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Using Flexbox Today (CSS Summit 2016)

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With solidified syntax and great browser support, flexbox, the CSS layout module that can make your layouts more flexible and responsive with ease, is finally ready to be used in your real-world work. We’ll talk about the when, what, and how of using flexbox today: when it’s a great choice use flexbox (and when not to), what UI and UX problems it can help you solve, and how to add it to your layouts in a robust way that doesn’t harm non-supporting browsers or accessibility. You’ll learn a step-by-step process for deciding on and deploying flexbox, with lots of examples along the way of flexbox in the wild.

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Using Flexbox Today (CSS Summit 2016)

  1. 1. Flexbox Zoe Mickley Gillenwater @zomigiCSS Summit July 2016 TODAY USING
  2. 2. I work for Psst…you can too: www.workingatbooking.com
  3. 3. My portfolio site from 2000
  4. 4. My portfolio site from 2000
  5. 5. tables positioning floats inline-block table-cell flexbox grid multi-column exclusions shapes regions flexbox
  6. 6. when what flexbox how
  7. 7. Deciding when to use and not use flexbox WHEN ¨ 1.
  8. 8. What browsers do I need to support? Don’t ask yourself this—it’s irrelevant here (IMO)
  9. 9. Flexbox has 96.8% coverage worldwide We support IE 7-9 at Booking, but still use flexbox as progressive enhancement.
  10. 10. Do I want to create a layout in 1 dimension (row OR column) or 2 dimensions? Hat-tip to Rachel Andrew: https://rachelandrew.co.uk/archives/2016/03/30/should-i-use-grid-or-flexbox/
  11. 11. Flexbox is not a grid ¨  Not meant for or great at whole page layout ¨  Flex items only care about space in their own row/column ¨  They don’t care about lining up in the other dimension
  12. 12. Demo by Rachel Andrew: http://codepen.io/rachelandrew/pen/YqqdXL
  13. 13. Flexbox is best for: ¨  UI components ¨  Simple whole page layouts (not grid-based) ¨  Enhancing a complex layout’s alignment, spacing, etc. (not controlling placement)
  14. 14. Do I need my content to dictate sizing and placement, or do I need to control these?
  15. 15. Content determines boxes’ size and placement (Mega-useful when content is unknown and variable, or readability is a top priority.) Structure determines content’s size and placement (P.S. Flexbox can do this too, if you want. It’s just the reverse that doesn’t work so well.) Flexbox Grids
  16. 16. Does flexbox offer me anything I can’t already get from an existing layout method?
  17. 17. New things flexbox offers ¨  Content-driven, unit-less sizes ¨  Content-driven, media-query-less layout changes ¨  Mixed-unit layouts ¨  Equal-height columns ¨  Vertical centering and other alignments ¨  Spacing out or stretching items to fill unknown width/height ¨  Combining content wrapping and block wrapping ¨  Pinning items without overlaps ¨  Visual order different than HTML/reading order
  18. 18. Components flexbox can enhance and UI/UX problems it can help you solve WHAT ¨ 2.
  19. 19. content-driven, unit-less sizes
  20. 20. How big do I make this thing?
  21. 21. % em/rem vw/vh
  22. 22. Relative units of measurement are your best guess at the ideal, but they’re still a guess.
  23. 23. Flexbox gets us closer to the ideal, because it lets us design without units.
