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libmemdraw: never point Buffer.alpha to nil (thanks mischief)

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the boolcopy optimization doesnt doesnt use Buffer.alpha, tho
the debug function dumpbuf() still can dereference it. to keep
it simple, always have Buffer.alpha point to the channel or
&ones when not used.
This commit is contained in:
cinap_lenrek 2014-12-30 12:44:42 +01:00
parent 5935eeb6de
commit 9f880e595c
1 changed files with 8 additions and 9 deletions
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17
sys/src/libmemdraw/draw.c
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@ -405,7 +405,7 @@ struct Buffer {
uchar *red;
uchar *grn;
uchar *blu;
uchar *alpha;
uchar *alpha; /* is &ones when unused, never nil */
uchar *grey;
ulong *rgba;
int delta; /* number of bytes to add to pointer to get next pixel to the right */
@ -1677,7 +1677,7 @@ DBG print("%x\n", w[-1]);
b.grey = buf+copyalpha;
b.red = b.grn = b.blu = buf+copyalpha;
b.delta = copyalpha+1;
DBG print("alpha %x grey %x\n", b.alpha ? *b.alpha : 0xFF, *b.grey);
DBG print("alpha %x grey %x\n", *b.alpha, *b.grey);
}else{
b.blu = buf+copyalpha;
b.grn = buf+copyalpha+1;
@ -1695,7 +1695,7 @@ writebyte(Param *p, uchar *w, Buffer src)
{
Memimage *img;
int i, isalpha, isgrey, nb, delta, dx, adelta;
uchar ff, *red, *grn, *blu, *grey, *alpha;
uchar *red, *grn, *blu, *grey, *alpha;
ulong u, mask;
img = p->img;
@ -1714,11 +1714,8 @@ writebyte(Param *p, uchar *w, Buffer src)
isgrey = img->flags&Fgrey;
adelta = src.delta;
if(isalpha && (alpha == nil || alpha == &ones)){
ff = 0xFF;
alpha = &ff;
if(isalpha && alpha == &ones)
adelta = 0;
}
if((img->flags&Fbytes) != 0){
int ogry, ored, ogrn, oblu, oalp;
@ -1829,7 +1826,8 @@ readptr(Param *p, uchar *s, int y)
USED(s);
q = p->bytermin + y*p->bwidth;
b.red = q; /* ptr to data */
b.grn = b.blu = b.grey = b.alpha = nil;
b.grn = b.blu = b.grey = nil;
b.alpha = &ones;
b.rgba = (ulong*)q;
b.delta = p->img->depth/8;
return b;
@ -1947,7 +1945,8 @@ genconv(Param *p, uchar *buf, int y)
}
b.red = buf;
b.blu = b.grn = b.grey = b.alpha = nil;
b.blu = b.grn = b.grey = nil;
b.alpha = &ones;
b.rgba = (ulong*)buf;
b.delta = 0;