Variable Side Ratio Card With Conic Gradients Assembly Alongside the Diagonal

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I lately got here throughout an fascinating drawback. I needed to implement a grid of playing cards with a variable (user-set) side ratio that was saved in a –ratio customized property. Packing containers with a sure side ratio are a basic drawback in CSS and one which bought simpler to resolve lately, particularly since we bought aspect-ratio, however the difficult half right here was that every of the playing cards wanted to have two conic gradients at reverse corners assembly alongside the diagonal. One thing like this:

Person set side ratio playing cards.

The problem right here is that, whereas it’s straightforward to make an abrupt change in a linear-gradient() alongside the diagonal of a variable side ratio field utilizing for instance a route prefer to high left which adjustments with the side ratio, a conic-gradient() wants both an angle or a share representing how far it has gone round a full circle.

Take a look at this information for a refresher on how conic gradients work.

The straightforward resolution

The spec now contains trigonometric and inverse trigonometric features, which may assist us right here — the angle of the diagonal with the vertical is the arctangent of the side ratio atan(var(–ratio)) (the left and high edges of the rectangle and the diagonal type a proper triangle the place the tangent of the angle fashioned by the diagonal with the vertical is the width over the peak — exactly our side ratio).

The angle of the diagonal with the vertical (edge).

Placing it into code, now we have:

–ratio: 3/ 2;
aspect-ratio: var(–ratio);
–angle: atan(var(–ratio));
/* beneath the diagonal */
conic-gradient(from var(–angle) at 0 100%,
#319197, #ff7a18, #af002d calc(90deg – var(–angle)), clear 0%),
/* above the diagonal */
conic-gradient(from calc(.5turn + var(–angle)) at 100% 0,
#ff7a18, #af002d, #319197 calc(90deg – var(–angle)));

Nonetheless, no browser at the moment implements trigonometric and inverse trigonometric features, so the straightforward resolution is only a future one and never one that might truly work anyplace as we speak.

The JavaScript resolution

We are able to after all compute the –angle within the JavaScript from the –ratio worth.

let angle = Math.atan(1/ratio.break up(‘/’).map(c => +c.trim()).cut back((a, c) => c/a, 1));
doc.physique.type.setProperty(‘–angle’, `${+(180*angle/Math.PI).toFixed(2)}deg`)

However what if utilizing JavaScript gained’t do? What if we actually want a pure CSS resolution? Properly, it’s a bit hacky, however it may be completed!

The hacky CSS resolution

That is an thought I bought from a peculiarity of SVG gradients that I truthfully discovered very irritating once I first encountered.

Let’s say now we have a gradient with a pointy transition at 50% going from backside to high since in CSS, that’s a gradient at a 0° angle. Now let’s say now we have the identical gradient in SVG and we alter the angle of each gradients to the identical worth.

In CSS, that’s:

linear-gradient(45deg, var(–stop-list));

In SVG, now we have:

<linearGradient id=’g’ y1=’100%’ x2=’0%’ y2=’0%’
gradientTransform=’rotate(45 .5 .5)’>
<!– the gradient stops –>

As it may be seen beneath, these two don’t give us the identical consequence. Whereas the CSS gradient actually is at 45°, the SVG gradient rotated by the identical 45° has that sharp transition between orange and crimson alongside the diagonal, although our field isn’t sq., so the diagonal isn’t at 45°!

45° CSS vs. SVG gradient (stay demo).

It’s because our SVG gradient will get drawn inside a 1×1 sq. field, rotated by 45°, which places the abrupt change from orange to crimson alongside the sq. diagonal. Then this sq. is stretched to suit the rectangle, which mainly adjustments the diagonal angle.

Observe that this SVG gradient distortion occurs provided that we don’t change the gradientUnits attribute of the linearGradient from its default worth of objectBoundingBox to userSpaceOnUse.

