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Adding Backgrounds to Directly Loaded SVGs

My primary SVG viewer is Firefox.  This is partly because it’s always running, so the startup time is essentially zero.  It also allows me to directly inspect and modify elements of the SVG element through the Web Inspector, which can be handy.

But I’ve run into a problem more than once, which is that if I load an SVG file in Firefox, the browser window’s background defaults to white, and a lot of times I’m trying to view images that are partially or entirely white.  I started thinking that if there were a way to make the window background medium gray, that would solve the problem with rare downsides, since I can’t remember trying to view an all-medium-gray SVG.

After a question on Twitter and some ideas from Tibor Martini, I realized I could use Stylish to give the SVG files a background through CSS.  I didn’t want to select all SVGs, only those I was loading directly, so I tried this:

svg:root {background: gray;}

And it worked!  So I decided to make it more robust by doing a multicolor gradient, and grayscaling it on hover.  I couldn’t use filter because that would grayscale the whole image, rather than just the background, but that was easy to work around.  I ended up with this:

svg:root {background: linear-gradient(135deg, hsl(0,50%,60%), hsl(180,50%,40%));}
svg:root:hover {background: linear-gradient(135deg, hsl(0,0%,60%), hsl(180,0%,40%));}

Which works great!  Except that I discovered Firefox applies it to all SVGs, even those loaded into HTML documents via img.  SVGs apparently define their own roots, which I hadn’t expected, but I can see how it might make sense.  So I poked around in MDN until I came up with this:

@-moz-document url-prefix(file:) {
    svg:root {background: linear-gradient(135deg, hsl(0,50%,60%), hsl(180,50%,40%));}
    svg:root:hover {background: linear-gradient(135deg, hsl(0,0%,60%), hsl(180,0%,40%));}

And that’s exactly what I wanted.  If it’s useful to you, have at it.  Just paste that into a new Stylish rule in Firefox, and you should be good to go.

If you’re on Chrome, you can import the above into Stylish and create a new rule, but it hasn’t worked for me, and I’m not sure why not.  Removing :root didn’t fix it when I tried, and that shouldn’t matter anyway: I can see in Chrome’s user styles that svg:root is used and applied.  And my Stylish toolbar icon shows the rule is being applied.  It just doesn’t do anything I can see.  If anyone can figure out how to make it work, or explain why it can’t work, I’d love to know in the comments!

Gridded Headings v. Justified Headings

Amongst the reactions to Gridded Headings, Benjamin de Cock pointed out there’s another way to arrive at the same place I did.  Instead of this:


…Benjamin pointed out one could instead do this:

justify-content: center;

That’s right: without explicitly specifying any grid columns, but just setting the grid items themselves to be centered, the same behaviors emerge.  Clever!

What’s interesting is that the behaviors are not precisely the same.  While mostly identical behaviors occur with either approach, there are a few subtle differences and a much different possibility space.  I’ll consider each in turn.

First, the differences.  First of all, the small gutters defined by the first and third grid column tracks—the ones defined to be minmax(1em,1fr)—aren’t present in the justify-content version.  This means the headings will jam right up against the edge of the grid container if things get narrow enough.

Side separation versus side smashing.  Grid on the left, justify-content on the right.

So we either need to re-establish them with grid-template-columns, which would seem to put us right back where we were, or else apply side margins to the heading and subheading.  Something like this:

div h2, div h3 {margin-right: 1rem; margin-left: 1rem;}

Either way, that side separation has to be defined (assuming you want it there).  Having to set those separations as margins feels a little clumsy to me, though not hugely so.  Doing all the sizing and separation in a single grid-template-columns declaration feels cleaner to me, though I admit that may be partly due to my current Gridfatuation.

There is another difference worth exploring.  If the content gets wider than the space available, the grid-template-columns approach means the content will overflow to the right (in LTR writing modes).  If it falls offscreen, it can be scrolled to read.  With justify-content: center, the content stays centered within the box, overflowing to both sides.  The content to the left may not be accessible via scrollbar.

How track sizing and content justification handle overspill.  Grid on the left, justify-content on the right.

So if you have a large headline containing a lengthy unhyphenated word, like “Kazakhstan” or “emoluments”, you might prefer one result over the other.

