hojtsy Messages: 241 Registered: January 2006 Location: Budapest, Hungary
Experienced Member
Invoking BackPaint() withouth parameters is equivalent to BackPaint(FULLBACKPAINT). Any and all documentation about this enum value is "Whole area of Ctrl is backpainted". This short description can be understood in a whole lot of ways. My understanding was that it instructs the Ctrl class to paint the full area of the widget to the background color before calling the overloaded Paint method. I tried to search in the upp sources to find where and how this FULLBACKPAINT is used. I found that it is used in the Ctrl::CtrlPaint method. I tried to decrypt how that method works, and it seems that it uses the undocumented BackDraw class to buffer the drawing operations done in Ctrl::Paint. Now I see that this can avoid flickering, but still don't understand what is that connection with "Whole area of Ctrl is backpainted"?! It is quite possible to do multiple drawing operations (like overlapping images or polygons) in a sequence which could result in flickering even if you do not backpaint the whole Ctrl. In such case you would also activate this mode, and not because of backpainting. So is it possible that both the name and the documentation of this mode is missleading? Or am I missunderstanding something?
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