Print info message when hiding the UI that shows how to get it back

- Print the information message informing about the keybdining if it exists
  - Add new function `keyBindingsForAction` that returns the list of keys that are bound to a specific action
  - Change the parameter to the `keyBindings` function to be optional, causing it to return all actions bound to keys

data/assets/actions/default_actions.asset

@@ -47,7 +47,20 @@ local ToggleRollFriction = {
 local ToggleMainGui = {
   Identifier = "os.ToggleMainGui",
   Name = "Toggle main GUI",
-  Command = [[openspace.invertBooleanProperty("Modules.CefWebGui.Visible")]],
+  Command = [[
+    openspace.invertBooleanProperty("Modules.CefWebGui.Visible")
+
+    if not openspace.propertyValue("Modules.CefWebGui.Visible") then
+      local action_id = "os.ToggleMainGui"
+      local keys = openspace.keyBindingsForAction(action_id)
+      if #keys > 0 then
+        local key = keys[1]
+        openspace.printInfo(
+          "Hiding the user interface. You can restore it with the '" .. key .. "' key"
+        )
+      end
+    end
+  ]],
   Documentation = "Toggles the main GUI",
   GuiPath = "/System/GUI",
   IsLocal = true

src/interaction/keybindingmanager.cpp

@@ -119,6 +119,7 @@ scripting::LuaLibrary KeybindingManager::luaLibrary() {
         {
             codegen::lua::BindKey,
             codegen::lua::KeyBindings,
+            codegen::lua::KeyBindingsForAction,
             codegen::lua::ClearKey,
             codegen::lua::ClearKeys
         }

src/interaction/keybindingmanager_lua.inl

@@ -49,22 +49,60 @@ namespace {
 }
 
 /**
- * Returns the strings of the script that are bound to the passed key and whether they
- * were local or remote key binds.
+ * Returns the identifiers of the action that are bound to the passed key and whether they
+ * were local or remote key binds. If no key is provided, all bound keybindings are
+ * returned instead.
+ *
+ * \param key The key for which to return the keybindings. If no key is provided, all
+ *        keybindings are returned
  */
-[[codegen::luawrap]] std::vector<std::string> keyBindings(std::string key) {
+[[codegen::luawrap]] std::vector<std::string> keyBindings(std::optional<std::string> key)
+{
     using namespace openspace;
 
-    using K = KeyWithModifier;
-    using V = std::string;
-    const std::vector<std::pair<K, V>>& info = global::keybindingManager->keyBinding(
-        stringToKey(key)
-    );
+    std::vector<std::string> res;
+    if (key.has_value()) {
+        using K = KeyWithModifier;
+        using V = std::string;
+        const std::vector<std::pair<K, V>>& info = global::keybindingManager->keyBinding(
+            stringToKey(*key)
+        );
+
+        res.reserve(info.size());
+        for (const std::pair<K, V>& it : info) {
+            res.push_back(it.second);
+        }
+    }
+    else {
+        const std::multimap<KeyWithModifier, std::string>& keybinds =
+            global::keybindingManager->keyBindings();
+
+        res.reserve(keybinds.size());
+        for (const std::pair<const KeyWithModifier, std::string>& it : keybinds) {
+            res.push_back(it.second);
+        }
+
+        // Actions might be bound to different actions
+        std::unique(res.begin(), res.end());
+    }
+    return res;
+}
+
+/**
+ * Returns the keybinds to which the provided action is bound. As actions can be bound to
+ * multiple keys, this function returns a list of all keys
+ */
+[[codegen::luawrap]] std::vector<std::string> keyBindingsForAction(std::string action) {
+    using namespace openspace;
+
+    const std::multimap<KeyWithModifier, std::string>& keybinds =
+        global::keybindingManager->keyBindings();
 
     std::vector<std::string> res;
-    res.reserve(info.size());
-    for (const std::pair<K, V>& it : info) {
-        res.push_back(it.second);
+    for (const std::pair<const KeyWithModifier, std::string>& it : keybinds) {
+        if (it.second == action) {
+            res.push_back(keyToString(it.first));
+        }
     }
     return res;
 }