override onpaint
-
What does it really mean when overriding the OnPaint event? example if possible. thank you Donkaiser
That doesn't mean anything really. You can't override an event. You can, however, override a virtual method, such as Control.OnPaint(EventArgs). Overriding a method means that when the base implementation of OnPaint is invoked (the base, in this case, meaning Control.OnPaint) the overridden implementation is invoked. The method call "slides down" the class hierarchy and calls the most derived class's override of the method (unless the method is sealed with the 'sealed' modifier, but forget about that for now). Josh
-
That doesn't mean anything really. You can't override an event. You can, however, override a virtual method, such as Control.OnPaint(EventArgs). Overriding a method means that when the base implementation of OnPaint is invoked (the base, in this case, meaning Control.OnPaint) the overridden implementation is invoked. The method call "slides down" the class hierarchy and calls the most derived class's override of the method (unless the method is sealed with the 'sealed' modifier, but forget about that for now). Josh
-
I want to use OnPaint to keep updating my drawings which mean i need to raise OnPaint event whenever i want to. so how can i raise an event? Donkaiser
-
I want to use OnPaint to keep updating my drawings which mean i need to raise OnPaint event whenever i want to. so how can i raise an event? Donkaiser
-
You could raise the paint event yourself, but that is not recommended. Just invalidate the control using the Invalidate method, and it will be redrawn. --- b { font-weight: normal; }
-
It's not possible to raise the OnPaint event. (You can't raise any event outside yours) What you need ist the .Refresh Method. This causes a Paint Event of Controls. That means: yourform or yourcontrol.Refresh(); All the best, Martin
yes i main concern is flikering because at every update of my drawing the whole thing got redrawn. panel.invalidate() and panel.refresh() fliker the screen. Is there a solution for that of by the way im developing in the CF 2.0. so possibilities are very limited. Donkaiser
-
yes i main concern is flikering because at every update of my drawing the whole thing got redrawn. panel.invalidate() and panel.refresh() fliker the screen. Is there a solution for that of by the way im developing in the CF 2.0. so possibilities are very limited. Donkaiser
-
yes i main concern is flikering because at every update of my drawing the whole thing got redrawn. panel.invalidate() and panel.refresh() fliker the screen. Is there a solution for that of by the way im developing in the CF 2.0. so possibilities are very limited. Donkaiser
you can also override the PaintBackground. But the problem is because you see the client area when it redraws. You should create an off screen buffer. write to it, then write to the client after its all done. then you wont see any flicker. WinForms is not a very good graphical program. And this is very complicated. I recommend an MFC book to fully understand how to control painting. Although a method may exist to limit the flickering. I dont know of one and I use API's to contol that. But, a little flicker is okay for a business program. Nick 1 line of code equals many bugs. So don't write any!!
-
yes i main concern is flikering because at every update of my drawing the whole thing got redrawn. panel.invalidate() and panel.refresh() fliker the screen. Is there a solution for that of by the way im developing in the CF 2.0. so possibilities are very limited. Donkaiser
In order to reduce flickering you may have to use a technique which is commonly reffered to double-buffering. What that means is that you create graphics context in the background and draw there. When you're done, you 'swap' the two graphics contexts. What that means is that you basically copy the back buffer graphics context's contents to the active graphics context. A quick search for double buffering will most likely give you all the information that you need. ---- www.digitalGetto.com
-
Call
_Control_.Invalidate(). This will invalidate the entire region of the control and force a WM_PAINT message to be sent to the control's window. This message is what triggers the OnPaint event. Dave Kreskowiak Microsoft MVP - Visual Basic -
In order to reduce flickering you may have to use a technique which is commonly reffered to double-buffering. What that means is that you create graphics context in the background and draw there. When you're done, you 'swap' the two graphics contexts. What that means is that you basically copy the back buffer graphics context's contents to the active graphics context. A quick search for double buffering will most likely give you all the information that you need. ---- www.digitalGetto.com
I try to implement double buffer but i can't get the handle of the SetStyle method this.SetStyle(ControlStyles.UserPaint, true); this.SetStyle(ControlStyles.AllPaintingInWmPaint, true); this.SetStyle(ControlStyles.DoubleBuffer, true); this.SetStyle(ControlStyles.UserPaint, true); this.SetStyle(ControlStyles.AllPaintingInWmPaint, true); this.SetStyle(ControlStyles.DoubleBuffer, true); VS2005 give me the error saying that SetStyle and ControlStyles is not contained in the definition of the form. how can i get the handle on this function to use on a panel to prevent flickering? Donkaiser Donkaiser
-
you can also override the PaintBackground. But the problem is because you see the client area when it redraws. You should create an off screen buffer. write to it, then write to the client after its all done. then you wont see any flicker. WinForms is not a very good graphical program. And this is very complicated. I recommend an MFC book to fully understand how to control painting. Although a method may exist to limit the flickering. I dont know of one and I use API's to contol that. But, a little flicker is okay for a business program. Nick 1 line of code equals many bugs. So don't write any!!
