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Laying out Elements with CSS

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  1. Laying out Elements with CSS

  2. Objectives • Assess the CSS box model • Set element width and borders • Set margins and padding • Align elements with float • Control page flow with clear HTML5 and CSS3 – Illustrated, 2nd Edition

  3. Objectives (continued) • Implement fixed positioning • Implement relative positioning • Control stacking order • Implement absolute positioning HTML5 and CSS3 – Illustrated, 2nd Edition

  4. Assess the CSS Box Model • Box model: used by CSS to represent characteristics of every web page element • Treats element as rectangular box • border: border surrounding element • margin: space from border to neighboring/parent element • padding: space between border and element content HTML5 and CSS3 – Illustrated, 2nd Edition

  5. Assess the CSS Box Model (continued) • The CSS box model HTML5 and CSS3 – Illustrated, 2nd Edition

  6. Assess the CSS Box Model (continued) • Box model properties HTML5 and CSS3 – Illustrated, 2nd Edition

  7. Assess the CSS Box Model (continued) • CSS units of measure • Relative units: ems, percent, rems • Absolute units: pixels • Commonly used CSS units of measure HTML5 and CSS3 – Illustrated, 2nd Edition

  8. Assess the CSS Box Model (continued) • Size of padding, margin, and border increase the amount of space occupied by an element • Dimensions of these properties not included in specified width / height • Specified width and height refer only to the content of an element • To calculate add the total space, add the width value to the padding, margin, and border values HTML5 and CSS3 – Illustrated, 2nd Edition

  9. Assess the CSS Box Model (continued) • Calculating web page space occupied by an element HTML5 and CSS3 – Illustrated, 2nd Edition

  10. Assess the CSS Box Model (continued) • Collapse: When bottom margin of one element is adjacent to top margin of another, the margins combine to the size of the larger of the two • Affects element size planning • Separate property for each side of padding and margin, e.g. • padding-top: 2px; • margin-right: 1em; HTML5 and CSS3 – Illustrated, 2nd Edition

  11. Set Element Widthand Borders • Margin, padding, and border are shorthand properties • Assign values to multiple CSS properties • Assign values to all four sides of an element • Assign these values using a single declaration • Can set width, style, or color of any or all sides of an element HTML5 and CSS3 – Illustrated, 2nd Edition

  12. Set Element Widthand Borders (continued) • Specific properties for the box model • Reset rule: resets one or more common properties to a common baseline, e.g. • border: 0 HTML5 and CSS3 – Illustrated, 2nd Edition

  13. Set Element Widthand Borders (continued) • Code with width and border declarations HTML5 and CSS3 – Illustrated, 2nd Edition

  14. Set Element Widthand Borders (continued) • width and border declarations rendered in a browser and developer tools opened to show box model HTML5 and CSS3 – Illustrated, 2nd Edition

  15. Set Margins and Padding • Use the shorthand property to assign multiple values • Separate each value with a space • Meaning of different number of values • Assign auto to left and right margins to center the element horizontally HTML5 and CSS3 – Illustrated, 2nd Edition

  16. Set Margins and Padding(continued) • Example of padding using three values and margin using two values • Example of margin set to auto HTML5 and CSS3 – Illustrated, 2nd Edition

  17. Align Elements with float • Page flow: the order of elements in the HTML document • User agents render HTML top to bottom • Easy to create layouts with elements stacked vertically • Use float, clear, and width properties to create columns of text and graphics parallel to each other • Use width property to assign width to each of the columns HTML5 and CSS3 – Illustrated, 2nd Edition

  18. Align Elements with float(continued) • Example of float applied to element • Use float to create multicolumn layouts HTML5 and CSS3 – Illustrated, 2nd Edition

  19. Align Elements with float(continued) • Code with float and result in browser HTML5 and CSS3 – Illustrated, 2nd Edition

  20. Control Page Flow with clear • float gives basic control over layout • clear gives more precise control • Prevents floated elements from being displayed to the left, right, or on the side of another element • clear property values HTML5 and CSS3 – Illustrated, 2nd Edition