Primary thought

We can’t use SVG right here because it solely has linear and radial gradients, however not conic ones. Nonetheless, we are able to put our CSS conic gradients in a sq. field and use the 45° angle to make them meet alongside the diagonal:

aspect-ratio: 1/ 1;
width: 19em;
/* beneath the diagonal */
conic-gradient(from 45deg at 0 100%,
#319197, #ff7a18, #af002d 45deg, clear 0%),
/* above the diagonal */
conic-gradient(from calc(.5turn + 45deg) at 100% 0,
#ff7a18, #af002d, #319197 45deg);

Then we are able to stretch this sq. field utilizing a scaling remodel – the trick is that the ‘/’ within the 3/ 2 is a separator when used as an aspect-ratio worth, however will get parsed as division inside a calc():

–ratio: 3/ 2;
remodel: scaley(calc(1/(var(–ratio))));

You’ll be able to play with altering the worth of –ratio within the editable code embed beneath to see that, this manner, the 2 conic gradients at all times meet alongside the diagonal:

CodePen Embed Fallback

Observe that this demo will solely work in a browser that helps aspect-ratio. This property is supported out of the field in Chrome 88+ (present model is 90), however Firefox nonetheless wants the structure.css.aspect-ratio.enabled flag to be set to true in about:config. And in case you’re utilizing Safari… properly, I’m sorry!

Enabling the flag in Firefox.

Points with this method and how you can get round them

Scaling the precise .card factor would hardly ever be a good suggestion although. For my use case, the playing cards are on a grid and setting a directional scale on them messes up the structure (the grid cells are nonetheless sq., although we’ve scaled the .card parts in them). In addition they have textual content content material which will get weirdly stretched by the scaley() operate.

The answer is to offer the precise playing cards the specified aspect-ratio and use a fully positioned ::earlier than positioned behind the textual content content material (utilizing z-index: -1) with the intention to create our background. This pseudo-element will get the width of its .card father or mother and is initially sq.. We additionally set the directional scaling and conic gradients from earlier on it. Observe that since our completely positioned ::earlier than is top-aligned with the highest fringe of its .card father or mother, we must also scale it relative to this edge as properly (the transform-origin must have a worth of 0 alongside the y axis, whereas the x axis worth doesn’t matter and may be something).

physique {
–ratio: 3/ 2;
/* different structure and prettifying types */

.card {
place: relative;
aspect-ratio: var(–ratio);

&::earlier than {
place: absolute;
z-index: -1; /* place it behind textual content content material */

aspect-ratio: 1/ 1; /* make card sq. */
width: 100%;

/* make it scale relative to the highest edge it is aligned to */
transform-origin: 0 0;
/* give it desired side ratio with transforms */
remodel: scaley(calc(1/(var(–ratio))));
/* set background */
/* beneath the diagonal */
conic-gradient(from 45deg at 0 100%,
#319197, #af002d, #ff7a18 45deg, clear 0%),
/* above the diagonal */
conic-gradient(from calc(.5turn + 45deg) at 100% 0,
#ff7a18, #af002d, #319197 45deg);
content material: ”;

Observe that we’ve moved from CSS to SCSS on this instance.

That is significantly better, as it may be seen within the embed beneath, which can also be editable so you may play with the –ratio and see how every part adapts properly as you modify its worth.

CodePen Embed Fallback

Padding issues

Since we haven’t set a padding on the cardboard, the textual content might go all the way in which to the sting and even barely out of bounds given it’s a bit slanted.

Lack of padding inflicting issues.

That shouldn’t be too troublesome to repair, proper? We simply add a padding, proper? Properly, after we do this, we uncover the structure breaks!

Including a padding breaks the structure. (Demo)

It’s because the aspect-ratio we’ve set on our .card parts is that of the .card field specified by box-sizing. Since we haven’t explicitly set any box-sizing worth, its present worth is the default one, content-box. Including a padding of the identical worth round this field provides us a padding-box of a unique side ratio that doesn’t coincide with that of its ::earlier than pseudo-element anymore.

