add scaleX and scaleY

[danfishgold]

I saw the TODO where you wanted to give them cooler names, but I think these names are less confusing and more in line with Elm GraphicSVG and Elm Graphics.

I implemented this with a tuple scale : (Float, Float), but it could have been done with a record. I'm not sure which is better.

[timjs]

Thanks for the pull request @danfishgold, your code looks great! I think a tuple is the best way to go here.

Two questions:

• Can you create a simple example showing scaling in X and Y directions and add it to the examples directory? I use it for regression testing as visual debugging is bad to automate.
• Can you describe why you think scaleX and scaleY are less confusing than broaden and lengthen? I'm leaning towards your side, but need some more confidence before fixing the api. Same holds for skewX and skewY compared to slant and tilt which seem nice, but can be confusing to remember which is in the x and which in the y direction.

[danfishgold]

skewX and skewY are the names used in svg (and css) transforms. People who are familiar with this will know what these functions mean, and beginners will have an easier time Googling for help. Also, as a non-native English speaker, I don't know the difference between skew, tilt, and slant so I prefer to explicitly state the axis.

I don't have as strong a case for scale, but if there's skewX and skewY, I think there should be scaleX and scaleY. If you still prefer nicer names I don't think lengthen is a good fit because there are cases where it might be ambiguous: lengthening a rectangle (or a bus, or a snake) means increasing its longer side, which isn't necessarily along the Y axis.

[timjs]

You totally convinced me! Especially that function names will be easily recognised is a big plus.

Thanks for changing the docs, can you make a small example? Then I'll merge your request.

[Kwarrtz]

I'm a little late to the party, but I think it's worth pointing out that words like lengthen and broaden tend to suggest an increase in size (i.e. a scale factor of greater than 1), which is not desirable here. scale and skew also have the bonus of being familiar to those with backgrounds in linear algebra.

[timjs]

Even more reasons to use scaleX/Y and skewX/Y instead of fancy names!

Thanks for your opinion @Kwarrtz.

[danfishgold]

I can't think of a basic example for scaleX and scaleY because for simple stuff you can use rectangles instead of squares and ellipses instead of circles 😅

[timjs]

I'll think of something :wink: