370032 - svg images don't scale up with webpage using ctrl+= and ctrl+-

Status: RESOLVED DUPLICATE of bug 291785

(Core :: SVG, defect)

Description

[Christ]

User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1.1) Gecko/20070124 BonEcho/2.0.0.1
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.1.1) Gecko/20070124 BonEcho/2.0.0.1

when changing the size of webpages using ctrl+= and ctrl+-, scalable vector graphics aren't scaled accordingly.  only texts inside these graphics are modified.  the site linked above uses pt size for the images SPECIFICALLY so they'll be scaled accordingly as if for a font of the same size.  as you can see, using ctrl+= and ctrl+- fails to scale the scalable vector graphics.

Reproducible: Always

Steps to Reproduce:
1.click link
2.wait a few seconds
3.hit ctrl+= ctrl+= ctrl+= to make the webpage larger.
Actual Results:  
scalable vector graphics stay the same size, text in them is enlarged.

Expected Results:  
scalable vector graphics with height/width specified in relative units (anything except px) should scale up proportionally to the rest of the content.  text in the SVG should also scale as it does now.

Comment 1

[Eli Friedman]

If you want the SVG to scale with the text, you should be using "em" units.  

Summary of the different kinds of units:
Points/inches/cm/etc. are absolute units.  Assuming your OS's DPI setting is correct, one inch on the screen should correspond to one real inch.
Pixels are a special kind of unit; they are approximately 1/96 in, but vary in size depending on the device (for example, on a 300dpi printer, 1 "pixel" is 3 device pixels).
Em and ex units are dependent on the font size of the associated node.

See bug 177805 and bug 4821 for more discussion.

Comment 2

[Christ]

this is hardly related to either of those bugs, neither of which presents a solution as yet.  furthermore, using em as the image size on an inline SVG image (as seen in the example above) causes the SVG image to simply not display.

I would like this bug to be re-evaluated by someone with experience working with SVG, who understands the underlying concepts and motivating principals behind it.

I maintain that an image that is scalable by design should be scaled when displayed when applicable.  if it's specified using the same unit as a piece of text which is also scaled, it should be scaled as well to provide a pleasant and consistent user experience.

Comment 3

[Eli Friedman]

(In reply to comment #2)
> this is hardly related to either of those bugs, neither of which presents a
> solution as yet.  furthermore, using em as the image size on an inline SVG
> image (as seen in the example above) causes the SVG image to simply not
> display.

Oops, that's bug 305859.  Sorry, I haven't really done much SVG authoring.

> I would like this bug to be re-evaluated by someone with experience working
> with SVG, who understands the underlying concepts and motivating principals
> behind it.

Fine, moving component to SVG.

> I maintain that an image that is scalable by design should be scaled when
> displayed when applicable.

Yes, I agree.  The issue is whether text zoom can really scale images in a reasonable manner.

> if it's specified using the same unit as a piece of
> text which is also scaled, it should be scaled as well to provide a pleasant
> and consistent user experience.

So basically, you're requesting that text zoom scale inline SVG.

I'm pretty sure that would just end up being more confusing, but I guess it's a legitimate request.  "The same unit as the text" would be even more confusing; imagine that 1in != 72pt.

Comment 4

[Christ]

well, what I mean is if a font set in point size scales when changing the fonts, then an svg image set in point sizes should also scale.

furthermore, if the image is set to 48pt, it should measure the same height as a piece of text at 48 point as well.  the same should also apply to any other units of measure that are adjustable with ctrl+= and ctrl+-.

it just makes sense if you think about it, and since it IS svg, it shouldn't be too difficult to do.

thank you for reconsiddering my bug report, and for moving it to a more appropriate location.  I didn't see SVG when I posted it ^,.,^

Comment 5

[Robert Longson [:longsonr]]

Neither the image nor the text should scale.

Comment 6

[Robert Longson [:longsonr]]

Could have gone for invalid instead (i.e. image should not scale) but duplicate gets you to the text scale discussion which, hopefully, is helpful.