Method UpdateMouseWheel

extern/imgui/imgui.cpp:4584–4674

}

void ImGui::UpdateMouseWheel()
{
    ImGuiContext& g = *GImGui;

    // Reset the locked window if we move the mouse or after the timer elapses.
    // FIXME: Ideally we could refactor to have one timer for "changing window w/ same axis" and a shorter timer for "changing window or axis w/ other axis" (#3795)
    if (g.WheelingWindow != NULL)
    {
        g.WheelingWindowReleaseTimer -= g.IO.DeltaTime;
        if (IsMousePosValid() && ImLengthSqr(g.IO.MousePos - g.WheelingWindowRefMousePos) > g.IO.MouseDragThreshold * g.IO.MouseDragThreshold)
            g.WheelingWindowReleaseTimer = 0.0f;
        if (g.WheelingWindowReleaseTimer <= 0.0f)
            LockWheelingWindow(NULL, 0.0f);
    }

    ImVec2 wheel;
    wheel.x = TestKeyOwner(ImGuiKey_MouseWheelX, ImGuiKeyOwner_None) ? g.IO.MouseWheelH : 0.0f;
    wheel.y = TestKeyOwner(ImGuiKey_MouseWheelY, ImGuiKeyOwner_None) ? g.IO.MouseWheel : 0.0f;

    //IMGUI_DEBUG_LOG("MouseWheel X:%.3f Y:%.3f\n", wheel_x, wheel_y);
    ImGuiWindow* mouse_window = g.WheelingWindow ? g.WheelingWindow : g.HoveredWindow;
    if (!mouse_window || mouse_window->Collapsed)
        return;

    // Zoom / Scale window
    // FIXME-OBSOLETE: This is an old feature, it still works but pretty much nobody is using it and may be best redesigned.
    if (wheel.y != 0.0f && g.IO.KeyCtrl && g.IO.FontAllowUserScaling)
    {
        LockWheelingWindow(mouse_window, wheel.y);
        ImGuiWindow* window = mouse_window;
        const float new_font_scale = ImClamp(window->FontWindowScale + g.IO.MouseWheel * 0.10f, 0.50f, 2.50f);
        const float scale = new_font_scale / window->FontWindowScale;
        window->FontWindowScale = new_font_scale;
        if (window == window->RootWindow)
        {
            const ImVec2 offset = window->Size * (1.0f - scale) * (g.IO.MousePos - window->Pos) / window->Size;
            SetWindowPos(window, window->Pos + offset, 0);
            window->Size = ImFloor(window->Size * scale);
            window->SizeFull = ImFloor(window->SizeFull * scale);
        }
        return;
    }
    if (g.IO.KeyCtrl)
        return;

    // 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)
    const bool swap_axis = g.IO.KeyShift && !g.IO.ConfigMacOSXBehaviors;
    if (swap_axis)
    {
        wheel.x = wheel.y;
        wheel.y = 0.0f;
    }

    // Maintain a rough average of moving magnitude on both axises
    // FIXME: should by based on wall clock time rather than frame-counter
    g.WheelingAxisAvg.x = ImExponentialMovingAverage(g.WheelingAxisAvg.x, ImAbs(wheel.x), 30);