scaleFactor strangeness

[Richard Gaskin]

Mark Waddingham wrote:
> On 2015-10-14 00:38, Richard Gaskin wrote:
>> Can we have the scalingFactor available for the contents of groups?
>> <http://quality.runrev.com/show_bug.cgi?id=11842>
>
> This would indeed be nice (and, indeed, it has come up many times
> before) - however there are two problems.
>
> The first is that all co-ordinates from a script point of view in the
> engine are integers, rather than floating point. This becomes important
> when you are starting to talk about transformations - for example
> scaling down an object of width 9 by a factor of 2 means the object's
> width is 4.5. So in this scenario the rect of an object within a scaled
> group would be inaccurate with how things are currently.
>
> The second is that the current script's co-ordinate model is such that
> all co-ordinates are relative to the top-left of the current card rather
> than the owning group.
>
> Now, the first can probably be ignored if the second is solved and
> co-ordinates are always expressed relative to the containing groups
> co-ordinate system (i.e. if you put a 10x10 button at 10,10 inside a
> group which scales things down by half, then the buttons rect would be
> 10,10,20,20 but it would appear at 5,5,10,10 on the card). However, I'm
> not sure how that squares up with script's idea of what co-ordinates
> should be relative to from a script point of view - we've all got very
> used to a single flat co-ordinate system which means there's no need for
> transforming between 'co-ordinates relative to one object' to
> 'co-ordinates relative to another object'.

Maybe those could be handled as the HTML Canvas does, in which the 
coordinates you use remain the same and the scale factor takes case of 
the translation for us when rendering.

<http://www.w3schools.com/tags/canvas_scale.asp>
<http://www.w3schools.com/tags/canvas_translate.asp>

Isn't that how Skia's canvas works also?

Workable for LC?

If we need to know the on-screen physical rect of a control (as distinct 
from its logical scaled rect) perhaps "the effective rect"?

-- 
  Richard Gaskin
  Fourth World Systems
  Software Design and Development for the Desktop, Mobile, and the Web
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