Backends: Win32: minor optimization not submitting gamepad input if packet number has not changed. (#8556)

To be honest I don't believe this is valuable as an optimization, but it makes debug stepping a little nicer.

backends/imgui_impl_win32.cpp

@@ -21,6 +21,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2025-09-23: Inputs: Minor optimization not submitting gamepad input if packet number has not changed.
 //  2025-09-18: Call platform_io.ClearPlatformHandlers() on shutdown.
 //  2025-04-30: Inputs: Fixed an issue where externally losing mouse capture (due to e.g. focus loss) would fail to claim it again the next subsequent click. (#8594)
 //  2025-03-10: When dealing with OEM keys, use scancodes instead of translated keycodes to choose ImGuiKey values. (#7136, #7201, #7206, #7306, #7670, #7672, #8468)
@@ -124,6 +125,7 @@ struct ImGui_ImplWin32_Data
     HMODULE                     XInputDLL;
     PFN_XInputGetCapabilities   XInputGetCapabilities;
     PFN_XInputGetState          XInputGetState;
+    DWORD                       XInputPacketNumber;
 #endif
 
     ImGui_ImplWin32_Data()      { memset((void*)this, 0, sizeof(*this)); }
@@ -355,6 +357,9 @@ static void ImGui_ImplWin32_UpdateGamepads(ImGuiIO& io)
     if (!bd->HasGamepad || bd->XInputGetState == nullptr || bd->XInputGetState(0, &xinput_state) != ERROR_SUCCESS)
         return;
     io.BackendFlags |= ImGuiBackendFlags_HasGamepad;
+    if (bd->XInputPacketNumber != 0 && bd->XInputPacketNumber == xinput_state.dwPacketNumber)
+        return;
+    bd->XInputPacketNumber = xinput_state.dwPacketNumber;
 
     #define IM_SATURATE(V)                      (V < 0.0f ? 0.0f : V > 1.0f ? 1.0f : V)
     #define MAP_BUTTON(KEY_NO, BUTTON_ENUM)     { io.AddKeyEvent(KEY_NO, (gamepad.wButtons & BUTTON_ENUM) != 0); }

docs/CHANGELOG.txt

@@ -54,6 +54,8 @@ Other Changes:
   which may be dangling when using backend in e.g. DLL. (#8945, #2769)
 - Backends: OpenGL3: fixed GL loader to work on Haiku OS which does not support
   `RTLD_NOLOAD`. (#8952) [@Xottab-DUTY, @threedeyes]
+- Backends: Win32: minor optimization not submitting gamepad io again if
+  XInput's dwPacketNumber has not changed. (#8556) [@MidTerm-CN]
 - Examples: SDL2+DirectX11: Try WARP software driver if hardware driver is
   not available. (#5924, #5562)
 - Examples: SDL3+DirectX11: Added SDL3+DirectX11 example. (#8956, #8957) [@tomaz82]