#pragma warning(disable : 4127)    // disable warning: conditional expression is constant

#define CLASS_NAME    "GameApp"

#define release_com(p)    do { if(p) { (p)->Release(); (p) = NULL; } } while(0)

typedef unsigned char uchar;

IDirect3D9*                g_d3d;
IDirect3DDevice9*        g_device;
IDirect3DVertexBuffer9* g_vertex_buffer;

struct sCustomVertex
{
    float x, y, z;
    DWORD color;
};

#define D3DFVF_CUSTOM_VERTEX (D3DFVF_XYZ | D3DFVF_DIFFUSE)

void setup_world_matrix()
{
    D3DXMATRIX mat_world;
    D3DXMatrixIdentity(&mat_world);

float angle = (timeGetTime() % 1000) * (2 * D3DX_PI) / 1000.0f;

D3DXQUATERNION quat;
    D3DXMATRIX mat_rotation;

D3DXQuaternionRotationYawPitchRoll(&quat, angle, angle, angle);
    D3DXMatrixRotationQuaternion(&mat_rotation, &quat);
    D3DXMatrixMultiply(&mat_world, &mat_rotation, &mat_world);

g_device->SetTransform(D3DTS_WORLD, &mat_world);
}

void setup_view_proj_matrices()
{
    // setup view matrix

D3DXVECTOR3 eye(0.0f, 3.0f, -5.0f);
    D3DXVECTOR3 at(0.0f,  0.0f,   0.0f);
    D3DXVECTOR3 up(0.0f,  1.0f,   0.0f);

D3DXMATRIX mat_view;
    D3DXMatrixLookAtLH(&mat_view, &eye, &at, &up);
    g_device->SetTransform(D3DTS_VIEW, &mat_view);

// setup projection matrix
    D3DXMATRIX mat_proj;
    D3DXMatrixPerspectiveFovLH(&mat_proj, D3DX_PI/4, 1.0f, 1.0f, 100.0f);
    g_device->SetTransform(D3DTS_PROJECTION, &mat_proj);
}

void init_vb()
{    
    g_device->CreateVertexBuffer(50 * 2 * sizeof(sCustomVertex), 0, D3DFVF_CUSTOM_VERTEX, D3DPOOL_DEFAULT, 
                                 &g_vertex_buffer, NULL);

sCustomVertex* vertices;

g_vertex_buffer->Lock(0, 0, (void**)&vertices, 0);

for(int i = 0; i < 50; i++)
    {
        float theta = (2 * D3DX_PI * i) / (50 - 1);

vertices[2 * i + 0].x      = sin(theta);
        vertices[2 * i + 0].y      = -1.0f;
        vertices[2 * i + 0].z      = cos(theta);            
        vertices[2 * i + 0].color = 0x88FF0000;

vertices[2 * i + 1].x      = sin(theta);
        vertices[2 * i + 1].y      = 1.0f;
        vertices[2 * i + 1].z      = cos(theta);            
        vertices[2 * i + 1].color = 0x8844FF00;
    }
    
    g_vertex_buffer->Unlock();
}

bool init_d3d(HWND hwnd)
{
    g_d3d = Direct3DCreate9(D3D_SDK_VERSION);

if(g_d3d == NULL)
        return false;

D3DPRESENT_PARAMETERS d3dpp;
    ZeroMemory(&d3dpp, sizeof(d3dpp));

d3dpp.Windowed            = TRUE;
    d3dpp.SwapEffect        = D3DSWAPEFFECT_DISCARD;
    d3dpp.BackBufferFormat    = D3DFMT_UNKNOWN;

if(FAILED(g_d3d->CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hwnd, D3DCREATE_SOFTWARE_VERTEXPROCESSING,
                                  &d3dpp, &g_device)))
    {
        return false;
    }

init_vb();
    setup_view_proj_matrices();

g_device->SetRenderState(D3DRS_CULLMODE, D3DCULL_NONE);
    g_device->SetRenderState(D3DRS_LIGHTING, FALSE);

g_device->SetRenderState(D3DRS_ALPHABLENDENABLE, TRUE);
    g_device->SetRenderState(D3DRS_SRCBLEND,  D3DBLEND_SRCALPHA);
    g_device->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);

return true;
}

void cleanup()
{
    release_com(g_vertex_buffer);
    release_com(g_device);
    release_com(g_d3d);
}

inline void extract_argb(D3DCOLOR color, uchar* alpha, uchar* red, uchar* green, uchar* blue)
{
    // Extract alpha, red, green, blue from D3D color value.

