Hello,
Could you review the fix:
bug: https://bugs.openjdk.java.net/browse/JDK-8158370
webrev: http://cr.openjdk.java.net/~alexsch/8158370/webrev.00
Char advance in user space is calculated with float precision. That
leads that summed up char advances in user space can have small rounding
error.
To draw a substring of a text as selected it needs to draw the
selected text from the string location plus the preceding text width.
The selected text location is close to an integer value for an
integer scale:
(textX + sum(charAdvanceInDevSpave/scale) + transformTranslate) *
scale // both textX and transformTranslate have integer value
The situation is different for floating point scales. Now (textX +
transformTranslate) * scale can be a floating point value like N.5 where
N is some integer value. The sum(charAdvanceInDevSpave/scale) * scale is
close to an integer.
Sum of these values can be M.499.. which is rounded to M or M.500..
which is rounded to M+1.
Because of this a selected text can be shifted to one pixel left from
the required position.
The proposed fix rounds the text coordinates to the closest half
integer value if it is necessary in dev space.
Thanks,
Alexandr.
