Keep momentary input on the widget the cursor is on

Tests across layers, as asked, and the fifth one found a defect older than
this branch: a press fired on a widget the cursor had just left, because the
frame its hover ends is a frame it still gets dispatched on, and `should_run`
only ever looked at the cursor. A button in the corner of a list therefore
clicked when the press landed anywhere else in the row.

A widget that is not under the cursor now sees a cursor with nothing
momentary in it, which settles both halves of the question at once: it is not
its press to receive, and not its press to take from the layers below.

`CursorSense` and `CursorButton` derive `Debug`, so a failure says which
sense fired rather than `left != right`.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Cargo.lock

@@ -234,18 +234,18 @@ dependencies = [
 
 [[package]]
 name = "bit-set"
-version = "0.8.0"
+version = "0.10.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "08807e080ed7f9d5433fa9b275196cfc35414f66a0c79d864dc51a0d825231a3"
+checksum = "09ec2f926cc3060f09db9ebc5b52823d85268d24bb917e472c0c4bea35780a7d"
 dependencies = [
  "bit-vec",
 ]
 
 [[package]]
 name = "bit-vec"
-version = "0.8.0"
+version = "0.9.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5e764a1d40d510daf35e07be9eb06e75770908c27d411ee6c92109c9840eaaf7"
+checksum = "b71798fca2c1fe1086445a7258a4bc81e6e49dcd24c8d0dd9a1e57395b603f51"
 
 [[package]]
 name = "bit_field"
@@ -274,12 +274,6 @@ dependencies = [
  "core2",
 ]
 
-[[package]]
-name = "block"
-version = "0.1.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0d8c1fef690941d3e7788d328517591fecc684c084084702d6ff1641e993699a"
-
 [[package]]
 name = "block2"
 version = "0.5.1"
@@ -289,6 +283,15 @@ dependencies = [
  "objc2 0.5.2",
 ]
 
+[[package]]
+name = "block2"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cdeb9d870516001442e364c5220d3574d2da8dc765554b4a617230d33fa58ef5"
+dependencies = [
+ "objc2 0.6.4",
+]
+
 [[package]]
 name = "built"
 version = "0.8.0"
@@ -391,9 +394,9 @@ checksum = "9330f8b2ff13f34540b44e946ef35111825727b38d33286ef986142615121801"
 
 [[package]]
 name = "cfg_aliases"
-version = "0.2.1"
+version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "613afe47fcd5fac7ccf1db93babcb082c5994d996f20b8b159f2ad1658eb5724"
+checksum = "f079e83a288787bcd14a6aea84cee5c87a67c5a3e660c30f557a3d24761b3527"
 
 [[package]]
 name = "clipboard-win"
@@ -406,9 +409,9 @@ dependencies = [
 
 [[package]]
 name = "codespan-reporting"
-version = "0.12.0"
+version = "0.13.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fe6d2e5af09e8c8ad56c969f2157a3d4238cebc7c55f0a517728c38f7b200f81"
+checksum = "af491d569909a7e4dee0ad7db7f5341fef5c614d5b8ec8cf765732aba3cff681"
 dependencies = [
  "serde",
  "termcolor",
@@ -450,16 +453,6 @@ dependencies = [
  "libc",
 ]
 
-[[package]]
-name = "core-foundation"
-version = "0.10.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b2a6cd9ae233e7f62ba4e9353e81a88df7fc8a5987b8d445b4d90c879bd156f6"
-dependencies = [
- "core-foundation-sys",
- "libc",
-]
-
 [[package]]
 name = "core-foundation-sys"
 version = "0.8.7"
@@ -473,8 +466,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c07782be35f9e1140080c6b96f0d44b739e2278479f64e02fdab4e32dfd8b081"
 dependencies = [
  "bitflags 1.3.2",
- "core-foundation 0.9.4",
+ "core-foundation",
- "core-graphics-types 0.1.3",
+ "core-graphics-types",
  "foreign-types",
  "libc",
 ]
@@ -486,18 +479,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "45390e6114f68f718cc7a830514a96f903cccd70d02a8f6d9f643ac4ba45afaf"
 dependencies = [
  "bitflags 1.3.2",
- "core-foundation 0.9.4",
+ "core-foundation",
- "libc",
-]
-
-[[package]]
-name = "core-graphics-types"
-version = "0.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3d44a101f213f6c4cdc1853d4b78aef6db6bdfa3468798cc1d9912f4735013eb"
-dependencies = [
- "bitflags 2.10.0",
- "core-foundation 0.10.1",
  "libc",
 ]
 
@@ -739,15 +721,6 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "77ce24cb58228fbb8aa041425bb1050850ac19177686ea6e0f41a70416f56fdb"
 
-[[package]]
-name = "font-types"
-version = "0.10.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "39a654f404bbcbd48ea58c617c2993ee91d1cb63727a37bf2323a4edeed1b8c5"
-dependencies = [
- "bytemuck",
-]
-
 [[package]]
 name = "font-types"
 version = "0.12.4"
@@ -771,7 +744,7 @@ dependencies = [
  "objc2-core-text",
  "objc2-foundation 0.3.2",
  "parlance",
- "read-fonts 0.41.0",
+ "read-fonts",
  "roxmltree",
  "smallvec",
  "windows",
@@ -806,6 +779,30 @@ version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "aa9a19cbb55df58761df49b23516a86d432839add4af60fc256da840f66ed35b"
 
+[[package]]
+name = "futures-core"
+version = "0.3.34"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "92d699e522242e69e3003b94ecc1f960f3a5e015aa7c5d7486e65ad01dd94f5e"
+
+[[package]]
+name = "futures-task"
+version = "0.3.34"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cd417de3d1d015fc3bfd2b1ea46dfc7bab72ef86f1cc7cc9c78e728b34a6d1fd"
+
+[[package]]
+name = "futures-util"
+version = "0.3.34"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0d50a92467f8ba5dd6e3ee5d4bd04d73ab2e4e1c44474a0674821dfce14b79bc"
+dependencies = [
+ "futures-core",
+ "futures-task",
+ "pin-project-lite",
+ "slab",
+]
+
 [[package]]
 name = "fxhash"
 version = "0.2.1"
@@ -860,9 +857,9 @@ dependencies = [
 
 [[package]]
 name = "glow"
-version = "0.16.0"
+version = "0.17.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c5e5ea60d70410161c8bf5da3fdfeaa1c72ed2c15f8bbb9d19fe3a4fad085f08"
+checksum = "29038e1c483364cc6bb3cf78feee1816002e127c331a1eec55a4d202b9e1adb5"
 dependencies = [
  "js-sys",
  "slotmap",
@@ -893,26 +890,6 @@ dependencies = [
  "windows",
 ]
 