if(alpha != NULL) *alpha = uchar((color >> 24) & 0xff);
    if(red   != NULL) *red   = uchar((color >> 16) & 0xff);
    if(green != NULL) *green = uchar((color >> 8) & 0xff);
    if(blue  != NULL) *blue  = uchar(color & 0xff);
}

void render()
{
    g_device->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(5, 5, 5), 1.0f, 0);

g_device->BeginScene();

setup_world_matrix();

g_device->SetStreamSource(0, g_vertex_buffer, 0, sizeof(sCustomVertex));
    g_device->SetFVF(D3DFVF_CUSTOM_VERTEX);
    g_device->DrawPrimitive(D3DPT_TRIANGLESTRIP, 0, 2 * 50 - 2);

// change all vertices's color and alpha

sCustomVertex* vertex;

g_vertex_buffer->Lock(0, 50 * 2 * sizeof(sCustomVertex), (void**)&vertex, 0);

for(int i = 0; i < 50 * 2; i++)
    {    
        uchar alpha, red, green, blue;
        extract_argb(vertex->color, &alpha, &red, &green, &blue);

if(++alpha > 255)    alpha = 0;
        if(++red > 255)        red = 0;
        if(++green > 255)    green = 0;
        if(++blue > 255)    blue = 0;

vertex->color = D3DCOLOR_RGBA(red, green, blue, alpha);

vertex++;
    }

g_vertex_buffer->Unlock();

g_device->EndScene();

g_device->Present(NULL, NULL, NULL, NULL);
}

LRESULT WINAPI WinProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch(msg)
    {
    case WM_KEYDOWN:
        switch(wParam)
        {
        case VK_ESCAPE:
            DestroyWindow(hwnd);
            break;

case 48:    // press key "0", disable alpha blend.
            g_device->SetRenderState(D3DRS_ALPHABLENDENABLE, FALSE);
            break;

case 49:    // press key "1", enable alpha blend.
            g_device->SetRenderState(D3DRS_ALPHABLENDENABLE, TRUE);
            break;
        }        
            
        break;

case WM_DESTROY:        
        PostQuitMessage(0);
        return 0;
    }

return DefWindowProc(hwnd, msg, wParam, lParam);
}

int WINAPI WinMain(HINSTANCE inst, HINSTANCE, LPSTR, INT)
{
    WNDCLASSEX wc;

wc.cbSize            = sizeof(WNDCLASSEX);
    wc.style            = CS_CLASSDC;
    wc.lpfnWndProc        = WinProc;
    wc.cbClsExtra        = 0;
    wc.cbWndExtra        = 0;
    wc.hInstance        = inst;
    wc.hIcon            = NULL;
    wc.hCursor            = NULL;
    wc.hbrBackground    = NULL;
    wc.lpszMenuName        = NULL;
    wc.lpszClassName    = CLASS_NAME;
    wc.hIconSm            = NULL;

if(! RegisterClassEx(&wc))
        return -1;

HWND hwnd = CreateWindow(CLASS_NAME, "Direct3D App", WS_OVERLAPPEDWINDOW, 200, 100, 600, 500,
                             NULL, NULL, wc.hInstance, NULL);

if(hwnd == NULL)
        return -1;

if(init_d3d(hwnd))
    {
        ShowWindow(hwnd, SW_SHOWDEFAULT);
        UpdateWindow(hwnd);

MSG msg;
        ZeroMemory(&msg, sizeof(msg));

while(msg.message != WM_QUIT)
        {
            if(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
            {
                TranslateMessage(&msg);
                DispatchMessage(&msg);
            }
                
            render();
            Sleep(10);
        }
    }

cleanup();
    UnregisterClass(CLASS_NAME, wc.hInstance);

return 0;
}