Backends, Inputs: Made horizontal scroll wheel and horizontal scroll direction consistent accross backends/os. (#4019, #6096, #1463)

Documented assumptions.

backends/imgui_impl_glfw.cpp

@@ -16,6 +16,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2023-02-01: Inputs: flipping both wheel axises when running on Emscripten's GLFW emulation. (#6096)
 //  2023-01-04: Inputs: Fixed mods state on Linux when using Alt-GR text input (e.g. German keyboard layout), could lead to broken text input. Revert a 2022/01/17 change were we resumed using mods provided by GLFW, turns out they were faulty.
 //  2022-11-22: Perform a dummy glfwGetError() read to cancel missing names with glfwGetKeyName(). (#5908)
 //  2022-10-18: Perform a dummy glfwGetError() read to cancel missing mouse cursors errors. Using GLFW_VERSION_COMBINED directly. (#5785)
@@ -283,6 +284,13 @@ void ImGui_ImplGlfw_ScrollCallback(GLFWwindow* window, double xoffset, double yo
     if (bd->PrevUserCallbackScroll != nullptr && window == bd->Window)
         bd->PrevUserCallbackScroll(window, xoffset, yoffset);
 
+#if defined(__EMSCRIPTEN__)
+    // Emscripten's GLFW emulation reports grossly mis-scaled and flipped scroll events.
+    // The scale is still currently incorrect, see #4019 #6096 for details.
+    xoffset /= -120.0f;
+    yoffset /= -120.0f;
+#endif
+
     ImGuiIO& io = ImGui::GetIO();
     io.AddMouseWheelEvent((float)xoffset, (float)yoffset);
 }

backends/imgui_impl_sdl.cpp

@@ -18,6 +18,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2023-02-01: Flipping SDL_MOUSEWHEEL 'wheel.x' value to match other backends and offer consistent horizontal scrolling direction. (#4019, #6096, #1463)
 //  2022-10-11: Using 'nullptr' instead of 'NULL' as per our switch to C++11.
 //  2022-09-26: Inputs: Disable SDL 2.0.22 new "auto capture" (SDL_HINT_MOUSE_AUTO_CAPTURE) which prevents drag and drop across windows for multi-viewport support + don't capture when drag and dropping. (#5710)
 //  2022-09-26: Inputs: Renamed ImGuiKey_ModXXX introduced in 1.87 to ImGuiMod_XXX (old names still supported).
@@ -260,7 +261,7 @@ bool ImGui_ImplSDL2_ProcessEvent(const SDL_Event* event)
         }
         case SDL_MOUSEWHEEL:
         {
-            float wheel_x = (event->wheel.x > 0) ? 1.0f : (event->wheel.x < 0) ? -1.0f : 0.0f;
+            float wheel_x = (event->wheel.x < 0) ? 1.0f : (event->wheel.x > 0) ? -1.0f : 0.0f; // About the clamping and flipped axis: see #4019
             float wheel_y = (event->wheel.y > 0) ? 1.0f : (event->wheel.y < 0) ? -1.0f : 0.0f;
             io.AddMouseWheelEvent(wheel_x, wheel_y);
             return true;

backends/imgui_impl_win32.cpp

@@ -34,6 +34,7 @@ typedef DWORD (WINAPI *PFN_XInputGetState)(DWORD, XINPUT_STATE*);
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2023-02-02: Inputs: Flipping WM_MOUSEHWHEEL (horizontal mouse-wheel) value to match other backends and offer consistent horizontal scrolling direction. (#4019, #6096, #1463)
 //  2022-10-11: Using 'nullptr' instead of 'NULL' as per our switch to C++11.
 //  2022-09-28: Inputs: Convert WM_CHAR values with MultiByteToWideChar() when window class was registered as MBCS (not Unicode).
 //  2022-09-26: Inputs: Renamed ImGuiKey_ModXXX introduced in 1.87 to ImGuiMod_XXX (old names still supported).
@@ -565,7 +566,7 @@ IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hwnd, UINT msg, WPARA
         io.AddMouseWheelEvent(0.0f, (float)GET_WHEEL_DELTA_WPARAM(wParam) / (float)WHEEL_DELTA);
         return 0;
     case WM_MOUSEHWHEEL:
-        io.AddMouseWheelEvent((float)GET_WHEEL_DELTA_WPARAM(wParam) / (float)WHEEL_DELTA, 0.0f);
+        io.AddMouseWheelEvent(-(float)GET_WHEEL_DELTA_WPARAM(wParam) / (float)WHEEL_DELTA, 0.0f);
         return 0;
     case WM_KEYDOWN:
     case WM_KEYUP:

