events: Add integer wheel fields for sdl2-compat

It's way simpler to just add them back to SDL3 than emulate them purely in sdl2-compat.

Author: cgutman

include/SDL3/SDL_events.h

@@ -492,6 +492,8 @@ typedef struct SDL_MouseWheelEvent
     SDL_MouseWheelDirection direction; /**< Set to one of the SDL_MOUSEWHEEL_* defines. When FLIPPED the values in X and Y will be opposite. Multiply by -1 to change them back */
     float mouse_x;      /**< X coordinate, relative to window */
     float mouse_y;      /**< Y coordinate, relative to window */
+    Sint32 integer_x;   /**< The amount scrolled horizontally, accumulated to whole scroll "ticks" (added in 3.2.12) */
+    Sint32 integer_y;   /**< The amount scrolled vertically, accumulated to whole scroll "ticks" (added in 3.2.12) */
 } SDL_MouseWheelEvent;
 
 /**

src/events/SDL_events.c

@@ -625,9 +625,10 @@ int SDL_GetEventDescription(const SDL_Event *event, char *buf, int buflen)
 #undef PRINT_MBUTTON_EVENT
 
         SDL_EVENT_CASE(SDL_EVENT_MOUSE_WHEEL)
-        (void)SDL_snprintf(details, sizeof(details), " (timestamp=%u windowid=%u which=%u x=%g y=%g direction=%s)",
+        (void)SDL_snprintf(details, sizeof(details), " (timestamp=%u windowid=%u which=%u x=%g y=%g integer_x=%d integer_y=%d direction=%s)",
                            (uint)event->wheel.timestamp, (uint)event->wheel.windowID,
                            (uint)event->wheel.which, event->wheel.x, event->wheel.y,
+                           (int)event->wheel.integer_x, (int)event->wheel.integer_y,
                            event->wheel.direction == SDL_MOUSEWHEEL_NORMAL ? "normal" : "flipped");
         break;
 

src/events/SDL_mouse.c

@@ -1040,18 +1040,14 @@ void SDL_SendMouseWheel(Uint64 timestamp, SDL_Window *window, SDL_MouseID mouseI
         SDL_SetMouseFocus(window);
     }
 
-    // Accumulate fractional wheel motion if integer mode is enabled
-    if (mouse->integer_mode_flags & 2) {
-        mouse->integer_mode_residual_scroll_x = SDL_modff(mouse->integer_mode_residual_scroll_x + x, &x);
-        mouse->integer_mode_residual_scroll_y = SDL_modff(mouse->integer_mode_residual_scroll_y + y, &y);
-    }
-
     if (x == 0.0f && y == 0.0f) {
         return;
     }
 
     // Post the event, if desired
     if (SDL_EventEnabled(SDL_EVENT_MOUSE_WHEEL)) {
+        float integer_x, integer_y;
+
         if (!mouse->relative_mode || mouse->warp_emulation_active) {
             // We're not in relative mode, so all mouse events are global mouse events
             mouseID = SDL_GLOBAL_MOUSE_ID;
@@ -1062,11 +1058,26 @@ void SDL_SendMouseWheel(Uint64 timestamp, SDL_Window *window, SDL_MouseID mouseI
         event.common.timestamp = timestamp;
         event.wheel.windowID = mouse->focus ? mouse->focus->id : 0;
         event.wheel.which = mouseID;
-        event.wheel.x = x;
-        event.wheel.y = y;
         event.wheel.direction = direction;
         event.wheel.mouse_x = mouse->x;
         event.wheel.mouse_y = mouse->y;
+
+        mouse->residual_scroll_x = SDL_modff(mouse->residual_scroll_x + x, &integer_x);
+        event.wheel.integer_x = (Sint32)integer_x;
+
+        mouse->residual_scroll_y = SDL_modff(mouse->residual_scroll_y + y, &integer_y);
+        event.wheel.integer_y = (Sint32)integer_y;
+
+        // Return the accumulated values in x/y when integer wheel mode is enabled.
+        // This is necessary for compatibility with sdl2-compat 2.32.54.
+        if (mouse->integer_mode_flags & 2) {
+            event.wheel.x = integer_x;
+            event.wheel.y = integer_y;
+        } else {
+            event.wheel.x = x;
+            event.wheel.y = y;
+        }
+
         SDL_PushEvent(&event);
     }
 }

src/events/SDL_mouse_c.h

@@ -99,8 +99,6 @@ typedef struct
     Uint8 integer_mode_flags; // 1 to enable mouse quantization, 2 to enable wheel quantization
     float integer_mode_residual_motion_x;
     float integer_mode_residual_motion_y;
-    float integer_mode_residual_scroll_x;
-    float integer_mode_residual_scroll_y;
 
     // Data common to all mice
     SDL_Window *focus;
@@ -109,6 +107,8 @@ typedef struct
     float x_accu;
     float y_accu;
     float last_x, last_y; // the last reported x and y coordinates
+    float residual_scroll_x;
+    float residual_scroll_y;
     double click_motion_x;
     double click_motion_y;
     bool has_position;