[Scummvm-devel] Scaler updates

[Michael Bandsmer]

I'm looking for the opinion of the core developers on whether I can do
a bit of scaler revamping.  See
<http://sourceforge.net/tracker/?func=detail&atid=418822&aid=1536248&group_id=37116>
and lordhoto's suggestions there.

The main reason I want to do this is to add support for very basic 4x
scaling, to support full-screen operation for those of us with cheap
LCD monitors.  These cheap LCD monitors are designed to run in their
native resolutions, otherwise they (a) distort the pixel aspect ratio
and (b) do ugly inter-pixel blurring -- hence my desire for ScummVM to
do upscaling to 1280xN, which will support my LCD's native resolution
while filling the whole screen-width.

I submitted a first attempt at a patch for AdvMame4x and Normal4x (see
above), but as lordhoto pointed out, this patch perpetuates a
long-standing hack in our scalers, namely, that some scalers look
beyond the borders of the requested rectangle in order to figure out
how to draw the requested rectangle.  I believe this is done so that
there aren't graphical glitches at the borders of updated rects.  In
our current design, we accommodate this behavior by allocating an extra
border around all surfaces to be scaled, to prevent out-of-bounds
memory accesses.

So I have 2 questions:

(1) Would the inclusion of these simple 4x scalers be acceptable to the
rest of the ScummVM development team?

and

(2) It was suggested (see above link) that our long-standing scaler
hack be revisited and fixed somehow, as a prerequisite for the
incorporation of these 4x scalers.  Do you agree with this?  Is the
concept of a "MAX_SCALER_REACH" sufficient in order to address this
(see my patch)?

Note: lordhoto's other suggested prerequisite, i.e. a (4/3)x scaler,
shouldn't be a problem---I'm happy to do this if we decide to go this
route.

Anyway, I'm looking forward to working on this, if a consensus can be
reached that these 4x scalers are okay for general inclusion.

Mike Bandsmer


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