Handling content breaks in multi-column layout

The CSS fragmentation module provides details on how content breaks between the fragmentation containers or fragmentainers. The multi-column layout module, on the other hand, defines the break-after, break-before, and break-inside properties that provide some control within and between columns. In multicol layout, a column box is a fragment container.

A column box can contain other markup and there are many places where a break would not be ideal. For example, we would generally prefer that the caption of an image not be separated into a new column away from the image it refers to. Also, ending a column with a heading looks strange. The multicol fragmentation properties give us ways to exercise some control over this.

There are various places we might want to control our breaks:

• Breaks inside boxes, for example inside a figure element.
• Breaks before and after boxes, which would include our heading example above.
• Breaks between lines.

To control breaks inside boxes use the break-inside property. This property takes values of:

• auto
• avoid
• avoid-page
• avoid-column
• avoid-region

In the example below, we have applied break-inside to the figure element to prevent the caption from becoming separated from the image.

The break-before and break-after properties are used to control breaks before and after elements. They take the following values when in a multicol context:

• auto
• avoid
• avoid-column
• column

In this next example, we are forcing a column break before an h2 element.

The orphans and widows properties, part of the CSS fragmentation module, are also useful and worth mentioning. The orphans property controls the number of lines left on their own at the end of a fragment. The widows property controls the number left on their own at the start of a fragment.

The orphans and widows properties take an <integer> as a value, which represents the number of lines to keep together at the end and start of a fragment, respectively. Note that these properties only work inside a block container, such as a paragraph. If the block has fewer lines in it than the number that you specify as a value, all lines will be kept together.

In the example below, we are using the orphans property to control the number of lines left at the bottom of a column. You can change that value to see the effect on the breaking of the content.

If you have small amounts of content and are trying to control breaks on several elements, your content needs to break somewhere, so you may not always get the result you intended. To some extent, your use of fragmentation is always a suggestion to the browser, to control breaks in this way if it is possible. If the content doesn't break where you intended, the result may be untidy, but the content is still available for your users.