idlegravity
asked on
How to update one region of the view...
I've got a large, double-buffered, scrollable view in an SDI app. When the user clicks in the view, the corresponding value in the document is toggled, and the the view needs to be updated to show the change.
Currently I just Invalidate() the view and cause it to be redrawn, but it's big enough that it's just too slow to redraw the whole thing every time the user interacts with it. I am trying to figure out how to update just a small region of the view. I would like to be able to update a region without going through all the nested loops of the OnDraw() function (I know that you can use clipping regions so that OnDraw() only updates a specific region, it would still take too long to go through everything I have in there).
Thanks for your help, experts!
Currently I just Invalidate() the view and cause it to be redrawn, but it's big enough that it's just too slow to redraw the whole thing every time the user interacts with it. I am trying to figure out how to update just a small region of the view. I would like to be able to update a region without going through all the nested loops of the OnDraw() function (I know that you can use clipping regions so that OnDraw() only updates a specific region, it would still take too long to go through everything I have in there).
Thanks for your help, experts!
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Jaime Olivares
If the information you present has a tabular format, then CListView in "Report mode" derived window will be more suitable for your needs, because it allows you to update row by row using owner draw feature, and of course has scrollbar.
GetUpdateRect only receives the enclosing update rectangle of the update region that is determined by one or more calls to InvalidateRect.
Therefore, use InvalidateRect as Nass98 told you and the next painting happens automatically ...
(from MSDN)
Windows sends a WM_PAINT message whenever the CWnd update region is not empty and there are no other messages in the application queue for that window.
Regards, Alex
Therefore, use InvalidateRect as Nass98 told you and the next painting happens automatically ...
(from MSDN)
Windows sends a WM_PAINT message whenever the CWnd update region is not empty and there are no other messages in the application queue for that window.
Regards, Alex
? - without using GetUpdateRect how does idlegravity know what to repaint, as he says it is too big to repaint the complete view (as he presumable does at present) and since when does windows draw the contents of your view.
>> without using GetUpdateRect how does idlegravity know what to repaint
Look to your post above:
The update rectangle retrieved by the BeginPaint member function is identical to that retrieved
by the GetUpdateRect member function.
The BeginPaint member function automatically validates the update region, so any call to
GetUpdateRect made immediately after a call to BeginPaint retrieves an empty update region.
So InvalidateRect is first (you have to say what regions became invalid) and BeginPaint gets the rectangle to update. You could call GetUpdateRect if you are actively drawing but not in OnDraw as you would get an empty rectangle. Furthermore, if you already have to know the update rectangle before calling InvalidateRect, there is no need to retrieve that rectangle again, except there are more than one regions to update.
Regards, Alex
Look to your post above:
The update rectangle retrieved by the BeginPaint member function is identical to that retrieved
by the GetUpdateRect member function.
The BeginPaint member function automatically validates the update region, so any call to
GetUpdateRect made immediately after a call to BeginPaint retrieves an empty update region.
So InvalidateRect is first (you have to say what regions became invalid) and BeginPaint gets the rectangle to update. You could call GetUpdateRect if you are actively drawing but not in OnDraw as you would get an empty rectangle. Furthermore, if you already have to know the update rectangle before calling InvalidateRect, there is no need to retrieve that rectangle again, except there are more than one regions to update.
Regards, Alex
void CMyView::OnPaint()
{
GetUpdateRect(&m_rectUpdat
CPaintDC dc(this); // device context for painting
OnDraw(&dc);
}
m_rectUpdate contains the rectangle to redraw
{
GetUpdateRect(&m_rectUpdat
CPaintDC dc(this); // device context for painting
OnDraw(&dc);
}
m_rectUpdate contains the rectangle to redraw
this is actually better
void CMyView::OnPaint()
{
GetUpdateRect(&m_rectUpdat
CScrollView::OnPaint(); //or whatever your base class is
}
m_rectUpdate contains the rectangle to redraw
void CMyView::OnPaint()
{
GetUpdateRect(&m_rectUpdat
CScrollView::OnPaint(); //or whatever your base class is
}
m_rectUpdate contains the rectangle to redraw