docs/CHANGELOG.txt

@@ -35,6 +35,36 @@ HOW TO UPDATE?
  VERSION 1.89.3 (In Progress)
 -----------------------------------------------------------------------
 
+Breaking changes:
+
+- Inputs, Scrolling: Made horizontal scroll wheel and horizontal scroll direction consistent
+  accross backends/os. (#4019, #6096, #1463) [@PathogenDavid, @ocornut, @rokups]
+  - Clarified that 'wheel_y > 0.0f' scrolls Up, 'wheel_y > 0.0f' scrolls Down.
+  - Clarified that 'wheel_x > 0.0f' scrolls Left, 'wheel_x > 0.0f' scrolls Right.
+  - Backends: Win32: flipping WM_MOUSEHWHEEL value to match other backends and
+    offer consistent horizontal scrolling direction. (#4019)
+  - Backends: SDL: flipping SDL_MOUSEWHEEL 'wheel.x' value to match other backends and
+    offer consistent horizontal scrolling direction. (#4019)
+  - Backends: GLFW+Emscripten: flipping both wheels axises + scaling magnitude down when
+    running on Emscripten's GLFW emulation. (#6096) [@topolarity]
+  - Shift+WheelY support on non-OSX machines was already correct. (#2424, #1463)
+    (whereaas on OSX machines Shift+WheelY turns into WheelX at the OS level).
+  - If you use a custom-backend, you should verify that:
+    - Wheel up (*) emit wheel_y > 0.0f values and scrolls up.
+    - Wheel down (*) emit wheel_y < 0.0f values and scrolls down.
+    - Wheel left (*) or mod+wheel up emit wheel_x > 0.0f values and scroll Left.
+    - Wheel right (*) or mod+wheel down emits wheel_x < 0.0f values and scroll Right.
+    - (*) both axises flipped on OSX for mouse and touchpad when 'Natural Scrolling' is on.
+    - (*) both axises flipped On Windows for touchpad only when 'Settings->Touchpad->Down motion scrolls up' is set.
+    - You can use 'Demo->Tools->Debug Log->IO" to visualize values submitted to Dear ImGui.
+  - Known issues remaining with Emscripten:
+    - The magnitude of wheeling values on Emscripten setups is still mostly wrong. (#6096)
+    - When running the Emscripten app on a Mac with a mouse, SHIFT+WheelY doesn't turn into WheelX.
+      This is because we don't know that we are running on Mac and apply our own Shift+swapping
+      on top of OSX' own swapping, so wheel axises are swapped twice. Emscripten apps may need
+      to find a way to detect this and set io.ConfigMacOSXBehaviors manually (if you know a way
+      let us know!), or offer the "OSX-style behavior" option to their user.
+
 All changes:
 
 - Window: Avoid rendering shapes for hidden resize grips.

