imgui refactor - #1066

# a floating window is auto-sized by imgui and can be dragged by the user
@figure.add_imgui_window(location="floating", title="floating", window_flags=imgui.WindowFlags_.none)
def floating_gui(fig):
    if imgui.button("randomize"):
        fig[0, 0]["image"].data = np.random.rand(128, 128)

# append elements to the standard right-click menu
@figure.append_imgui_right_click()
def more_items(fig):
    imgui.separator()
    if imgui.menu_item("Autoscale all subplots", "", False)[0]:
        for subplot in fig:
            subplot.auto_scale()


# a popup set on a subplot replaces the standard menu within that subplot
@figure[0, 1].set_imgui_right_click()
def line_popup(subplot):
    imgui.text(f"subplot: {subplot.name}")
    imgui.separator()
    _, line.thickness = imgui.slider_float("thickness", line.thickness, 1.0, 20.0)
    changed, color = imgui.color_edit3("color", tuple(float(c) for c in line.colors)[:3])
    if changed:
        line.colors = (*color, 1.0)

# a popup can contain any imgui elements, it is not restricted to menu items
def image_processing(image):
    ui = image.metadata

    imgui.text(image.name)
    imgui.separator()

    changed_noise, ui["noise"] = imgui.slider_float("noise sigma", ui["noise"], 0.0, 100.0)
    changed_filter, ui["filter"] = imgui.checkbox("gaussian filter", ui["filter"])

    imgui.begin_disabled(not ui["filter"])
    changed_sigma, ui["sigma"] = imgui.slider_float("filter sigma", ui["sigma"], 0.1, 10.0)
    imgui.end_disabled()

    if imgui.button("reset"):
        ui.update(noise=0.0, sigma=1.0, filter=False)
        changed_noise = True

    if changed_noise or changed_filter or changed_sigma:
        data = raw[image] + np.random.normal(scale=ui["noise"], size=raw[image].shape)

        if ui["filter"]:
            data = gaussian_filter(data, sigma=ui["sigma"])

        image.data = data

# create an edge window
@figure.add_imgui_window(location="right", size=200, title="controls")
def gui(fig):
    if imgui.button("randomize"):
        fig[0, 0]["line"].data[:, 1] = np.random.rand(100)


# append more elements to the same window
@figure.append_imgui_window(location="right")
def more(fig):
    line = fig[0, 0]["line"]
    _, line.thickness = imgui.slider_float("thickness", v=line.thickness, v_min=2.0, v_max=50.0)


# append a button to the subplot toolbar that toggles axes visibility
@figure[0, 0].append_imgui_window(location="toolbar")
def toolbar_extra(subplot):
    imgui.same_line()
    _, subplot.axes.visible = imgui.checkbox(fa.ICON_FA_RULER_COMBINED, subplot.axes.visible)
    if imgui.is_item_hovered(0):
        imgui.set_tooltip("Axes visibility")