  24. 24. Example: a responsive form from http://jobs.theguardian.com/
  25. 25. My copy of that form Same floats, same percentage widths
  26. 26. The trouble with explicit sizing Since the select and button are sized by a percentage, not sized automatically by their content, this can happen: Box too small for its content Box too big for its content
  27. 27. Use the flex property instead Tells browser starting size (including content size) and whether item can grow or shrink width: 33.333% flex: auto Fill up remaining space width: 16.666% flex: none Size to content exactly
  28. 28. Form fields are a pain in the butt The fields and button don’t all match each other exactly in height
  29. 29. Fix alignment with flexbox Turn each field wrapper into flex container so field inside will stretch to match height of line: .flexbox .jobs-form_field-wrapper { display: flex; align-items: stretch; /* default */ width: auto; } Fields misaligned without flexbox Fields match height due to align-items
  30. 30. Smarter sizing Non-flexbox Flexbox enhanced
  31. 31. Content-driven sizing on Booking.com Last year’s sidebar searchbox design, with fixed-width select fields
  32. 32. Content-driven sizing on Booking.com Non-flexbox Flexbox enhanced
  33. 33. Content-driven sizing on Booking.com .sb-dates { display: flex; } .sb-dates__icon { flex: 0 0 23px; } .sb-dates__select-day { flex: 1 0 auto; margin: 0 6px; } .sb-dates__select-month { flex: 1 1 auto; } flex container main axis flex items
  34. 34. Defining the flex property flex-grow how much flex item will grow relative to other items if extra space is available (proportion of extra space that it gets) flex-shrink how much item will shrink relative to others if there is not enough space (proportion of overflow that gets shaved off) flex-basis the initial starting size before free space is distributed (any standard width/height value, including auto)
  35. 35. Translating the flex property .sb-dates { display: flex; } .sb-dates__icon { flex: 0 0 23px; } .sb-dates__select-day { flex: 1 0 auto; margin: 0 6px; } .sb-dates__select-month { flex: 1 1 auto; } Start out 23px wide, and don’t grow or shrink further Start out sized to your content, then grow with 1 share of any extra space available, but don’t ever shrink Start out sized to your content, then grow with 1 share of extra space, but if there’s an overflow shrink
  36. 36. Mixed-unit layout is easier with calc(), but not even it can do: calc(100% - 23px - the width of the day field in Greek)
  37. 37. Taking advantage of variable space Task: add a message about low availability of the room price shown: “We have only X left on our site!” How about right here in this lovely big gap?
  38. 38. Taking advantage of variable space Problem: the gap is not always big enough to hold a sentence of text
  39. 39. Taking advantage of variable space Solution: use flexbox to place text beside price when space allows; otherwise, it can wrap below price
  40. 40. Progressive enhancement Non-flexbox Flexbox enhanced
  41. 41. Content-driven layout change 2 columns 3 columns
  42. 42. RWD content-driven layout change Narrow: 1 column Wide: 2 columns
  43. 43. RWD content-driven layout change .article-header { display: flex; flex-flow: row wrap; margin-left: -20px; } .article-header-image { flex: 1 1 320px; padding-left: 20px; } When 320px + 20em can fit together, layout shifts to 1 row/2 columns .article-header-text { flex: 1 1 20em; padding-left: 20px; }
  44. 44. Layout change without media query 1.  Let the blocks wrap and stack when needed: .article-header { display: flex; flex-direction: row; flex-wrap: wrap; } /* default */
  45. 45. Layout change without media query 2.  Size the blocks to control their wrapping point: .article-header-image { flex: 1 1 320px; padding-left: 20px; } .article-header-text { flex: 1 1 20em; padding-left: 20px; }
  46. 46. Stretching to fill unknown width/height flex: 1 1 auto align-content: space-between
  47. 47. Improved wrapping in RWD layout With float or text-align With flex or justify-content
  48. 48. Flexbox is great for spacing and aligning stuff, especially shifting content in RWD.
  49. 49. Demo: full-width nav bar ¨  All links on same line ¨  First link flush left, last link flush right ¨  Equal spaces between all links
  50. 50. Trying display:table-cell J All links on same line J First link flush left, last link flush right L Equal spaces between all links
  51. 51. Spacing with table-layout:fixed
  52. 52. Starter centered nav bar, no flexbox .menu-list { margin: 0; padding: 0; list-style: none; text-align: center; } http://codepen.io/zomigi/pen/vKjbbY/ .menu-list-item { display: inline-block; padding: 16px 32px; }
  53. 53. Enhanced to full-width with flexbox .menu-list { display: flex; justify-content: space-between; /* equally spaces items across width */ margin: 0; padding: 0; list-style: none; text-align: center; /* fallback */ } .menu-list-item { display: inline-block; /* fallback */ padding: 0 .5em; /* fallback */ }
  54. 54. Combine with inline-block Non-flexbox fallback version Flexbox version
  55. 55. This works vertically too.
