[interfacekit] Re: :) Again - BBitmap

> > Look for example at BPrintJob,
> > BPrintJob::DrawView() needs the given view to be attached to a window
> > because the drawing commands need to reach the app_server. "The view
> > must be
> > attached to a window; that is, it must be known to the Application
> > Server."
>
> I fail to get what BPrintJob has to do with bitmap drawing.

It's quite simple. When you attach a view to a bitmap, which accepts views,
the view is attached to an offscreen window, which means it gets a server
counterpart, and a connection to the app_server.
This connection is needed to print the view.
With a local drawing library, you don't have a connection, which means that
a view attached to this "local drawing bitmap" cannot be printed, which
means it's not backwards compatible. This is just one example of something
which has to be changed if you make the BBitmap change. I'm now almost
working for two years on my app_server. I noticed there are lots of "hidden"
connections in the Be API, so a change which looks simple can take lots of
work on many other seemingly unrelated things to make it all work again.

> > I would write an API like the BPicture one,
> > a BeginDrawBitmap(bitmap) and EndDrawBitmap(). All the drawing
> > instructions
> > received between those calls would be rendered into the bitmap
> > instead of
> > the window. This would make a lot of sense, since you would most
> > likely call
> > view->Draw(view->Bounds()) from a window thread anyway, so why not
> > let that
> > server thread do the work?
>
> Though I don't get the last part,

I R5, when you draw in a BBitmap, you often call the views drawing functions
from another BWindow thread.

BWindow::something()
{
        fBitmap->Lock();
        fViewAttachedToTheBitmap->Draw(someRect);
        fBitmap->Unlock();
}

That's why I proposed this, it's the same thread that's occupied with the
drawing, and there are no BBitmap threads needed and rendering still happens
on the server, in one place (Btw, rendering also includes all clipping
calculations, and the management of clipping regions).

BWindow::something()
{
        BeginDrawBitmap(fBitmap);
        fViewAttachedToTheWindow->Draw(someRect);
        EndDrawBitmap();
}

I know you still need a BWindow, but at least you can use one window to draw
in any bitmap you want.

Marc Flerackers

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