examples/example_emscripten_glfw_opengl3/Makefile

@@ -0,0 +1,91 @@
+#
+# Makefile to use with GLFW+emscripten
+# See https://emscripten.org/docs/getting_started/downloads.html
+# for installation instructions.
+#
+# This Makefile assumes you have loaded emscripten's environment.
+# (On Windows, you may need to execute emsdk_env.bat or encmdprompt.bat ahead)
+#
+# Running `make` will produce three files:
+#  - web/index.html
+#  - web/index.js
+#  - web/index.wasm
+#
+# All three are needed to run the demo.
+
+CC = emcc
+CXX = em++
+WEB_DIR = web
+EXE = $(WEB_DIR)/index.html
+IMGUI_DIR = ../..
+SOURCES = main.cpp
+SOURCES += $(IMGUI_DIR)/imgui.cpp $(IMGUI_DIR)/imgui_demo.cpp $(IMGUI_DIR)/imgui_draw.cpp $(IMGUI_DIR)/imgui_tables.cpp $(IMGUI_DIR)/imgui_widgets.cpp
+SOURCES += $(IMGUI_DIR)/backends/imgui_impl_glfw.cpp $(IMGUI_DIR)/backends/imgui_impl_opengl3.cpp
+OBJS = $(addsuffix .o, $(basename $(notdir $(SOURCES))))
+UNAME_S := $(shell uname -s)
+CPPFLAGS =
+LDFLAGS =
+EMS =
+
+##---------------------------------------------------------------------
+## EMSCRIPTEN OPTIONS
+##---------------------------------------------------------------------
+
+# ("EMS" options gets added to both CPPFLAGS and LDFLAGS, whereas some options are for linker only)
+EMS += -s USE_GLFW=3
+EMS += -s DISABLE_EXCEPTION_CATCHING=1
+LDFLAGS += -s WASM=1 -s ALLOW_MEMORY_GROWTH=1 -s NO_EXIT_RUNTIME=0 -s ASSERTIONS=1
+
+# Uncomment next line to fix possible rendering bugs with Emscripten version older then 1.39.0 (https://github.com/ocornut/imgui/issues/2877)
+#EMS += -s BINARYEN_TRAP_MODE=clamp
+#EMS += -s SAFE_HEAP=1    ## Adds overhead
+
+# Emscripten allows preloading a file or folder to be accessible at runtime.
+# The Makefile for this example project suggests embedding the misc/fonts/ folder into our application, it will then be accessible as "/fonts"
+# See documentation for more details: https://emscripten.org/docs/porting/files/packaging_files.html
+# (Default value is 0. Set to 1 to enable file-system and include the misc/fonts/ folder as part of the build.)
+USE_FILE_SYSTEM ?= 0
+ifeq ($(USE_FILE_SYSTEM), 0)
+LDFLAGS += -s NO_FILESYSTEM=1
+CPPFLAGS += -DIMGUI_DISABLE_FILE_FUNCTIONS
+endif
+ifeq ($(USE_FILE_SYSTEM), 1)
+LDFLAGS += --no-heap-copy --preload-file ../../misc/fonts@/fonts
+endif
+
+##---------------------------------------------------------------------
+## FINAL BUILD FLAGS
+##---------------------------------------------------------------------
+
+CPPFLAGS += -I$(IMGUI_DIR) -I$(IMGUI_DIR)/backends
+#CPPFLAGS += -g
+CPPFLAGS += -Wall -Wformat -Os $(EMS)
+LDFLAGS += --shell-file shell_minimal.html $(EMS)
+
+##---------------------------------------------------------------------
+## BUILD RULES
+##---------------------------------------------------------------------
+
+%.o:%.cpp
+	$(CXX) $(CPPFLAGS) $(CXXFLAGS) -c -o $@ $<
+
+%.o:$(IMGUI_DIR)/%.cpp
+	$(CXX) $(CPPFLAGS) $(CXXFLAGS) -c -o $@ $<
+
+%.o:$(IMGUI_DIR)/backends/%.cpp
+	$(CXX) $(CPPFLAGS) $(CXXFLAGS) -c -o $@ $<
+
+all: $(EXE)
+	@echo Build complete for $(EXE)
+
+$(WEB_DIR):
+	mkdir $@
+
+serve: all
+	python3 -m http.server -d $(WEB_DIR)
+
+$(EXE): $(OBJS) $(WEB_DIR)
+	$(CXX) -o $@ $(OBJS) $(LDFLAGS)
+
+clean:
+	rm -rf $(OBJS) $(WEB_DIR)

