Add config relative path environment variable

src/Application.cc

@@ -19,7 +19,9 @@
 #include <queue>
 
 #include <ignition/common/Console.hh>
+#include <ignition/common/Filesystem.hh>
 #include <ignition/common/SignalHandler.hh>
+#include <ignition/common/StringUtils.hh>
 #include <ignition/common/SystemPaths.hh>
 #include <ignition/common/Util.hh>
 
@@ -222,24 +224,50 @@ bool Application::LoadConfig(const std::string &_config)
     return false;
   }
 
+  std::string configFull = _config;
+
+  // Check if the passed in config file exists.
+  // (If the default config path doesn't exist yet, it's expected behavior.
+  // It will be created the first time the user presses "Save configuration".)
+  if (!common::exists(configFull) && (configFull != this->DefaultConfigPath()))
+  {
+    // If not, then check environment variable
+    std::string configPathEnv;
+    common::env("GZ_GUI_RESOURCE_PATH", configPathEnv);
+
+    if (!configPathEnv.empty())
+    {
+      std::vector<std::string> parentPaths = common::Split(configPathEnv, ':');
+      for (auto parentPath : parentPaths)
+      {
+        std::string tempPath = common::joinPaths(parentPath, configFull);
+        if (common::exists(tempPath))
+        {
+          configFull = tempPath;
+          break;
+        }
+      }
+    }
+  }
+
   // Use tinyxml to read config
   tinyxml2::XMLDocument doc;
-  auto success = !doc.LoadFile(_config.c_str());
+  auto success = !doc.LoadFile(configFull.c_str());
   if (!success)
   {
     // We do not show an error message if the default config path doesn't exist
     // yet. It's expected behavior, it will be created the first time the user
     // presses "Save configuration".
-    if (_config != this->DefaultConfigPath())
+    if (configFull != this->DefaultConfigPath())
     {
-      ignerr << "Failed to load file [" << _config << "]: XMLError"
+      ignerr << "Failed to load file [" << configFull << "]: XMLError"
              << std::endl;
     }
 
     return false;
   }
 
-  ignmsg << "Loading config [" << _config << "]" << std::endl;
+  ignmsg << "Loading config [" << configFull << "]" << std::endl;
 
   // Clear all previous plugins
   auto plugins = this->dataPtr->mainWin->findChildren<Plugin *>();

src/Application_TEST.cc

@@ -172,6 +172,28 @@ TEST(ApplicationTest, IGN_UTILS_TEST_DISABLED_ON_WIN32(LoadConfig))
     auto testSourcePath = std::string(PROJECT_SOURCE_PATH) + "/test/";
     EXPECT_TRUE(app.LoadConfig(testSourcePath + "config/test.config"));
   }
+
+  // Test environment variable and relative path
+  {
+    // Environment variable not set
+    Application app(g_argc, g_argv);
+    EXPECT_FALSE(app.LoadConfig("ignore.config"));
+
+    // Invalid path
+    setenv("GZ_GUI_RESOURCE_PATH", "invalidPath", 1);
+    EXPECT_FALSE(app.LoadConfig("ignore.config"));
+
+    // Valid path
+    setenv("GZ_GUI_RESOURCE_PATH",
+        (std::string(PROJECT_SOURCE_PATH) + "/test/config").c_str(), 1);
+    EXPECT_TRUE(app.LoadConfig("ignore.config"));
+
+    // Multiple paths, one valid
+    setenv("GZ_GUI_RESOURCE_PATH",
+        ("banana:" + std::string(PROJECT_SOURCE_PATH) + "/test/config" +
+        ":orange").c_str(), 1);
+    EXPECT_TRUE(app.LoadConfig("ignore.config"));
+  }
 }
 
 //////////////////////////////////////////////////

src/cmd/cmdgui.rb.in

@@ -52,7 +52,10 @@ COMMANDS = {  'gui' =>
                        "                             The default verbosity is 1, use -v without\n"\
                        "                             arguments for level 3.\n"\
                        "\n" +
-                       COMMON_OPTIONS,
+                       COMMON_OPTIONS + "\n\n" +
+                       "Environment variables:                                                  \n"\
+                       "  GZ_GUI_RESOURCE_PATH    Colon separated paths used to locate GUI     \n"\
+                       " resources such as configuration files.                                 \n"\
             }
 
 #

tutorials/07_config.md

@@ -15,9 +15,19 @@ By default, Ignition GUI will load the config file at
 Configuration files can also be loaded from the command line or through the
 C++ API.
 
-From the command line, use the `--config` / `-c` option, for example:
+From the command line, use the `--config` / `-c` option.
+For example, you can specify an absolute path:
 
-`ign gui -c path/to/example.config`
+`ign gui -c /absolute/path/to/example.config`
+
+Or a path relative to the current working directory:
+
+`ign gui -c relative/path/to/example.config`
+
+Or a path relative to a custom directory, which you can specify by setting the
+environment variable `GZ_GUI_RESOURCE_PATH`, like so:
+
+`GZ_GUI_RESOURCE_PATH=/absolute/path/to/ ign gui --config example.config`
 
 From the C++ API, pass the file path to
 [Application::LoadConfig](https://ignitionrobotics.org/api/gui/3.0/classignition_1_1gui_1_1Application.html#a03c4c3a1b1e58cc4bff05658f21fff17).