teaching machines

CS 318 Lab 6 – Div, Classes, and IDs

February 8, 2017 by . Filed under cs318, lectures, spring 2017.

Dear students,

Last time we dropped into the world of CSS as a means of applying style to our information hierarchies. Learning CSS is a little like learning how to conjure springtime. You suddenly have the power to make things bloom and look beautiful. But it will take a lot of practice. This class spins around you practicing with your instructors around, so please do ask questions to help deepen your understanding.

I want to introduce three big ideas before we dive in to the lab exercises. We will use mark up some information about the presidents:

Barack Obama
2009-2017

George W. Bush
2001-2009

Bill Clinton
1993-2001

George H. W. Bush
1989-1993

Ronald Reagan
1981-1989

Jimmy Carter
1977-1981

First is that HTML’s visual elements fall into two basic categories: block elements and phrase elements. You’ve seen some block elements already: h1, ul, ol, and p. Blocks elements appear on their own line. Phrase elements appear inline. You’ve seen some of these: a, img, strong, em. You’ll encounter this block vs. phrase dichotomy a lot, and one of the exercises below shows you a way to make a block element become an inline element.

Second is that we can create new generic elements to group together our information any time we want. We can create a generic block element using div:

<div>
Name: Barack Obama<br>
Terms: 2
</div>


Web designers say that div is semantically neutral. You don’t really know what’s in it, unlike a p or an h1. In this sense, the div element is a lot like an unlabeled folder. We can also create unlabeled phrase elements using span:

<div>
Name: <span>Barack Obama</span><br>
Email: <span>2</span>
</div>


Some very successful websites use only div and span almost exclusively.

Third is the notion of labeling elements on a finer grained scale. Suppose we don’t want to style all p elements the same way. Perhaps the first paragraph should appear a little bigger than the others. We can mark up our element and give it a label using the id attribute:

<p id="lead">
...
</p>


And then in the CSS, we create a rule for just this ID:

#lead {
font-size: 120%;
}


An ID gives an element a unique label. No other element should have that same ID. Suppose instead we want to create our own category of elements. For that, we can use the class attribute.

<div class="twotermer">
Name: <span class="democrat">Barack Obama</span><br>
...
</div>

<div class="onetermer">
...
</div>

<div class="twotermer">
...
</div>


In the CSS, we can apply a style to that category of elements like so:

.twotermer {
font-size: 120%;
}

.democrat {
color: blue;
}


Here’s your TODO list for next time:

• You have about a week left before the project proposal is due. I’ll have the contract up tomorrow morning.
• Investigate four CSS properties on MDN. Summarize their effect on a quarter sheet.

See you then!

Sincerely,

Lab

We have a few goals for today’s lab:

• Use divs to create “chunks” of information.
• Continue practicing with adding style via CSS.
• Use class and id attributes to gain more control of what elements we style.

Your task is to create several independent pages with no overarching story.

Partners

Create a lab06 directory in your cs318 project. In file partners.html, provide your names.

Two by Two

Create a 2×2 grid of squares that shows a border around the square that has been most recently clicked on. For example, in this rendering, the top-left square was most recently selected:

Achieve this by doing the following:

1. In twobytwo.html, create a sequence of four divs, each with class square. Include an external stylesheet twobytwo.css, in which you give every square a width of 100px, a height of 100px, and an orange background color. Give each a border using these three properties: border-width, border-style, and border-color.
2. Rearrange the four squares into a 2×2 grid. A div is a proud block element, so its succeeding element will appear on the line below it. To allow two divs to appear in the same line, give square‘s display property the value inline-block. What else do you need to do to make a 2×2 grid?
3. Make the top-left div link a to file named topleft.html. Do likewise for the other divs, but use each corner’s name. All told, you have should four anchor elements linking to topleft.html, topright.html, bottomleft.html, and bottomright.html.
4. Copy twobytwo.html four times to the four files you’ve linked to in the previous step. Yes, they all have the same content, and this should feel silly.
5. In topleft.html, give the top left square an ID of highlighted. In topright.html, give the top right square the highlighted ID. And so on in the other two files.
6. In twobytwo.css, tweak the square class to have a transparent border color. You should see all the borders disappear. Give the highlighted element a non-transparent border color. You are using the highlighted rule to override the more generic square rule. Overriding is fun!

There are better ways to accomplish this sort of selection, ways that require only a single HTML page and eliminate the redundancy. But these ways are the subject of CS 319.