Actually, if you set the style of the control to OptimizedDoubleBuffer it will handle all of the double buffer work for you. That is if you are using VS 2005
-
I try to implement double buffer but i can't get the handle of the SetStyle method this.SetStyle(ControlStyles.UserPaint, true); this.SetStyle(ControlStyles.AllPaintingInWmPaint, true); this.SetStyle(ControlStyles.DoubleBuffer, true); this.SetStyle(ControlStyles.UserPaint, true); this.SetStyle(ControlStyles.AllPaintingInWmPaint, true); this.SetStyle(ControlStyles.DoubleBuffer, true); VS2005 give me the error saying that SetStyle and ControlStyles is not contained in the definition of the form. how can i get the handle on this function to use on a panel to prevent flickering? Donkaiser Donkaiser
I'm not 100% sure but I think if you want to use the standard doublebuffering that .NET 2.0 GDI+ is offering you have to implement some other functions to support it. Make sure you find a good article on that. It's not trivial at first but once you grasp the fundamentals it should be straight forwards. Also, did you mention using the Compact Framework?! That may be the reason. Google for an example of how to implement double buffering in C# with .NET 1.0/1.1... that is not using the .SetStyle and ControlStyles.DoubleBuffer. Good luck ---- www.digitalGetto.com
-
Call
_Control_.Invalidate(). This will invalidate the entire region of the control and force a WM_PAINT message to be sent to the control's window. This message is what triggers the OnPaint event. Dave Kreskowiak Microsoft MVP - Visual Basic -
Sorry missunderstanding, I was wondering about... " You could raise the paint event yourself, but that is not recommended. " How can you do that? Thanks for more Info, Martin -- modified at 15:15 Thursday 29th June, 2006
Simply call Invalidate anywhere else in the control's code, except inside the Paint handler. Dave Kreskowiak Microsoft MVP - Visual Basic
-
Simply call Invalidate anywhere else in the control's code, except inside the Paint handler. Dave Kreskowiak Microsoft MVP - Visual Basic
-
Sorry again, You can really believe me when I'm saiing that I understand the Invalidate Method. What I did not understand is what Guffa said before. But maybe, my C# is better than my english. Thank again, Martin
What he means is that you should NOT call the Paint method directly. If you do, you can have very unexpected and strange results. You should only be painting the control when Windows expects you to. When it wants you to repaint, it'll send the WM_PAINT message to your control, thereby firing the Paint event. When you call Invalidate, your telling the control to invalidate its client area. You haven't actually fired the Paint event. The control will let Windows know that it has to repaint itself. Windows will then figure out when it is safe for you to repaint your window and send back the paint message when it is appropriate for you to repaint. Dave Kreskowiak Microsoft MVP - Visual Basic -- modified at 19:17 Thursday 29th June, 2006
-
What he means is that you should NOT call the Paint method directly. If you do, you can have very unexpected and strange results. You should only be painting the control when Windows expects you to. When it wants you to repaint, it'll send the WM_PAINT message to your control, thereby firing the Paint event. When you call Invalidate, your telling the control to invalidate its client area. You haven't actually fired the Paint event. The control will let Windows know that it has to repaint itself. Windows will then figure out when it is safe for you to repaint your window and send back the paint message when it is appropriate for you to repaint. Dave Kreskowiak Microsoft MVP - Visual Basic -- modified at 19:17 Thursday 29th June, 2006