In this guide we will explain the flow-relative mappings between physical dimension properties and logical properties used for sizing elements on our pages.
When specifying the size of an item, the Logical Properties and Values specification gives you the ability to indicate sizing as it relates to the flow of text (inline and block) rather than physical sizing which relates to the physical dimensions of horizontal and vertical (e.g. left and right). While these flow relative mappings may well become the default for many of us, in a design you may well use both physical and logical sizing. You might want some features to always relate to the physical dimensions whatever the writing mode.
Mappings for dimensions
The table below provides mappings between logical and physical properties. These mappings assume that you are in a
horizontal-tb writing mode, such as English or Arabic, in which case
width would be mapped to
|Logical Property||Physical Property|
Width and height example
The logical mappings for
inline-size, which sets the length in the inline dimension and
block-size, which sets the length in the block dimension. When working in English, replacing
block-size will give the same layout.
In the live example below I have set the Writing Mode to
horizontal-tb. Change it to
vertical-rl and you will see that the first example — which uses
height — remains the same size in each dimension, despite the text becoming vertical. The second example — which uses
block-size — will follow the text direction as if the entire block has rotated.
Min-width and min-height example
There are also mappings for
min-height — these are
min-block-size. These work in the same way as the
block-size properties, but setting a minimum rather than a fixed size.
Try changing the example below to
vertical-rl, as with the first example, to see the effect it has. I am using
min-height in the first example and
min-block-size in the second.
Max-width and max-height example
Logical keywords for resize
resize property sets whether or not an item can be resized and has physical values of
resize property also has logical keyword values. Using
resize: inline allows resizing in the inline dimension and
resize: block allow resizing in the block dimension.
The keyword value of
both for the resize property works whether you are thinking physically or logically. It sets both dimensions at once. Try playing with the below example.
Note that currently the logical values for resize are only supported by Firefox.