#include <windows.h>
#include <time.h>
 //V-6
LPCSTR registration_error_message = "Couldn't initialize class!";
LPCSTR registration_error_title = "Error: initializing";
LPCSTR creating_window_error_title = "Error: creating";
 LPCSTR creating_window_error_message = "Couldn't create window!";
LPCSTR button_show_text = "Show";
LPCSTR button_clear_text = "Clear";
LPCSTR button_about_text = "About";
LPCSTR main_window_name = "Hello App";
LPCSTR main_window_class = "hello_class";
LPCSTR about_text = "Sergey Rakhmanov (IU3-21B)";
LRESULT CALLBACK window_callback(HWND, UINT, WPARAM, LPARAM);
HINSTANCE hInst;
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow) {
HWND main_window;
 MSG msg;
WNDCLASSEX wc;
wc.cbSize = sizeof(wc);
 wc.style = CS_HREDRAW | CS_VREDRAW;
wc.lpfnWndProc = window_callback;
wc.lpszMenuName = NULL;
 wc.lpszClassName = main_window_class;
 wc.cbWndExtra = 0;
wc.cbClsExtra = 0;
wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
 wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
 wc.hInstance = hInstance;
if(!RegisterClassEx(&wc)){
 MessageBox(NULL, registration_error_message, registration_error_title, MB_OK);
return NULL;
}
main_window = CreateWindow(main_window_class, main_window_name, WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInstance, NULL);

if(!main_window){MessageBox(NULL, creating_window_error_message, creating_window_error_title, MB_OK); return NULL; }
ShowWindow(main_window, iCmdShow);
 UpdateWindow(main_window);
while(GetMessage(&msg, NULL, 0, 0)){ TranslateMessage(&msg); DispatchMessage(&msg); }
return msg.wParam ;
 }

#define BTN_WIDTH 150
#define BTN_HEIGHT 20
 LRESULT CALLBACK window_callback(HWND hwnd, UINT iMsg, WPARAM wParam, LPARAM lParam){
 HDC hdc;
 PAINTSTRUCT ps;
 RECT rect;
HWND button_show, button_clear, button_author;
 int loword;
static int choise = 0;
static HPEN hpen;
static HBRUSH hbrush;
switch (iMsg) {
case WM_CREATE :
button_show = CreateWindow ("button", button_show_text, WS_CHILD | WS_VISIBLE | BS_PUSHBUTTON, 100, 50, BTN_WIDTH, BTN_HEIGHT, hwnd, (HMENU) 1, hInst, NULL);
button_clear = CreateWindow ("button", button_clear_text, WS_CHILD | WS_VISIBLE | BS_PUSHBUTTON, 100, 100, BTN_WIDTH, BTN_HEIGHT, hwnd, (HMENU) 2, hInst, NULL);
 button_author = CreateWindow ("button", button_about_text, WS_CHILD | WS_VISIBLE |BS_PUSHBUTTON, 100, 250, BTN_WIDTH, BTN_HEIGHT, hwnd, (HMENU) 3, hInst, NULL);
return 0;

case WM_COMMAND :
hpen = CreatePen(PS_SOLID, 10,RGB(204, 51, 0));
hbrush = CreateSolidBrush(RGB(204, 51, 0));
loword=LOWORD(wParam);

switch(loword){
case 1: choise = 1; break; case 2: choise = 2; break; case 3: choise = 3; break; default: break; }

InvalidateRect(hwnd, NULL, TRUE);
return 0;
 case WM_PAINT:
hdc = BeginPaint(hwnd, &ps);
GetClientRect(hwnd, &rect);
SelectObject(hdc, hbrush);
SelectObject(hdc, hpen);
 switch(choise){
case 1:
 Rectangle(hdc, 600, 100, 624, 300);
 hbrush = CreateSolidBrush(RGB(0, 255, 0));
 hpen = CreatePen(PS_SOLID, 10,RGB(0, 255, 0));
 SelectObject(hdc, hbrush);
SelectObject(hdc, hpen);
Ellipse(hdc, 525, 50, 698, 200);
break;
case 2:
break; case 3:
 TextOut(hdc, 500, 100, about_text, strlen(about_text));
 break; }
EndPaint(hwnd, &ps); return 0; case WM_DESTROY : PostQuitMessage(0); return 0; } return DefWindowProc (hwnd, iMsg, wParam, lParam) ; }