Tagged: layout

Today I learned that on macOS, with the default scrollbar setting enabled, classic scrollbars are shown automatically when a mouse is connected. I used to believe that, mouse or not, users needed to explicitly change the scrollbar appearance to get the classic scrollbars.

This is relevant for everyone who builds websites because when classic scrollbars are shown, the value of 100vw includes the scrollbar width. This can cause an unexpected horizontal overflow if the layout relies on 100vw for full-width elements. Additionally, they affect media queries, which assume scrollbars don’t exist when evaluating viewport width.

Having said that, these aren’t new issues. Classic scrollbars are shown by default on Windows, where the same behaviours apply.

Further reading:

• The large, small, and dynamic viewport units | Blog | web.dev
• New CSS Viewport Units Do Not Solve The Classic Scrollbar Problem — Smashing Magazine
• Get the scrollbar width using only CSS
• Full-Bleed Layout with Modern CSS – Frontend Masters Blog

In Level 3 of the Display specification, the value of display is defined as two keywords. These keywords define the outer value of display, which will be inline or block and therefore define how the element behaves in the layout alongside other elements. They also define the inner value of the element — or how the direct children of that element behave.

This means that when you say display: grid, what you are really saying is display: block grid. You are asking for a block level grid container. An element that will have all of the block attributes — you can give it height and width, margin and padding, and it will stretch to fill the container. The children of that container, however, have been given the inner value of grid so they become grid items. How those grid items behave is defined in the CSS Grid Specification: the display spec gives us a way to tell the browser that this is the layout method we want to use.

As simply put by Rachel:

When you define layout on a box in CSS, you are defining what happens to this box in terms of how it behaves in relation to all of the other boxes in the layout. You are also defining how the children of that box behave.