examples/example_emscripten_glfw_opengl3/main.cpp

@@ -0,0 +1,167 @@
+// Dear ImGui: standalone example application for Emscripten, using GLFW + OpenGL3
+// (Emscripten is a C++-to-javascript compiler, used to publish executables for the web. See https://emscripten.org/)
+// If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
+// Read online: https://github.com/ocornut/imgui/tree/master/docs
+
+// This is mostly the same code as the GLFW + OpenGL3 example, simply with the modifications needed to run on Emscripten.
+// It is possible to combine both code into a single source file that will compile properly on Desktop and using Emscripten.
+// See https://github.com/ocornut/imgui/pull/2492 as an example on how to do just that.
+
+#include "imgui.h"
+#include "imgui_impl_glfw.h"
+#include "imgui_impl_opengl3.h"
+#include <stdio.h>
+#include <emscripten.h>
+#define GL_SILENCE_DEPRECATION
+#if defined(IMGUI_IMPL_OPENGL_ES2)
+#include <GLES2/gl2.h>
+#endif
+#include <GLFW/glfw3.h> // Will drag system OpenGL headers
+
+// Emscripten requires to have full control over the main loop. We're going to store our GLFW book-keeping variables globally.
+// Having a single function that acts as a loop prevents us to store state in the stack of said function. So we need some location for this.
+GLFWwindow*     g_Window = NULL;
+
+static void glfw_error_callback(int error, const char* description)
+{
+    fprintf(stderr, "Glfw Error %d: %s\n", error, description);
+}
+
+// For clarity, our main loop code is declared at the end.
+static void main_loop(void*);
+
+int main(int, char**)
+{
+    // Setup window
+    glfwSetErrorCallback(glfw_error_callback);
+    if (!glfwInit())
+        return 1;
+
+    // For the browser using Emscripten, we are going to use WebGL1 with GL ES2. See the Makefile. for requirement details.
+    // It is very likely the generated file won't work in many browsers. Firefox is the only sure bet, but I have successfully
+    // run this code on Chrome for Android for example.
+    const char* glsl_version = "#version 100";
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 2);
+    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
+    glfwWindowHint(GLFW_CLIENT_API, GLFW_OPENGL_ES_API);
+
+    // Create window with graphics context
+    GLFWwindow* window = glfwCreateWindow(1280, 720, "Dear ImGui GLFW+Emscripten example", NULL, NULL);
+    if (window == NULL)
+        return 1;
+    glfwMakeContextCurrent(window);
+    glfwSwapInterval(1); // Enable vsync
+    g_Window = window;
+
+    // Setup Dear ImGui context
+    IMGUI_CHECKVERSION();
+    ImGui::CreateContext();
+    ImGuiIO& io = ImGui::GetIO(); (void)io;
+    //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
+    //io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+
+    // For an Emscripten build we are disabling file-system access, so let's not attempt to do a fopen() of the imgui.ini file.
+    // You may manually call LoadIniSettingsFromMemory() to load settings from your own storage.
+    io.IniFilename = NULL;
+
+    // Setup Dear ImGui style
+    ImGui::StyleColorsDark();
+    //ImGui::StyleColorsLight();
+
+    // Setup Platform/Renderer backends
+    ImGui_ImplGlfw_InitForOpenGL(window, true);
+    ImGui_ImplOpenGL3_Init(glsl_version);
+
+    // Load Fonts
+    // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
+    // - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
+    // - If the file cannot be loaded, the function will return NULL. Please handle those errors in your application (e.g. use an assertion, or display an error and quit).
+    // - The fonts will be rasterized at a given size (w/ oversampling) and stored into a texture when calling ImFontAtlas::Build()/GetTexDataAsXXXX(), which ImGui_ImplXXXX_NewFrame below will call.
+    // - Use '#define IMGUI_ENABLE_FREETYPE' in your imconfig file to use Freetype for higher quality font rendering.
+    // - Read 'docs/FONTS.md' for more instructions and details.
+    // - Remember that in C/C++ if you want to include a backslash \ in a string literal you need to write a double backslash \\ !
+    // - Emscripten allows preloading a file or folder to be accessible at runtime. See Makefile for details.
+    //io.Fonts->AddFontDefault();
+#ifndef IMGUI_DISABLE_FILE_FUNCTIONS
