Re: [AD] fix for using transformations without a display and make blending mode a per-display state

[Peter Wang <novalazy@xxxxxxxxxx>]

On 2010-03-03, Elias Pschernig <elias.pschernig@xxxxxxxxxx> wrote:
> This patch does not move the current transformation out of the display
> into TLS (it was the solution Trent agreed to in the opengl fix thread)
> but instead makes the blending mode a per-display property just as the
> current transformations already was.
> 
> For something like drawing into a memory bitmap to still work when there
> is no current display, I used a trick suggested by Evert on allegro.cc -
> as a special case store the per-display state in TLS anyway if there is
> no display. (In the code an empty ALLEGRO_DISPLAY is put into
> tls->memory_display, which has no other function but to contain a
> current transformation and blending state.)

I fixed(?) a simple problem in al_use_transform where the
current_display->vt may be NULL.  I don't know how many other places
need a similar fix.

Peter