Two SVG bugs

[srush]

• Newlines \n in svg specification seems to break in some browsers.
• Images that are too large and then scaled down cause Affine to think transformation are degenerate.

Small temporary fixes.

[danoneata]

Hey! Thanks for the fixes!

The image fix works only for the SVG backend, right? I wonder if it would be more flexible (backend agnostic) to apply the scaling only when we create the image primitive:

 def image(local_path: str, url_path: Optional[str]) -> Diagram:
     from chalk.core import Primitive

-    return Primitive.from_shape(Image(local_path, url_path))
+    return Primitive.from_shape(Image(local_path, url_path)).scale(0.05)

Somewhat unrelated, but what should the url_path argument from the image function be set to (I see that's used only in the SVG backend)?

[danoneata]

Ah, I now see that things are a bit more complicated that I've imagined: if I understand correctly, the SVG backend doesn't display the image loaded from the local_path, but the one specified by url_path? The image from the local_path is used to retrieve the size?

[srush]

I think we need a couple long term fixes.

1. figure out why large scaling ops break the degenerate check in affine.
2. make image backend specific. Diagrams also has some backend specific code (svgtext)
3. pull out and document scaling constants. I.e default images to local width 1? Not sure what is right to do here.

[danoneata]

Okay! So I guess you are suggesting to merge these temporary fixes for the time being and create separate issues for the long-term problems, right? I'm fine with that, but I just wanted to point out that the current changes will affect the image rendering with cairo (since the Image's width and height do not match the true width and height of the PIL image data); I don't have a satisfactory solution—maybe we could try resizing the image by the 0.05 factor in the from_pil function?

     format: cairo.Format = cairo.FORMAT_ARGB32
+    im = im.resize((int(im.width * 0.05), int(im.height * 0.05)))
     if "A" not in im.getbands():

[srush]

We don't need to merge. I'll fix Cairo for real here.

Mostly just sent this to remind myself since I needed it in my code.

[danoneata]

Ah, cool! Sorry for misunderstanding! I'll take a look at #113 then if you haven't started already working on it.