Re: [XaraXtreme-dev] OSRenderRegion::DrawTransformedBitmap

[Alex Bligh <alex@xxxxxxxxxxx>]

Phil,

> > It does indeed run very slowly, I think because it's trying to background
> > redraw the gallery or something - certainly doesn't look like it is
> > rectangle merging.
>
> GRenderRegions do not background render in themselves - background 
> rendering is handled by the View classes which shoudl not be involved here.
> Related: I've noticed that rectangle merging appears to be disabled on a 
> document view when the bitmap gallery is opened and dragged around. But 
> only while the gallery window falls partly inside, partly outside the 
> view. As soon as the gallery  window falls entirely within the view 
> rect, region merging seems to start up again.

Bizarre. No idea!

> > However, fixing up the text is not a simple exercize. The way
> > DrawFixedSystemText seems to work in GRenderRegion is it plots it to the
> > MSW equivalent of a memory DC. This then gets into a kernel bitmap, 
> > and is
> > plotted as a bitmap using the normal GDraw routines. But this itself 
> > is not
> > particularly simple, because the wxMemoryDC will be in wxImage format, 
> > and
> > I am left with the former problem but in reverse, i.e. how to get the
> > wxImage into a KernelBitmap format. So I've got just as much odd code to
> > write!
>
> No scaling or resampling involved this time... ???

True. Actually it occurred to me that I could do the resampling myself
no worse than StretchDIB does it (i.e. badly) in about 2 lines of code
at the same time as the OilBitmap to image conversion, so that's the
memory issue fixed. But again, see below.

> I realise there are reasons why maybe this stuff has to be tackled in 
> the long run for other areas of the program - just pointing out possible 
> options.

Well further investigation shows I read the code wrong. It only does a
StretchDIB when printing. Otherwise it called the (still disabled)
call to render a bitmap fill into a rectangle, which does indeed use
GDraw to do it, even in OSRenderRegion. So hopefully I can just nurse
that back into life and all will be well.

Alex