From 58abae105fd5ec339c3a663b2f5fdc40a1f17b86 Mon Sep 17 00:00:00 2001
From: Nathaniel Walizer <robots.are.love@gmail.com>
Date: Fri, 3 Jan 2025 10:54:39 -0800
Subject: [PATCH] Add gamepad support

---
 src/sdl_input.c | 80 ++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 70 insertions(+), 10 deletions(-)

diff --git a/src/sdl_input.c b/src/sdl_input.c
index ac04a9a..8a818a2 100644
--- a/src/sdl_input.c
+++ b/src/sdl_input.c
@@ -3,27 +3,50 @@
 #include "input.h"
 
 
-static int filter(void*, SDL_Event* event) {
+static SDL_GameController* sdl_find_gamepad() {
+    int i = SDL_NumJoysticks() - 1;
+    for ( ; i >= 0 && !SDL_IsGameController(i); --i);
+    return (i < 0 ? NULL : SDL_GameControllerOpen(i));
+}
+
+static void sdl_lose_gamepad(void* data) {
+    SDL_GameController* gamepad = (SDL_GameController*)data;
+    if (NULL != gamepad) SDL_GameControllerClose(gamepad);
+}
+
+static int sdl_match_gamepad(SDL_JoystickID id, void* data) {
+    SDL_GameController* gamepad = (SDL_GameController*)data;
+    return (    SDL_JoystickInstanceID(
+                        SDL_GameControllerGetJoystick(gamepad))
+                    == id);
+}
+
+static int sdl_event_filter(void*, SDL_Event* event) {
     return (    SDL_QUIT == event->type ||
                 SDL_KEYDOWN == event->type ||
-                SDL_KEYUP == event->type
+                SDL_KEYUP == event->type ||
+                SDL_CONTROLLERDEVICEADDED == event->type ||
+                SDL_CONTROLLERDEVICEREMOVED == event->type
             );
 }
 
-
-static int sdl_input_init(nes_Input_Reader*) {
-    int status = SDL_Init(SDL_INIT_EVENTS);
+static int sdl_input_init(nes_Input_Reader* reader) {
+    int status = SDL_Init(SDL_INIT_EVENTS |
+                          SDL_INIT_GAMECONTROLLER);
 
     if (status == 0) {
-        SDL_SetEventFilter(filter, NULL);
+        reader->data = sdl_find_gamepad();
+        SDL_SetEventFilter(sdl_event_filter, NULL);
     }
 
     return status;
 }
 
-static void sdl_input_done(nes_Input_Reader*) {}
+static void sdl_input_done(nes_Input_Reader* input) {
+    sdl_lose_gamepad(input->data);
+}
 
-static const int keycodes[nes_controller_num_buttons] = {
+static const int sdl_keycodes[nes_controller_num_buttons] = {
     SDLK_a,
     SDLK_s,
     SDLK_q,
@@ -36,11 +59,23 @@ static const int keycodes[nes_controller_num_buttons] = {
 
 static int button_index(int keycode) {
     int index = nes_controller_num_buttons - 1;
-    for ( ; index > 0 && keycode != keycodes[index]; --index);
+    for ( ; index > 0 && keycode != sdl_keycodes[index]; --index);
     return index;
 }
 
-static int sdl_input_update(nes_Input_Reader*, nes_input* input) {
+static const int sdl_gamepad_buttons[nes_controller_num_buttons] = {
+    SDL_CONTROLLER_BUTTON_A,
+    SDL_CONTROLLER_BUTTON_B,
+    SDL_CONTROLLER_BUTTON_BACK,
+    SDL_CONTROLLER_BUTTON_START,
+    SDL_CONTROLLER_BUTTON_DPAD_UP,
+    SDL_CONTROLLER_BUTTON_DPAD_DOWN,
+    SDL_CONTROLLER_BUTTON_DPAD_LEFT,
+    SDL_CONTROLLER_BUTTON_DPAD_RIGHT,
+};
+
+static int sdl_input_update(nes_Input_Reader* reader,
+                            nes_input* input) {
     int status = 0;
 
     SDL_Event event = {0};
@@ -58,6 +93,31 @@ static int sdl_input_update(nes_Input_Reader*, nes_input* input) {
             } else {
                 input->controllers[0].buttons &= ~mask;
             }
+
+        } else if (SDL_CONTROLLERDEVICEADDED == event.type) {
+            if (NULL == reader->data) {
+                reader->data = sdl_find_gamepad();
+            }
+
+        } else if (SDL_CONTROLLERDEVICEREMOVED == event.type) {
+            if (sdl_match_gamepad(event.cdevice.which,
+                                  reader->data)) {
+                sdl_lose_gamepad(reader->data);
+                reader->data = sdl_find_gamepad();
+            }
+        }
+    }
+
+    if (NULL != reader->data) {
+        SDL_GameController* gamepad = (SDL_GameController*)reader->data;
+
+        for (int b = 0; b < nes_controller_num_buttons; ++b) {
+            if (SDL_GameControllerGetButton(
+                    gamepad, sdl_gamepad_buttons[b])) {
+                input->controllers[0].buttons |= (1 << b);
+            } else {
+                input->controllers[0].buttons &= ~(1 << b);
+            }
         }
     }