C++ MFC overriden OnPaint() not painting on another computer - c++

Question

I added code to OnPaint() and it paints correctly on my Windows 10 laptop, but the painting is not shown on another computer (Windows 8). I'm a novice at painting and I probably did something wrong - maybe with invalidate and updatewindow. Regardless, here is my code:
I am painting on a dialog window; the code for OnPaint() is mostly created by Visual Studios - I simply added DrawValveImage() at the end. Also, here is picture that shows what DrawValveImage() draws. I don't think you need to look at all the code for DrawValveImage() to solve the problem; I think my error is my placement of the calling of DrawValveImage(). Maybe OnPaint() isn't the right event for custom painting.
void CCleaningAndScreeningDlg::OnPaint()
{
if (IsIconic())
{
CPaintDC dc(this); // device context for painting
SendMessage(WM_ICONERASEBKGND, reinterpret_cast<WPARAM>(dc.GetSafeHdc()), 0);
// Center icon in client rectangle
int cxIcon = GetSystemMetrics(SM_CXICON);
int cyIcon = GetSystemMetrics(SM_CYICON);
CRect rect;
GetClientRect(&rect);
int x = (rect.Width() - cxIcon + 1) / 2;
int y = (rect.Height() - cyIcon + 1) / 2;
// Draw the icon
dc.DrawIcon(x, y, m_hIcon);
}
else
{
CDialogEx::OnPaint();
}
DrawValveImage();
}
void CCleaningAndScreeningDlg::DrawValveImage()
{
//my own drawing
CClientDC* pDC = new CClientDC(this);
pDC->SelectStockObject(NULL_BRUSH);
COLORREF blueBorder = RGB(67, 99, 155);
COLORREF blueFill = RGB(218, 227, 243);
int x1 = 1050;
int y1 = 50;
int width = 300;
int x2 = x1 + width;
int y2 = y1 + width;
CPen pen;
CBrush brush;
pen.CreatePen(PS_SOLID, 5, blueBorder);
brush.CreateSolidBrush(blueFill);
// select brush and pen
pDC->SelectObject(&pen);
pDC->SelectObject(&brush);
if (valveImageDrawn == FALSE)
pDC->Ellipse(x1, y1, x2, y2);
DeleteObject(brush);
DeleteObject(pen);
DeleteObject(&brush);
DeleteObject(&pen);
int heightWidth = width;
int smallHeightWidth = heightWidth / 7;
int radiusFromOriginSmallCircle = heightWidth / 2.75;
for (int circleIndex = 0; circleIndex < 10; circleIndex++) {
POINT centerSmallCircle = FindPointOnCircle(POINT{ heightWidth / 2, heightWidth / 2 }, radiusFromOriginSmallCircle, (circleIndex * 360 / 10) - 90);
int smallCircleX = centerSmallCircle.x - smallHeightWidth / 2 + x1;
int smallCircleY = centerSmallCircle.y - smallHeightWidth / 2 + y1;
rectangle smallCircleRect = { smallCircleX, smallCircleY, smallCircleX + smallHeightWidth, smallCircleY + smallHeightWidth };
rectsSmallCircles[circleIndex] = smallCircleRect;
bool greenFilled = false;
if (valvePosition - 1 == circleIndex) {
CPen pen;
CBrush brush;
COLORREF greenFill = RGB(181, 230, 29);
pen.CreatePen(PS_SOLID, 5, blueBorder);
brush.CreateSolidBrush(greenFill);
pDC->SelectObject(&pen);
pDC->SelectObject(&brush);
pDC->Ellipse(smallCircleRect.x1, smallCircleRect.y1, smallCircleRect.x2, smallCircleRect.y2);
DeleteObject(brush);
DeleteObject(pen);
DeleteObject(&brush);
DeleteObject(&pen);
greenFilled = true; //if mouse clicked and green color is painted on the valve image
}
else {
CPen pen;
CBrush brush;
pen.CreatePen(PS_SOLID, 5, blueBorder);
brush.CreateSolidBrush(blueFill);
pDC->SelectObject(&pen);
pDC->SelectObject(&brush);
pDC->Ellipse(smallCircleRect.x1, smallCircleRect.y1, smallCircleRect.x2, smallCircleRect.y2);
DeleteObject(brush);
DeleteObject(pen);
DeleteObject(&brush);
DeleteObject(&pen);
}
CString circleText;
int CircleNumber = circleIndex + 1;
circleText.Format(_T("%d"), CircleNumber);
CRect testRect = { smallCircleRect.x1,
smallCircleRect.y1, smallCircleRect.x2, smallCircleRect.y2 };
pDC->SetBkMode(TRANSPARENT);
CClientDC dc(this);
CFont font;
VERIFY(font.CreateFont(
30, // nHeight
0, // nWidth
0, // nEscapement
0, // nOrientation
FW_BOLD, // nWeight
FALSE, // bItalic
FALSE, // bUnderline
0, // cStrikeOut
ANSI_CHARSET, // nCharSet
OUT_DEFAULT_PRECIS, // nOutPrecision
CLIP_DEFAULT_PRECIS, // nClipPrecision
DEFAULT_QUALITY, // nQuality
DEFAULT_PITCH | FF_SWISS, // nPitchAndFamily
_T("Arial"))); // lpszFacename
CFont* def_font = pDC->SelectObject(&font);
pDC->DrawText(circleText, testRect, DT_SINGLELINE | DT_VCENTER | DT_CENTER);
pDC->SelectObject(def_font);
font.DeleteObject();
}
//redraw the combobox infront of the valve-image
UpdateData(TRUE);
comboPorts.Invalidate();
comboPorts.UpdateWindow();
valveImageDrawn = true;
}