-[[package]]
-name = "gpu-descriptor"
-version = "0.3.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b89c83349105e3732062a895becfc71a8f921bb71ecbbdd8ff99263e3b53a0ca"
-dependencies = [
- "bitflags 2.10.0",
- "gpu-descriptor-types",
- "hashbrown 0.15.5",
-]
-
-[[package]]
-name = "gpu-descriptor-types"
-version = "0.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fdf242682df893b86f33a73828fb09ca4b2d3bb6cc95249707fc684d27484b91"
-dependencies = [
- "bitflags 2.10.0",
-]
-
 [[package]]
 name = "half"
 version = "2.7.1"
@@ -933,7 +910,7 @@ checksum = "c03d949a14aa089bbb282f7dd76a498a7f684428e4257202efc119ec010376f9"
 dependencies = [
  "bitflags 2.10.0",
  "bytemuck",
- "read-fonts 0.41.0",
+ "read-fonts",
  "smallvec",
 ]
 
@@ -972,12 +949,6 @@ version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fc0fef456e4baa96da950455cd02c081ca953b141298e41db3fc7e36b1da849c"
 
-[[package]]
-name = "hexf-parse"
-version = "0.2.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dfa686283ad6dd069f105e5ab091b04c62850d3e4cf5d67debad1933f55023df"
-
 [[package]]
 name = "icu_collections"
 version = "2.3.0"
@@ -1108,9 +1079,9 @@ checksum = "ae293c039020f9ec10710af98d29ce6aa2051486638b49c9a6409f3b4a9e98ad"
 
 [[package]]
 name = "image"
-version = "0.25.9"
+version = "0.25.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e6506c6c10786659413faa717ceebcb8f70731c0a60cbae39795fdf114519c1a"
+checksum = "85ab80394333c02fe689eaf900ab500fbd0c2213da414687ebf995a65d5a6104"
 dependencies = [
  "bytemuck",
  "byteorder-lite",
@@ -1126,8 +1097,8 @@ dependencies = [
  "rayon",
  "rgb",
  "tiff",
- "zune-core 0.5.0",
+ "zune-core",
- "zune-jpeg 0.5.8",
+ "zune-jpeg",
 ]
 
 [[package]]
@@ -1247,11 +1218,12 @@ dependencies = [
 
 [[package]]
 name = "js-sys"
-version = "0.3.83"
+version = "0.3.105"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "464a3709c7f55f1f721e5389aa6ea4e3bc6aba669353300af094b29ffbdde1d8"
+checksum = "ce57d20d1ea864ce2ac172ab472d409214f4fd359f0b2a2775abdf522e2af99e"
 dependencies = [
- "once_cell",
+ "cfg-if",
+ "futures-util",
  "wasm-bindgen",
 ]
 
@@ -1280,9 +1252,9 @@ checksum = "7a79a3332a6609480d7d0c9eab957bca6b455b91bb84e66d19f5ff66294b85b8"
 
 [[package]]
 name = "libc"
-version = "0.2.179"
+version = "0.2.189"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c5a2d376baa530d1238d133232d15e239abad80d05838b4b59354e5268af431f"
+checksum = "3eaf3ede3fee6db1a4c2ee091bf8a8b4dccdc6d17f656fb07896ee72867612f2"
 
 [[package]]
 name = "libfuzzer-sys"
@@ -1375,15 +1347,6 @@ dependencies = [
  "imgref",
 ]
 
-[[package]]
-name = "malloc_buf"
-version = "0.0.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "62bb907fe88d54d8d9ce32a3cceab4218ed2f6b7d35617cafe9adf84e43919cb"
-dependencies = [
- "libc",
-]
-
 [[package]]
 name = "maybe-rayon"
 version = "0.1.1"
@@ -1409,21 +1372,6 @@ dependencies = [
  "libc",
 ]
 
-[[package]]
-name = "metal"
-version = "0.33.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c7047791b5bc903b8cd963014b355f71dc9864a9a0b727057676c1dcae5cbc15"
-dependencies = [
- "bitflags 2.10.0",
- "block",
- "core-graphics-types 0.2.0",
- "foreign-types",
- "log",
- "objc",
- "paste",
-]
-
 [[package]]
 name = "miniz_oxide"
 version = "0.8.9"
@@ -1436,9 +1384,9 @@ dependencies = [
 
 [[package]]
 name = "moxcms"
-version = "0.7.11"
+version = "0.8.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ac9557c559cd6fc9867e122e20d2cbefc9ca29d80d027a8e39310920ed2f0a97"
+checksum = "bb85c154ba489f01b25c0d36ae69a87e4a1c73a72631fc6c0eb6dde34a73e44b"
 dependencies = [
  "num-traits",
  "pxfm",
@@ -1446,9 +1394,9 @@ dependencies = [
 
 [[package]]
 name = "naga"
-version = "28.0.0"
+version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "618f667225063219ddfc61251087db8a9aec3c3f0950c916b614e403486f1135"
+checksum = "a616d2fb8c89516ac2723a581f69d6c18576046bed761bd6b305e5618e6ae130"
 dependencies = [
  "arrayvec",
  "bit-set",
@@ -1457,11 +1405,11 @@ dependencies = [
  "cfg_aliases",
  "codespan-reporting",
  "half",
- "hashbrown 0.16.1",
+ "hashbrown 0.17.1",
- "hexf-parse",
  "indexmap",
  "libm",
  "log",
+ "naga-types",
  "num-traits",
  "once_cell",
  "rustc-hash",
@@ -1470,6 +1418,18 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "naga-types"
+version = "30.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "590afbf58a6f4f62873cd5cff4468061844bafa1cdf399cc954537c22d768d49"
+dependencies = [
+ "hashbrown 0.17.1",
+ "indexmap",
+ "rustc-hash",
+ "thiserror 2.0.17",
+]
+
 [[package]]
 name = "ndk"
 version = "0.9.0"
@@ -1594,15 +1554,6 @@ dependencies = [
  "syn 2.0.113",
 ]
 
-[[package]]
-name = "objc"
-version = "0.2.7"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "915b1b472bc21c53464d6c8461c9d3af805ba1ef837e1cac254428f4a77177b1"
-dependencies = [
- "malloc_buf",
-]
-
 [[package]]
 name = "objc-sys"
 version = "0.3.5"
@@ -1635,13 +1586,13 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e4e89ad9e3d7d297152b17d39ed92cd50ca8063a89a9fa569046d41568891eff"
 dependencies = [
  "bitflags 2.10.0",
- "block2",
+ "block2 0.5.1",
  "libc",
  "objc2 0.5.2",
  "objc2-core-data",
  "objc2-core-image",
  "objc2-foundation 0.2.2",
- "objc2-quartz-core",
+ "objc2-quartz-core 0.2.2",
 ]
 
