Box scaling (custom aspect ratios)

[brenocq]

This PR implements the custom aspect ratio proposed in #15 and #24

The plot box can now be scaled using the context menu (right-click), or programmatically.

Change with context menu

Here is an example of changing the box scale using the context menu.

Peek.2025-01-04.14-15.mp4

Change with code

And here is the new demo demonstrating how to do it through code (from implot3d_demo.cpp).

Peek.2025-01-04.14-16.mp4

The demo code:

void DemoBoxScale() {
    constexpr int N = 100;
    float xs[N], ys[N], zs[N];
    for (int i = 0; i < N; ++i) {
        float t = i / (float)(N - 1);
        xs[i] = sinf(t * 2.0f * IM_PI);
        ys[i] = cosf(t * 4.0f * IM_PI);
        zs[i] = t * 2.0f - 1.0f;
    }

    static float scale[3] = {1.0f, 1.0f, 1.0f};
    ImGui::SliderFloat3("Box Scale", scale, 0.1f, 2.0f, "%.2f");

    if (ImPlot3D::BeginPlot("##BoxScale")) {
        ImPlot3D::SetupBoxScale(scale[0], scale[1], scale[2]);
        ImPlot3D::PlotLine("3D Curve", xs, ys, zs, N);
        ImPlot3D::EndPlot();
    }
}

Other changes

• Added IMPLOT_DISABLE_OBSOLETE_FUNCTIONS to implot3d.cpp and implot3d_demo.cpp to avoid using deprecated ImGui API
• Improved Locator_Default to change the grid depending on the plot box scale