+    //io.Fonts->AddFontFromFileTTF("fonts/segoeui.ttf", 18.0f);
+    io.Fonts->AddFontFromFileTTF("fonts/DroidSans.ttf", 16.0f);
+    //io.Fonts->AddFontFromFileTTF("fonts/Roboto-Medium.ttf", 16.0f);
+    //io.Fonts->AddFontFromFileTTF("fonts/Cousine-Regular.ttf", 15.0f);
+    //io.Fonts->AddFontFromFileTTF("fonts/ProggyTiny.ttf", 10.0f);
+    //ImFont* font = io.Fonts->AddFontFromFileTTF("fonts/ArialUni.ttf", 18.0f, NULL, io.Fonts->GetGlyphRangesJapanese());
+    //IM_ASSERT(font != NULL);
+#endif
+
+    // This function call won't return, and will engage in an infinite loop, processing events from the browser, and dispatching them.
+    emscripten_set_main_loop_arg(main_loop, NULL, 0, true);
+}
+
+static void main_loop(void* arg)
+{
+    IM_UNUSED(arg); // We can pass this argument as the second parameter of emscripten_set_main_loop_arg(), but we don't use that.
+
+    // Our state (make them static = more or less global) as a convenience to keep the example terse.
+    static bool show_demo_window = true;
+    static bool show_another_window = false;
+    static ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);
+
+    // Poll and handle events (inputs, window resize, etc.)
+    // You can read the io.WantCaptureMouse, io.WantCaptureKeyboard flags to tell if dear imgui wants to use your inputs.
+    // - When io.WantCaptureMouse is true, do not dispatch mouse input data to your main application, or clear/overwrite your copy of the mouse data.
+    // - When io.WantCaptureKeyboard is true, do not dispatch keyboard input data to your main application, or clear/overwrite your copy of the keyboard data.
+    // Generally you may always pass all inputs to dear imgui, and hide them from your application based on those two flags.
+    glfwPollEvents();
+
+    // Start the Dear ImGui frame
+    ImGui_ImplOpenGL3_NewFrame();
+    ImGui_ImplGlfw_NewFrame();
+    ImGui::NewFrame();
+
+    // 1. Show the big demo window (Most of the sample code is in ImGui::ShowDemoWindow()! You can browse its code to learn more about Dear ImGui!).
+    if (show_demo_window)
+        ImGui::ShowDemoWindow(&show_demo_window);
+
+    // 2. Show a simple window that we create ourselves. We use a Begin/End pair to create a named window.
+    {
+        static float f = 0.0f;
+        static int counter = 0;
+
+        ImGui::Begin("Hello, world!");                                // Create a window called "Hello, world!" and append into it.
+
+        ImGui::Text("This is some useful text.");                     // Display some text (you can use a format strings too)
+        ImGui::Checkbox("Demo Window", &show_demo_window);            // Edit bools storing our window open/close state
+        ImGui::Checkbox("Another Window", &show_another_window);
+
+        ImGui::SliderFloat("float", &f, 0.0f, 1.0f);                  // Edit 1 float using a slider from 0.0f to 1.0f
+        ImGui::ColorEdit3("clear color", (float*)&clear_color);       // Edit 3 floats representing a color
+
+        if (ImGui::Button("Button"))                                  // Buttons return true when clicked (most widgets return true when edited/activated)
+            counter++;
+        ImGui::SameLine();
+        ImGui::Text("counter = %d", counter);
+
+        ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / ImGui::GetIO().Framerate, ImGui::GetIO().Framerate);
+        ImGui::End();
+    }
+
+    // 3. Show another simple window.
+    if (show_another_window)
+    {
+        ImGui::Begin("Another Window", &show_another_window);         // Pass a pointer to our bool variable (the window will have a closing button that will clear the bool when clicked)
+        ImGui::Text("Hello from another window!");
+        if (ImGui::Button("Close Me"))
+            show_another_window = false;
+        ImGui::End();
+    }
+
+    // Rendering
+    ImGui::Render();
+    int display_w, display_h;
+    glfwGetFramebufferSize(g_Window, &display_w, &display_h);
+    glViewport(0, 0, display_w, display_h);
+    glClearColor(clear_color.x * clear_color.w, clear_color.y * clear_color.w, clear_color.z * clear_color.w, clear_color.w);
+    glClear(GL_COLOR_BUFFER_BIT);
+    ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
+
+    glfwSwapBuffers(g_Window);
+}

