Method ColorButton

src/external/imgui/imgui_widgets.cpp:5764–5842

A little color square. Return true when clicked. FIXME: May want to display/ignore the alpha component in the color display? Yet show it in the tooltip. 'desc_id' is not called 'label' because we don't display it next to the button, but only in the tooltip. Note that 'col' may be encoded in HSV if ImGuiColorEditFlags_InputHSV is set.

// 'desc_id' is not called 'label' because we don't display it next to the button, but only in the tooltip.
// Note that 'col' may be encoded in HSV if ImGuiColorEditFlags_InputHSV is set.
bool ImGui::ColorButton(const char* desc_id, const ImVec4& col, ImGuiColorEditFlags flags, const ImVec2& size_arg)
{
    ImGuiWindow* window = GetCurrentWindow();
    if (window->SkipItems)
        return false;

    ImGuiContext& g = *GImGui;
    const ImGuiID id = window->GetID(desc_id);
    const float default_size = GetFrameHeight();
    const ImVec2 size(size_arg.x == 0.0f ? default_size : size_arg.x, size_arg.y == 0.0f ? default_size : size_arg.y);
    const ImRect bb(window->DC.CursorPos, window->DC.CursorPos + size);
    ItemSize(bb, (size.y >= default_size) ? g.Style.FramePadding.y : 0.0f);
    if (!ItemAdd(bb, id))
        return false;

    bool hovered, held;
    bool pressed = ButtonBehavior(bb, id, &hovered, &held);

    if (flags & ImGuiColorEditFlags_NoAlpha)
        flags &= ~(ImGuiColorEditFlags_AlphaPreview | ImGuiColorEditFlags_AlphaPreviewHalf);

    ImVec4 col_rgb = col;
    if (flags & ImGuiColorEditFlags_InputHSV)
        ColorConvertHSVtoRGB(col_rgb.x, col_rgb.y, col_rgb.z, col_rgb.x, col_rgb.y, col_rgb.z);

    ImVec4 col_rgb_without_alpha(col_rgb.x, col_rgb.y, col_rgb.z, 1.0f);
    float grid_step = ImMin(size.x, size.y) / 2.99f;
    float rounding = ImMin(g.Style.FrameRounding, grid_step * 0.5f);
    ImRect bb_inner = bb;
    float off = 0.0f;
    if ((flags & ImGuiColorEditFlags_NoBorder) == 0)
    {
        off = -0.75f; // The border (using Col_FrameBg) tends to look off when color is near-opaque and rounding is enabled. This offset seemed like a good middle ground to reduce those artifacts.
        bb_inner.Expand(off);
    }
    if ((flags & ImGuiColorEditFlags_AlphaPreviewHalf) && col_rgb.w < 1.0f)
    {
        float mid_x = IM_ROUND((bb_inner.Min.x + bb_inner.Max.x) * 0.5f);
        RenderColorRectWithAlphaCheckerboard(window->DrawList, ImVec2(bb_inner.Min.x + grid_step, bb_inner.Min.y), bb_inner.Max, GetColorU32(col_rgb), grid_step, ImVec2(-grid_step + off, off), rounding, ImDrawFlags_RoundCornersRight);
        window->DrawList->AddRectFilled(bb_inner.Min, ImVec2(mid_x, bb_inner.Max.y), GetColorU32(col_rgb_without_alpha), rounding, ImDrawFlags_RoundCornersLeft);
    }
    else
    {
        // Because GetColorU32() multiplies by the global style Alpha and we don't want to display a checkerboard if the source code had no alpha
        ImVec4 col_source = (flags & ImGuiColorEditFlags_AlphaPreview) ? col_rgb : col_rgb_without_alpha;
        if (col_source.w < 1.0f)
            RenderColorRectWithAlphaCheckerboard(window->DrawList, bb_inner.Min, bb_inner.Max, GetColorU32(col_source), grid_step, ImVec2(off, off), rounding);
        else
            window->DrawList->AddRectFilled(bb_inner.Min, bb_inner.Max, GetColorU32(col_source), rounding);
    }
    RenderNavHighlight(bb, id);
    if ((flags & ImGuiColorEditFlags_NoBorder) == 0)
    {
        if (g.Style.FrameBorderSize > 0.0f)
            RenderFrameBorder(bb.Min, bb.Max, rounding);
        else
            window->DrawList->AddRect(bb.Min, bb.Max, GetColorU32(ImGuiCol_FrameBg), rounding); // Color button are often in need of some sort of border
    }