 [[package]]
@@ -1663,7 +1614,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "74dd3b56391c7a0596a295029734d3c1c5e7e510a4cb30245f8221ccea96b009"
 dependencies = [
  "bitflags 2.10.0",
- "block2",
+ "block2 0.5.1",
  "objc2 0.5.2",
  "objc2-core-location",
  "objc2-foundation 0.2.2",
@@ -1675,7 +1626,7 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a5ff520e9c33812fd374d8deecef01d4a840e7b41862d849513de77e44aa4889"
 dependencies = [
- "block2",
+ "block2 0.5.1",
  "objc2 0.5.2",
  "objc2-foundation 0.2.2",
 ]
@@ -1687,7 +1638,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "617fbf49e071c178c0b24c080767db52958f716d9eabdf0890523aeae54773ef"
 dependencies = [
  "bitflags 2.10.0",
- "block2",
+ "block2 0.5.1",
  "objc2 0.5.2",
  "objc2-foundation 0.2.2",
 ]
@@ -1722,10 +1673,10 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "55260963a527c99f1819c4f8e3b47fe04f9650694ef348ffd2227e8196d34c80"
 dependencies = [
- "block2",
+ "block2 0.5.1",
  "objc2 0.5.2",
  "objc2-foundation 0.2.2",
- "objc2-metal",
+ "objc2-metal 0.2.2",
 ]
 
 [[package]]
@@ -1734,7 +1685,7 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "000cfee34e683244f284252ee206a27953279d370e309649dc3ee317b37e5781"
 dependencies = [
- "block2",
+ "block2 0.5.1",
  "objc2 0.5.2",
  "objc2-contacts",
  "objc2-foundation 0.2.2",
@@ -1763,7 +1714,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0ee638a5da3799329310ad4cfa62fbf045d5f56e3ef5ba4149e7452dcf89d5a8"
 dependencies = [
  "bitflags 2.10.0",
- "block2",
+ "block2 0.5.1",
  "dispatch",
  "libc",
  "objc2 0.5.2",
@@ -1797,7 +1748,7 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a1a1ae721c5e35be65f01a03b6d2ac13a54cb4fa70d8a5da293d7b0020261398"
 dependencies = [
- "block2",
+ "block2 0.5.1",
  "objc2 0.5.2",
  "objc2-app-kit 0.2.2",
  "objc2-foundation 0.2.2",
@@ -1810,11 +1761,23 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dd0cba1276f6023976a406a14ffa85e1fdd19df6b0f737b063b95f6c8c7aadd6"
 dependencies = [
  "bitflags 2.10.0",
- "block2",
+ "block2 0.5.1",
  "objc2 0.5.2",
  "objc2-foundation 0.2.2",
 ]
 
+[[package]]
+name = "objc2-metal"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a0125f776a10d00af4152d74616409f0d4a2053a6f57fa5b7d6aa2854ac04794"
+dependencies = [
+ "bitflags 2.10.0",
+ "block2 0.6.2",
+ "objc2 0.6.4",
+ "objc2-foundation 0.3.2",
+]
+
 [[package]]
 name = "objc2-quartz-core"
 version = "0.2.2"
@@ -1822,10 +1785,24 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e42bee7bff906b14b167da2bac5efe6b6a07e6f7c0a21a7308d40c960242dc7a"
 dependencies = [
  "bitflags 2.10.0",
- "block2",
+ "block2 0.5.1",
  "objc2 0.5.2",
  "objc2-foundation 0.2.2",
- "objc2-metal",
+ "objc2-metal 0.2.2",
+]
+
+[[package]]
+name = "objc2-quartz-core"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "96c1358452b371bf9f104e21ec536d37a650eb10f7ee379fff67d2e08d537f1f"
+dependencies = [
+ "bitflags 2.10.0",
+ "objc2 0.6.4",
+ "objc2-core-foundation",
+ "objc2-core-graphics",
+ "objc2-foundation 0.3.2",
+ "objc2-metal 0.3.2",
 ]
 
 [[package]]
@@ -1845,7 +1822,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b8bb46798b20cd6b91cbd113524c490f1686f4c4e8f49502431415f3512e2b6f"
 dependencies = [
  "bitflags 2.10.0",
- "block2",
+ "block2 0.5.1",
  "objc2 0.5.2",
  "objc2-cloud-kit",
  "objc2-core-data",
@@ -1853,7 +1830,7 @@ dependencies = [
  "objc2-core-location",
  "objc2-foundation 0.2.2",
  "objc2-link-presentation",
- "objc2-quartz-core",
+ "objc2-quartz-core 0.2.2",
  "objc2-symbols",
  "objc2-uniform-type-identifiers",
  "objc2-user-notifications",
@@ -1865,7 +1842,7 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "44fa5f9748dbfe1ca6c0b79ad20725a11eca7c2218bceb4b005cb1be26273bfe"
 dependencies = [
- "block2",
+ "block2 0.5.1",
  "objc2 0.5.2",
  "objc2-foundation 0.2.2",
 ]
@@ -1877,7 +1854,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "76cfcbf642358e8689af64cee815d139339f3ed8ad05103ed5eaf73db8d84cb3"
 dependencies = [
  "bitflags 2.10.0",
- "block2",
+ "block2 0.5.1",
  "objc2 0.5.2",
  "objc2-core-location",
  "objc2-foundation 0.2.2",
@@ -1971,7 +1948,7 @@ dependencies = [
  "linebender_resource_handle",
  "parlance",
  "parley_data",
- "skrifa 0.44.0",
+ "skrifa",
 ]
 
 [[package]]
@@ -2275,9 +2252,9 @@ dependencies = [
 
 [[package]]
 name = "ravif"
-version = "0.12.0"
+version = "0.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ef69c1990ceef18a116855938e74793a5f7496ee907562bd0857b6ac734ab285"
+checksum = "e52310197d971b0f5be7fe6b57530dcd27beb35c1b013f29d66c1ad73fbbcc45"
 dependencies = [
  "avif-serialize",
  "imgref",
@@ -2294,6 +2271,18 @@ version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "20675572f6f24e9e76ef639bc5552774ed45f1c30e2951e1e99c59888861c539"
 
+[[package]]
+name = "raw-window-metal"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "40d213455a5f1dc59214213c7330e074ddf8114c9a42411eb890c767357ce135"
+dependencies = [
+ "objc2 0.6.4",
+ "objc2-core-foundation",
+ "objc2-foundation 0.3.2",
+ "objc2-quartz-core 0.3.2",
+]
+
 [[package]]
 name = "rayon"
 version = "1.11.0"
@@ -2314,16 +2303,6 @@ dependencies = [
  "crossbeam-utils",
 ]
 
-[[package]]
-name = "read-fonts"
-version = "0.36.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5eaa2941a4c05443ee3a7b26ab076a553c343ad5995230cc2b1d3e993bdc6345"
-dependencies = [
- "bytemuck",
- "font-types 0.10.1",
-]
-
 [[package]]
 name = "read-fonts"
 version = "0.41.0"
@@ -2331,7 +2310,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "046a7d674daf459825b32f5062056d6882db0d2f5a479fbd76ccfc870ac18709"
 dependencies = [
  "bytemuck",
- "font-types 0.12.4",
+ "font-types",
  "once_cell",
 ]
 
@@ -2506,16 +2485,6 @@ dependencies = [
  "quote",
 ]
 
-[[package]]
-name = "skrifa"
-version = "0.39.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9c9eb0b904a04d09bd68c65d946617b8ff733009999050f3b851c32fb3cfb60e"
-dependencies = [
- "bytemuck",
- "read-fonts 0.36.0",
-]
-
 [[package]]
 name = "skrifa"
 version = "0.44.0"
@@ -2523,7 +2492,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "819ab7d62b1d3e72d9d9dea5650bac30424f9111364bb94928dbf5ecad1baa68"
 dependencies = [
  "bytemuck",
- "read-fonts 0.41.0",
+ "read-fonts",
 ]
 
 [[package]]
@@ -2583,9 +2552,9 @@ dependencies = [
 
 [[package]]
 name = "spirv"
-version = "0.3.0+sdk-1.3.268.0"
+version = "0.4.0+sdk-1.4.341.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eda41003dc44290527a59b13432d4a0379379fa074b70174882adfbdfd917844"
+checksum = "d9571ea910ebd84c86af4b3ed27f9dbdc6ad06f17c5f96146b2b671e2976744f"
 dependencies = [
  "bitflags 2.10.0",
 ]
@@ -2614,7 +2583,7 @@ version = "0.2.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6c2499c2d826531388872b2268718aed907a39bd785ab0dcfe57fab26283f92e"
 dependencies = [
- "skrifa 0.39.0",
+ "skrifa",
  "yazi",
  "zeno",
 ]
@@ -2703,16 +2672,16 @@ dependencies = [
 
 [[package]]
 name = "tiff"
-version = "0.10.3"
+version = "0.11.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "af9605de7fee8d9551863fd692cce7637f548dbd9db9180fcc07ccc6d26c336f"
+checksum = "b63feaf3343d35b6ca4d50483f94843803b0f51634937cc2ec519fc32232bc52"
 dependencies = [
  "fax",
  "flate2",
  "half",
  "quick-error",
  "weezl",
- "zune-jpeg 0.4.21",
+ "zune-jpeg",
 ]
 
 [[package]]
@@ -2885,9 +2854,9 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen"
-version = "0.2.106"
+version = "0.2.128"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0d759f433fa64a2d763d1340820e46e111a7a5ab75f993d1852d70b03dbb80fd"
+checksum = "aecb87a33d3b0c5e3b7aa46336eaf486cffafbd281b195e4c8b80d50df2351bf"
 dependencies = [
  "cfg-if",
  "once_cell",
@@ -2898,22 +2867,19 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-futures"
-version = "0.4.56"
+version = "0.4.78"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "836d9622d604feee9e5de25ac10e3ea5f2d65b41eac0d9ce72eb5deae707ce7c"
+checksum = "6ef4c5d3d2cdf5c54f4231181768f5510842e350db025faf1f7163b1030ed928"
 dependencies = [
- "cfg-if",
  "js-sys",
- "once_cell",
  "wasm-bindgen",
- "web-sys",
 ]
 
 [[package]]
 name = "wasm-bindgen-macro"
-version = "0.2.106"
+version = "0.2.128"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "48cb0d2638f8baedbc542ed444afc0644a29166f1595371af4fecf8ce1e7eeb3"
+checksum = "a690d511e3c1a8b3a55e33511e3c2c00c78415cd23650f32b808627f5696b9ed"
 dependencies = [
  "quote",
  "wasm-bindgen-macro-support",
@@ -2921,22 +2887,22 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-macro-support"
-version = "0.2.106"
+version = "0.2.128"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cefb59d5cd5f92d9dcf80e4683949f15ca4b511f4ac0a6e14d4e1ac60c6ecd40"
+checksum = "411e4887f0071ef2d2164a9d5fdf2d20efbef78fccd3a78b0c10a1dc5295e48a"
 dependencies = [
  "bumpalo",
  "proc-macro2",
  "quote",
- "syn 2.0.113",
+ "syn 3.0.5",
  "wasm-bindgen-shared",
 ]
 
 [[package]]
 name = "wasm-bindgen-shared"
-version = "0.2.106"
+version = "0.2.128"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cbc538057e648b67f72a982e708d485b2efa771e1ac05fec311f9f63e5800db4"
+checksum = "81941cd78d0c92026c33e5e01312845a4cb1e9af3407f9134b100dd03144103e"
 dependencies = [
  "unicode-ident",
 ]
@@ -3052,9 +3018,9 @@ dependencies = [
 
 [[package]]
 name = "web-sys"
-version = "0.3.83"
+version = "0.3.105"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9b32828d774c412041098d182a8b38b16ea816958e07cf40eec2bc080ae137ac"
+checksum = "9fbddc4a036f00ec4f18c83445bd3115cb306a91da554919a099d9222fe4a7f8"
 dependencies = [
  "js-sys",
  "wasm-bindgen",
@@ -3078,9 +3044,9 @@ checksum = "a28ac98ddc8b9274cb41bb4d9d4d5c425b6020c50c46f25559911905610b4a88"
 
 [[package]]
 name = "wgpu"
-version = "28.0.0"
+version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f9cb534d5ffd109c7d1135f34cdae29e60eab94855a625dcfe1705f8bc7ad79f"
+checksum = "527ccdf43dd5b2e8676eed9984ce00e2bbb0a1b85b70c1969dcb6cd2eb55ab9e"
 dependencies = [
  "arrayvec",
  "bitflags 2.10.0",
@@ -3088,7 +3054,7 @@ dependencies = [
  "cfg-if",
  "cfg_aliases",
  "document-features",
- "hashbrown 0.16.1",
+ "hashbrown 0.17.1",
  "js-sys",
  "log",
  "naga",
@@ -3108,9 +3074,9 @@ dependencies = [
 
