WTL RedrawWindow parameterrs

Question

I'm new to the WTL C++. I'm really confused about the parameters that go into the RedrawWindows function especially for the flags. I'm just trying to update a window everytime I draw a line, but I don't exactly understand how

LRESULT  CDrawView::OnLButtonUp(UINT uMsg, WPARAM wParam, LPARAM lParam, BOOL& bHandled)
{
    int xPos= GET_X_LPARAM(lParam);
    int yPos = GET_Y_LPARAM(lParam);
    end.X = xPos;
    end.Y = yPos;

    Pen pen(Color(0, 0, 255));
    m_GraphicsImage.DrawLine(&pen, start.X, start.Y, end.X, end.Y);

I try to call RedrawWindow here,

RedrawWIndow(NULL,NULL, NULL, RDW_INTERNALPAINT)

So everytime I release the left mouse button the window gets updated. I'm having a really hard time understanding the parameters that go into the Redraw Function. I tried putting them all null minus the last one but Visual studio says that the function doesn't take 4 parameters even though I read the msdn microsoft...

Can you show us the call that you attempted and the error it gave? — Joseph Mansfield, Mar 26 '13 at 17:56
i have tried all the different flags for the fourth parameter and visual studio tells me that RedrawWindow does not take 4 arguments — user1665569, Mar 26 '13 at 18:02
What you are trying to achieve exactly? I doubt you need `RedrawWindow` in first place. — Roman R., Mar 26 '13 at 18:06
As of now the user presses the left mouse button, and after he releases it a line is supposed to be drawn. This line is only showing up for me, when i maximize the window — user1665569, Mar 26 '13 at 18:08
Why are you using RedrawWindow? In general, all of your drawing should happen in response to WM_PAINT. You probably should add the new line segment to a data structure, then call Invalidate, and the WM_PAINT handler should draw all the line segments in the data structure. — Adrian McCarthy, Mar 26 '13 at 20:03

Drew Dormann · Accepted Answer · 2013-03-26T18:29:28.597

0

You are not calling the global RedrawWindow.

You're calling the member function CWindow::RedrawWindow, which takes 3 parameters.

BOOL RedrawWindow(
   LPCRECT lpRectUpdate = NULL,
   HRGN hRgnUpdate = NULL,
   UINT flags = RDW_INVALIDATE | RDW_UPDATENOW | RDW_ERASE 
); throw()

Edit: These three parameters all have default arguments, meaning they don't need to be supplied an RedrawWindow() alone should work.

edited Mar 26 '13 at 18:29

answered Mar 26 '13 at 18:14

Drew Dormann

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i tried that and Visual Studio says that "#define RDW_INVALIDATE and that argument of type "int" is incompatible with parameter of type HRGN" – user1665569 Mar 26 '13 at 18:20
1

Is he using WTL or MFC? `CWnd::RedrawWindow` is an MFC function, and he claims to be using WTL. – Nik Bougalis Mar 26 '13 at 18:21
i'm using WTL @NikBougalis – user1665569 Mar 26 '13 at 18:23
@NikBougalis I'm woindering the same, given the error `function doesn't take 4 parameters`. Editing with a second stab at it... – Drew Dormann Mar 26 '13 at 18:24
1

You *should* be able to just do `RedrawWindow();` – Nik Bougalis Mar 26 '13 at 18:27
error C2660: 'ATL::CWindow::RedrawWindow' : function does not take 4 arguments... This is what i keep getting – user1665569 Mar 26 '13 at 18:27
Nik you are right. just doing RedrawWindow() without any parameters did the trick...i don't understand why because when i looked at the msdn it said it needed some arguments – user1665569 Mar 26 '13 at 18:29
2

You are looking at the Windows API version of the function on MSDN - which accepts a number of arguments. But you are not using the Windows API version of the function, you are using a framework (WTL) which has its own version of most Windows API functions. – Nik Bougalis Mar 26 '13 at 18:30

score 0 · Answer 2 · answered Mar 26 '13 at 20:58

This is not the way you should use and you are supposed to be using the API. Your mouse button handler should call Invalidate() or InvalidateRect with specific part of the window you are marking as needing an update. Your window will then receive WM_PAINT event at the first OS convenience and your paint handler would paint the line.

RedrawWindow might work out this time, however is likely to be a base of a next problem very soon because you are already on the wrong way.

WTL RedrawWindow parameterrs

2 Answers2