Linux: add support to get proxy settings from GSettings, if available.

We dynamically load the necessary symbols since these APIs aren't available
in all versions of the glib libraries we target. We also do some checks to
figure out whether to use gsettings of gconf settings. This works on both
Ubuntu 11.04 (where we should use gconf) and Fedora 15 (gsettings).
BUG=80453

Review URL: http://codereview.chromium.org/6999016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@85968 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/ui/webui/options/advanced_options_utils_gtk.cc

@@ -7,18 +7,22 @@
 #include "chrome/browser/ui/webui/options/advanced_options_utils.h"
 
 #include "base/environment.h"
+#include "base/file_path.h"
+#include "base/file_util.h"
 #include "base/nix/xdg_util.h"
 #include "base/process_util.h"
+#include "base/string_util.h"
 #include "content/browser/browser_thread.h"
 #include "content/browser/tab_contents/tab_contents.h"
 #include "content/common/process_watcher.h"
 
-// Command used to configure GNOME proxy settings. The command was renamed
-// in January 2009, so both are used to work on both old and new systems.
-// As on April 2011, many systems do not have the old command anymore.
-// TODO(thestig) Remove the old command in the future.
-const char* kOldGNOMEProxyConfigCommand[] = {"gnome-network-preferences", NULL};
-const char* kGNOMEProxyConfigCommand[] = {"gnome-network-properties", NULL};
+// Command used to configure GNOME 2 proxy settings.
+const char* kGNOME2ProxyConfigCommand[] = {"gnome-network-properties", NULL};
+// In GNOME 3, we might need to run gnome-control-center instead. We try this
+// only after gnome-network-properties is not found, because older GNOME also
+// has this but it doesn't do the same thing. See below where we use it.
+const char* kGNOME3ProxyConfigCommand[] = {"gnome-control-center", "network",
+                                           NULL};
 // KDE3 and KDE4 are only slightly different, but incompatible. Go figure.
 const char* kKDE3ProxyConfigCommand[] = {"kcmshell", "proxy", NULL};
 const char* kKDE4ProxyConfigCommand[] = {"kcmshell4", "proxy", NULL};
@@ -43,6 +47,30 @@ void ShowLinuxProxyConfigUrl(TabContents* tab_contents) {
 // Start the given proxy configuration utility.
 bool StartProxyConfigUtil(TabContents* tab_contents, const char* command[]) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  // base::LaunchApp() returns true ("success") if the fork() succeeds, but not
+  // necessarily the exec(). We'd like to be able to use StartProxyConfigUtil()
+  // to search possible options and stop on success, so we search $PATH first to
+  // predict whether the exec is expected to succeed.
+  // TODO(mdm): this is a useful check, and is very similar to some code in
+  // proxy_config_service_linux.cc. It should probably be in base:: somewhere.
+  scoped_ptr<base::Environment> env(base::Environment::Create());
+  std::string path;
+  if (!env->GetVar("PATH", &path)) {
+    LOG(ERROR) << "No $PATH variable. Assuming no " << command[0] << ".";
+    return false;
+  }
+  std::vector<std::string> paths;
+  Tokenize(path, ":", &paths);
+  bool found = false;
+  for (size_t i = 0; i < paths.size(); ++i) {
+    FilePath file(paths[i]);
+    if (file_util::PathExists(file.Append(command[0]))) {
+      found = true;
+      break;
+    }
+  }
+  if (!found)
+    return false;
   std::vector<std::string> argv;
   for (size_t i = 0; command[i]; ++i)
     argv.push_back(command[i]);
@@ -65,10 +93,16 @@ void DetectAndStartProxyConfigUtil(TabContents* tab_contents) {
   bool launched = false;
   switch (base::nix::GetDesktopEnvironment(env.get())) {
     case base::nix::DESKTOP_ENVIRONMENT_GNOME: {
-      launched = StartProxyConfigUtil(tab_contents, kGNOMEProxyConfigCommand);
+      launched = StartProxyConfigUtil(tab_contents, kGNOME2ProxyConfigCommand);
       if (!launched) {
+        // We try this second, even though it's the newer way, because this
+        // command existed in older versions of GNOME, but it didn't do the
+        // same thing. The older command is gone though, so this should do
+        // the right thing. (Also some distributions have blurred the lines
+        // between GNOME 2 and 3, so we can't necessarily detect what the
+        // right thing is based on indications of which version we have.)
         launched = StartProxyConfigUtil(tab_contents,
-                                        kOldGNOMEProxyConfigCommand);
+                                        kGNOME3ProxyConfigCommand);
       }
       break;
     }