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Using calc() in Padded Containers
3:57Learn how to use calc() to display full-width elements when placed inside padded containers.
Okay, so now you're going to learn
how to display full width elements
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when placed inside padded containers.
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Normally when you apply
padding to a container,
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the padding creates white
space around its content.
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It pushes content like images,
paragraphs, and headings inwards.
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Sometimes you don't want padding to
effect all the elements in a container.
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For instance, you might want white
space around the text only, but
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no space around an image above the texts.
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Now there are several methods you can
use to get around the padding and
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it usually involves a little bit of math.
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And the math gets trickier when you don't
know the exact width of the container
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because it's fluid.
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So let's see how Calc can
help us figure this out.
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You can follow along in workspaces by
clicking the Launch Workspace button
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on this page.
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So in the workspace, the index.html
file contains a div container
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with the class card, and inside card
we have a heading and two paragraphs.
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Now when we preview this
page in the browser,
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notice how the card container has
padding on the left and right sides.
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The padding adds extra white
space around the text.
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So now I want to add an image
inside this container.
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Back in my Index.html file
inside the card container,
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right about the h3 element,
I'm going to add an image element.
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And I want to add this mountians.jpg
image inside the card container.
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So as the source value I'm
going to type mountians.jpg.
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Then I'm going to open
up my style.css file and
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scroll down to this Calc Styles
comment section here.
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So right below the comment,
I'm going to target the image element
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and give it a max width of 100%.
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So when we view it in the browser,
the padding on the left and right sides of
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the card container creates a gap on
the left and right sides of the image.
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Now I want the image to be the full
width of its card container.
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That would look much nicer.
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So, we can take advantage of the calc
function to get around this padding issue.
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Back in the image rule,
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I'm going to change the max-width
value to a calc function.
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So I'll type calc, and as the expression,
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I'm going to type 100% + 3em.
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Adding 3em to the total width
of the image makes up for
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the 1.5em padding on the left and
right sides of the card container.
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So when we preview it in the browser
we can see how the image is now wider.
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But, I still see a 1.5
m gap on the left side.
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Now I can remove the 1.5m padding
gap with a negative left margin.
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So back in my image rule right
below the max-width declaration.
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I'm going to add a margin-left property,
and
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I'll set the value to -1.5em.
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All right, so when I save the style
sheet and refresh the browser,
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we can see how the main image takes
up the full width of its container.
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While preserving the padding
around the text.
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So it's that simple.
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The image also remains flexible and
maintains its proportions no matter what.
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So for instance if I go back to the style
sheet, and scroll up to the card
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rule here, and if I change the card
containers width file to say 30%.
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When I refresh the page,
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notice how the image scales to
the width of the card container.
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