  56. 56. Demo: full-height menu
  57. 57. Demo: full-height menu .menu-list { display: flex; flex-direction: column; justify-content: space-between; } .menu-list-item { height: 100%; display: flex; align-items: center; } .menu-list { display: flex; flex-direction: column; } .menu-list-item { flex: 1 0 auto; display: flex; align-items: center; } justify-content version flex version
  58. 58. Demo: full-height menu .menu-list { display: flex; flex-direction: column; justify-content: space-between; } .menu-list-item { height: 100%; display: flex; align-items: center; } .menu-list { display: flex; flex-direction: column; } .menu-list-item { flex: 1 0 auto; display: flex; align-items: center; } justify-content version flex version
  59. 59. Flexbox can also enhance visual ordering.
  60. 60. order integer to specify flow order of flex items 0 0 0 default source order 0 0 1 0 0 re-ordered 0 0 0 0 -1 re-ordered 0 0 2 1 0 re-ordered 1 0
  61. 61. Reorder for good, not evil.
  62. 62. Demo: moving a photo on mobile
  63. 63. Demo: moving a photo on mobile Desktop: HTML order (no flexbox)Mobile: reordered
  64. 64. Use flexbox order in mobile styles .recipe { display: flex; flex-direction: column; } .recipe figure { order: -1; /* before all items with default order: 0 */ } .recipe figure img { width: 100%; }
  65. 65. Turn off flexbox in desktop styles @media screen and (min-width:800px) { .recipe { display: block; /* turn off flexbox */ } .recipe figure { float: right; width: 55%; } }
  66. 66. Demo: moving a photo on mobile Flexbox enhanced Non-flexbox
  67. 67. Reordering on The Guardian 12 3 4 56 flex-direction: row-reverse flex-direction: row-reverse 1 2 3 4 5 6
  68. 68. These examples don’t look wrong or broken without flexbox. Flexbox just enhances their sizing and spacing to look better.
  69. 69. Step-by-step process for adding flexbox to your UI components effectively HOW ¨ 3.
  70. 70. Don’t freak out
  71. 71. Decide whether flexbox is the right tool for the job
  72. 72. Decide which versions of flexbox to support standard, 2011/2012, and/or 2009
  73. 73. Browser support approaches to choose ¨  Use only the non-prefixed, standard syntax ¨  … plus browser-prefixed versions of standard syntax ¨  … plus -ms- prefixed 2011/2012 syntax ¨  … plus -webkit- prefixed 2009 syntax http://caniuse.com/#feat=flexbox
  74. 74. I recommend you skip the ‘09 syntax ¨  It’s slower to render than current syntax* ¨  Doesn’t support wrapping ¨  Its browsers have small market share ¨  If using flexbox for progressive enhancement, its browsers can get same fallback given to non-supporting browsers * http://updates.html5rocks.com/2013/10/Flexbox-layout-isn-t-slow
  75. 75. Let tools add browser variants for you Which variants do you want? Best tool to handle that All the things! Autoprefixer Bourbon (Sass) Only the standard syntax, with and without prefixes Compass (Sass) Some other combination (such as everything except 2009) Sass or LESS mixins, such as https://github.com/mastastealth/ sass-flex-mixin
  76. 76. Add Modernizr as needed with flexbox Flexbox and fallback styles can often co- exist, but sometimes need to isolate them http://zomigi.com/blog/using-modernizr-with-flexbox/
  77. 77. Or use @supports .gallery-item { display: inline-block; } @supports (flex-wrap: wrap) { .gallery { display: flex; flex-wrap: wrap; } } https://developer.mozilla.org/en-US/docs/Web/CSS/@supports But IE 10-11, which do support flexbox but don’t support @supports, won’t get these styles
  78. 78. Choose and add appropriate starter/fallback layout CSS
  79. 79. Things to consider Do I need content blocks to wrap? not table-cell Do I want to prevent blocks from wrapping? floats, inline-block, but table-cell best Do I need content-driven sizes? floats, but table-cell or inline-block best Do I need vertical alignment? inline-block, table-cell Do I need horizontal alignment? floats, table-cell, inline- block only with preset sizes
  80. 80. Pick your starter layout CSS ¨  Floats ¨  table-cell ¨  inline-block ¨  Absolute positioning Flexbox will override: Flexbox will not override: Just use whatever you normally would; flexbox plays nicely with most of them.
  81. 81. A real example of this process
  82. 82. Split left-right layout Task: lay out review score and price, on opposite sides of same line Needs: ¨  content-driven sizing ¨  horizontal alignment ¨  wrapping score price or “sold out”
  83. 83. Adding the starter CSS .iw_mini_review_score_wrapper { float: left; } .iw_mini_price_wrapper { float: right; }
  84. 84. Start adding flexbox!
  85. 85. Decide whether entire component needs to be block or inline-block display:flex or inline-flex
  86. 86. Creating the block flex container .iw_mini_details_wrapper { display: flex; } .iw_mini_review_score_wrapper { float: left; } .iw_mini_price_wrapper { float: right; } Flex container sits on a new row below, like a block element
  87. 87. Decide flow of flex items
  88. 88. Things to consider Lay out horizontally or vertically? flex-direction:row or column Allow boxes to wrap? flex-wrap:wrap, wrap-reverse or nowrap Order different than source? order values; flex-direction: row-reverse or column-reverse
  89. 89. Allowing wrapping .iw_mini_details_wrapper { display: flex; flex-wrap: wrap; } .iw_mini_review_score_wrapper { float: left; } .iw_mini_price_wrapper { float: right; } Allows second block to wrap down if needed
  90. 90. Decide which items can grow to fill space, shrink to avoid overflow, or must stay at a certain size
  91. 91. Tips for setting flex values ¨  Write out full flex values, rather than using single-digit and keyword values ¤  flex: 1 1 0% instead of flex: 1 ¤  Hidden default values can lead to mistakes ¤  Avoids IE 10-11 bugs ¨  Think about it backwards: first decide flex-basis, then -shrink, then -grow
  92. 92. Tips for setting flex-basis values ¨  Acts like min-width when wrapping on ¨  If flex-wrap off and flex-shrink on, browser can go smaller than flex-basis ¨  Be careful with flex-basis:0 when wrapping ¨  Use flex-basis:auto whenever possible
  93. 93. Setting flex-shrink ¨  Always have at least 1 item per line that can shrink (or wrap, or both)
  94. 94. Setting flex-grow ¨  Decide what to do with extra space ¤  Fill it up? (flex-grow: 1, 2, etc.) ¤  Leave it? (flex-grow: 0)
  95. 95. Setting flex values .iw_mini_details_wrapper { display: flex; flex-wrap: wrap; } .iw_mini_review_score_wrapper { float: left; flex: 0 1 auto; } .iw_mini_price_wrapper { float: right; flex: 0 1 auto; } Size to content, shrink smaller if you have to, don’t grow bigger (default value)
  96. 96. Decide how to align flex items
  97. 97. Main axis alignment (horizontal when row, vertical when column) Cross axis alignment (vertical when row, horizontal when column) (P.S. Also responsible for equal-height columns) justify-content align-items
  98. 98. Controlling alignment .iw_mini_details_wrapper { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: baseline; } .iw_mini_review_score_wrapper { float: left; } .iw_mini_price_wrapper { float: right; } Moves first item to left, last item to right
  99. 99. Improved wrapping Non-flexbox Flexbox enhanced
  100. 100. Flexbox with float fallback .iw_mini_details_wrapper { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: baseline; } .iw_mini_review_score_wrapper { float: left; } .iw_mini_price_wrapper { float: right; } Flexbox properties on container override floating automatically in supporting browsers Floating gets used by old browsers
  101. 101. Test
  102. 102. Testing your flexbox ¨  Too Flexy bookmarklet for toggling Modernizr flexbox classes: http://chriswrightdesign.github.io/tooflexy/ ¨  If reordering, check tabbing and screen reading order to make sure it’s still logical
  103. 103. Fix bugs
  104. 104. Fixing browsers’ flexbox bugs ¨  Read explanations and workarounds by Philip Walton: https://github.com/philipwalton/flexbugs ¨  Let PostCSS fix some for you: https://github.com/luisrudge/postcss-flexbugs-fixes
  105. 105. Summing up the process 1.  Decide whether to use flexbox and which browser versions of it 2.  Choose and add starter layout CSS 3.  Choose and add flexbox CSS 1.  Block or inline-block container 2.  Flow 3.  Flex to control sizing 4.  Alignment 4.  Test and fix bugs
  106. 106. Flexbox is not for the future. You can use flexbox today.
  107. 107. Thanks! Zoe Mickley Gillenwater @zomigi design@zomigi.com zomigi.com