Add initial support for the XDG Base Directory spec

Spec version 0.7 from https://standards.freedesktop.org/basedir-spec/basedir-spec-0.7.html
(latest as of this commit).

Three virtual methods are added to OS for the various XDG paths we will use:
- OS::get_data_path gives XDG_DATA_HOME, or if missing:
  ~/.local/share on X11, ~/Library/Application Support/ on macOS and %APPDATA% on Windows
- OS::get_config_path gives XDG_CONFIG_HOME, or if missing:
  ~/.config on X11, ~/Library/Application Support/ on macOS and %APPDATA% on Windows
- OS::get_cache_path gives XDG_CACHE_HOME, or if missing:
  ~/.cache on X11, ~/Library/Caches on macOS and %APPDATA% on Windows

So for Windows there are no changes, for Linux we follow the full split spec
and for macOS stuff will move from ~/.godot to ~/Library/Application Support/Godot.

Support for system-wide installation of templates on Unix was removed for now,
as it's a bit hackish and I don't think anyone uses it.

user:// will still be OS::get_data_path() + "/godot/app_userdata/$name" by
default, but when using the application/config/use_shared_user_dir option
it will now use XDG_DATA_HOME/$name, e.g. ~/.local/share/MyGame.

For now everything still goes in EditorSettings::get_settings_dir(), but
this will be changed in a later commit to make use of the new splitting
where relevant.

Part of #3513.

2 files changed, 50 insertions, 13 deletions

diff --git a/core/os/os.cpp b/core/os/os.cpp
index ea0f5de8bd..8d050c1c4c 100644
--- a/core/os/os.cpp
+++ b/core/os/os.cpp
@@ -33,6 +33,7 @@
 #include "input.h"
 #include "os/file_access.h"
 #include "project_settings.h"
+#include "version_generated.gen.h"
 
 #include <stdarg.h>
 
@@ -262,16 +263,7 @@ String OS::get_locale() const {
 	return "en";
 }
 
-String OS::get_resource_dir() const {
-
-	return ProjectSettings::get_singleton()->get_resource_path();
-}
-
-String OS::get_system_dir(SystemDir p_dir) const {
-
-	return ".";
-}
-
+// Helper function used by OS_Unix and OS_Windows
 String OS::get_safe_application_name() const {
 	String an = ProjectSettings::get_singleton()->get("application/config/name");
 	Vector<String> invalid_char = String("\\ / : * ? \" < > |").split(" ");
@@ -281,11 +273,51 @@ String OS::get_safe_application_name() const {
 	return an;
 }
 
+// Path to data, config, cache, etc. OS-specific folders
+
+// Get properly capitalized engine name for system paths
+String OS::get_godot_dir_name() const {
+
+	// Default to lowercase, so only override when different case is needed
+	return String(_MKSTR(VERSION_SHORT_NAME)).to_lower();
+}
+
+// OS equivalent of XDG_DATA_HOME
+String OS::get_data_path() const {
+
+	return ".";
+}
+
+// OS equivalent of XDG_CONFIG_HOME
+String OS::get_config_path() const {
+
+	return ".";
+}
+
+// OS equivalent of XDG_CACHE_HOME
+String OS::get_cache_path() const {
+
+	return ".";
+}
+
+// OS specific path for user://
 String OS::get_user_data_dir() const {
 
 	return ".";
 };
 
+// Absolute path to res://
+String OS::get_resource_dir() const {
+
+	return ProjectSettings::get_singleton()->get_resource_path();
+}
+
+// Access system-specific dirs like Documents, Downloads, etc.
+String OS::get_system_dir(SystemDir p_dir) const {
+
+	return ".";
+}
+
 Error OS::shell_open(String p_uri) {
 	return ERR_UNAVAILABLE;
 };
diff --git a/core/os/os.h b/core/os/os.h
index a421833e49..474cb60627 100644
--- a/core/os/os.h
+++ b/core/os/os.h
@@ -200,7 +200,6 @@ public:
 	virtual void set_low_processor_usage_mode(bool p_enabled);
 	virtual bool is_in_low_processor_usage_mode() const;
 
-	virtual String get_installed_templates_path() const { return ""; }
 	virtual String get_executable_path() const;
 	virtual Error execute(const String &p_path, const List<String> &p_arguments, bool p_blocking, ProcessID *r_child_id = NULL, String *r_pipe = NULL, int *r_exitcode = NULL, bool read_stderr = false) = 0;
 	virtual Error kill(const ProcessID &p_pid) = 0;
@@ -334,11 +333,15 @@ public:
 	virtual String get_locale() const;
 
 	String get_safe_application_name() const;
+	virtual String get_godot_dir_name() const;
+
+	virtual String get_data_path() const;
+	virtual String get_config_path() const;
+	virtual String get_cache_path() const;
+
 	virtual String get_user_data_dir() const;
 	virtual String get_resource_dir() const;
 
-	virtual Error move_to_trash(const String &p_path) { return FAILED; }
-
 	enum SystemDir {
 		SYSTEM_DIR_DESKTOP,
 		SYSTEM_DIR_DCIM,
@@ -352,6 +355,8 @@ public:
 
 	virtual String get_system_dir(SystemDir p_dir) const;
 
+	virtual Error move_to_trash(const String &p_path) { return FAILED; }
+
 	virtual void set_no_window_mode(bool p_enable);
 	virtual bool is_no_window_mode_enabled() const;