Add user-facing error reporting

Signed-off-by: Ikey Doherty <ikey@solus-project.com>

src/shim/lsi.c

@@ -12,7 +12,9 @@
 #define _GNU_SOURCE
 
 #include <assert.h>
+#include <errno.h>
 #include <pwd.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/stat.h>
@@ -184,6 +186,41 @@ const char *lsi_preload_list()
         return "/usr/$LIB/libX11.so.6:/usr/$LIB/libstdc++.so.6";
 }
 
+void lsi_report_failure(const char *s, ...)
+{
+        autofree(char) *report = NULL;
+        autofree(char) *emit = NULL;
+        va_list va;
+        va_start(va, s);
+        if (vasprintf(&report, s, va) < 0) {
+                fputs("Critical internal error\n", stderr);
+                return;
+        }
+        va_end(va);
+
+        /* Display not set, just go ahead and stderr it */
+        if (!getenv("DISPLAY")) {
+                goto stderr_log;
+        }
+
+        if (asprintf(&emit,
+                     "zenity --title \"%s\" --icon-name='steam' --error --text='%s'",
+                     PACKAGE_NAME,
+                     report) < 0) {
+                goto stderr_log;
+        }
+
+        if (system(emit) != 0) {
+                fprintf(stderr, "%s: Failed to launch Zenity: %s\n", PACKAGE_NAME, strerror(errno));
+                goto stderr_log;
+        }
+        return;
+
+stderr_log:
+        fputs(PACKAGE_NAME " failure: \n\t", stderr);
+        fprintf(stderr, "%s\n", report);
+}
+
 /*
  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
  *

src/shim/lsi.h

@@ -75,6 +75,12 @@ const char *lsi_preload_list(void);
  */
 bool lsi_system_requires_preload(void);
 
+/**
+ * Report a failure to the user. In the instance that DISPLAY is set, we'll
+ * attempt to make use of zenity
+ */
+void lsi_report_failure(const char *s, ...);
+
 /*
  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
  *

src/shim/shim.c

@@ -76,7 +76,9 @@ int main(int argc, char **argv)
         /* Go execute steam. */
         if (execv(exec_command, (char **)n_argv) < 0) {
                 /* TODO: Use Zenity when we have a UI */
-                fprintf(stderr, "Failed to launch Steam: %s [%s]\n", strerror(errno), STEAM_BINARY);
+                lsi_report_failure("Failed to launch Steam: %s [%s]",
+                                   strerror(errno),
+                                   STEAM_BINARY);
                 return EXIT_FAILURE;
         }
 }