[squeakland] Found Bug But Not Sure How to Proceed To Fix

Bob Arning arning315 at comcast.net
Sat Mar 3 13:34:32 UTC 2018

I guess Etoys always had a bit of a preference for rounded corners and 
softer shapes, so it may be expecting too much for rotated rectangles 
all to grid nicely along their top (or left) edge. As it stands

- the expandBy: 1 ensures that the rotated ones are drawn down and right 
from the non-rotated one

- even the rotated ones are drawn at differing positions within the 
expanded bounds

- in trying to see if this second effect is an error or some profound 
mathematical truth, I noticed (in versions 3.2 through 5.1 anyway) that 
the fallback code in WarpBlt>>warpBitsSmoothing:sourceMap: does not 
function correctly in all cases. To see this, get a RectangleMorph and 
rotate it with the blue handle. Then comment out the primitive call in 
WarpBlt>>warpBitsSmoothing:sourceMap: and try rotating the rectangle 
again. Different, eh? I guess figuring this out is the first step in 
seeing if the rotated rects could line up nicely.

On 3/3/18 7:44 AM, Bert Freudenberg wrote:
> On 3 March 2018 at 02:37, David T. Lewis <lewis at mail.msen.com 
> <mailto:lewis at mail.msen.com>>wrote:
>     Does anything bad happen if the "expandBy: 1" is removed? I tried
>     removing it
>     in my Squeak trunk image, and "CompassDialMorph new openInWorld"
>     (which is one
>     user of TransformationMorph) seems to work nicely.
> ​I bet it's there to avoid gribblies left behind when dragging.​ The 
> damage rectangle needs to be large enough to cover every pixel touched 
> even in rotated versions.
> ​Maybe the ​
> ​"​
> truncated​ expandBy: 1
> ​"​ should be something like "rounded outwards"?
> But generally speaking, as long as we have the warpblt hack + integer 
> coords instead of a proper hierarchical transform framework we will 
> run into these rounding issues again and again.
> ​- Bert -​
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