Bulbapedia

Create a mini Bulbapedia showing 6 characters from Pokemon in a page that looks like this:

I don’t know much about Pokemon, even though it first came out when I was a kid. I’m just trying to feel young and hip to earn your respect.

Speaking of respect, let’s respect these steps to get our mini Bulbapedia up and running:

1. Create two files: pokemon.html and pokemon.css. Add the boilerplate, the mindless text that is present in every HTML file.
2. Find any six characters from Bulbapedia whose images have a transparent background. The transparent background is important, as we will be adding in our own background color. For the time being, paste their URLs in a handy little HTML comment:
<!--
Text inside a comment doesn't render. We can leave ourselves notes!
http://url1
http://url2
http://url3
http://url4
http://url5
http://url6
-->

3. Create a div for the first card and give it class card and ID card1. Give the card three child elements:
• An img, using your first URL as the image’s source.
• A div with class name to the card. Give as its content the character’s name.
• A p element with a blurb about the character borrowed from the Bulbapedia profile.
How does the card look? Probably ungainly.
4. In CSS, set the width of class card to 200px, have it display as an inline-block, and give it a mute border using the border-style, border-color, and border-width properties. Rounds its corners by setting the border-radius property.
5. How does the image look? It probably busts out of the div. Fix that in CSS by adding a block for only images that are child elements of a card:
.card img {

}

Recall from your reading that this is called a descendent selector. These are very useful for narrowing the portion of your information hierarchy to which you apply a style. Set its width to be 100% of the space allotted to it by its parent card.
6. Style class name so that the text is bold, centered, and uses a sans-serif font. Use the text-align, font-weight, and font-family properties.
7. Style p elements within a card to use a sans-serif font.
8. Style card1 so that its background color complements the character.
9. Once you’re satisfied with your first card, copy and paste to make your remaining cards, customizing the URLs and blurbs accordingly. Update the IDs so that you have card1, card2, all the way through card6. Add rules to your CSS to give an appropriate and unique background color to each card.
10. You may find the six cards to be staggered vertically. Set card‘s vertical-align property to top to push them all up against the top margin. The default value is baseline, which lines them up with the bottom of any neighboring text.
11. Choose three of your favorite cards and give them a second class: favorite. An element can belong to many classes, but it must have only one ID. For example, we can say that a paragraph is a member of both unimportant and funny like so:
<p id="joke19" class="unimportant funny">
...
</p>

12. Style favorite so that it has a prominent border. Use the border-style, border-width, and border-color properties.
13. Tweak the margin or padding as you see fit. We’ll talk more about these next week.

FAQ

Create a stylized frequently asked questions (FAQ) page like this one, whose questions and answers are courtesy of the Girls Scouts:

We’ll also apply some fonts to fancy things up.

Achieve this by doing the following:

1. Create two files: faq.html and faq.css. Add the boilerplate.
2. Locate a FAQ through an internet search, and copy and paste some its text into your HTML file. Include at least three question-answer pairs. Make each question an h3 element. Make each answer a p element of class answer.
3. Set the body‘s background color so that it complements your subject matter.
4. Style the h3s to have a font-size of 24pt and an appropriate color.
5. Visit Google Fonts and identify a strong and thick heading font. Click the plus icon to select it and then expand the selected dialog at the bottom of the window. Copy the link tag and paste it next to your own link tag in faq.html. This will make the font available in your web page.
6. Paste the font-family setting in your rule for h3. Did the font change? It should have.
7. Add a text-shadow setting to h3. This property expects four values: text-shadow: x-offset y-offset blur-radius color. To lean a black shadow right more than down and give a subtle blur, you’d write: text-shadow: 4px 1px 5px #000000. Use values that you think look good.
8. Pick a second font in Google Fonts for the answer text. Copy the new link tag from the selected dialog and paste it over your old one. You should see that this one loads both your fonts. Set the font-family of the answer class to use this second font.
9. Shrink the spacing between the headings and answer text by setting the margin-bottom and margin-top properties to 0.

Publish

Now, open GitHub Desktop and select your cs318 project. You should see a list of changes. Commit them and synchronize. Verify that all pages have been uploaded by visiting https://USERNAME.github.io/cs318/lab06 in your browser.

Validate

Now, visit the W3C CSS Validator. Note that this validator looks similar to the one we’ve been using, but it is different. This one checks CSS; the other did not. Paste in the URLs to your pages, one at a time, and address all concerns raised by the validator. Fix your changes on the local machine, commit, and sync, until the validator reports no issues.