\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -17,7 +17,7 @@ msgstr ""
 "Content-Type: text/plain; charset=CHARSET\n"
 "Content-Transfer-Encoding: 8bit\n"
 
-#: libx52/x52_strerror.c:23 libx52io/io_strings.c:101
+#: libx52/x52_strerror.c:23 libx52io/io_strings.c:101 vkm/vkm_common.c:25
 msgid "Success"
 msgstr ""
 
@@ -29,7 +29,7 @@ msgstr ""
 msgid "Insufficient memory"
 msgstr ""
 
-#: libx52/x52_strerror.c:26
+#: libx52/x52_strerror.c:26 vkm/vkm_common.c:29
 msgid "Invalid parameter"
 msgstr ""
 
@@ -85,7 +85,7 @@ msgstr ""
 msgid "System call interrupted"
 msgstr ""
 
-#: libx52/x52_strerror.c:66 libx52io/io_strings.c:125
+#: libx52/x52_strerror.c:66 libx52io/io_strings.c:125 vkm/vkm_common.c:52
 #, c-format
 msgid "Unknown error %d"
 msgstr ""
@@ -233,6 +233,34 @@ msgstr ""
 msgid "Read timeout"
 msgstr ""
 
+#: vkm/vkm_common.c:26
+msgid "Unknown error"
+msgstr ""
+
+#: vkm/vkm_common.c:27
+msgid "Not ready"
+msgstr ""
+
+#: vkm/vkm_common.c:28
+msgid "Out of memory"
+msgstr ""
+
+#: vkm/vkm_common.c:30
+msgid "Not supported"
+msgstr ""
+
+#: vkm/vkm_common.c:31
+msgid "Virtual device failure"
+msgstr ""
+
+#: vkm/vkm_common.c:32
+msgid "Unable to write event"
+msgstr ""
+
+#: vkm/vkm_common.c:33
+msgid "No state change"
+msgstr ""
+
 #: evtest/ev_test.c:110
 #, c-format
 msgid "Device ID: vendor 0x%04x product 0x%04x version 0x%04x\n"

po/xx_PL.po

@@ -7,7 +7,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: libx52 0.2.3\n"
 "Report-Msgid-Bugs-To: https://github.com/nirenjan/libx52/issues\n"
-"POT-Creation-Date: 2026-03-27 08:32-0700\n"
+"POT-Creation-Date: 2026-03-27 20:52-0700\n"
 "PO-Revision-Date: 2026-03-27 08:33-0700\n"
 "Last-Translator: Nirenjan Krishnan <nirenjan@gmail.com>\n"
 "Language-Team: Dummy Language for testing i18n\n"
@@ -17,7 +17,7 @@ msgstr ""
 "Content-Transfer-Encoding: 8bit\n"
 "X-Generator: Poedit 3.4.2\n"
 
-#: libx52/x52_strerror.c:23 libx52io/io_strings.c:101
+#: libx52/x52_strerror.c:23 libx52io/io_strings.c:101 vkm/vkm_common.c:25
 msgid "Success"
 msgstr "Uccesssay"
 
@@ -29,7 +29,7 @@ msgstr "Initializationay ailurefay"
 msgid "Insufficient memory"
 msgstr "Insufficientay emorymay"
 
-#: libx52/x52_strerror.c:26
+#: libx52/x52_strerror.c:26 vkm/vkm_common.c:29
 msgid "Invalid parameter"
 msgstr "Invaliday arameterpay"
 
@@ -85,7 +85,7 @@ msgstr "Ipepay erroray"
 msgid "System call interrupted"
 msgstr "Ystemsay allcay interrupteday"
 
-#: libx52/x52_strerror.c:66 libx52io/io_strings.c:125
+#: libx52/x52_strerror.c:66 libx52io/io_strings.c:125 vkm/vkm_common.c:52
 #, c-format
 msgid "Unknown error %d"
 msgstr "Unknownay erroray %d"
@@ -233,6 +233,36 @@ msgstr "I/O erroray"
 msgid "Read timeout"
 msgstr "Eadray imeouttay"
 
+#: vkm/vkm_common.c:26
+#, fuzzy
+msgid "Unknown error"
+msgstr "Unknownay erroray %d"
+
+#: vkm/vkm_common.c:27
+msgid "Not ready"
+msgstr ""
+
+#: vkm/vkm_common.c:28
+msgid "Out of memory"
+msgstr ""
+
+#: vkm/vkm_common.c:30
+#, fuzzy
+msgid "Not supported"
+msgstr "Operationay otnay upportedsay"
+
+#: vkm/vkm_common.c:31
+msgid "Virtual device failure"
+msgstr ""
+
+#: vkm/vkm_common.c:32
+msgid "Unable to write event"
+msgstr ""
+
+#: vkm/vkm_common.c:33
+msgid "No state change"
+msgstr ""
+
 #: evtest/ev_test.c:110
 #, c-format
 msgid "Device ID: vendor 0x%04x product 0x%04x version 0x%04x\n"

vkm/meson.build

@@ -25,9 +25,19 @@ endif
 lib_vkm = library('vkm', vkm_files + vkm_platform_files,
   install: true,
   version: vkm_version,
-  dependencies: [vkm_dep],
+  dependencies: [vkm_dep, dep_intl],
   include_directories: [includes])
 