 [[package]]
 name = "wgpu-core"
-version = "28.0.0"
+version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8bb4c8b5db5f00e56f1f08869d870a0dff7c8bc7ebc01091fec140b0cf0211a9"
+checksum = "14c018fce9b6270aa203c2fdd56f3cce996713534bd757e4ea58c8560b121f14"
 dependencies = [
  "arrayvec",
  "bit-set",
@@ -3119,10 +3085,11 @@ dependencies = [
  "bytemuck",
  "cfg_aliases",
  "document-features",
- "hashbrown 0.16.1",
+ "hashbrown 0.17.1",
  "indexmap",
  "log",
  "naga",
+ "naga-types",
  "once_cell",
  "parking_lot",
  "portable-atomic",
@@ -3135,66 +3102,70 @@ dependencies = [
  "wgpu-core-deps-emscripten",
  "wgpu-core-deps-windows-linux-android",
  "wgpu-hal",
+ "wgpu-naga-bridge",
  "wgpu-types",
 ]
 
 [[package]]
 name = "wgpu-core-deps-apple"
-version = "28.0.0"
+version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "87b7b696b918f337c486bf93142454080a32a37832ba8a31e4f48221890047da"
+checksum = "061f3d319a40d39d00b1ecc2c33b89fe21d4e6fe01859df3500a3a8ecccd6b68"
 dependencies = [
  "wgpu-hal",
 ]
 
 [[package]]
 name = "wgpu-core-deps-emscripten"
-version = "28.0.0"
+version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "34b251c331f84feac147de3c4aa3aa45112622a95dd7ee1b74384fa0458dbd79"
+checksum = "d98b86cf4abf524a902dd35f18ca6a3f08fc2ae9847c8f10b48e30491b1f0b86"
 dependencies = [
  "wgpu-hal",
 ]
 
 [[package]]
 name = "wgpu-core-deps-windows-linux-android"
-version = "28.0.0"
+version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "68ca976e72b2c9964eb243e281f6ce7f14a514e409920920dcda12ae40febaae"
+checksum = "7586165fd5f6d881cb9ce4bb71f40d6caab2c0f1837e3fc1d9788a197fb6004f"
 dependencies = [
  "wgpu-hal",
 ]
 
 [[package]]
 name = "wgpu-hal"
-version = "28.0.0"
+version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "293080d77fdd14d6b08a67c5487dfddbf874534bb7921526db56a7b75d7e3bef"
+checksum = "b6b7fb58561a792bc237628ba0792e332de418fefe145f13b5ed8201e6d52f58"
 dependencies = [
  "android_system_properties",
  "arrayvec",
  "ash",
  "bit-set",
  "bitflags 2.10.0",
- "block",
+ "block2 0.6.2",
  "bytemuck",
  "cfg-if",
  "cfg_aliases",
- "core-graphics-types 0.2.0",
  "glow",
  "glutin_wgl_sys",
  "gpu-allocator",
- "gpu-descriptor",
+ "hashbrown 0.17.1",
- "hashbrown 0.16.1",
  "js-sys",
  "khronos-egl",
  "libc",
  "libloading",
  "log",
- "metal",
  "naga",
+ "naga-types",
  "ndk-sys",
- "objc",
+ "objc2 0.6.4",
+ "objc2-core-foundation",
+ "objc2-core-graphics",
+ "objc2-foundation 0.3.2",
+ "objc2-metal 0.3.2",
+ "objc2-quartz-core 0.3.2",
  "once_cell",
  "ordered-float",
  "parking_lot",
@@ -3203,26 +3174,44 @@ dependencies = [
  "profiling",
  "range-alloc",
  "raw-window-handle",
+ "raw-window-metal",
  "renderdoc-sys",
  "smallvec",
+ "static_assertions",
  "thiserror 2.0.17",
  "wasm-bindgen",
+ "wayland-sys",
  "web-sys",
+ "wgpu-naga-bridge",
  "wgpu-types",
  "windows",
  "windows-core",
+ "windows-result",
+]
+
+[[package]]
+name = "wgpu-naga-bridge"
+version = "30.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d2f62e73117bb7a62bfd9c5a5841438a823f6566c6442a808ee269d2d055c081"
+dependencies = [
+ "naga",
+ "wgpu-types",
 ]
 
 [[package]]
 name = "wgpu-types"
-version = "28.0.0"
+version = "30.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e18308757e594ed2cd27dddbb16a139c42a683819d32a2e0b1b0167552f5840c"
+checksum = "99dad6f1fbdbbdb4c278a6508b059d44688f5cebddf78d005a46a31340269286"
 dependencies = [
  "bitflags 2.10.0",
  "bytemuck",
  "js-sys",
  "log",
+ "naga-types",
+ "raw-window-handle",
+ "static_assertions",
  "web-sys",
 ]
 
@@ -3586,12 +3575,12 @@ dependencies = [
  "android-activity",
  "atomic-waker",
  "bitflags 2.10.0",
- "block2",
+ "block2 0.5.1",
  "bytemuck",
  "calloop",
  "cfg_aliases",
  "concurrent-queue",
- "core-foundation 0.9.4",
+ "core-foundation",
  "core-graphics",
  "cursor-icon",
  "dpi",
@@ -3858,12 +3847,6 @@ dependencies = [
  "syn 3.0.5",
 ]
 
-[[package]]
-name = "zune-core"
-version = "0.4.12"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3f423a2c17029964870cfaabb1f13dfab7d092a62a29a89264f4d36990ca414a"
-
 [[package]]
 name = "zune-core"
 version = "0.5.0"
@@ -3879,20 +3862,11 @@ dependencies = [
  "simd-adler32",
 ]
 
-[[package]]
-name = "zune-jpeg"
-version = "0.4.21"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "29ce2c8a9384ad323cf564b67da86e21d3cfdff87908bc1223ed5c99bc792713"
-dependencies = [
- "zune-core 0.4.12",
-]
-
 [[package]]
 name = "zune-jpeg"
 version = "0.5.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e35aee689668bf9bd6f6f3a6c60bb29ba1244b3b43adfd50edd554a371da37d5"
 dependencies = [
- "zune-core 0.5.0",
+ "zune-core",
 ]

