> François Revol wrote: > >> "François Revol" <revol@xxxxxxx> wrote: > >> > >>> Still calling DrawBitmap a lot on a bitmap that doesn't change > >>> would > >>> be > >>> awful if you force sending it each time, it would void the > > > > purpose. > >>> > >> You don't necessarily have to send it; but you might want to check > >> (locally) if something changed. > >> > > > > Yes we can always maintain a checksum but that means we have to > > calculate it quite often... > > > > François. > > > > > Couldn't a call back hook be used instead? Add a pointer that by > default > is null, and everytime a change is made, check to see if that pointer > is > still null. If it isn't, then call the function referenced by the I don't understand. apps can use BBitmap::Bits() to get a pointer to the internal bitmap data. They usually cache it and use it whenever they feel like it to update the bitmap, then sometimes later call DrawBitmap or other stuff without notifying. There is no way to know when changes happen there. François.