Beyond that, the further possibilities are a lot richer with Grid than with content justification.  Center-justifying the content means exactly that: the element boxes are centered.  So if you were interested in taking the heading and subheading, acting as an apparent unit, and shift them toward one side or another, this would be much easier to accomplish with Grid.

Suppose we want there to be three times as much space to one side of the headings’ column as the other.  Here’s what that would look like:


That’s it.  One number changed, and the whole setup is offset from the center without losing the coherence of the original demo.

The same thing could likely be approximated with justify-content using side margins on the heading elements, but it wouldn’t be precisely the same, even with percentages.  fr is a very special beast, and permits very unique results.

The other major difference in possibilities is that with Grid, we can rearrange elements visually without ever touching the source.  Suppose we wanted to put the subhead above the heading in some layouts, but not others.  (Whether those different designs live on different pages or at different breakpoints, it really doesn’t matter.)  With Grid, that’s as simple as rewriting the grid template in a line or three of CSS.  The h2 remains ahead of h3 in the HTML.

With justify-content, you’d still have to write that same grid template, or else switch to flexbox and use flex-direction: column-reverse or some such.  That would work if you want to just switch the display order of two headings in a single column.  It tends to fall down for anything more demanding than that.

This is not to say Benjamin came up with a bad alternative!  I like it quite a bit, precisely because it has similar outcomes to my original idea, thus shedding light on creative ways Grid and content alignment can be combined.  But I like it even more for its differences, which shed even more light on how the two things operate.

In that combination of similarity and difference, I can sense an incredible range of capability, chock full of nuance and brimming with possibility.  There are going to be ways to put these things together that nobody has figured out yet.  I know I keep saying this, but there’s a vast landscape opening, so vast that I don’t think we can even guess how far it extends yet, let alone have mapped its terrain.

Chrome Grid Bug Update

I mentioned late last week, in my post about Chrome 57 having landed Grid layout, that there is a bug that affects some people.  Well, further investigation has revealed that the bug doesn’t seem to be in the Grid layout engine.  Instead, disabling selected extensions makes the bug go away.

The odd part is that the extension seems to vary.  In my case, disabling Window Resizer fixed the problem.  Before you think it’s all their fault, though, Rachel Andrew discovered that disabling Window Resizer in her copy of Chrome did not solve the problem.  For her, it was disabling the LastPass extension that did it.  I don’t even have the LastPass extension installed on my machine, in any browser.

So: if you run into this problem, try disabling extensions to see if that fixes it.  If so, you can enable them one at a time and test to see which one triggers the bug.  With any luck, a fix will be found soon and deployed via auto-updating.  And if you find out anything else, please let us know on the bug report!

Doubled Grids

Chrome 57 released yesterday, not quite a week ahead of schedule, with Grid support enabled.  So that’s two browsers with Grid support in the space of two days, including the most popular browser in the world right now.  Safari has it enabled in Technology Preview builds, and just blogged an introduction to Grid, so it definitely feels like it’ll be landing there soon as well.  No word from Edge, so far as I know.

I did discover a Chrome bug in Grid this morning, albeit one that might be fairly rare.  I filed a bug report, but the upshot is this: most or all of an affected page is rendered, and then gets blanked.  I ran into a similar bug earlier this year, and it seemed to affect people semi-randomly—others with the same OS as me didn’t see it, and others with different OSes did see it.  This leads me to suspect it’s related to graphics cards, but I have no proof of that at all.  If you can reproduce the bug, and more importantly come up with a reliable way to fix it, please comment on the Chromium bug!

Grid Inspection

I said yesterday I would write up the process of adding Grid to meyerweb, and I did.  I started it last night and I finished it this morning, and when I was done with the first draft I discovered I’d written almost four thousand words.

So I pitched it to an online magazine, and they accepted, so it should be ready in the next couple of weeks.  Probably not long after Chrome ships its Grid implementation into public release, in fact.  I’ll certainly share the news when it’s available.

In the meantime, you can inspect live grids for yourself, whether here or at Grid by Example or The Experimental Layout Lab of Jen Simmons or wherever else.  All you need is Firefox 52, though Firefox Nightly is recommended for reasons I’ll get to in a bit.

In Firefox 52, if you inspect an element that has display: grid assigned to it, you’ll get a little waffle icon in the inspector, like so:

Mmmmmm, waffles.

