From 9a4fd69f6dd6f9cdf89c744bb7a796bc9db0a0b2 Mon Sep 17 00:00:00 2001
From: ocornut <omar@miracleworld.net>
Date: Wed, 10 Dec 2025 18:35:22 +0100
Subject: [PATCH] Backends: GLFW: avoid repeated
 glfwSetCursor()/glfwSetInputMode() calls when unnecessary.

---
 backends/imgui_impl_glfw.cpp | 17 ++++++++++++++---
 docs/CHANGELOG.txt           |  2 ++
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/backends/imgui_impl_glfw.cpp b/backends/imgui_impl_glfw.cpp
index ac176a080..d088e9693 100644
--- a/backends/imgui_impl_glfw.cpp
+++ b/backends/imgui_impl_glfw.cpp
@@ -29,6 +29,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2025-12-10: Avoid repeated glfwSetCursor()/glfwSetInputMode() calls when unnecessary. Lowers overhead for very high framerates (e.g. 10k+ FPS).
 //  2025-11-06: Lower minimum requirement to GLFW 3.0. Though a recent version e.g GLFW 3.4 is highly recommended.
 //  2025-09-18: Call platform_io.ClearPlatformHandlers() on shutdown.
 //  2025-09-15: Content Scales are always reported as 1.0 on Wayland. FramebufferScale are always reported as 1.0 on X11. (#8920, #8921)
@@ -188,6 +189,7 @@ struct ImGui_ImplGlfw_Data
     GLFWwindow*             MouseWindow;
 #if GLFW_HAS_CREATECURSOR
     GLFWcursor*             MouseCursors[ImGuiMouseCursor_COUNT];
+    GLFWcursor*             LastMouseCursor;
 #endif
     ImVec2                  LastValidMousePos;
     bool                    IsWayland;
@@ -849,15 +851,24 @@ static void ImGui_ImplGlfw_UpdateMouseCursor()
         GLFWwindow* window = bd->Window;
         if (imgui_cursor == ImGuiMouseCursor_None || io.MouseDrawCursor)
         {
-            // Hide OS mouse cursor if imgui is drawing it or if it wants no cursor
-            glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_HIDDEN);
+            if (bd->LastMouseCursor != nullptr)
+            {
+                // Hide OS mouse cursor if imgui is drawing it or if it wants no cursor
+                glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_HIDDEN);
+                bd->LastMouseCursor = nullptr;
+            }
         }
         else
         {
             // Show OS mouse cursor
             // FIXME-PLATFORM: Unfocused windows seems to fail changing the mouse cursor with GLFW 3.2, but 3.3 works here.
 #if GLFW_HAS_CREATECURSOR
-            glfwSetCursor(window, bd->MouseCursors[imgui_cursor] ? bd->MouseCursors[imgui_cursor] : bd->MouseCursors[ImGuiMouseCursor_Arrow]);
+            GLFWcursor* cursor = bd->MouseCursors[imgui_cursor] ? bd->MouseCursors[imgui_cursor] : bd->MouseCursors[ImGuiMouseCursor_Arrow];
+            if (bd->LastMouseCursor != cursor)
+            {
+                glfwSetCursor(window, cursor);
+                bd->LastMouseCursor = cursor;
+            }
 #endif
             glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_NORMAL);
         }
diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
index 2353faddb..32008203d 100644
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -87,6 +87,8 @@ Other Changes:
     non-ASCII values to io.AddInputCharacter(). (#9099)
   - Debug Log: can output to debugger on Windows. (#5855)
 - Backends:
+  - GLFW: Avoid repeated glfwSetCursor()/glfwSetInputMode() calls when unnecessary.
+    Lowers overhead for very high framerates (e.g. 10k+ FPS). [@maxliani]
   - SDL_GPU3: macOS version can use MSL shaders in order to support macOS 10.14+
     (vs Metallib shaders requiring macOS 14+). Requires application calling
     SDL_CreateGPUDevice() with SDL_GPU_SHADERFORMAT_MSL. (#9076) [@Niminem]