examples/example_emscripten_glfw_opengl3/shell_minimal.html

@@ -0,0 +1,64 @@
+<!doctype html>
+<html lang="en-us">
+  <head>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, minimum-scale=1, user-scalable=no"/>
+    <title>Dear ImGui GLFW+Emscripten example</title>
+    <style>
+        body { margin: 0; background-color: black }
+        .emscripten {
+            position: absolute;
+            top: 0px;
+            left: 0px;
+            margin: 0px;
+            border: 0;
+            width: 100%;
+            height: 100%;
+            overflow: hidden;
+            display: block;
+            image-rendering: optimizeSpeed;
+            image-rendering: -moz-crisp-edges;
+            image-rendering: -o-crisp-edges;
+            image-rendering: -webkit-optimize-contrast;
+            image-rendering: optimize-contrast;
+            image-rendering: crisp-edges;
+            image-rendering: pixelated;
+            -ms-interpolation-mode: nearest-neighbor;
+        }
+    </style>
+  </head>
+  <body>
+    <canvas class="emscripten" id="canvas" oncontextmenu="event.preventDefault()"></canvas>
+    <script type='text/javascript'>
+      var Module = {
+        preRun: [],
+        postRun: [],
+        print: (function() {
+            return function(text) {
+                text = Array.prototype.slice.call(arguments).join(' ');
+                console.log(text);
+            };
+        })(),
+        printErr: function(text) {
+            text = Array.prototype.slice.call(arguments).join(' ');
+            console.error(text);
+        },
+        canvas: (function() {
+            var canvas = document.getElementById('canvas');
+            //canvas.addEventListener("webglcontextlost", function(e) { alert('FIXME: WebGL context lost, please reload the page'); e.preventDefault(); }, false);
+            return canvas;
+        })(),
+        setStatus: function(text) {
+            console.log("status: " + text);
+        },
+        monitorRunDependencies: function(left) {
+            // no run dependencies to log
+        }
+      };
+      window.onerror = function() {
+        console.log("onerror: " + event);
+      };
+    </script>
+    {{{ SCRIPT }}}
+  </body>
+</html>

imgui.cpp

@@ -1467,7 +1467,7 @@ void ImGuiIO::AddMouseButtonEvent(int mouse_button, bool down)
     g.InputEventsQueue.push_back(e);
 }
 
-// Queue a mouse wheel event (most mouse/API will only have a Y component)
+// Queue a mouse wheel event (some mouse/API may only have a Y component)
 void ImGuiIO::AddMouseWheelEvent(float wheel_x, float wheel_y)
 {
     ImGuiContext& g = *GImGui;
@@ -8488,7 +8488,8 @@ void ImGui::UpdateMouseWheel()
 
     // Mouse wheel scrolling
     // As a standard behavior holding SHIFT while using Vertical Mouse Wheel triggers Horizontal scroll instead
-    // (we avoid doing it on OSX as it the OS input layer handles this already)
+    // - We avoid doing it on OSX as it the OS input layer handles this already.
+    // - However this means when running on OSX over Emcripten, Shift+WheelY will incur two swappings (1 in OS, 1 here), cancelling the feature.
     const bool swap_axis = g.IO.KeyShift && !g.IO.ConfigMacOSXBehaviors;
     if (swap_axis)
     {

imgui.h

@@ -23,7 +23,7 @@
 // Library Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals, e.g. '#if IMGUI_VERSION_NUM > 12345')
 #define IMGUI_VERSION               "1.89.3 WIP"
-#define IMGUI_VERSION_NUM           18925
+#define IMGUI_VERSION_NUM           18926
 #define IMGUI_HAS_TABLE
 
