[PATCH 1/2] d2d1: Implement ID2D1Bitmap1::Map().

[Dmitry Timoshkov]

Nikolay Sivov <nsivov at codeweavers.com> wrote:

> >> It also says that it's supported in effects for DISCARD | WRITE, and
> >> there is a movement in this area on patch list, so might not be entirely
> >> theoretical.
> >>
> >> But anyway, it's impossible to guess, this needs some tests for
> >> different options, maybe CreateBitmap() fails for anything than READ or
> >> NONE. In that case you don't need to handle anything else, and if Map
> >> only works for bitmaps with CPU_READ, you probably can map resource
> >> without a copy.
> > The application I have here passes a bitmap without CPU_READ flag, so
> > ::Map() fails, and that's the reason for creating a staging texture.
> > Initially I had the code that calls ::Map() for the bitmap->resource,
> > and if that fails then creates a staging texture. What approach would
> > be better: check that bitmap was created with CPU_READ flag, or always
> > try to map bitmap->resource and fallback to a staging texture if that
> > fails?
> 
> Bitmap always references same resource, and resource parameters can't 
> change, so in principle you'll know which path will work when bitmap is 
> created.

So, to sum it up, ::Map() should have dedicated code paths for bitmaps with
and without CPU_READ flag.

> It's probably fine to have support only for READ map, and have a fixme, 
> with error return value otherwise.
> 
> For CPU_READ flag, we probably should have a fixme too.
> 
> Note that you don't release staging texture on unmap, and 
> d3d11_map_from_d2d1_map_options() seems wrong because D3D11_MAP_* is not 
> a mask.

Thanks for noticing these bugs, good catch.

> >> Another question is what happens with
> >> CreateBitmapFromDxgiSurface if you give it unmappable surface, but
> >> CPU_READ option.
> > Is that accepatable to leave this question aside for the initial implementation?
> >
> I quickly tested this with existing tests that are using swapchain 
> buffer. It fails to map on windows, but with this patch it works. So 
> there is already a discrepancy.

Probably having a fixme or a comment mentioning that scenario could also
be acceptable?

-- 
Dmitry.