Click it, and Firefox will draw the grid lines on the page for you in a lovely shade of purple.  It will even fill in grid gaps (which are a thing) with a crosshatch-y pattern.  It’s a quick way to visualize what the grid’s template values are creating.

If you have Firefox Nightly, there’s an even more powerful tool at your disposal.  First, go into the inspector’s settings, and make sure “Enable layout panel” is checked.  You may or may not have to restart the browser at this point—I did, but YEMV—but once it’s up and running, there will be a “Layout” panel to go with the other panels on the right side of the Inspector.  There you get the box model stuff, as well as a checklist of grids on the current page.

The Layout panel

For each grid on the page—not just the element you’re inspecting—you can set your own color for the gridlines, though those color choices do not currently persist, even across page reloads.  You can also turn on number labels for the grid lines, which are currently tiny and black no matter what you do.  And if you allow grid lines to extend into infinity, you can turn the page into a blizzard of multicolored lines, assuming there are several grids present.

This panel is very much in its infancy, so we can expect future enhancements.  Things like color persistence and better grid line labels are already on the to-do list, I’m told, as well as several more ambitious features.  Even as it is, I find it valuable in constructing new grids and diagnosing the situation when things go sideways.  (Occasionally, literally sideways: I was playing with writing-mode in grid contexts today.)

There’s another, possibly simpler, way to enable the Layout panel, which I learned about courtesy Andrei Petcu.  You type about:config into the URL bar, then enter layoutview into the search field.  Double-click “devtools.layoutview.enabled” to set it to “true”, and it will be ready to go.  Thanks, Andrei!

So go ahead—inspect those grids!

Welcome to the Grid

Grid is public.  It’s live right now in the latest Firefox release, Firefox 52.

It will similarly be live in the next public Chrome release, due in the next week or so.

It’s here.  I almost can’t believe it.

For well more than a decade now, when asked what CSS needs more than anything, I’ve said it needs real, actual layout.  “A layout-shaped hole at its heart” is a phrase I may have used a fair few times.

Rachel Andrew had a great article last week about “Learning CSS Grid Layout”, which charts a sensible course for getting used to grid.  It also busted a few myths about grid.  I recommend it highly.

There’s one more myth I’d like to do my best to bust, which I’ll summarize as a comment I’ve seen many times: “Ugh, tables again?”

The underlying assumption here is: grids are just tables with a new syntaxThis is entirely untrue.

I mean, yes, you can recreate 1990s-era table-based layout techniques with grid, in much the same way you can recreate the submit button with two JS libraries and a complex front-end framework.  The ability to do it doesn’t necessarily make it a good idea.

(Though you might, from time to time, find the ability useful.  Here’s what I mean: you can take a bunch of data contained in arbitrary markup someone else is producing, and lay it out in a tabular format.  It would be far preferable to have the data in actual table markup, but if that’s not an option, grid will give you a potential solution.)

I have an example of just one way grids are different than tables.  I just last Friday finished writing the last chapter of CSS: The Definitive Guide, 4th Edition, covering filters, blending, clipping, and masking.  (I finished the grid chapter late last year, so it’s already available in the early-access title.)  Almost all the figures in the book were created by building HTML+CSS pages, and taking high-resolution screen captures with Firefox’s screenshot command.  Here’s one.

Compositing masks

The way these are displayed is actually the inverse of their source order.  I wanted them to be in document source such that the compositing steps were in chronological order, so that’s how I wrote them.  Once I laid them out that way in the figure, using grid, I realized it made more sense to arrange them visually, with the bottom layer at the bottom of the figure, the next above that, all leading up to the result at the top.

So I just rearranged them on the grid, by assigning grid row numbers.  The document source wasn’t touched.  A bit simplified, the CSS to do that looked something like this:

ol li:nth-child(1) {grid-row: 4;}
ol li:nth-child(2) {grid-row: 3;}
ol li:nth-child(3) {grid-row: 2;}
ol li:nth-child(4) {grid-row: 1;}

Because the compositing examples (the “columns” in the layout) were represented as ordered lists, with the grid set up to place each image with some captioning, I could just change their order.  So yes, it looks like a table, but the underlying structure is anything but table-like.  Just to get each column of examples grouped together with tables, I’d have to nest tables, or accept a one-row table with each cell containing some other structure.  Rearranging the columns would mean doing markup surgery, instead of just reassigning their layout placement via CSS.