  21. Control Page Flow with clear(continued) • Example of clear property HTML5 and CSS3 – Illustrated, 2nd Edition

  22. Control Page Flow with clear(continued) • Code including clear property and how it is rendered in a browser HTML5 and CSS3 – Illustrated, 2nd Edition

  23. Implement FixedPositioning • fixed positioning keeps an element in the same location, even when the page is scrolled • Use the position property with the value of fixed • Then specify • Horizontal position using left or right • Vertical positing using top or bottom HTML5 and CSS3 – Illustrated, 2nd Edition

  24. Implement Fixed Positioning (continued) • Commonly used position properties • Properties and values for fixed positioning HTML5 and CSS3 – Illustrated, 2nd Edition

  25. Implement Fixed Positioning (continued) • Example showing fixed positioning HTML5 and CSS3 – Illustrated, 2nd Edition

  26. Implement Fixed Positioning (continued) • Code including fixed value and how it is rendered in a browser HTML5 and CSS3 – Illustrated, 2nd Edition

  27. Implement Relative Positioning • Relative positioning: adjusting default position of an element • Preserves space allotted to element in default page flow • Set position property to relative • Style exact location using the properties • left and right for horizontal positioning • top and bottom for vertical positioning HTML5 and CSS3 – Illustrated, 2nd Edition

  28. Implement Relative Positioning (continued) • CSS properties and values for relative positioning HTML5 and CSS3 – Illustrated, 2nd Edition

  29. Implement Relative Positioning (continued) • Implementing relative positioning and page flow HTML5 and CSS3 – Illustrated, 2nd Edition

  30. Implement Relative Positioning (continued) • Code using relative positioning and how it is rendered in a browser HTML5 and CSS3 – Illustrated, 2nd Edition

  31. Control stacking order • Stacking elements: positioning elements so that they can overlap • Additional possibilities for layouts • Applies only to positioned element • Elements placed in new layer • Requires careful planning • Stacking order controlled by values assigned to z-index property HTML5 and CSS3 – Illustrated, 2nd Edition

  32. Control Stacking Order(continued) HTML5 and CSS3 – Illustrated, 2nd Edition Stacking positioned elements

  33. Control Stacking Order(continued) HTML5 and CSS3 – Illustrated, 2nd Edition Code to stack and how it is rendered in a browser

  34. Implement AbsolutePositioning • Absolute positioning: takes element out of page flow entirely • Allows other elements to flow into space element would have occupied • Set position property to absolute • Style exact location using left, right, top, and bottom properties • Location is calculated relative to closest ancestor element that has position applied to it HTML5 and CSS3 – Illustrated, 2nd Edition

  35. Implement AbsolutePositioning (continued) • Absolute positioning and page flow • Properties and values HTML5 and CSS3 – Illustrated, 2nd Edition

  36. Implement AbsolutePositioning (continued) • Code to absolutely position an element and the result in a browser HTML5 and CSS3 – Illustrated, 2nd Edition

  37. Summary • Box model: used by CSS to represent characteristics of elements • Treats element as rectangular box • Defines border, margin and padding • Margins of adjacent elements can collapse into one margin • Specify borderwidth, style, and/or color of any or all sides HTML5 and CSS3 – Illustrated, 2nd Edition

  38. Summary (continued) • Use multiple values to assign margin and padding values to different sides • Use float to change the default page flow • Use clear to create a more precise layout • Use float, clear and width to create multicolumn layouts HTML5 and CSS3 – Illustrated, 2nd Edition

  39. Summary (continued) • Fixed positioning: keeps an element in the same position, even when the page is scrolled • Relative positioning: adjusting location of element relative to its page flow location using position property • Space preserved HTML5 and CSS3 – Illustrated, 2nd Edition

  40. Summary (continued) • Use z-index to create a stacking order for elements • Stacked elements are placed in new layers • Absolute positioning: takes elements out of page flow entirely • Other elements reflow into empty space HTML5 and CSS3 – Illustrated, 2nd Edition

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