text: /*
   * Copyright 2011-2021 Branimir Karadzic. All rights reserved.
   * License: https://github.com/bkaradzic/bgfx#license-bsd-2-clause
   */
  
  #include "common.h"
  #include "bgfx_utils.h"
  #include "imgui/imgui.h"
  
  #include <bx/rng.h>
  
  namespace
  {
  
  const uint32_t kDimWidth  = 11;
  const uint32_t kDimHeight = 11;
  
  struct PosColorVertex
  {
  	float m_x;
  	float m_y;
  	float m_z;
  	uint32_t m_abgr;
  
  	static void init()
  	{
  		ms_layout
  			.begin()
  			.add(bgfx::Attrib::Position, 3, bgfx::AttribType::Float)
  			.add(bgfx::Attrib::Color0,   4, bgfx::AttribType::Uint8, true)
  			.end();
  	};
  
  	static bgfx::VertexLayout ms_layout;
  };
  
  bgfx::VertexLayout PosColorVertex::ms_layout;
  
  static PosColorVertex s_cubeVertices[] =
  {
  	{-1.0f,  1.0f,  1.0f, 0xff000000 },
  	{ 1.0f,  1.0f,  1.0f, 0xff0000ff },
  	{-1.0f, -1.0f,  1.0f, 0xff00ff00 },
  	{ 1.0f, -1.0f,  1.0f, 0xff00ffff },
  	{-1.0f,  1.0f, -1.0f, 0xffff0000 },
  	{ 1.0f,  1.0f, -1.0f, 0xffff00ff },
  	{-1.0f, -1.0f, -1.0f, 0xffffff00 },
  	{ 1.0f, -1.0f, -1.0f, 0xffffffff },
  };
  
  static const uint16_t s_cubeTriList[] =
  {
  	0, 1, 2, // 0
  	1, 3, 2,
  	4, 6, 5, // 2
  	5, 6, 7,
  	0, 2, 4, // 4
  	4, 2, 6,
  	1, 5, 3, // 6
  	5, 7, 3,
  	0, 4, 1, // 8
  	4, 5, 1,
  	2, 3, 6, // 10
  	6, 3, 7,
  };
  
  static const uint16_t s_cubeTriStrip[] =
  {
  	0, 1, 2,
  	3,
  	7,
  	1,
  	5,
  	0,
  	4,
  	2,
  	6,
  	7,
  	4,
  	5,
  };
  
  class ExampleDynamic : public entry::AppI
  {
  public:
  	ExampleDynamic(const char* _name, const char* _description, const char* _url)
  		: entry::AppI(_name, _description, _url)
  	{
  	}
  
  	void init(int32_t _argc, const char* const* _argv, uint32_t _width, uint32_t _height) override
  	{
  		BX_UNUSED(s_cubeTriList, s_cubeTriStrip);
  
  		Args args(_argc, _argv);
  
  		m_width  = _width;
  		m_height = _height;
  		m_debug  = BGFX_DEBUG_NONE;
  		m_reset  = BGFX_RESET_VSYNC;
  
  		bgfx::Init init;
  		init.type     = args.m_type;
  		init.vendorId = args.m_pciId;
  		init.resolution.width  = m_width;
  		init.resolution.height = m_height;
  		init.resolution.reset  = m_reset;
  		bgfx::init(init);
  
  		// Enable debug text.
  		bgfx::setDebug(m_debug);
  
  		// Set view 0 clear state.
  		bgfx::setViewClear(0
  				, BGFX_CLEAR_COLOR|BGFX_CLEAR_DEPTH
  				, 0x303030ff
  				, 1.0f
  				, 0
  				);
  
  		// Create vertex stream declaration.
  		PosColorVertex::init();
  
  		// Create static vertex buffer.
  		for (uint32_t yy = 0; yy < kDimHeight; ++yy)
  		{
  			for (uint32_t xx = 0; xx < kDimWidth; ++xx)
  			{
  				m_vbh[yy*kDimWidth+xx] = bgfx::createDynamicVertexBuffer(
  					// Static data can be passed with bgfx::makeRef
  					  bgfx::makeRef(s_cubeVertices, sizeof(s_cubeVertices) )
  					, PosColorVertex::ms_layout
  					);
  			}
  		}
  
  		// Create static index buffer.
  		m_ibh = bgfx::createDynamicIndexBuffer(
  				// Static data can be passed with bgfx::makeRef
  				bgfx::makeRef(s_cubeTriStrip, sizeof(s_cubeTriStrip) )
  				);
  
  		// Create program from shaders.
  		m_program = loadProgram("vs_cubes", "fs_cubes");
  
  		m_timeOffset = bx::getHPCounter();
  
  		imguiCreate();
  	}
  
  	virtual int shutdown() override
  	{
  		imguiDestroy();
  
  		// Cleanup.
  		bgfx::destroy(m_ibh);
  		for (uint32_t yy = 0; yy < kDimHeight; ++yy)
  		{
  			for (uint32_t xx = 0; xx < kDimWidth; ++xx)
  			{
  				bgfx::destroy(m_vbh[yy*kDimWidth+xx]);
  			}
  		}
  
  		bgfx::destroy(m_program);
  
