imgui_juce
==========

JUCE [1] backend for Dear ImGui [2].

I don't recommend using JUCE for prototyping DSP code, but
if you have no better options, using ImGui with this library
should make your life a lot easier.

Pros:
  + No more listener/attachment/callback bullshit (you won't
    believe how many layers of callbacks are used just to
    set a single parameter using APVTS's SliderAttachment).

    You can write declarative code for GUI now:

        ImGui::Text("Hello, world %d", 123);
        if (ImGui::Button("Save"))
          DoStuff();

  + No more GUI layout positioning bullshit. Spend your time
    on DSP code.

  + It's much easier now to integrate custom non-float
    parameters into your plugin.

  + There are a ton of useful extensions for ImGui you can
    use for easier debugging. See imnodes [3], implot [4],
    and the list on ImGui wiki [5].

  + You can mix JUCE GUI components and ImGui. ImGui only
    needs a Component for mouse/keyboard input and a
    OpenGLContext for rendering. You can, for example, only
    enable the ImGui component for debugging and disable it
    in the final release.

Cons:
  - GUI is recomputed each frame at 60 FPS, probably less
    efficient than JUCE, but at least it's using OpenGL.

  - JUCE's keypress callbacks are extremely inefficient for
    ImGui, though you can disable it by setting

        setWantsKeyboardFocus(false);

  - Component and layout can be less customizable than JUCE.
    You probably only want to use it for prototyping.

  - Slider skew not supported by default. You need to write
    your own component for that (contributions welcome).
    ImGui do have logarithmic slider built-in though.

  - You need a patched version of ImGui for use in audio
    plugins (see Note below).

Usage
-----

The backend exposes three functions

    #include <imgui_impl_juce/imgui_impl_juce.h>

    void ImGui_ImplJuce_Init(juce::Component&, juce::OpenGLContext&);
    void ImGui_ImplJuce_Shutdown();
    void ImGui_ImplJuce_NewFrame();

You need to create a juce::OpenGLRenderer and call the three
functions in

    void newOpenGLContextCreated();
    void openGLContextClosing();
    void renderOpenGL();

respectively. See

    ./examples/mwe/src/ImGuiComponent.h

for a complete minimal working example.

If you need an audio plugin example, see

    ./examples/sine/

CMake Usage
-----------

If you are using CMake, call `add_subdirectory` on the
current directory after JUCE directory is added. Then link
your application target to `imgui_imple_juce`. For example,

    target_link_libraries(app
      # other stuff libs
      PRIVATE
        imgui_impl_juce)

See

    ./examples/mwe/CMakeLists.txt

for a complete example.

Note
----

By default ImGui only support a single instance running
because it uses a global state

    ImGuiContext* GImGui = NULL;

This is probably fine if you are writing a GUI application,
but if you are writing an audio plugin, the plugin will
crash if you add multiple instances of the plugin in DAW and
open two GUIs at the same time.

You need to patch ImGui and make the global state thread local

    thread_local ImGuiContext* GImGui = NULL;

in order to support multiple instances of ImGui running at
the same time on different threads. See

    ./examples/sine/patches/imgui/multi_instance.patch

for details.

You need a similar patch if you want to use imnodes or
ImPlot in your plugin. For a ImPlot example, see

    ./examples/scope/patches/implot/multi_instance.patch

License
-------

The imgui_juce library is licensed under the GNU Lesser
General Public License v3.0 (LGPLv3).

Examples are placed under public domain.

Donate
------

If this library saves valuable development time for you,
consider donate to support this project:

    https://ko-fi.com/krjst

--------------------------

[1]: https://github.com/juce-framework/JUCE
[2]: https://github.com/ocornut/imgui
[3]: https://github.com/Nelarius/imnodes
[4]: https://github.com/epezent/implot
[5]: https://github.com/ocornut/imgui/wiki/Useful-Extensions