 /*
@@ -1968,7 +1968,7 @@ struct ImGuiIO
     IMGUI_API void  AddKeyAnalogEvent(ImGuiKey key, bool down, float v);    // Queue a new key down/up event for analog values (e.g. ImGuiKey_Gamepad_ values). Dead-zones should be handled by the backend.
     IMGUI_API void  AddMousePosEvent(float x, float y);                     // Queue a mouse position update. Use -FLT_MAX,-FLT_MAX to signify no mouse (e.g. app not focused and not hovered)
     IMGUI_API void  AddMouseButtonEvent(int button, bool down);             // Queue a mouse button change
-    IMGUI_API void  AddMouseWheelEvent(float wh_x, float wh_y);             // Queue a mouse wheel update
+    IMGUI_API void  AddMouseWheelEvent(float wheel_x, float wheel_y);       // Queue a mouse wheel update. wheel_y<0: scroll down, wheel_y>0: scroll up, wheel_x<0: scroll right, wheel_x>0: scroll left.
     IMGUI_API void  AddFocusEvent(bool focused);                            // Queue a gain/loss of focus for the application (generally based on OS/platform focus of your window)
     IMGUI_API void  AddInputCharacter(unsigned int c);                      // Queue a new character input
     IMGUI_API void  AddInputCharacterUTF16(ImWchar16 c);                    // Queue a new character input from a UTF-16 character, it can be a surrogate
@@ -2018,8 +2018,8 @@ struct ImGuiIO
     // (reading from those variables is fair game, as they are extremely unlikely to be moving anywhere)
     ImVec2      MousePos;                           // Mouse position, in pixels. Set to ImVec2(-FLT_MAX, -FLT_MAX) if mouse is unavailable (on another screen, etc.)
     bool        MouseDown[5];                       // Mouse buttons: 0=left, 1=right, 2=middle + extras (ImGuiMouseButton_COUNT == 5). Dear ImGui mostly uses left and right buttons. Other buttons allow us to track if the mouse is being used by your application + available to user as a convenience via IsMouse** API.
-    float       MouseWheel;                         // Mouse wheel Vertical: 1 unit scrolls about 5 lines text.
-    float       MouseWheelH;                        // Mouse wheel Horizontal. Most users don't have a mouse with a horizontal wheel, may not be filled by all backends.
+    float       MouseWheel;                         // Mouse wheel Vertical: 1 unit scrolls about 5 lines text. >0 scrolls Up, <0 scrolls Down. Hold SHIFT to turn vertical scroll into horizontal scroll.
+    float       MouseWheelH;                        // Mouse wheel Horizontal. >0 scrolls Left, <0 scrolls Right. Most users don't have a mouse with a horizontal wheel, may not be filled by all backends.
     bool        KeyCtrl;                            // Keyboard modifier down: Control
     bool        KeyShift;                           // Keyboard modifier down: Shift
     bool        KeyAlt;                             // Keyboard modifier down: Alt

imgui_demo.cpp

@@ -457,6 +457,7 @@ void ImGui::ShowDemoWindow(bool* p_open)
             ImGui::Checkbox("io.ConfigWindowsResizeFromEdges", &io.ConfigWindowsResizeFromEdges);
             ImGui::SameLine(); HelpMarker("Enable resizing of windows from their edges and from the lower-left corner.\nThis requires (io.BackendFlags & ImGuiBackendFlags_HasMouseCursors) because it needs mouse cursor feedback.");
             ImGui::Checkbox("io.ConfigWindowsMoveFromTitleBarOnly", &io.ConfigWindowsMoveFromTitleBarOnly);
+            ImGui::Checkbox("io.ConfigMacOSXBehaviors", &io.ConfigMacOSXBehaviors);
             ImGui::Checkbox("io.MouseDrawCursor", &io.MouseDrawCursor);
             ImGui::SameLine(); HelpMarker("Instruct Dear ImGui to render a mouse cursor itself. Note that a mouse cursor rendered via your application GPU rendering path will feel more laggy than hardware cursor, but will be more in sync with your other visuals.\n\nSome desktop applications may use both kinds of cursors (e.g. enable software cursor only when resizing/dragging something).");
             ImGui::Text("Also see Style->Rendering for rendering options.");