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Horizontal mouse wheel support
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This patch adds support for the horizontal mouse wheel in ImGui. It
affects windows that can be scrolled, as long as the Ctrl key is not
being pressed.

The scrolling speed has been set empirically so that it matches the
scrolling speed on the Firefox browser when the horizontal wheel is
used.

Internally, it adds a MouseHorizWheel to ImGuiIO, which is then used in
NewFrame to scroll the current window.

The SDL/GL2, SDL/GL3, GLFW/GL2 and GLFW/GL3 examples has been modified
to use it.
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@tseeker
tseeker committed Nov 27, 2017
1 parent 0f955b8 commit 77a3107
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Showing 6 changed files with 45 additions and 8 deletions.
9 changes: 6 additions & 3 deletions examples/opengl2_example/imgui_impl_glfw.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@
static GLFWwindow* g_Window = NULL;
static double g_Time = 0.0f;
static bool g_MouseJustPressed[3] = { false, false, false };
static float g_MouseHorizWheel = 0.0f;
static float g_MouseWheel = 0.0f;
static GLuint g_FontTexture = 0;

Expand Down Expand Up @@ -136,9 +137,10 @@ void ImGui_ImplGlfwGL2_MouseButtonCallback(GLFWwindow*, int button, int action,
g_MouseJustPressed[button] = true;
}

void ImGui_ImplGlfwGL2_ScrollCallback(GLFWwindow*, double /*xoffset*/, double yoffset)
void ImGui_ImplGlfwGL2_ScrollCallback(GLFWwindow*, double xoffset, double yoffset)
{
g_MouseWheel += (float)yoffset; // Use fractional mouse wheel.
g_MouseHorizWheel += (float)xoffset; // Use fractional mouse wheel.
g_MouseWheel += (float)yoffset;
}

void ImGui_ImplGlfwGL2_KeyCallback(GLFWwindow*, int key, int, int action, int mods)
Expand Down Expand Up @@ -296,8 +298,9 @@ void ImGui_ImplGlfwGL2_NewFrame()
g_MouseJustPressed[i] = false;
}

io.MouseHorizWheel = g_MouseHorizWheel;
io.MouseWheel = g_MouseWheel;
g_MouseWheel = 0.0f;
g_MouseHorizWheel = g_MouseWheel = 0.0f;

// Hide OS mouse cursor if ImGui is drawing it
glfwSetInputMode(g_Window, GLFW_CURSOR, io.MouseDrawCursor ? GLFW_CURSOR_HIDDEN : GLFW_CURSOR_NORMAL);
Expand Down
9 changes: 6 additions & 3 deletions examples/opengl3_example/imgui_impl_glfw_gl3.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,7 @@
static GLFWwindow* g_Window = NULL;
static double g_Time = 0.0f;
static bool g_MouseJustPressed[3] = { false, false, false };
static float g_MouseHorizWheel = 0.0f;
static float g_MouseWheel = 0.0f;
static GLuint g_FontTexture = 0;
static int g_ShaderHandle = 0, g_VertHandle = 0, g_FragHandle = 0;
Expand Down Expand Up @@ -155,9 +156,10 @@ void ImGui_ImplGlfwGL3_MouseButtonCallback(GLFWwindow*, int button, int action,
g_MouseJustPressed[button] = true;
}

void ImGui_ImplGlfwGL3_ScrollCallback(GLFWwindow*, double /*xoffset*/, double yoffset)
void ImGui_ImplGlfwGL3_ScrollCallback(GLFWwindow*, double xoffset, double yoffset)
{
g_MouseWheel += (float)yoffset; // Use fractional mouse wheel.
g_MouseHorizWheel += (float)xoffset; // Use fractional mouse wheel.
g_MouseWheel += (float)yoffset;
}

void ImGui_ImplGlfwGL3_KeyCallback(GLFWwindow*, int key, int, int action, int mods)
Expand Down Expand Up @@ -408,8 +410,9 @@ void ImGui_ImplGlfwGL3_NewFrame()
g_MouseJustPressed[i] = false;
}

io.MouseHorizWheel = g_MouseHorizWheel;
io.MouseWheel = g_MouseWheel;
g_MouseWheel = 0.0f;
g_MouseHorizWheel = g_MouseWheel = 0.0f;

// Hide OS mouse cursor if ImGui is drawing it
glfwSetInputMode(g_Window, GLFW_CURSOR, io.MouseDrawCursor ? GLFW_CURSOR_HIDDEN : GLFW_CURSOR_NORMAL);
Expand Down
8 changes: 7 additions & 1 deletion examples/sdl_opengl2_example/imgui_impl_sdl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
// Data
static double g_Time = 0.0f;
static bool g_MousePressed[3] = { false, false, false };
static float g_MouseHorizWheel = 0.0f;
static float g_MouseWheel = 0.0f;
static GLuint g_FontTexture = 0;

Expand Down Expand Up @@ -134,6 +135,10 @@ bool ImGui_ImplSdlGL2_ProcessEvent(SDL_Event* event)
{
case SDL_MOUSEWHEEL:
{
if (event->wheel.x > 0)
g_MouseHorizWheel = 1;
if (event->wheel.x < 0)
g_MouseHorizWheel = -1;
if (event->wheel.y > 0)
g_MouseWheel = 1;
if (event->wheel.y < 0)
Expand Down Expand Up @@ -285,8 +290,9 @@ void ImGui_ImplSdlGL2_NewFrame(SDL_Window *window)
io.MouseDown[2] = g_MousePressed[2] || (mouseMask & SDL_BUTTON(SDL_BUTTON_MIDDLE)) != 0;
g_MousePressed[0] = g_MousePressed[1] = g_MousePressed[2] = false;

io.MouseHorizWheel = g_MouseHorizWheel;
io.MouseWheel = g_MouseWheel;
g_MouseWheel = 0.0f;
g_MouseWheel = g_MouseHorizWheel = 0.0f;

