Backends: SDL, Win32: Fixed inverted horizontal mouse wheel axis. (oc…

…ornut#4019)
rokups · Oct 14, 2021 · 3c9858a · 3c9858a
1 parent 13cdf2f
commit 3c9858a
Show file tree

Hide file tree

Showing 3 changed files with 22 additions and 3 deletions.
diff --git a/backends/imgui_impl_sdl.cpp b/backends/imgui_impl_sdl.cpp
@@ -18,6 +18,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2021-08-25: Inputs: Fixed inverted horizontal mouse wheel axis. (#4019)
 //  2021-08-17: Calling io.AddFocusEvent() on SDL_WINDOWEVENT_FOCUS_GAINED/SDL_WINDOWEVENT_FOCUS_LOST.
 //  2021-07-29: Inputs: MousePos is correctly reported when the host platform window is hovered but not focused (using SDL_GetMouseFocus() + SDL_HINT_MOUSE_FOCUS_CLICKTHROUGH, requires SDL 2.0.5+)
 //  2021-06-29: *BREAKING CHANGE* Removed 'SDL_Window* window' parameter to ImGui_ImplSDL2_NewFrame() which was unnecessary.
@@ -67,6 +68,7 @@
 #endif
 #define SDL_HAS_MOUSE_FOCUS_CLICKTHROUGH    SDL_VERSION_ATLEAST(2,0,5)
 #define SDL_HAS_VULKAN                      SDL_VERSION_ATLEAST(2,0,6)
+#define SDL_HAS_X11_HORIZONTAL_SCROLL_FIX   SDL_VERSION_ATLEAST(2,0,17)
 
 // SDL Data
 struct ImGui_ImplSDL2_Data
@@ -119,8 +121,14 @@ bool ImGui_ImplSDL2_ProcessEvent(const SDL_Event* event)
     {
     case SDL_MOUSEWHEEL:
         {
-            if (event->wheel.x > 0) io.MouseWheelH += 1;
-            if (event->wheel.x < 0) io.MouseWheelH -= 1;
+            // SDL prior to 2.0.17 produced inverted horizontal scroll wheel values when running on X11.
+#if SDL_HAS_X11_HORIZONTAL_SCROLL_FIX
+            const int horizontal_axis_mul = 1;
+#else
+            static const int horizontal_axis_mul = strncmp(SDL_GetCurrentVideoDriver(), "x11", 3) == 0 ? -1 : +1;
+#endif
+            if (event->wheel.x > 0) io.MouseWheelH -= 1 * horizontal_axis_mul;
+            if (event->wheel.x < 0) io.MouseWheelH += 1 * horizontal_axis_mul;
             if (event->wheel.y > 0) io.MouseWheel += 1;
             if (event->wheel.y < 0) io.MouseWheel -= 1;
             return true;

diff --git a/backends/imgui_impl_win32.cpp b/backends/imgui_impl_win32.cpp
@@ -33,6 +33,7 @@ typedef DWORD (WINAPI *PFN_XInputGetState)(DWORD, XINPUT_STATE*);
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2021-08-25: Inputs: Fixed inverted horizontal mouse wheel axis. (#4019)
 //  2021-08-17: Calling io.AddFocusEvent() on WM_SETFOCUS/WM_KILLFOCUS messages.
 //  2021-08-02: Inputs: Fixed keyboard modifiers being reported when host windo doesn't have focus.
 //  2021-07-29: Inputs: MousePos is correctly reported when the host platform window is hovered but not focused (using TrackMouseEvent() to receive WM_MOUSELEAVE events).
@@ -415,7 +416,7 @@ IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hwnd, UINT msg, WPARA
         io.MouseWheel += (float)GET_WHEEL_DELTA_WPARAM(wParam) / (float)WHEEL_DELTA;
         return 0;
     case WM_MOUSEHWHEEL:
-        io.MouseWheelH += (float)GET_WHEEL_DELTA_WPARAM(wParam) / (float)WHEEL_DELTA;
+        io.MouseWheelH -= (float)GET_WHEEL_DELTA_WPARAM(wParam) / (float)WHEEL_DELTA;
         return 0;
     case WM_KEYDOWN:
     case WM_KEYUP:

diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
@@ -30,6 +30,16 @@ HOW TO UPDATE?
   and API updates have been a little more frequent lately. They are documented below and in imgui.cpp and should not affect all users.
 - Please report any issue!
 
+
+-----------------------------------------------------------------------
+ VERSION 1.86 WIP (In Progress)
+-----------------------------------------------------------------------
+
+Other Changes:
+
+- Backends: SDL, Win32: Fixed inverted horizontal mouse wheel axis. (#4019)
+
+
 -----------------------------------------------------------------------
  VERSION 1.85 (Released 2021-10-12)
 -----------------------------------------------------------------------