Instead, I was able to represent the content in the best available structure (ordered lists) and then arrange them on a grid in the best way I could visually.  For that matter, I could responsively change the layout from a six-column grid to a three-column grid to un-gridded lists as the viewport got more and more narrow.  As, in fact, I did—check it out.  If you make the window narrow enough, Grid is dropped entirely so you can see the base structure and content.

This ability to place grid items without respect to source order is a powerful tool, and like all powerful tools it can be used for good or ill.  It’s possible to assemble a visually usable layout out of the most inaccessible, horrible markup structures imaginable.  It’s also possible to assemble a visually usable layout from clean, accessible markup in ways we’ve never even dared dream.

Combine grids with other CSS features, and you can really create art.  Jen Simmmons has a layout lab site, and her 2016 main-page design is… well, go see it in a grid-capable browser, like today’s release of Firefox.  Realize it’s all text, no images, no scripting.  Just markup and style.

And the style is remarkably simple for what’s being accomplished.  It’s not too alien a syntax, but it will likely take some time to adjust to using it.  It’s taken me some time, as I’ve experimented and written about it.  Unlearning my float habits has taken some work, and I don’t know that I’m completely done.  I do know that it’s been worth it many times over.

I’ve done a few experiments with the layout of a local copy of meyerweb, and done some frankly goofy things to the design along the way.  I’m hoping to convert what’s up here to a simple grid layout in the next few days, make it a slightly more complex grid shortly after that, and then maybe—maybe—actually do some redesigning for the first time in over a decade, to take advantage of grid more fully.  Jen has a great six-minute video exploring a few features of grid and the grid inspection tool now built into Firefox, which I recommend to anyone curious to know more.

So if you’re thinking of grid as tables 2.0, please, stop.  Table-style layouts are the first one percent of what grid offers.  There are works of art and undiscovered techniques waiting in the other 99 percent.

Scaling SVG Clipping Paths for CSS Use

I’ve been working a lot with the clip-path property recently, as I write the chapter on filters, blends, clipping, and masking for CSS: The Definitive Guide’s long-delayed 4th edition (available now in early-release format!).  One of the nifty things you can do with clipping paths is define them with percentage-based coordinates.  For example, here’s a hexagon-like clipping path:

clip-path: polygon(50% 0, 100% 25%, 100% 75%, 50% 100%, 0 75%, 0 25%);

That starts at the center top (50% 0), goes to the right edge, quarter-down (100% 25%), and so on.

When I got to SVG-based clipping, which you can use with the CSS pattern clip-path: url(#pathID), I tried and failed with this:

<clipPath id="hexlike">
  <polygon points="50% 0, 100% 25%, 100% 75%, 50% 100%, 0 75%, 0 25%" />

It didn’t work because, as I discovered to my horror, SVG does not allow percentage coordinates.  I could just strip all the percent signs out, but that would be the same as saying this in CSS:

clip-path: polygon(50px 0, 100px 25px, 100px 75px, 50px 100px, 0 75px, 0 25px);

I didn’t want pixels, though.  I want percentages, darn it all!

So I asked around on Twitter, and Markus Stange pointed me to the solution: converting all the SVG coordinates to the range 0–1 and using the clipPathUnits attribute.  The working version looks like this:

<clipPath id="hexlike" clipPathUnits="objectBoundingBox">
  <polygon points="0.5 0, 1 0.25, 1 0.75, 0.5 1, 0 0.75, 0 0.25"/>
A hexlike clipping path.

That yields the same result as the polygon() CSS shape with the percentages I showed before.

All that is great if you’re writing your own SVG shapes and can make sure you set it up properly, but what if someone hands you a shape to be used as a clip path and it’s in absolute coordinates like 100 75?  If you’re really lucky, the shape has a viewbox of 0 0 100 100 (or all the coordinate points are in that range) and you can just divide all the coordinate points by 100 to get the proper values.  But that’s really tedious for any but the simplest of shapes, and besides, what if it has some other viewbox?  That’s where the transform attribute saves the day.