With a view to higher perceive this, let’s say our aspect-ratio is 4/ 1 and the width of the content-box is 16rem (256px). This implies the peak of the content-box is 1 / 4 of this width, which computes to 4rem (64px). So the content-box is a 16rem×4rem (256px×64px) rectangle.

Now let’s say we add a padding of 1rem (16px) alongside each edge. The width of the padding-box is due to this fact 18rem (288px, as it may be seen within the animated GIF above) — computed because the width of the content-box, which is 16rem (256px) plus 1rem (16px) on the left and 1rem on the fitting from the padding. Equally, the peak of the padding-box is 6rem (96px) — computed as the peak of the content-box, which is 4rem (64px), plus 1rem (16px) on the high and 1rem on the backside from the padding).

This implies the padding-box is a 18rem×6rem (288px×96px) rectangle and, since 18 = 3⋅6, it has a 3/ 1 side ratio which is totally different from the 4/ 1 worth we’ve set for the aspect-ratio property! On the similar time, the ::earlier than pseudo-element has a width equal to that of its father or mother’s padding-box (which we’ve computed to be 18rem or 288px) and its side ratio (set by scaling) remains to be 4/ 1, so its visible peak computes to 4.5rem (72px). This explains why the background created with this pseudo — scaled down vertically to a 18rem×4.5rem (288px×72px) rectangle — is now shorter than the precise card — a 18rem×6rem (288px×96px) rectangle now with the padding.

So, it appears like the answer is fairly easy — we have to set box-sizing to border-box to repair our drawback as this utilized the aspect-ratio on this field (similar to the padding-box after we don’t have a border).

Certain sufficient, this fixes issues… however solely in Firefox!

Exhibiting the distinction between Chromium (high) and Firefox (backside).

The textual content ought to be middle-aligned vertically as we’ve given our .card parts a grid structure and set place-content: middle on them. Nonetheless, this doesn’t occur in Chromium browsers and it turns into a bit extra apparent why after we take out this final declaration — in some way, the cell within the card’s grid will get the three/ 1 side ratio too and overflows the cardboard’s content-box:

Checking the cardboard’s grid with vs. with out place-content: middle.

Luckily, this can be a recognized Chromium bug that ought to most likely get fastened within the coming months.

Within the meantime, what we are able to do to get round that is take away the box-sizing, padding and place-content declarations from the .card factor, transfer the textual content in a toddler factor (or within the ::after pseudo if it’s only a one-liner and we’re lazy, although an precise baby is the higher thought if we wish the textual content to remain selectable) and make {that a} grid with a padding.

.card {
/* similar as earlier than,
minus the box-sizing, place-content and padding declarations
the final two of which which we transfer on the kid factor */

&__content {
place-content: middle;
padding: 1em

CodePen Embed Fallback

Rounded corners

Let’s say we additionally need our playing cards to have rounded corners. Since a directional remodel just like the scaley on the ::earlier than pseudo-element that creates our background additionally distorts nook rounding, it outcomes that the only option to obtain that is to set a border-radius on the precise .card factor and lower out every part outdoors that rounding with overflow: hidden.

Non-uniform scaling distorts nook rounding. (Demo)

Nonetheless, this turns into problematic if sooner or later we wish another descendant of our .card to be seen outdoors of it. So, what we’re going to do is about the border-radius instantly on the ::earlier than pseudo that creates the cardboard background and reverse the directional scaling remodel alongside the y axis on the y part of this border-radius:

$r: .5rem;

.card {
/* similar as earlier than */

&::earlier than {
border-radius: #{$r}/ calc(#{$r}*var(–ratio));
remodel: scaley(calc(1/(var(–ratio))));
/* similar as earlier than */

CodePen Embed Fallback

Last consequence

Placing all of it collectively, right here’s an interactive demo that permits altering the side ratio by dragging a slider – each time the slider worth adjustments, the –ratio variable is up to date:

CodePen Embed Fallback

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