Cargo.toml

@@ -29,9 +29,9 @@ edition = "2024"
 [workspace.dependencies]
 pollster = "0.4.0"
 winit = "0.30.12"
-wgpu = "28.0.0"
+wgpu = "30.0.1"
 bytemuck = "1.23.1"
-image = "0.25.6"
+image = "0.25.10"
 parley = "0.11.1"
 swash = "0.2.10"
 fxhash = "0.2.1"

core/src/render/mod.rs

@@ -186,8 +186,8 @@ impl UiRenderNode {
         for source in &registry.sources()[self.primitives.len()..] {
             let render = (source.render)(device, queue);
             let data_layout = Self::data_layout(device, source.stride);
-            let mut groups = vec![&self.shared_layout, &data_layout];
+            let mut groups = vec![Some(&self.shared_layout), Some(&data_layout)];
-            groups.extend(render.layout());
+            groups.extend(render.layout().map(Some));
             let layout = device.create_pipeline_layout(&PipelineLayoutDescriptor {
                 label: Some(source.label),
                 bind_group_layouts: &groups,
@@ -219,7 +219,7 @@ impl UiRenderNode {
             vertex: VertexState {
                 module: &module,
                 entry_point: Some("vs_main"),
-                buffers: &[PrimitiveInstance::desc()],
+                buffers: &[Some(PrimitiveInstance::desc())],
                 compilation_options: Default::default(),
             },
             fragment: Some(FragmentState {

src/default/render.rs

@@ -22,7 +22,20 @@ impl UiRenderer {
     }
 
     pub fn draw(&mut self) {
-        let output = self.surface.get_current_texture().unwrap();
+        let output = match self.surface.get_current_texture() {
+            CurrentSurfaceTexture::Success(texture) => texture,
+            CurrentSurfaceTexture::Suboptimal(texture) => {
+                self.surface.configure(&self.device, &self.config);
+                texture
+            }
+            CurrentSurfaceTexture::Outdated | CurrentSurfaceTexture::Lost => {
+                self.surface.configure(&self.device, &self.config);
+                return;
+            }
+            CurrentSurfaceTexture::Timeout
+            | CurrentSurfaceTexture::Occluded
+            | CurrentSurfaceTexture::Validation => return,
+        };
         let view = output
             .texture
             .create_view(&TextureViewDescriptor::default());
@@ -46,7 +59,7 @@ impl UiRenderer {
 
         self.queue.submit(std::iter::once(encoder.finish()));
         self.window.pre_present_notify();
-        output.present();
+        self.queue.present(output);
     }
 
     pub fn resize(&mut self, size: &PhysicalSize<u32>) {
@@ -65,9 +78,10 @@ impl UiRenderer {
     pub fn new(window: Arc<Window>) -> Self {
         let size = window.inner_size();
 
-        let instance = Instance::new(&InstanceDescriptor {
+        let instance = Instance::new(InstanceDescriptor {
             backends: Backends::PRIMARY,
-            ..Default::default()
+            display: Some(Box::new(window.clone())),
+            ..InstanceDescriptor::new_without_display_handle()
         });
 
         let surface = instance
@@ -79,6 +93,7 @@ impl UiRenderer {
                 power_preference: PowerPreference::default(),
                 compatible_surface: Some(&surface),
                 force_fallback_adapter: false,
+                apply_limit_buckets: false,
             })
             .block_on()
             .expect("Could not get adapter!");
@@ -105,6 +120,7 @@ impl UiRenderer {
         let config = SurfaceConfiguration {
             usage: TextureUsages::RENDER_ATTACHMENT,
             format: surface_format,
+            color_space: SurfaceColorSpace::Auto,
             width: size.width,
             height: size.height,
             present_mode: PresentMode::AutoVsync,

src/default/sense.rs

@@ -4,14 +4,14 @@ use std::{
     rc::Rc,
 };
 
-#[derive(Clone, Copy, PartialEq)]
+#[derive(Debug, Clone, Copy, PartialEq)]
 pub enum CursorButton {
     Left,
     Right,
     Middle,
 }
 
-#[derive(Clone, Copy, PartialEq)]
+#[derive(Debug, Clone, Copy, PartialEq)]
 pub enum CursorSense {
     PressStart(CursorButton),
     Pressing(CursorButton),
@@ -205,6 +205,19 @@ impl SensorUi for UiRenderState {
                 }
                 hovered_here |= over;
 
+                // Momentary input belongs to whatever the cursor is on. A
+                // widget it has just left still hears its hover ending, but
+                // a press landing elsewhere is neither its press to receive
+                // nor its press to take.
+                let cursor = match over {
+                    true => cursor.clone(),
+                    false => CursorState {
+                        pos: cursor.pos,
+                        exists: cursor.exists,
+                        ..Default::default()
+                    },
+                };
+
                 for senses in rsc.events_mut().get_type::<CursorSense>().registered(*id) {
                     for sense in senses.iter() {
                         if matches(sense, &cursor, sensor.hover) {
@@ -213,8 +226,6 @@ impl SensorUi for UiRenderState {
                     }
                 }
 
-                let cursor = cursor.clone();
-
                 let data = CursorData {
                     pos: cursor.pos - region.top_left,
                     size: region.bot_right - region.top_left,

tests/draw_cost.rs

@@ -4,20 +4,19 @@
 //!
 //!     cargo test --release --test draw_cost -- --ignored --nocapture
 //!
-//! **Read the instruction count, not the clock.** Wall time here swings by 2x
+//! Wall time is the wrong number to read for anything under a few percent --
-//! between runs of one binary on this machine -- more under `cargo test` than
+//! it varied by 2x between runs of one unchanged binary where instructions
-//! run directly -- while instructions retired are stable to 0.1%:
+//! retired varied by 0.1%. Count those instead:
 //!
 //!     perf stat -e instructions:u target/release/.../draw_cost-* --ignored
 //!
-//! Measured that way on 2026-09-13, drawing each primitive through its own
+//! That is how `PrimitiveRender` was measured against a match in the renderer:
-//! `PrimitiveRender` rather than a match in the renderer costs **6
+//! 6 instructions per list drawn, against the ~5,400 wgpu spends recording
-//! instructions per list drawn**, which is 0.1% of a frame at both 256 and
+//! one.
-//! 1024 layers. Recording one list into the pass costs wgpu ~5,400.
 //!
-//! The instance is leaked on purpose. Dropping the last one makes the Vulkan
+//! The instance is leaked deliberately. A Vulkan loader may unload the driver
-//! loader unload Mesa's ICD, which faults when a thread that touched Vulkan
+//! when the last one drops, which can fault as a thread that used it exits --
-//! exits -- and libtest runs every test on a spawned thread.
+//! and every test runs on a spawned thread.
 
 use std::time::Instant;
 