For example, suppose you get an SVG file that looks like this (with the actual path coordinates removed because there are a lot of them):

<svg version="1.1" xmlns=""
  xmlns:xlink="" viewBox="0 0 329.6667 86">
  <clipPath id="cloud02">
    <path d="…(coordinates go here)…"/>

First, add the clipPathUnits attribute to the <clipPath> element:

<svg version="1.1" xmlns=""
 xmlns:xlink="" viewBox="0 0 329.6667 86">
  <clipPath id="cloud02" clipPathUnits="objectBoundingBox">
    <path d="…(coordinates go here)…"/>

Next, look at the viewBox attribute on the <svg> element itself.  The value there is 329.6667 86.  That means 329.6667 coordinate units horizontally, and 86 units vertically.  So all you need to do now is divide all the horizontal values by 329.6667, and the vertical values by 86.  Which would be super tedious, except we have scaling transforms at our disposal:

<svg version="1.1" xmlns=""
  xmlns:xlink="" viewBox="0 0 329.6667 86">
  <clipPath id="cloud02" clipPathUnits="objectBoundingBox"
   transform="scale(0.003033 0.0116279)">
    <path d="…(coordinates go here)…"/>

Those two values are 1/329.6667 and 1/86, respectively, and they effectively scale every point in the d attribute to fit into the needed 0–1 range.  (That’s not precisely what happens, but the outcome is the same.)  Thus we have an SVG clipping path that scales with the element and fits to its dimensions!

This works just as well for other markup patterns.  To return to the hexlike path from before, assume it was written like this:

<svg version="1.1" xmlns=""
 xmlns:xlink="" viewBox="0 0 100 100">
  <clipPath id="hexlike">
    <polygon points="50 0, 100 25, 100 75, 50 100, 0 75, 0 25" />

If that were applied as-is, via clip-path: url(#hexlike), it would create a hex-like clipping path that fits a 100px by 100px box, positioned in the top left of the element (in left-to-right languages, I presume).  The quick fix:

<svg version="1.1" xmlns=""
 xmlns:xlink="" viewBox="0 0 100 100">
  <clipPath id="hexlike" clipPathUnits="objectBoundingBox"
    <polygon points="50 0, 100 25, 100 75, 50 100, 0 75, 0 25" />

Bingo bango bongo, it will now scale to the element’s dimensions, whatever those turn out to be.

Of course, if you apply that to something like a short paragraph, it will be verrrrry stretched out, but the same would be true with a percentage-based polygon() shape.  The beauty here is that you can scale any coordinate set, so if you have a tiny path that you want to blow up, or a huge path you want to shrink down, you can transform it without using clipPathUnits to stretch it over the bounding box.  Something like this:

<svg version="1.1" xmlns=""
 xmlns:xlink="" viewBox="0 0 100 100">
  <clipPath id="hexlike" transform="scale(4)">
    <polygon points="50 0, 100 25, 100 75, 50 100, 0 75, 0 25" />

That gets you a hexlike shape that fits a 400px by 400px box, for example.

Now all CSS needs is the ability to size and position clipping paths in a manner similar background images, and we’ll be in clover.  I hope such properties are in the WG’s mind, because I’d love to be able to just point an at SVG clipping path, and then say something like clip-path-position: center; clip-path-size: contain;.  That would remove the need for fiddling with SVG attributes altogether.

Thanks to Markus Stange for the technique and his invaluable assistance in proofreading this article.

Element Dragging in Web Inspectors

Yesterday, I was looking at an existing page, wondering if it would be improved by rearranging some of the elements.  I was about to fire up the git engine (spawn a branch, check it out, do edits, preview them, commit changes, etc., etc.) when I got a weird thought: could I just drag elements around in the Web Inspector in my browser of choice, Firefox Nightly, so as to quickly try out various changes without having to open an editor?  Turns out the answer is yes, as demonstrated in this video!
Youtube: “Dragging elements in Firefox Nightly’s Web Inspector”
Since I recorded the video, I’ve learned that this same capability exists in public-release Firefox, and has been in Chrome for a while.  It’s probably been in Firefox for a while, too.  What I was surprised to find was how many other people were similarly surprised that this is possible, which is why I made the video.  It’s probably easier to understand to video if it’s full screen, or at least expanded, but I think the basic idea gets across even in small-screen format.  Share and enjoy!
July 2017