[PIU] Pierdolony Tangens

#include <windows.h>
#include <string>
#include <cmath>

using std::wstring;

HINSTANCE hInst;
const wstring NazwaKlasy(L"Klasa");
const wstring NazwaApp(L"Psinus");
int iDiv = 2;
float Pi = 3.14f;

HPEN Pen[2];
/////////////////////////////////////////////////////////////////////////////////////////////////


static void OnWM_PAINT(HWND Wnd)
{
    PAINTSTRUCT PS;
    BeginPaint(Wnd, &PS);

    RECT R, E;
    GetClientRect(Wnd, &R);

    POINT Z = { 700,700 };
    SetMapMode(PS.hdc, MM_ISOTROPIC);
    SetWindowExtEx(PS.hdc, Z.x, Z.y, NULL);                        //zakres okna
    SetViewportExtEx(PS.hdc, R.right, R.bottom, NULL);            //zakres ukł wsp
    SetViewportOrgEx(PS.hdc, R.right / 2, R.bottom / 2, NULL);    //pocz ukł wsp
    E.left = R.left + ((R.right - R.left) / 10);
    E.right = R.right - ((R.right - R.left) / 10);
    E.top = R.top + ((R.bottom - R.top) / 10);
    E.bottom = R.bottom - ((R.bottom - R.top) / 10);

    SelectObject(PS.hdc, Pen[0]);



    //MoveToEx( PS.hdc, 0, -250, NULL );
    MoveToEx(PS.hdc, 0, -((E.bottom - E.top) / iDiv), NULL);
    LineTo(PS.hdc, 0, ((E.bottom - E.top) / iDiv));

    MoveToEx(PS.hdc, -((E.right - E.left) / iDiv), 0, NULL);
    LineTo(PS.hdc, (E.right - E.left) / iDiv, 0);


    SelectObject(PS.hdc, Pen[1]);
    float ytan;
    float ytans;
    for (float drzwi = -(E.right - E.left) / iDiv; drzwi <= (E.right - E.left) / iDiv; drzwi += iDiv)
    {
        ytan = 100 * tan((drzwi * Pi) / 180);
        ytans = 100 * tan(((drzwi - 4) * Pi) / 180);
        if ((ytans <= ((E.bottom - E.top) / iDiv) && ytans >= -((E.bottom - E.top) / iDiv)) && (ytan <= ((E.bottom - E.top) / iDiv) && ytan >= -((E.bottom - E.top) / iDiv)))
        {
            MoveToEx(PS.hdc, drzwi, ytan, NULL);
            LineTo(PS.hdc, drzwi - 4, ytans);
        }
    }

    EndPaint(Wnd, &PS);
}

static LRESULT CALLBACK FunkcjaOkienkowa(HWND Wnd, UINT Komunikat, WPARAM wParam, LPARAM lParam)
{
    switch (Komunikat)
    {
    case WM_PAINT:
    {
        OnWM_PAINT(Wnd);
    }break;

    case WM_DESTROY:
    {
        PostQuitMessage(0);
    }break;

    default: return DefWindowProc(Wnd, Komunikat, wParam, lParam);
    }

    return 0;
}

const static bool Rejestruj()
{
    WNDCLASSEX wc;
    wc.cbSize = sizeof(WNDCLASSEX);
    wc.cbClsExtra = wc.cbWndExtra = 0;
    wc.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
    wc.hInstance = hInst;
    wc.lpfnWndProc = &FunkcjaOkienkowa;
    wc.lpszClassName = NazwaKlasy.c_str();
    wc.lpszMenuName = NULL;
    wc.style = CS_HREDRAW | CS_VREDRAW;
    return (RegisterClassEx(&wc) != 0);
}


INT WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)
{
    hInst = hInstance;
    Pen[0] = CreatePen(PS_SOLID, 1, 0x00FFFFFF);
    Pen[1] = CreatePen(PS_SOLID, 1, RGB(255, 0, 0));


    Rejestruj();

    HWND GlowneOkno = CreateWindowEx(0, NazwaKlasy.c_str(), NazwaApp.c_str(), WS_OVERLAPPEDWINDOW | WS_VISIBLE, 50, 50, 700, 700, 0, 0, hInstance, 0);

    MSG msg;

    while (GetMessage(&msg, 0, 0, 0) > 0)
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    UnregisterClass(NazwaKlasy.c_str(), hInstance);

    return msg.wParam;
}