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FS#13970 - lcd_drawline() different depending on drawing direction try#2

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Last patch didn't swap both x and y so was wrong and messed up the coord pair
I didn't want to add more swapping due to extra overhead

ultimately the issue is that you have 1/2 pixel error (-1 0 1)
and when doing the reverse line the error is on the wrong side
so instead get the first point from the opposite dinc

Change-Id: I141c4af36a601314f2b509a9ebfcfab3b5213bcd
This commit is contained in:
William Wilgus 2026-08-05 11:40:02 -04:00
parent 20c763ff89
commit dcdb539ca5
1 changed files with 24 additions and 16 deletions
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40
firmware/drivers/lcd-bitmap-common.c
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@ -911,6 +911,18 @@ void LCDFN(drawline)(int x1, int y1, int x2, int y2)
dinc2 = (deltay - deltax) * 2;
xinc1 = 1;
yinc1 = 0;
if (x1 > x2)
{
xinc1 = -xinc1;
xinc2 = -xinc2;
}
if (y1 > y2)
{
d += dinc2;
yinc1 = -yinc1;
yinc2 = -yinc2;
}
}
else
{
@ -920,25 +932,21 @@ void LCDFN(drawline)(int x1, int y1, int x2, int y2)
dinc2 = (deltax - deltay) * 2;
xinc1 = 0;
yinc1 = 1;
if (x1 > x2)
{
d += dinc2;
xinc1 = -xinc1;
xinc2 = -xinc2;
}
if (y1 > y2)
{
yinc1 = -yinc1;
yinc2 = -yinc2;
}
}
numpixels++; /* include endpoints */
if (x1 > x2)
{
/* swap their identities */
int x0 = x2;
x2 = x1;
x1 = x0;
}
if (y1 > y2)
{
/* swap their identities */
int y0 = y2;
y2 = y1;
y1 = y0;
}
x = x1;
y = y1;