// Hide OS mouse cursor if ImGui is drawing it
SDL_ShowCursor(io.MouseDrawCursor ? 0 : 1);
Expand Down
8 changes: 7 additions & 1 deletion examples/sdl_opengl3_example/imgui_impl_sdl_gl3.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
// Data
static double g_Time = 0.0f;
static bool g_MousePressed[3] = { false, false, false };
static float g_MouseHorizWheel = 0.0f;
static float g_MouseWheel = 0.0f;
static GLuint g_FontTexture = 0;
static int g_ShaderHandle = 0, g_VertHandle = 0, g_FragHandle = 0;
Expand Down Expand Up @@ -154,6 +155,10 @@ bool ImGui_ImplSdlGL3_ProcessEvent(SDL_Event* event)
{
case SDL_MOUSEWHEEL:
{
if (event->wheel.x > 0)
g_MouseHorizWheel = 1;
if (event->wheel.x < 0)
g_MouseHorizWheel = -1;
if (event->wheel.y > 0)
g_MouseWheel = 1;
if (event->wheel.y < 0)
Expand Down Expand Up @@ -396,8 +401,9 @@ void ImGui_ImplSdlGL3_NewFrame(SDL_Window* window)
io.MouseDown[2] = g_MousePressed[2] || (mouseMask & SDL_BUTTON(SDL_BUTTON_MIDDLE)) != 0;
g_MousePressed[0] = g_MousePressed[1] = g_MousePressed[2] = false;

io.MouseHorizWheel = g_MouseHorizWheel;
io.MouseWheel = g_MouseWheel;
g_MouseWheel = 0.0f;
g_MouseHorizWheel = g_MouseWheel = 0.0f;

// Hide OS mouse cursor if ImGui is drawing it
SDL_ShowCursor(io.MouseDrawCursor ? 0 : 1);
Expand Down
18 changes: 18 additions & 0 deletions imgui.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -628,6 +628,7 @@ static bool IsKeyPressedMap(ImGuiKey key, bool repeat = true);
static ImFont* GetDefaultFont();
static void SetCurrentFont(ImFont* font);
static void SetCurrentWindow(ImGuiWindow* window);
static void SetWindowScrollX(ImGuiWindow* window, float new_scroll_x);
static void SetWindowScrollY(ImGuiWindow* window, float new_scroll_y);
static void SetWindowPos(ImGuiWindow* window, const ImVec2& pos, ImGuiCond cond);
static void SetWindowSize(ImGuiWindow* window, const ImVec2& size, ImGuiCond cond);
Expand Down Expand Up @@ -2430,6 +2431,16 @@ void ImGui::NewFrame()
}
}

// Horizontal wheel scrolling; for consistency, only allowed if Ctrl is not pressed.
if (g.HoveredWindow && g.IO.MouseHorizWheel != 0.0f && !g.HoveredWindow->Collapsed)
{
ImGuiWindow* window = g.HoveredWindow;
if (!g.IO.KeyCtrl && !(window->Flags & ImGuiWindowFlags_NoScrollWithMouse))
{
SetWindowScrollX(window, window->Scroll.x - g.IO.MouseHorizWheel * 10.f);
}
}

// Pressing TAB activate widget focus
if (g.ActiveId == 0 && g.NavWindow != NULL && g.NavWindow->Active && IsKeyPressedMap(ImGuiKey_Tab, false))
g.NavWindow->FocusIdxTabRequestNext = 0;
Expand Down Expand Up @@ -5244,6 +5255,13 @@ ImVec2 ImGui::GetWindowPos()
return window->Pos;
}

static void SetWindowScrollX(ImGuiWindow* window, float new_scroll_x)
{
window->DC.CursorMaxPos.x += window->Scroll.x; // SizeContents is generally computed based on CursorMaxPos which is affected by scroll position, so we need to apply our change to it.
window->Scroll.x = new_scroll_x;
window->DC.CursorMaxPos.x -= window->Scroll.x;
}

static void SetWindowScrollY(ImGuiWindow* window, float new_scroll_y)
{
window->DC.CursorMaxPos.y += window->Scroll.y; // SizeContents is generally computed based on CursorMaxPos which is affected by scroll position, so we need to apply our change to it.
Expand Down
1 change: 1 addition & 0 deletions imgui.h
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Original file line number Diff line number Diff line change
Expand Up @@ -856,6 +856,7 @@ struct ImGuiIO
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: left, right, middle + extras. ImGui itself mostly only uses left button (BeginPopupContext** are using right button). Others buttons allows 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: 1 unit scrolls about 5 lines text.
float MouseHorizWheel; // Horizontal mouse wheel
bool MouseDrawCursor; // Request ImGui to draw a mouse cursor for you (if you are on a platform without a mouse cursor).
bool KeyCtrl; // Keyboard modifier pressed: Control
bool KeyShift; // Keyboard modifier pressed: Shift
Expand Down

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