Backends: SDL2, SDL3: SDL_EVENT_MOUSE_WHEEL event doesn't require dividing by 100.0f on Emscripten. (#4019, #6096, #1463)

Ref https://github.com/libsdl-org/SDL/issues/10454#issuecomment-2434187317

backends/imgui_impl_sdl2.cpp

@@ -21,6 +21,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024-10-24: Emscripten: from SDL 2.30.9, SDL_EVENT_MOUSE_WHEEL event doesn't require dividing by 100.0f.
 //  2024-09-09: use SDL_Vulkan_GetDrawableSize() when available. (#7967, #3190)
 //  2024-08-22: moved some OS/backend related function pointers from ImGuiIO to ImGuiPlatformIO:
 //               - io.GetClipboardTextFn    -> platform_io.Platform_GetClipboardTextFn
@@ -359,7 +360,7 @@ bool ImGui_ImplSDL2_ProcessEvent(const SDL_Event* event)
             float wheel_x = -(float)event->wheel.x;
             float wheel_y = (float)event->wheel.y;
 #endif
-#ifdef __EMSCRIPTEN__
+#if defined(__EMSCRIPTEN__) && !SDL_VERSION_ATLEAST(2,31,0)
             wheel_x /= 100.0f;
 #endif
             io.AddMouseSourceEvent(event->wheel.which == SDL_TOUCH_MOUSEID ? ImGuiMouseSource_TouchScreen : ImGuiMouseSource_Mouse);

backends/imgui_impl_sdl3.cpp

@@ -21,6 +21,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024-10-24: Emscripten: SDL_EVENT_MOUSE_WHEEL event doesn't require dividing by 100.0f on Emscripten.
 //  2024-09-03: Update for SDL3 api changes: SDL_GetGamepads() memory ownership revert. (#7918, #7898, #7807)
 //  2024-08-22: moved some OS/backend related function pointers from ImGuiIO to ImGuiPlatformIO:
 //               - io.GetClipboardTextFn    -> platform_io.Platform_GetClipboardTextFn
@@ -338,9 +339,6 @@ bool ImGui_ImplSDL3_ProcessEvent(const SDL_Event* event)
             //IMGUI_DEBUG_LOG("wheel %.2f %.2f, precise %.2f %.2f\n", (float)event->wheel.x, (float)event->wheel.y, event->wheel.preciseX, event->wheel.preciseY);
             float wheel_x = -event->wheel.x;
             float wheel_y = event->wheel.y;
-    #ifdef __EMSCRIPTEN__
-            wheel_x /= 100.0f;
-    #endif
             io.AddMouseSourceEvent(event->wheel.which == SDL_TOUCH_MOUSEID ? ImGuiMouseSource_TouchScreen : ImGuiMouseSource_Mouse);
             io.AddMouseWheelEvent(wheel_x, wheel_y);
             return true;

docs/CHANGELOG.txt

@@ -44,7 +44,8 @@ Breaking changes:
 Other changes:
 
 - Backends: DX12: Unmap() call specify written range. The range is informational and may be used by debug tools.
-
+- Backends: SDL3: Update for SDL3 api change: SDL_EVENT_MOUSE_WHEEL event doesn't require dividing by 100.0f 
+  on Emscripten target. (#4019, #6096, #1463)
 
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  VERSION 1.91.4 (Released 2024-10-18)