Prevent Flickering When Drawing - c++

Question

So I have this code to draw a rectangle on my screen:
LOGBRUSH m_LogBrush;
HBRUSH m_hBrush;
HPEN m_hPen;
HDC m_hDC;
void DrawBox(int x, int y, int r, int g, int b, int size, int thickness)
{
// Brush style to hollow
m_LogBrush.lbStyle = BS_NULL;
// Create a logical brush and select into the context
m_hBrush = CreateBrushIndirect(&m_LogBrush);
SelectObject(m_hDC, m_hBrush);
// Create a logical pen and select into the context
m_hPen = CreatePen(PS_SOLID, thickness, RGB(r, g, b));
SelectObject(m_hDC, m_hPen);
// Draw the rectangle
Rectangle(m_hDC, (x - size / 2), (y - size / 2), (x + size / 2), (y + size / 2));
// Remove the object
DeleteObject(m_hBrush);
DeleteObject(m_hPen);
}
However, when being called repeatedly inside a loop it flickers on the screen. I was wondering if there was a way to prevent this flicker?
Any help would be appreciated.
Thanks

Answer 1

This should not be an answer, but I can not post code in comments:
You have many GDI leaks in your code.
Copy/paste the following code and report us if flickering diminishes:
void DrawBox(int x, int y, int r, int g, int b, int size, int thickness)
{
// Brush style to hollow
m_LogBrush.lbStyle = BS_NULL;
// Create a logical brush and select into the context
m_hBrush = CreateBrushIndirect(&m_LogBrush);
HBRUSH hbrOldBrush = SelectObject(m_hDC, m_hBrush);
// Create a logical pen and select into the context
m_hPen = CreatePen(PS_SOLID, thickness, RGB(r, g, b));
HPEN hpOldPen = SelectObject(m_hDC, m_hPen);
// Draw the rectangle
Rectangle(m_hDC, (x - size / 2), (y - size / 2), (x + size / 2), (y + size / 2));
// Remove the object
SelectObject(m_hDC, hbrOldBrush); // first you must restore DC to original state
SelectObject(m_hDC, hpOldPen); // same here
DeleteObject(m_hBrush);
DeleteObject(m_hPen);
}
Read on MSDN about GDI leaks.
This should diminish flickering, but to completely remove flickering you should do the following:
Remove the CS_VREDRAW | CS_HREDRAW from your window class definition;
return 1L in your window procedure ( or TRUE in your dialog box procedure ) in response to WM_ERASEBKGND;
draw everything on a memory bitmap and then BitBlt it into your m_hDC -> this is called double buffering ( you can find many examples online );

Answer 2

/*Hi You May Change Your Code To This*/
LOGBRUSH m_LogBrush;
//HBRUSH m_hBrush;
//HPEN m_hPen;
//HDC m_hDC;
HWND m_hWND; //Your WindowHandle instead of your DC
//
void DrawBox(int x, int y, int r, int g, int b, int size, int thickness)
{
// Lock & Get Forground DC From m_hWND
HDC m_hDC = GetDC(m_hWND);
if (m_hDC != 0) //Make Sure It's ok
{
// Double Buffering Begins Here
// Create Background DC From m_hDC
HDC mem_m_hDC = CreateCompatibleDC(m_hDC);
// Calculate Window Bounds
RECT ClientRect = { 0 };
GetClientRect(m_hWND, &ClientRect);
// Create Background Buffer Frame
BITMAPINFO bmi = { 0 };
bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmi.bmiHeader.biWidth = ClientRect.right - ClientRect.left;
bmi.bmiHeader.biHeight = ClientRect.bottom - ClientRect.top;
bmi.bmiHeader.biBitCount = 32;
bmi.bmiHeader.biCompression = BI_RGB;
bmi.bmiHeader.biPlanes = 1;
HBITMAP memBMP = CreateDIBSection(mem_m_hDC, &bmi, DIB_RGB_COLORS, 0, 0, 0);
// Select Background Buffer Frame
SelectObject(mem_m_hDC, memBMP);
// Brush style to hollow
m_LogBrush.lbStyle = BS_NULL;
// Create a logical brush and select into the context
HBRUSH m_hBrush = CreateBrushIndirect(&m_LogBrush);
HGDIOBJ oldHGDIOBJ1 = SelectObject(m_hDC, m_hBrush); //Save Old Seleteed GDI Object To oldHGDIOBJ1
// Create a logical pen and select into the context
HPEN m_hPen = CreatePen(PS_SOLID, thickness, RGB(r, g, b));
HGDIOBJ oldHGDIOBJ2 = SelectObject(m_hDC, m_hPen); //Save Old Seleteed GDI Object To oldHGDIOBJ2
// Draw the rectangle in Background Memory DC
Rectangle(mem_m_hDC, (x - size / 2), (y - size / 2), (x + size / 2), (y + size / 2));
// Copy Background DC To Forground DC
BitBlt(m_hDC, 0, 0, bmi.bmiHeader.biWidth, bmi.bmiHeader.biHeight, mem_m_hDC, 0, 0, SRCCOPY);
// Delete Background Buffer Frame
DeleteObject(memBMP);
// Delete Background DC
DeleteDC(mem_m_hDC);
// Double Buffering Ends Here
// Unlock Forground DC
ReleaseDC(m_hWND, m_hDC);
// Remove the objects
DeleteObject(m_hBrush);
DeleteObject(m_hPen);
}
}