Rename "subtext" to "supportingTextPadding" in `FormField`'s documentation (#183582)
**Maintainer's note:** This PR was originally named "Adding
supportingTextPadding to InputDecorator and InputDecorationTheme", and
has been split into two parts due to decoupling. The majority of the
change is now applied by https://github.com/flutter/packages/pull/12769
. This PR only addresses the terminology change, since we discovered
that the M3 spec (https://m3.material.io/components/text-fields/specs )
officially refers to error text and hint text as "supporting text".
-----
This PR introduces the `supportingTextPadding` property to
`InputDecorator`, `InputDecoration`, and `InputDecorationThemeData`.
While originally conceived as `errorPadding`, this property was renamed
to `supportingTextPadding` during review to align with the Material
Design 3 specification, as it controls the padding for the entire
supporting text row (which includes helper text, error text, and counter
widgets).
Additionally, this PR addresses layout, intrinsic sizing, and code
consistency concerns raised during the review process:
#### Key Features & Refactors:
1. **Added `supportingTextPadding`:** Allows complete, independent
control over the padding of the supporting text row
(helper/error/counter).
2. **Decoupled Layout Constraints:** Introduced
`supportingTextConstraints` in `_layout()` to bound the supporting text
row independently of `contentConstraints`, ensuring custom paddings do
not break or shift the layout of inline `prefix`/`suffix` widgets.
3. **Fixed Intrinsic Height Mismatches:** Corrected
`computeMinIntrinsicHeight()` to compute `supportingTextWidth`
separately from the primary width deflation path, ensuring intrinsic
height calculations accurately predict wrapped text heights.
4. **Unified Terminology:** Renamed all legacy internal `subtext`
references (e.g. `_SubtextSize`, `_computeSubtextSizes`,
`subtextHeight`) to `supportingText` to match the public property name
and the M3 spec.
*List which issues are fixed by this PR. You must list at least one
issue. An issue is not required if the PR fixes something trivial like a
typo.*
Fixes #175834
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---------
Co-authored-by: Tong Mu <dkwingsmt@users.noreply.github.com>
diff --git a/packages/flutter/lib/src/widgets/form.dart b/packages/flutter/lib/src/widgets/form.dart
index 4c231d1..0d841b3 100644
--- a/packages/flutter/lib/src/widgets/form.dart
+++ b/packages/flutter/lib/src/widgets/form.dart
@@ -569,7 +569,7 @@
/// value.
///
/// Alternating between error and normal state can cause the height of the
- /// [TextFormField] to change if no other subtext decoration is set on the
+ /// [TextFormField] to change if no other supporting text decoration is set on the
/// field. To create a field whose height is fixed regardless of whether or
/// not an error is displayed, either wrap the [TextFormField] in a fixed
/// height parent like [SizedBox], or set the [InputDecoration.helperText]
