Use xcb-errors library if it is available

This library allows to get a human-readable string describing X11
requests, events, and errors. We now use this library to pretty-print
X11 errors if we get any.

To test this code, I added the following two lines to AwesomeWM so that
X11 errors are generated:

    xcb_set_input_focus(globalconf.connection, 42, 42, 42);
    xcb_randr_set_output_primary(globalconf.connection,
        globalconf.screen->root, 42);

Output without xcb-errors:

    X error: request=SetInputFocus (major 42, minor 0), error=BadValue (2)
    X error: request=(null) (major 140, minor 30), error=(null) (147)

Output with xcb-errors:

    X error: request=SetInputFocus (major 42, minor 0), error=Value (2)
    X error: request=RandR-SetOutputPrimary (major 140, minor 30), error=RandR-BadOutput (147)

Signed-off-by: Uli Schlachter <psychon@znc.in>

awesome.c

@@ -145,6 +145,9 @@ awesome_atexit(bool restart)
 
     /* Disconnect *after* closing lua */
     xcb_cursor_context_free(globalconf.cursor_ctx);
+#ifdef WITH_XCB_ERRORS
+    xcb_errors_context_free(globalconf.errors_ctx);
+#endif
     xcb_disconnect(globalconf.connection);
 
     close(sigchld_pipe[0]);
@@ -751,6 +754,11 @@ main(int argc, char **argv)
                 globalconf.visual->visual_id);
     }
 
+#ifdef WITH_XCB_ERRORS
+    if (xcb_errors_context_new(globalconf.connection, &globalconf.errors_ctx) < 0)
+        fatal("Failed to initialize xcb-errors");
+#endif
+
     /* Get a recent timestamp */
     acquire_timestamp();
 

awesomeConfig.cmake

@@ -13,6 +13,7 @@ autoOption(GENERATE_MANPAGES "generate manpages")
 option(COMPRESS_MANPAGES "compress manpages" ON)
 option(GENERATE_DOC "generate API documentation" ON)
 option(DO_COVERAGE "build with coverage" OFF)
+autoOption(WITH_XCB_ERRORS "build with xcb-errors")
 if (GENERATE_DOC AND DO_COVERAGE)
     message(STATUS "Not generating API documentation with DO_COVERAGE")
     set(GENERATE_DOC OFF)
@@ -213,6 +214,16 @@ if(WITH_DBUS)
         autoDisable(WITH_DBUS "DBus not found.")
     endif()
 endif()
+
+if(WITH_XCB_ERRORS)
+    pkg_check_modules(XCB_ERRORS xcb-errors)
+    if(XCB_ERRORS_FOUND)
+        set(AWESOME_OPTIONAL_LDFLAGS ${AWESOME_OPTIONAL_LDFLAGS} ${XCB_ERRORS_LDFLAGS})
+        set(AWESOME_OPTIONAL_INCLUDE_DIRS ${AWESOME_OPTIONAL_INCLUDE_DIRS} ${XCB_ERRORS_INCLUDE_DIRS})
+    else()
+        autoDisable(WITH_XCB_ERRORS "xcb-errors not found.")
+    endif()
+endif()
 # }}}
 
 # {{{ Install path and configuration variables

common/version.c

@@ -54,6 +54,11 @@ eprint_version(void)
 #else
     const char *has_dbus = "✘";
 #endif
+#ifdef WITH_XCB_ERRORS
+    const char *has_xcb_errors = "✔";
+#else
+    const char *has_xcb_errors = "✘";
+#endif
 #ifdef HAS_EXECINFO
     const char *has_execinfo = "✔";
 #else
@@ -63,12 +68,13 @@ eprint_version(void)
     printf("awesome %s (%s)\n"
            " • Compiled against %s (running with %s)\n"
            " • D-Bus support: %s\n"
+           " • xcb-errors support: %s\n"
            " • execinfo support: %s\n"
            " • xcb-randr version: %d.%d\n"
            " • LGI version: %s\n",
            AWESOME_VERSION, AWESOME_RELEASE,
            LUA_RELEASE, lua_tostring(L, -2),
-           has_dbus, has_execinfo,
+           has_dbus, has_xcb_errors, has_execinfo,
            XCB_RANDR_MAJOR_VERSION, XCB_RANDR_MINOR_VERSION,
            lua_tostring(L, -1));
     lua_close(L);

config.h

@@ -8,6 +8,7 @@
 #define AWESOME_DEFAULT_CONF  "@AWESOME_SYSCONFDIR@/rc.lua"
 
 #cmakedefine WITH_DBUS
+#cmakedefine WITH_XCB_ERRORS
 #cmakedefine HAS_EXECINFO
 
 #endif //_CONFIG_H_

docs/01-readme.md

@@ -102,6 +102,8 @@ Additionally, the following optional dependencies exist:
   generate slightly better backtraces on crashes
 - `Xephyr` or `Xvfb` for running integration tests
 - [GTK+ >= 3.10](https://www.gtk.org/) for `./themes/gtk/`
+- [xcb-errors](https://gitlab.freedesktop.org/xorg/lib/libxcb-errors) for
+  pretty-printing of X11 errors
 
 ## Running Awesome
 

event.c

@@ -1036,10 +1036,24 @@ xerror(xcb_generic_error_t *e)
            && e->major_code == XCB_CONFIGURE_WINDOW))
         return;
 
-    warn("X error: request=%s (major %d, minor %d), error=%s (%d)",
-         xcb_event_get_request_label(e->major_code),
+#ifdef WITH_XCB_ERRORS
+    const char *major = xcb_errors_get_name_for_major_code(
+            globalconf.errors_ctx, e->major_code);
+    const char *minor = xcb_errors_get_name_for_minor_code(
+            globalconf.errors_ctx, e->major_code, e->minor_code);
+    const char *extension = NULL;
+    const char *error = xcb_errors_get_name_for_error(
+            globalconf.errors_ctx, e->error_code, &extension);
+#else
+    const char *major = xcb_event_get_request_label(e->major_code);
+    const char *minor = NULL;
+    const char *extension = NULL;
+    const char *error = xcb_event_get_error_label(e->error_code);
+#endif
+    warn("X error: request=%s%s%s (major %d, minor %d), error=%s%s%s (%d)",
+         major, minor == NULL ? "" : "-", NONULL(minor),
          e->major_code, e->minor_code,
-         xcb_event_get_error_label(e->error_code),
+         NONULL(extension), extension == NULL ? "" : "-", error,
          e->error_code);
 
     return;

globalconf.h

@@ -33,6 +33,11 @@
 #include <xcb/xcb_xrm.h>
 #include <X11/Xresource.h>
 
+#include "config.h"
+#ifdef WITH_XCB_ERRORS
+#include <xcb/xcb_errors.h>
+#endif
+
 #include "objects/key.h"
 #include "common/xembed.h"
 #include "common/buffer.h"
@@ -82,6 +87,10 @@ typedef struct
     int default_screen;
     /** xcb-cursor context */
     xcb_cursor_context_t *cursor_ctx;
+#ifdef WITH_XCB_ERRORS
+    /** xcb-errors context */
+    xcb_errors_context_t *errors_ctx;
+#endif
     /** Keys symbol table */
     xcb_key_symbols_t *keysyms;
     /** Logical screens */