+vkm_strerror_test = executable('vkm-strerror-test',
+  'test_strerror.c',
+  'vkm_common.c',
+  build_by_default: false,
+  dependencies: [dep_cmocka, dep_intl],
+  include_directories: [includes],
+)
+
+test('vkm-strerror', vkm_strerror_test, protocol: 'tap')
+
 if host_machine.system() == 'linux' and dep_evdev.found()
   dep_evdev_headers = dep_evdev.partial_dependency(compile_args: true, link_args: false)
   vkm_linux_evdev_test = executable('vkm_linux_evdev_test',
@@ -37,7 +47,7 @@ if host_machine.system() == 'linux' and dep_evdev.found()
       'vkm_common.c',
     ),
     include_directories: [includes],
-    dependencies: [dep_cmocka, dep_evdev_headers],
+    dependencies: [dep_cmocka, dep_evdev_headers, dep_intl],
   )
   test('vkm_linux_evdev', vkm_linux_evdev_test)
 endif

vkm/test_strerror.c

@@ -0,0 +1,57 @@
+/*
+ * VKM — strerror unit tests
+ *
+ * Copyright (C) 2026 Nirenjan Krishnan (nirenjan@nirenjan.org)
+ *
+ * SPDX-License-Identifier: GPL-2.0-only WITH Classpath-exception-2.0
+ */
+
+#include <stdarg.h>
+#include <stddef.h>
+#include <setjmp.h>
+#include <cmocka.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "vkm.h"
+
+static void test_strerror(void **state)
+{
+    (void)state;
+
+    static const char *error_map[VKM_ERROR_MAX] = {
+        [VKM_SUCCESS] = "Success",
+        [VKM_ERROR_UNKNOWN] = "Unknown error",
+        [VKM_ERROR_NOT_READY] = "Not ready",
+        [VKM_ERROR_OUT_OF_MEMORY] = "Out of memory",
+        [VKM_ERROR_INVALID_PARAM] = "Invalid parameter",
+        [VKM_ERROR_NOT_SUPPORTED] = "Not supported",
+        [VKM_ERROR_DEV_FAILURE] = "Virtual device failure",
+        [VKM_ERROR_EVENT] = "Unable to write event",
+        [VKM_ERROR_NO_CHANGE] = "No state change",
+    };
+
+    static const char *unknown_fmt = "Unknown error %d";
+
+    char expected[256];
+
+    for (int i = -1; i <= (int)VKM_ERROR_MAX + 1; i++) {
+        if (i < 0 || i >= (int)VKM_ERROR_MAX || error_map[i] == NULL) {
+            snprintf(expected, sizeof(expected), unknown_fmt, i);
+        } else {
+            strncpy(expected, error_map[i], sizeof(expected));
+        }
+        assert_string_equal(expected, vkm_strerror(i));
+    }
+}
+
+static const struct CMUnitTest tests[] = {
+    cmocka_unit_test(test_strerror),
+};
+
+int main(void)
+{
+    cmocka_set_message_output(CM_OUTPUT_TAP);
+    cmocka_run_group_tests(tests, NULL, NULL);
+    return 0;
+}

vkm/vkm.h

@@ -96,6 +96,22 @@ typedef enum {
     VKM_ERROR_MAX,
 } vkm_error_code;
 
+/**
+ * @brief Return a short description for a \ref vkm_result / \ref vkm_error_code value
+ *
+ * The returned pointer refers to static storage and must not be freed. For
+ * unrecognized codes, the same static buffer may be overwritten by a later call.
+ *
+ * When native language support (NLS) is enabled at build time, these messages
+ * are translated like \ref libx52_strerror. Bind the \c libx52 text domain and
+ * set \c LC_MESSAGES as for other libx52 components.
+ *
+ * @param[in]   code    Value returned from a VKM API function
+ *
+ * @returns Pointer to a NUL-terminated description string
+ */
+const char *vkm_strerror(vkm_result code);
+
 /**
  * @brief Option list
  */

vkm/vkm_common.c

@@ -6,10 +6,54 @@
  * SPDX-LicenseIdentifier: GPL-2.0-only WITH Classpath-exception-2.0
  */
 
+#include "config.h"
+#include <stdio.h>
 #include <stdlib.h>
 
+#include "gettext.h"
+
 #include "vkm-internal.h"
 
+#define N_(str) gettext_noop(str)
+#define _(str)  dgettext(PACKAGE, str)
+
+/* Error buffer used for building custom error strings */
+static char error_buffer[256];
+
+/* List of error strings (indices must match \ref vkm_error_code) */
+static const char *error_string[] = {
+    N_("Success"),
+    N_("Unknown error"),
+    N_("Not ready"),
+    N_("Out of memory"),
+    N_("Invalid parameter"),
+    N_("Not supported"),
+    N_("Virtual device failure"),
+    N_("Unable to write event"),
+    N_("No state change"),
+};
+
+const char *vkm_strerror(vkm_result code)
+{
+    switch ((vkm_error_code)code) {
+    case VKM_SUCCESS:
+    case VKM_ERROR_UNKNOWN:
+    case VKM_ERROR_NOT_READY:
+    case VKM_ERROR_OUT_OF_MEMORY:
+    case VKM_ERROR_INVALID_PARAM:
+    case VKM_ERROR_NOT_SUPPORTED:
+    case VKM_ERROR_DEV_FAILURE:
+    case VKM_ERROR_EVENT:
+    case VKM_ERROR_NO_CHANGE:
+        return _(error_string[code]);
+
+    default:
+        snprintf(error_buffer, sizeof(error_buffer),
+                 _("Unknown error %d"), (int)code);
+        return error_buffer;
+    }
+}
+
 vkm_button_state _vkm_get_mouse_button_state(struct vkm_mouse_button_state *state, vkm_mouse_button button)
 {
     if (state == NULL) {