Answer 1

OnPaint() is the right method to do custom painting. When you override OnPaint(), you should not call the OnPaint() method of the base class. You are responsible to draw all of the content of the window on your own (except child windows).
You only need this code:
void CCleaningAndScreeningDlg::OnPaint()
{
CPaintDC dc(this); // constructor of CPaintDC calls ::BeginPaint()
DrawValveImage( dc ); // pass device context to the drawing function
// Destructor of CPaintDC automatically calls ::EndPaint()!
}
You can see that I have added a parameter to DrawValveImage. The declaration would look like this:
void DrawValveImage( CDC& dc );
Make sure that in your drawing function, you only use the dc parameter for drawing.
This is wrong:
CClientDC* pDC = new CClientDC(this);
You should not create any additional device contexts.
Example of another mistake:
pDC->SelectObject(&pen);
pDC->SelectObject(&brush);
if (valveImageDrawn == FALSE)
pDC->Ellipse(x1, y1, x2, y2);
DeleteObject(brush);
DeleteObject(pen);
DeleteObject(&brush);
DeleteObject(&pen);
First, you don't restore the original state of the device context before you delete objects selected into it. When an object is still selected into a device context, it cannot be deleted correctly. To fix that, store the return value of SelectObject() and SelectStockObject(), which is a pointer to the object previously selected in the device context (if you didn't select one, there is a default object). Before you delete the object, call SelectObject(), passing the stored pointer.
Second, why do you delete objects twice? Either let the object destroy itself automatically when it leaves the current scope or call the DeleteObject() member function (rarely needed).
Corrected code:
auto pOldPen = dc.SelectObject(&pen);
auto pOldBrush = dc.SelectObject(&brush);
if (valveImageDrawn == FALSE)
dc.Ellipse(x1, y1, x2, y2);
if(pOldPen)
dc.SelectObject(pOldPen);
if(pOldBrush)
dc.SelectObject(pOldBrush );
// No need for DeleteObject(), the destructor of each object will delete it at the
// end of the current scope (before the function returns). But if you actually need it
// (say you want to reuse the variable), it would look like this:
// pen.DeleteObject();
// brush.DeleteObject();
This code is unnecessary:
//redraw the combobox infront of the valve-image
UpdateData(TRUE);
comboPorts.Invalidate();
comboPorts.UpdateWindow();
Just set the WS_CLIPCHILDREN style of the dialog window (using the dialog editor) to prevent the painting code from drawing over the combo box.