  		// Shutdown bgfx.
  		bgfx::shutdown();
  
  		return 0;
  	}
  
  	bool update() override
  	{
  		if (!entry::processEvents(m_width, m_height, m_debug, m_reset, &m_mouseState) )
  		{
  			imguiBeginFrame(m_mouseState.m_mx
  				,  m_mouseState.m_my
  				, (m_mouseState.m_buttons[entry::MouseButton::Left  ] ? IMGUI_MBUT_LEFT   : 0)
  				| (m_mouseState.m_buttons[entry::MouseButton::Right ] ? IMGUI_MBUT_RIGHT  : 0)
  				| (m_mouseState.m_buttons[entry::MouseButton::Middle] ? IMGUI_MBUT_MIDDLE : 0)
  				,  m_mouseState.m_mz
  				, uint16_t(m_width)
  				, uint16_t(m_height)
  				);
  
  			showExampleDialog(this);
  
  			imguiEndFrame();
  
  			float time = (float)( (bx::getHPCounter()-m_timeOffset)/double(bx::getHPFrequency() ) );
  
  			const bx::Vec3 at  = { 0.0f, 0.0f,   0.0f };
  			const bx::Vec3 eye = { 0.0f, 0.0f, -35.0f };
  
  			// Set view and projection matrix for view 0.
  			{
  				float view[16];
  				bx::mtxLookAt(view, eye, at);
  
  				float proj[16];
  				bx::mtxProj(proj, 60.0f, float(m_width)/float(m_height), 0.1f, 100.0f, bgfx::getCaps()->homogeneousDepth);
  				bgfx::setViewTransform(0, view, proj);
  
  				// Set view 0 default viewport.
  				bgfx::setViewRect(0, 0, 0, uint16_t(m_width), uint16_t(m_height) );
  			}
  
  			// This dummy draw call is here to make sure that view 0 is cleared
  			// if no other draw calls are submitted to view 0.
  			bgfx::touch(0);
  
  			{
  				float angle = bx::frnd(&m_mwc);
  				float mtx[16];
  				bx::mtxRotateZ(mtx, angle);
  
  				const bgfx::Memory* mem = bgfx::copy(s_cubeVertices, sizeof(s_cubeVertices) );
  				PosColorVertex* vertex = (PosColorVertex*)mem->data;
  				const uint32_t abgr = m_mwc.gen();
  				for (uint32_t ii = 0; ii < BX_COUNTOF(s_cubeVertices); ++ii)
  				{
  					bx::store(&vertex[ii].m_x, bx::mul(bx::load<bx::Vec3>(&s_cubeVertices[ii].m_x), mtx) );
  					vertex[ii].m_abgr = abgr;
  				}
  
  				uint32_t idx = m_mwc.gen() % (kDimWidth*kDimHeight);
  				bgfx::update(m_vbh[idx], 0, mem);
  			}
  
  			// Submit 11x11 cubes.
  			for (uint32_t yy = 0; yy < kDimHeight; ++yy)
  			{
  				for (uint32_t xx = 0; xx < kDimWidth; ++xx)
  				{
  					float mtx[16];
  					bx::mtxRotateXY(mtx, time + xx*0.21f, time + yy*0.37f);
  					mtx[12] = -15.0f + float(xx)*3.0f;
  					mtx[13] = -15.0f + float(yy)*3.0f;
  					mtx[14] = 0.0f;
  
  					// Set model matrix for rendering.
  					bgfx::setTransform(mtx);
  
  					// Set vertex and index buffer.
  					bgfx::setVertexBuffer(0, m_vbh[yy*kDimWidth+xx]);
  					bgfx::setIndexBuffer(m_ibh);
  
  					// Set render states.
  					bgfx::setState(0
  						| BGFX_STATE_DEFAULT
  						| BGFX_STATE_PT_TRISTRIP
  						);
  
  					// Submit primitive for rendering to view 0.
  					bgfx::submit(0, m_program);
  				}
  			}
  
  			// Advance to next frame. Rendering thread will be kicked to
  			// process submitted rendering primitives.
  			bgfx::frame();
  
  			return true;
  		}
  
  		return false;
  	}
  
  	entry::MouseState m_mouseState;
  
  	bx::RngMwc m_mwc;
  	uint32_t m_width;
  	uint32_t m_height;
  	uint32_t m_debug;
  	uint32_t m_reset;
  	bgfx::DynamicVertexBufferHandle m_vbh[kDimWidth*kDimHeight];
  	bgfx::DynamicIndexBufferHandle m_ibh;
  	bgfx::ProgramHandle m_program;
  	int64_t m_timeOffset;
  };
  
  } // namespace
  
  ENTRY_IMPLEMENT_MAIN(
  	  ExampleDynamic
  	, "35-dynamic"
  	, "Dynamic buffers update."
  	, "https://bkaradzic.github.io/bgfx/examples.html#dynamic"
  	);
  