onepad: allow to save/reload SDL2 mapping from OnePAD2.ini file

SDL_GAMECONTROLLERCONFIG is nice but limited to a single entry. (Note it can still be used)

Option name is SDL2. Here an example

SDL2 = 03000000a306000020f6000011010000,PS2700 Rumble Pad,a:b1,b:b2,back:b8,dpdown:h0.4,dpleft:h0.8,dpright:h0.2,dpup:h0.1,guide:b12,leftshoulder:b4,leftstick:b10,lefttrigger:b6,leftx:a0,lefty:a1,rightshoulder:b5,rightstick:b11,righttrigger:b7,rightx:a2,righty:a4,start:b9,x:b0,y:b3,platform:Linux,

plugins/onepad/Linux/ini.cpp

@@ -100,6 +100,9 @@ void SaveConfig()
         for (auto const &it : conf->keysym_map[pad])
             fprintf(f, "PAD %d:KEYSYM 0x%x = %d\n", pad, it.first, it.second);
 
+    for (auto const &it : conf->sdl2_mapping)
+        fprintf(f, "SDL2 = %s\n", it.c_str());
+
     fclose(f);
 }
 
@@ -149,6 +152,10 @@ void LoadConfig()
             have_user_setting = true;
     }
 
+    char sdl2[512];
+    while (fscanf(f, "SDL2 = %511[^\n]\n", sdl2) == 1)
+        conf->sdl2_mapping.push_back(std::string(sdl2));
+
     if (!have_user_setting)
         DefaultKeyboardValues();
 

plugins/onepad/SDL/joystick.cpp

@@ -57,11 +57,13 @@ void JoystickInfo::EnumerateJoysticks(std::vector<std::unique_ptr<GamePad>> &vjo
             // SDL forget to add const for SDL_RWFromMem API...
             void *data = const_cast<void *>(g_bytes_get_data(bytes, &size));
 
-            int map = SDL_GameControllerAddMappingsFromRW(SDL_RWFromMem(data, size), 1);
-
-            fprintf(stdout, "onepad: load %d extra joystick map\n", map);
+            SDL_GameControllerAddMappingsFromRW(SDL_RWFromMem(data, size), 1);
 
             g_bytes_unref(bytes);
+
+            // Add user mapping too
+            for (auto const &map : conf->sdl2_mapping)
+                SDL_GameControllerAddMapping(map.c_str());
         }
     }
 
@@ -141,7 +143,7 @@ JoystickInfo::JoystickInfo(int id)
     if (m_controller == nullptr) {
         fprintf(stderr, "onepad: Joystick (%s,GUID:%s) isn't yet supported by the SDL2 game controller API\n"
                         "Fortunately you can use AntiMicro (https://github.com/AntiMicro/antimicro) or Steam to configure your joystick\n"
-                        "You can add a new mapping with the environment variable SDL_GAMECONTROLLERCONFIG\n"
+                        "The mapping can be stored in OnePAD2.ini as 'SDL2 = <...mapping description...>'\n"
                         "Please report it to us (https://github.com/PCSX2/pcsx2/issues) so we can add your joystick to our internal database.",
                 devname, guid);
 

plugins/onepad/controller.h

@@ -52,6 +52,7 @@ class PADconf
     u32 log;
     map<u32, u32> keysym_map[GAMEPAD_NUMBER];
     std::array<size_t, GAMEPAD_NUMBER> unique_id;
+    std::vector<std::string> sdl2_mapping;
 
     PADconf() { init(); }
 
@@ -64,6 +65,7 @@ class PADconf
             keysym_map[pad].clear();
         }
         unique_id.fill(0);
+        sdl2_mapping.clear();
     }
 
     void set_joy_uid(u32 pad, size_t uid)