renderer_opengl: Add support for custom shaders (#4578)

* Add Anaglyph 3D

Change 3D slider in-game

Change shaders while game is running

Move shader loading into function

Disable 3D slider setting when stereoscopy is off

The rest of the shaders

Address review issues

Documentation and minor fixups

Forgot clang-format

Fix shader release on SDL2-software rendering

Remove unnecessary state changes

Respect 3D factor setting regardless of stereoscopic rendering

Improve shader resolution passing

Minor setting-related improvements

Add option to toggle texture filtering

Rebase fixes

* One final clang-format

* Fix OpenGL problems

src/common/common_paths.h

@@ -43,6 +43,7 @@
 #define LOG_DIR "log"
 #define CHEATS_DIR "cheats"
 #define DLL_DIR "external_dlls"
+#define SHADER_DIR "shaders"
 
 // Filenames
 // Files in the directory returned by GetUserPath(UserPath::LogDir)

src/common/file_util.cpp

@@ -711,6 +711,7 @@ void SetUserPath(const std::string& path) {
     g_paths.emplace(UserPath::LogDir, user_path + LOG_DIR DIR_SEP);
     g_paths.emplace(UserPath::CheatsDir, user_path + CHEATS_DIR DIR_SEP);
     g_paths.emplace(UserPath::DLLDir, user_path + DLL_DIR DIR_SEP);
+    g_paths.emplace(UserPath::ShaderDir, user_path + SHADER_DIR DIR_SEP);
 }
 
 const std::string& GetUserPath(UserPath path) {

src/common/file_util.h

@@ -30,6 +30,7 @@ enum class UserPath {
     NANDDir,
     RootDir,
     SDMCDir,
+    ShaderDir,
     SysDataDir,
     UserDir,
 };