@@ -30,20 +29,20 @@ use wgpu::{Color as GpuColor, *};
 
 const SIZE: u32 = 1024;
 const FRAMES: u32 = 200;
-/// Reported as the best of this many batches. The mean moves by 15% between
+/// Reported as the best of this many batches, since the mean moves by more
-/// runs on this machine, which is more than the thing being measured.
+/// than the thing being measured.
 const BATCHES: u32 = 8;
 
 fn gpu() -> Option<(Device, Queue)> {
-    // Probed rather than assumed: this machine's Vulkan device comes and goes,
+    // Probed rather than assumed: there may be no Vulkan adapter, and GL is
-    // and GL is what is left when it is gone.
+    // what is left when there is not.
-    let all = Instance::new(&InstanceDescriptor::default());
+    let all = Instance::new(InstanceDescriptor::new_without_display_handle());
     let instance = match pollster::block_on(all.request_adapter(&RequestAdapterOptions::default()))
     {
         Ok(_) => all,
-        Err(_) => Instance::new(&InstanceDescriptor {
+        Err(_) => Instance::new(InstanceDescriptor {
             backends: Backends::GL,
-            ..Default::default()
+            ..InstanceDescriptor::new_without_display_handle()
         }),
     };
     // Leaked rather than dropped: see the note at the top of the file.
@@ -58,6 +57,7 @@ fn config(format: TextureFormat) -> SurfaceConfiguration {
     SurfaceConfiguration {
         usage: TextureUsages::RENDER_ATTACHMENT,
         format,
+        color_space: SurfaceColorSpace::Auto,
         width: SIZE,
         height: SIZE,
         present_mode: PresentMode::Fifo,

tests/pointer_routing.rs

@@ -1,9 +1,9 @@
-//! A widget takes only what it answers to: a button over a list takes the
+//! Input across layers: what a widget takes, what passes through it, and
-//! click and leaves the scroll. These drive `run_sensors` directly, which
+//! where hovering stops. These drive `run_sensors` directly, which needs no
-//! needs no GPU and no window.
+//! GPU and no window.
 
 use iris::prelude::*;
-use std::{cell::Cell, rc::Rc};
+use std::{cell::RefCell, rc::Rc};
 
 struct SenseRsc {
     ui: UiData,
@@ -41,140 +41,215 @@ impl HasEvents for SenseRsc {
     }
 }
 
-fn cursor_at(pos: Vec2) -> CursorState {
+const WINDOW: f32 = 100.0;
+
+/// Every sense that has fired on one widget since it was last read.
+#[derive(Default, Clone)]
+struct Fired(Rc<RefCell<Vec<CursorSense>>>);
+
+impl Fired {
+    fn take(&self) -> Vec<CursorSense> {
+        std::mem::take(&mut self.0.borrow_mut())
+    }
+}
+
+struct Ui {
+    rsc: SenseRsc,
+    render: UiRenderState,
+    state: (),
+}
+
+impl Ui {
+    fn new() -> Self {
+        Self {
+            rsc: SenseRsc {
+                ui: UiData::default(),
+                events: EventManager::default(),
+            },
+            render: UiRenderState::new(),
+            state: (),
+        }
+    }
+
+    fn listen<W: Widget + ?core::marker::Sized + 'static>(
+        &mut self,
+        widget: &StrongWidget<W>,
+        senses: impl Into<CursorSenses>,
+    ) -> Fired {
+        let fired = Fired::default();
+        let sink = fired.clone();
+        self.rsc
+            .register_event(widget.weak(), senses.into(), move |ctx, _rsc| {
+                sink.0.borrow_mut().push(ctx.data.sense)
+            });
+        fired
+    }
+
+    /// Stacks the widgets bottom first, each on its own layer, and lays them
+    /// out in a square window.
+    fn stack(&mut self, children: Vec<StrongWidget>) {
+        let root = self
+            .rsc
+            .ui
+            .widgets
+            .add_strong(Stack {
+                children,
+                size: StackSize::default(),
+            })
+            .any();
+        self.render.resize((WINDOW, WINDOW));
+        self.render.update(&root, &mut self.rsc);
+    }
+
+    fn cursor(&mut self, at: (f32, f32)) -> CursorState {
         CursorState {
-        pos,
+            pos: at.into(),
             exists: true,
             buttons: Default::default(),
             scroll_delta: Vec2::ZERO,
         }
+    }
+
+    fn run(&mut self, cursor: CursorState) {
+        self.render.run_sensors(
+            &mut self.rsc,
+            &mut self.state,
+            cursor,
+            (WINDOW, WINDOW).into(),
+        );
+    }
 }
 
-/// A button covering a list, on the layer above it: the list scrolls, the
+fn full(ui: &mut Ui) -> StrongWidget<Rect> {
-/// button clicks, and the returned flags say which fired.
+    rect(UiColor::WHITE).add_strong(&mut ui.rsc)
-fn button_over_list() -> (UiRenderState, SenseRsc, Rc<Cell<bool>>, Rc<Cell<bool>>) {
-    let mut rsc = SenseRsc {
-        ui: UiData::default(),
-        events: EventManager::default(),
-    };
-
-    // Both cover the whole window: the button "sitting over" the list.
-    let list = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
-    let list_weak = list.weak();
-    let button = rsc.ui.widgets.add_strong(Rect::new(UiColor::RED));
-    let button_weak = button.weak();
-
-    let scrolled = Rc::new(Cell::new(false));
-    let clicked = Rc::new(Cell::new(false));
-    {
-        let scrolled = scrolled.clone();
-        rsc.register_event(list_weak, CursorSense::Scroll, move |_ctx, _rsc| {
-            scrolled.set(true);
-        });
-    }
-    {
-        let clicked = clicked.clone();
-        rsc.register_event(button_weak, CursorSense::click(), move |_ctx, _rsc| {
-            clicked.set(true);
-        });
-    }
-
-    // A Stack draws each child on its own layer, in order.
-    let root = rsc
-        .ui
-        .widgets
-        .add_strong(Stack {
-            children: vec![list.any(), button.any()],
-            size: StackSize::default(),
-        })
-        .any();
-
-    let mut render = UiRenderState::new();
-    render.resize((100.0, 100.0));
-    render.update(&root, &mut rsc);
-
-    (render, rsc, scrolled, clicked)
 }
 
 #[test]
-fn a_button_over_a_list_scrolls_the_list_and_still_clicks() {
+fn hover_stops_at_the_topmost_widget() {
-    let (render, mut rsc, scrolled, clicked) = button_over_list();
+    let mut ui = Ui::new();
-    let mut state = ();
+    let (bottom, middle, top) = (full(&mut ui), full(&mut ui), full(&mut ui));
+    let bottom_hover = ui.listen(&bottom, CursorSense::HoverStart);
+    let middle_hover = ui.listen(&middle, CursorSense::HoverStart);
+    let top_hover = ui.listen(&top, CursorSense::HoverStart);
+    ui.stack(vec![bottom.any(), middle.any(), top.any()]);
 
-    let mut scroll = cursor_at((50.0, 50.0).into());
+    let cursor = ui.cursor((50.0, 50.0));
-    scroll.scroll_delta = (0.0, 10.0).into();
+    ui.run(cursor);
-    render.run_sensors(&mut rsc, &mut state, scroll, (100.0, 100.0).into());
 
