Problem with drawing a clock with Direct2D - c++

Question

I am trying to draw a clock with Direct2D. The program correctly gets the current time, however the error is when Direct2D draws the clock, since it seems that the clock is out of date with the current time. To get the current time, use the GetLocalTime() function and then map the values to transform them to an angle, so that they can be drawn. How could I fix it?
...
renderTarget->BeginDraw();
renderTarget->Clear(ColorF(ColorF::Black));
GetLocalTime(&sysTime);
wstring text = L"Hour: " + to_wstring(sysTime.wHour)
+ L"\nMinute: " + to_wstring(sysTime.wMinute)
+ L"\nSecond: " + to_wstring(sysTime.wSecond);
brush->SetColor(ColorF(ColorF::White));
renderTarget->DrawTextW(text.c_str(), text.length(), textFormat, textRect, brush);
D2D1_POINT_2F centerPoint = Point2F(320, 240);
FLOAT hourAngle = map(sysTime.wHour%12, 0, 12, 0, 360);
FLOAT minuteAngle = map(sysTime.wMinute, 0, 60, 0, 360);
FLOAT secondAngle = map(sysTime.wSecond, 0, 60, 0, 360);
brush->SetColor(ColorF(ColorF::DeepPink));
renderTarget->DrawEllipse(D2D1::Ellipse(centerPoint, 150, 150), brush, 5);
renderTarget->SetTransform(Matrix3x2F::Rotation(secondAngle, centerPoint));
brush->SetColor(ColorF(ColorF::Blue));
renderTarget->DrawLine(centerPoint,Point2F(centerPoint.x,centerPoint.y + 150*0.9), brush, 10,lineStrokeStyle);
renderTarget->SetTransform(Matrix3x2F::Rotation(minuteAngle, centerPoint));
brush->SetColor(ColorF(ColorF::White));
renderTarget->DrawLine(centerPoint,Point2F(centerPoint.x,centerPoint.y + 150*0.7), brush, 10, lineStrokeStyle);
renderTarget->SetTransform(Matrix3x2F::Rotation(hourAngle, centerPoint));
brush->SetColor(ColorF(ColorF::GreenYellow));
renderTarget->DrawLine(centerPoint, Point2F(centerPoint.x,centerPoint.y + 150*0.5), brush, 10,lineStrokeStyle);
renderTarget->SetTransform(Matrix3x2F::Identity());
HRESULT hrErr = renderTarget->EndDraw();
if (hrErr != S_OK) {
MessageBox(hWnd, L"Direct2D Error", L"Direct2D Error", MB_OK | MB_ICONERROR);
SafeRelease(&brush);
SafeRelease(&renderTarget);
SafeRelease(&factory);
}
...

Answer 1

Yes, you can use GetLocalTime to get the current local date and time. The problem may be in mapping the time to an angle.
But these can be solved, because there are very detailed examples in MSDN.
Instead of calculating the coordinates for the lines, we can calculate the angle and then apply a rotation transform. The following code shows a function that draws one clock hand. The fAngle parameter gives the angle of the hand, in degrees.
void Scene::DrawClockHand(float fHandLength, float fAngle, float fStrokeWidth)
{
m_pRenderTarget->SetTransform(
D2D1::Matrix3x2F::Rotation(fAngle, m_ellipse.point)
);
// endPoint defines one end of the hand.
D2D_POINT_2F endPoint = D2D1::Point2F(
m_ellipse.point.x,
m_ellipse.point.y - (m_ellipse.radiusY * fHandLength)
);
// Draw a line from the center of the ellipse to endPoint.
m_pRenderTarget->DrawLine(
m_ellipse.point, endPoint, m_pStroke, fStrokeWidth);
}
This code draws a vertical line, starting from the center of the clock face and ending at the point endPoint. The line is rotated around the center of the ellipse by applying a rotation transform. The center point for the rotation is the center of ellipse that forms the clock face.
void Scene::RenderScene()
{
m_pRenderTarget->Clear(D2D1::ColorF(D2D1::ColorF::SkyBlue));
m_pRenderTarget->FillEllipse(m_ellipse, m_pFill);
m_pRenderTarget->DrawEllipse(m_ellipse, m_pStroke);
// Draw hands
SYSTEMTIME time;
GetLocalTime(&time);
// 60 minutes = 30 degrees, 1 minute = 0.5 degree
const float fHourAngle = (360.0f / 12) * (time.wHour) + (time.wMinute * 0.5f);
const float fMinuteAngle =(360.0f / 60) * (time.wMinute);
DrawClockHand(0.6f, fHourAngle, 6);
DrawClockHand(0.85f, fMinuteAngle, 4);
// Restore the identity transformation.
m_pRenderTarget->SetTransform( D2D1::Matrix3x2F::Identity() );
}
Refer: Drawing Clock Hands
Debug:
The whole code sample:
Direct2D Clock Sample