mouse: Allow use of integer coordinates with fractional wheel events

SDL 2.0.18 added preciseX/Y to mouse wheel events, which we cannot
emulate in sdl2-compat without a mechanism to control integer position
and scroll deltas separately.

(cherry picked from commit aad1e35162623e191341ef6d85230c281645d0bc)

src/events/SDL_mouse.c

@@ -238,7 +238,11 @@ static void SDLCALL SDL_MouseIntegerModeChanged(void *userdata, const char *name
 {
     SDL_Mouse *mouse = (SDL_Mouse *)userdata;
 
-    mouse->integer_mode = SDL_GetStringBoolean(hint, false);
+    if (hint && *hint) {
+        mouse->integer_mode = (Uint8)SDL_atoi(hint);
+    } else {
+        mouse->integer_mode = 0;
+    }
 }
 
 // Public functions
@@ -730,7 +734,7 @@ static void SDL_PrivateSendMouseMotion(Uint64 timestamp, SDL_Window *window, SDL
                 y *= mouse->normal_speed_scale;
             }
         }
-        if (mouse->integer_mode) {
+        if (mouse->integer_mode >= 1) {
             // Accumulate the fractional relative motion and only process the integer portion
             mouse->xrel_frac = SDL_modff(mouse->xrel_frac + x, &x);
             mouse->yrel_frac = SDL_modff(mouse->yrel_frac + y, &y);
@@ -741,7 +745,7 @@ static void SDL_PrivateSendMouseMotion(Uint64 timestamp, SDL_Window *window, SDL
         y = (mouse->last_y + yrel);
         ConstrainMousePosition(mouse, window, &x, &y);
     } else {
-        if (mouse->integer_mode) {
+        if (mouse->integer_mode >= 1) {
             // Discard the fractional component from absolute coordinates
             x = SDL_truncf(x);
             y = SDL_truncf(y);
@@ -1019,7 +1023,7 @@ void SDL_SendMouseWheel(Uint64 timestamp, SDL_Window *window, SDL_MouseID mouseI
     }
 
     // Accumulate fractional wheel motion if integer mode is enabled
-    if (mouse->integer_mode) {
+    if (mouse->integer_mode >= 2) {
         mouse->wheel_x_frac = SDL_modff(mouse->wheel_x_frac + x, &x);
         mouse->wheel_y_frac = SDL_modff(mouse->wheel_y_frac + y, &y);
     }

src/events/SDL_mouse_c.h

@@ -104,7 +104,7 @@ typedef struct
     float wheel_y_frac;
     double click_motion_x;
     double click_motion_y;
-    bool integer_mode;
+    Uint8 integer_mode;
     bool has_position;
     bool relative_mode;
     bool relative_mode_warp_motion;