-    assert!(
+    assert_eq!(top_hover.take(), [CursorSense::HoverStart]);
-        scrolled.get(),
+    assert_eq!(
-        "a scroll over the button must still reach the list underneath it"
+        middle_hover.take(),
-    );
+        [],
-    assert!(
+        "hover is not shared with a layer below"
-        !clicked.get(),
-        "a scroll is not a click; the button must not have fired"
     );
+    assert_eq!(bottom_hover.take(), []);
+}
 
-    let mut click = cursor_at((50.0, 50.0).into());
+#[test]
-    click.buttons.left = ActivationState::Start;
+fn a_scroll_passes_through_every_widget_that_does_not_want_it() {
-    render.run_sensors(&mut rsc, &mut state, click, (100.0, 100.0).into());
+    let mut ui = Ui::new();
+    let (list, button, overlay) = (full(&mut ui), full(&mut ui), full(&mut ui));
+    let scrolled = ui.listen(&list, CursorSense::Scroll);
+    let clicked = ui.listen(&button, CursorSense::click());
+    let overlay_clicked = ui.listen(&overlay, CursorSense::click());
+    ui.stack(vec![list.any(), button.any(), overlay.any()]);
 
-    assert!(
+    let mut cursor = ui.cursor((50.0, 50.0));
-        clicked.get(),
+    cursor.scroll_delta = (0.0, 10.0).into();
-        "the button on top must still receive an actual click"
+    ui.run(cursor);
+
+    assert_eq!(
+        scrolled.take(),
+        [CursorSense::Scroll],
+        "two layers of click-only widgets do not stop a scroll"
     );
+    assert_eq!(clicked.take(), []);
+    assert_eq!(overlay_clicked.take(), []);
 }
 
 #[test]
 fn a_click_and_a_scroll_in_one_frame_go_to_different_widgets() {
-    let (render, mut rsc, scrolled, clicked) = button_over_list();
+    let mut ui = Ui::new();
-    let mut state = ();
+    let (list, button) = (full(&mut ui), full(&mut ui));
+    let scrolled = ui.listen(&list, CursorSense::Scroll);
+    let clicked = ui.listen(&button, CursorSense::click());
+    ui.stack(vec![list.any(), button.any()]);
 
-    let mut both = cursor_at((50.0, 50.0).into());
+    let mut cursor = ui.cursor((50.0, 50.0));
-    both.scroll_delta = (0.0, 10.0).into();
+    cursor.scroll_delta = (0.0, 10.0).into();
-    both.buttons.left = ActivationState::Start;
+    cursor.buttons.left = ActivationState::Start;
-    render.run_sensors(&mut rsc, &mut state, both, (100.0, 100.0).into());
+    ui.run(cursor);
 
-    assert!(
+    assert_eq!(clicked.take(), [CursorSense::click()]);
-        clicked.get(),
+    assert_eq!(
-        "the button takes the click it registered for"
+        scrolled.take(),
-    );
+        [CursorSense::Scroll],
-    assert!(
-        scrolled.get(),
         "taking the click must not take the scroll with it"
     );
 }
 
 #[test]
-fn leaving_a_widget_still_ends_its_hover() {
+fn only_the_topmost_listener_takes_a_press() {
-    let mut rsc = SenseRsc {
+    let mut ui = Ui::new();
-        ui: UiData::default(),
+    let (below, above) = (full(&mut ui), full(&mut ui));
-        events: EventManager::default(),
+    let below_clicked = ui.listen(&below, CursorSense::click());
-    };
+    let above_clicked = ui.listen(&above, CursorSense::click());
-    let widget = rsc.ui.widgets.add_strong(Rect::new(UiColor::WHITE));
+    ui.stack(vec![below.any(), above.any()]);
-    let ended = Rc::new(Cell::new(false));
-    {
-        let ended = ended.clone();
-        rsc.register_event(widget.weak(), CursorSense::HoverEnd, move |_ctx, _rsc| {
-            ended.set(true);
-        });
-    }
 
-    let root = widget.any();
+    let mut cursor = ui.cursor((50.0, 50.0));
-    let mut render = UiRenderState::new();
+    cursor.buttons.left = ActivationState::Start;
-    render.resize((100.0, 100.0));
+    ui.run(cursor);
-    render.update(&root, &mut rsc);
 
-    let mut state = ();
+    assert_eq!(above_clicked.take(), [CursorSense::click()]);
-    render.run_sensors(
+    assert_eq!(below_clicked.take(), [], "one press goes to one widget");
-        &mut rsc,
+}
-        &mut state,
+
-        cursor_at((50.0, 50.0).into()),
+#[test]
-        (100.0, 100.0).into(),
+fn a_press_beside_the_button_reaches_the_layer_below() {
+    let mut ui = Ui::new();
+    let list = full(&mut ui);
+    // The row above the list covers it, but only its left half is the button.
+    let button = full(&mut ui);
+    let gap = full(&mut ui);
+    let list_clicked = ui.listen(&list, CursorSense::click());
+    let button_clicked = ui.listen(&button, CursorSense::click());
+    let row = ui.rsc.ui.widgets.add_strong(Span {
+        children: vec![button.any(), gap.any()],
+        dir: Dir::RIGHT,
+        gap: 0.0,
+    });
+    ui.stack(vec![list.any(), row.any()]);
+
+    let mut on_button = ui.cursor((20.0, 50.0));
+    on_button.buttons.left = ActivationState::Start;
+    ui.run(on_button);
+    assert_eq!(button_clicked.take(), [CursorSense::click()]);
+    assert_eq!(list_clicked.take(), []);
+
+    let mut beside_it = ui.cursor((80.0, 50.0));
+    beside_it.buttons.left = ActivationState::Start;
+    ui.run(beside_it);
+    assert_eq!(button_clicked.take(), [], "the cursor is not on the button");
+    assert_eq!(
+        list_clicked.take(),
+        [CursorSense::click()],
+        "a press beside the button belongs to what is under it"
     );
-    assert!(!ended.get(), "the cursor is still on it");
+}
+
+#[test]
+fn leaving_a_widget_still_ends_its_hover() {
+    let mut ui = Ui::new();
+    let widget = full(&mut ui);
+    let hover = ui.listen(&widget, CursorSense::HoverStart | CursorSense::HoverEnd);
+    ui.stack(vec![widget.any()]);
+
+    let cursor = ui.cursor((50.0, 50.0));
+    ui.run(cursor);
+    assert_eq!(hover.take(), [CursorSense::HoverStart]);
 
-    let mut gone = cursor_at((50.0, 50.0).into());
+    let mut gone = ui.cursor((50.0, 50.0));
     gone.exists = false;
-    render.run_sensors(&mut rsc, &mut state, gone, (100.0, 100.0).into());
+    ui.run(gone);
-    assert!(ended.get(), "leaving a widget ends its hover");
+    assert_eq!(hover.take(), [CursorSense::HoverEnd]);
 }