TextAffinity enum Null safety
A way to disambiguate a TextPosition when its offset could match two different locations in the rendered string.
For example, at an offset where the rendered text wraps, there are two visual positions that the offset could represent: one prior to the line break (at the end of the first line) and one after the line break (at the start of the second line). A text affinity disambiguates between these two cases.
This affects only line breaks caused by wrapping, not explicit newline characters. For newline characters, the position is fully specified by the offset alone, and there is no ambiguity.
TextAffinity also affects bidirectional text at the interface between LTR and RTL text. Consider the following string, where the lowercase letters will be displayed as LTR and the uppercase letters RTL: "helloHELLO". When rendered, the string would appear visually as "helloOLLEH". An offset of 5 would be ambiguous without a corresponding TextAffinity. Looking at the string in code, the offset represents the position just after the "o" and just before the "H". When rendered, this offset could be either in the middle of the string to the right of the "o" or at the end of the string to the right of the "H".
Constructors
- TextAffinity()
-
const
Values
- upstream → const TextAffinity
-
The position has affinity for the upstream side of the text position, i.e. in the direction of the beginning of the string.
In the example of an offset at the place where text is wrapping, upstream indicates the end of the first line.
In the bidirectional text example "helloHELLO", an offset of 5 with TextAffinity upstream would appear in the middle of the rendered text, just to the right of the "o". See the definition of TextAffinity for the full example.
TextAffinity() - downstream → const TextAffinity
-
The position has affinity for the downstream side of the text position, i.e. in the direction of the end of the string.
In the example of an offset at the place where text is wrapping, downstream indicates the beginning of the second line.
In the bidirectional text example "helloHELLO", an offset of 5 with TextAffinity downstream would appear at the end of the rendered text, just to the right of the "H". See the definition of TextAffinity for the full example.
TextAffinity()
Properties
Methods
-
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a non-existent method or property is accessed.
inherited
-
toString(
) → String -
A string representation of this object.
inherited
Operators
-
operator ==(
Object other) → bool -
The equality operator.
inherited
Constants
-
values
→ const List<
TextAffinity> -
A constant List of the values in this enum, in order of their declaration.
[upstream, downstream]