ImguiFilamentBridge.h

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// Altered from Filament's ImGuiHelper.cpp
// Filament code is from somewhere close to v1.4.3 and is:
/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
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// Open3D alterations are:
// ----------------------------------------------------------------------------
// -                        Open3D: www.open3d.org                            -
// ----------------------------------------------------------------------------
// The MIT License (MIT)
//
// Copyright (c) 2018 www.open3d.org
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// The above copyright notice and this permission notice shall be included in
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#pragma once

#include <filament/Engine.h>
#include <filament/IndexBuffer.h>
#include <filament/Material.h>
#include <filament/MaterialInstance.h>
#include <filament/Texture.h>
#include <filament/VertexBuffer.h>
#include <filament/View.h>
#include <cstddef>  // <filament/Engine> recursive includes needs this, std::size_t especially
#include <memory>

struct ImDrawData;

namespace open3d {

namespace visualization {
class FilamentRenderer;
}

namespace gui {

struct Size;
class Window;

// Translates ImGui's draw commands into Filament primitives, textures, vertex
// buffers, etc. Creates a UI-specific Scene object and populates it with a
// Renderable. Does not handle event processing; clients can simply call
// ImGui::GetIO() directly and set the mouse state.
class ImguiFilamentBridge {
public:
    ImguiFilamentBridge(visualization::FilamentRenderer* renderer,
                        const Size& window_size);
    // The constructor creates its own Scene and places it in the given View.
    ImguiFilamentBridge(filament::Engine* engine,
                        filament::Scene* scene,
                        filament::Material* uiblit_material);
    ~ImguiFilamentBridge();

    // Helper method called after resolving fontPath; public so fonts can be
    // added by caller. Requires the appropriate ImGuiContext to be current
    void CreateAtlasTextureAlpha8(unsigned char* pixels,
                                  int width,
                                  int height,
                                  int bytes_per_px);

    // This populates the Filament View. Clients are responsible for
    // rendering the View. This should be called on every frame, regardless of
    // whether the Renderer wants to skip or not.
    void Update(ImDrawData* imguiData);

    void OnWindowResized(const Window& window);

private:
    void CreateBuffers(size_t num_required_buffers);
    void PopulateVertexData(size_t buffer_index,
                            size_t vb_size_in_bytes,
                            void* vb_data,
                            size_t ib_size_in_bytes,
                            void* ib_data);
    void CreateVertexBuffer(size_t buffer_index, size_t capacity);
    void CreateIndexBuffer(size_t buffer_index, size_t capacity);
    void SyncThreads();

private:
    struct Impl;
    std::unique_ptr<Impl> impl_;
};

}  // namespace gui
}  // namespace open3d