[PATCH 08/10] wined3d: make wined3d_device_update_surface operate with wined3d_texture and sub_resource_idx

[Henri Verbeet]

On 21 October 2015 at 12:57, Stefan Dösinger <stefandoesinger at gmail.com> wrote:
> I completely missed CopySubresourceRegion. This seems like a much
> better method to map UpdateSurface to than UpdateSubresource.
>
At first sight, yes. But it's actually not that obvious. Note that in
d3d10+ you don't have pure system memory resources like in earlier
versions, in d3d9 terms resources are always in the default or managed
pool. The way it's described in the documentation
CopySubresourceRegion() always copies between GPU buffers, while
UpdateSubresource() is for uploads. I had hoped to avoid thinking too
much about how to handle system memory resources for a while. That
said, perhaps wined3d_device_copy_sub_resource_region() could be a
useful intermediate step, even though that means we may end up
changing it to UpdateSubresource() anyway in the future.

>> Complexities of managing that aside, that would always imply at
>> least one copy of the data for d3d10+ updates.
> Ya, the design of d3d10's update_sub_resource kinda implies a copy.
> You can of course try to call GL right away with the
> application-provided pointer, but then the driver is likely to make a
> copy internally unless it is really clever too. It seems better to me
> to do the copy ourselves, write into a client storage buffer object
> and then blame the driver if it still insists on making an internal copy.
>
Yeah, we disagree there. I prefer to do the right thing and then fix
the driver if it doesn't know how to handle that.