feat(no_std): portable-atomic integration for targets with no atomic types (#2076)

Improves compatibility with no-std targets that don't support atomic
types.

We support three different scenarios depending on the target:
1. Terminal applications and other std targets (e.g. espidf):
- `std` enabled, `portable-atomic` disabled
2. Embedded targets with atomic types, bare metal x86, etc.:
- `std` disabled `portable-atomic` disabled
3. Embedded targets without atomic types (e.g. single-core MCUs):
- `std` disabled, `portable-atomic` enabled

Turning on `portable-atomic` together with `std` will fall back to `std`
atomic.

Cargo.lock

@@ -969,6 +969,12 @@ version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d9c4f5dac5e15c24eb999c26181a6ca40b39fe946cbe4c263c7209467bc83af2"
 
+[[package]]
+name = "foldhash"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "77ce24cb58228fbb8aa041425bb1050850ac19177686ea6e0f41a70416f56fdb"
+
 [[package]]
 name = "form_urlencoded"
 version = "1.2.1"
@@ -1153,7 +1159,18 @@ checksum = "9229cfe53dfd69f0609a49f65461bd93001ea1ef889cd5529dd176593f5338a1"
 dependencies = [
  "allocator-api2",
  "equivalent",
- "foldhash",
+ "foldhash 0.1.5",
+]
+
+[[package]]
+name = "hashbrown"
+version = "0.16.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5419bdc4f6a9207fbeba6d11b604d481addf78ecd10c11ad51e76c2f6482748d"
+dependencies = [
+ "allocator-api2",
+ "equivalent",
+ "foldhash 0.2.0",
 ]
 
 [[package]]
@@ -1448,7 +1465,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fe4cd85333e22411419a0bcae1297d25e58c9443848b11dc6a86fefe8c78a661"
 dependencies = [
  "equivalent",
- "hashbrown",
+ "hashbrown 0.15.5",
 ]
 
 [[package]]
@@ -1569,11 +1586,13 @@ dependencies = [
 
 [[package]]
 name = "kasuari"
-version = "0.4.7"
+version = "0.4.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "96d9e0d6a8bf886abccc1cbcac7d74f9000ae5882aedc4a9042188bbc9cd4487"
+checksum = "12a3d6645acdef96d256c1f9fd3be7ecfa60d8457520a50bbd1600b6053f8173"
 dependencies = [
- "hashbrown",
+ "hashbrown 0.16.0",
+ "portable-atomic",
+ "portable-atomic-util",
  "thiserror 2.0.16",
 ]
 
@@ -1685,7 +1704,7 @@ version = "0.16.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "86ea4e65087ff52f3862caff188d489f1fab49a0cb09e01b2e3f1a617b10aaed"
 dependencies = [
- "hashbrown",
+ "hashbrown 0.15.5",
 ]
 
 [[package]]
@@ -2212,6 +2231,21 @@ dependencies = [
  "ratatui",
 ]
 
+[[package]]
+name = "portable-atomic"
+version = "1.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f84267b20a16ea918e43c6a88433c2d54fa145c92a811b5b047ccbe153674483"
+
+[[package]]
+name = "portable-atomic-util"
+version = "0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d8a2f0d8d040d7848a709caf78912debcc3f33ee4b3cac47d73d1e1069e83507"
+dependencies = [
+ "portable-atomic",
+]
+
 [[package]]
 name = "potential_utf"
 version = "0.1.2"
@@ -2492,7 +2526,7 @@ dependencies = [
  "bitflags 2.9.2",
  "compact_str",
  "document-features",
- "hashbrown",
+ "hashbrown 0.15.5",
  "indoc",
  "itertools 0.14.0",
  "kasuari",
@@ -2570,7 +2604,7 @@ dependencies = [
  "color-eyre",
  "crossterm 0.29.0",
  "document-features",
- "hashbrown",
+ "hashbrown 0.15.5",
  "indoc",
  "instability",
  "itertools 0.14.0",

ratatui-core/Cargo.toml

@@ -43,6 +43,9 @@ anstyle = ["dep:anstyle"]
 ## enables conversions from colors in the [`palette`] crate to [`Color`](crate::style::Color).
 palette = ["std", "dep:palette"]
 
+## enables portable-atomic integration for targets that don't support atomic types.
+portable-atomic = ["kasuari/portable-atomic"]
+
 ## enables the backend code that sets the underline color. Underline color is only supported by
 ## the Crossterm backend, and is not supported on Windows 7.
 underline-color = []

ratatui/Cargo.toml

@@ -59,6 +59,9 @@ layout-cache = ["std", "ratatui-core/layout-cache"]
 ## enables conversions from colors in the [`palette`] crate to [`Color`](crate::style::Color).
 palette = ["std", "ratatui-core/palette", "dep:palette"]
 
+## enables portable-atomic integration for targets that don't support atomic types.
+portable-atomic = ["ratatui-core/portable-atomic"]
+
 ## Use terminal scrolling regions to make some operations less prone to
 ## flickering. (i.e. Terminal::insert_before).
 scrolling-regions = [