CSS Grid Overview

Written 2020-08-30

UI
Source: https://scotch.io/tutorials/deep-dive-into-css-grid-2
- And more added over time
Also See
- http://1linelayouts.glitch.me/ has a lot of nice CSS Grid examples
- Task Manager Example
Definitions
- “Grid lines“ are like lines between cells on a spreadsheet.
- “Grid tracks” are the rows and columns in the grid, where the content actually goes.
- Cells are the individual spaces in the tracks where content goes.
- Areas are cells combined together when they span more than one row or column.
display:grid sets the element to be a container for a grid layout.
Row and Column Sizing
- fr units
  - These units are new for Grid layout. fr stands for fraction, and 1fr represents one unit of space out of the sum of the fr units.
  - So 3fr 4fr 3fr would be 10 in all with the space allocated proportionally.
  - When fixed units are used alongside fractions, the fixed units get their space and the rest is allocated proportionally to the fractions.
- minmax(min, max) sets flexible sizing, with the size clamped to the values given.
- width: auto tells the item to use as much space as possible given the constraints of the other items. As a minimum, it is similar to width:min-content.
- width: fitcontent(200px) works like auto but with a maximum size
- If a CSS grid column does not have an explicit width then its min-width ends up similar to auto. This can sometimes cause undesired issues, like with large images or <pre> tags, and so using something like minmax(0px, 1fr) can help here.
Grid Layout
- grid-template-columns defines the grid column layout
  - It takes a variety of values.
  - 100px 100px 100px defines three columns each of 100px width, for example
- grid-template-rows works just like grid-template-columns but for rows
- If either rows or columns is omitted, the widest/longest element in the row or column is used for all elements.
- grid-template is shorthand for rows, columns, and grid-template-areas
- grid-auto-columns defines the size of columns not explicitly specified in the template. Likewise for grid-auto-rows
- grid-auto-flow defines how grid cells are added into the grid. row is the default which means that they go horizontally filling a row first. column can also be used to go vertically.
- Grid items can use grid-row-start and grid-row-end to define starting and ending grid indexes to span multiple grid spaces.
- grid-row and grid-column are shorthand for the start and end properties
  - grid-column: 3 / 5 would start at column 3 and end at column 5
  - grid-area: rowstart / columnstart / rowend / columnend can also be used
  - You can use negative numbers to indicate offsets from the end: 1 / -1 would span the entire row or column.
  - Instead of absolute widths you can use span to indicate widths.
    - 3 / span 2 to start at 3 with a width of 2, or span 2/ 5 to end at 5 and go back 2 from there.
- grid-template-area
  - This allows you to name different areas of the grid
  - ```
  grid-template-areas:
    "header     header   header"
    "sidebar-1  content  sidebar-2"
    "footer     footer   footer";
```
- When cells have the same name, CSS combines them into a single area that spans multiple cells.
- You can then use grid-area: header to indicate that an element should go in a particular grid spot.
- A . can indicate that a cell should be empty.
- grid-template combines the areas with the sizes
- ```
grid-template:
  "header header header" 80px
  "nav article article" 200px
   / 100px auto
```
  - The size at each line is the height of the row, and then the sizes after the slash at the end are the column widths.
  - You can also define the rows and columns separately
    - ```
    .grid {
      display: grid;
      grid-template-columns: 20px 100px [main-start] 1fr [main-end] 100px 20px;
      grid-template-rows: 100px [main-start] 100px [main-end] 100px;
    }
```
- So in this case the main area is named and the [main-start] and [main-end] delimiters specify its location and size.
- repeat just repeats some layout some number of times.
  - repeat(3, 1fr 2fr) expands to 1fr 2fr 1fr 2fr 1fr 2fr
  - repeat can be interspersed with other values too
  - repeat(auto-fill, values) repeats the values as much as possible without overflowing.
  - auto-fit works like auto-fill but empty tracks are collapsed.
  - grid-template-columns: repeat(auto-fill, minmax(50px, 1fr)) is a commonly-used technique to fit as many equally-spaced columns as possible, keeping a minimum width too.
- grid-row-gap and grid-column-gap define spacing between cells
- order sets the order in which cells appear if you want to do so explicitly.
- grid-auto-flow: dense can allow the grid system to place cells in the first empty grid spot, even if it’s before other items in the logical order.

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