#442 hq3x scaler is not redrawing properly

[Philip Kendall]

The HQ 3x scaler is not redrawing properly and leaves some "junk" behind. For an example, start Head over Heels then press "up" (Q by default). Note how the floor behind Head is corrupted - see attachment. The corruption goes away if something forces an entire screen redraw (e.g. change filter to triple size and then back to HQ 3x).

Visible in other games as well, this is just an easy one to reproduce.

[Sergio Baldoví]

Fix attached. Original code (hiend3d) use these guards:

    if (j>0)      prevline = -spL; else prevline = 0;
    if (j<Yres-1) nextline =  spL; else nextline = 0;

but Fuse's implementation removed them for hq2x. I guess because we usually scale rectangles intead of full frames.

hq3x keeps one guard but I think it isn't needed as rgb_image at gtkdisplay states:

"slightly bigger than the real screen to handle the smoothing filters which read around each pixel"

[Philip Kendall]

Looks good to me.

[Sergio Baldoví]

Thanks. Committed in [0eb11e].