diff --git a/Cargo.lock b/Cargo.lock
index 2755d5d..4cb46d6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -21,10 +21,10 @@ dependencies = [
 ]
 
 [[package]]
-name = "android_glue"
-version = "0.2.3"
+name = "android_log-sys"
+version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "000444226fcff248f2bc4c7625be32c63caccfecc2723a2b9f78a7487a49c407"
+checksum = "b8052e2d8aabbb8d556d6abbcce2a22b9590996c5f849b9c7ce4544a2e3b984e"
 
 [[package]]
 name = "ansi_term"
@@ -56,7 +56,7 @@ version = "0.30.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "69daec0742947f33a85931fa3cb0ce5f07929159dcbd1f0cbb5b2912e2978509"
 dependencies = [
- "libloading",
+ "libloading 0.5.2",
 ]
 
 [[package]]
@@ -116,9 +116,9 @@ dependencies = [
 
 [[package]]
 name = "cc"
-version = "1.0.50"
+version = "1.0.54"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "95e28fa049fda1c330bcf9d723be7663a899c4679724b34c81e9f5a326aab8cd"
+checksum = "7bbb73db36c1246e9034e307d0fba23f9a2e251faa47ade70c1bd252220c8311"
 
 [[package]]
 name = "cfg-if"
@@ -152,9 +152,9 @@ dependencies = [
 
 [[package]]
 name = "cocoa"
-version = "0.19.1"
+version = "0.20.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f29f7768b2d1be17b96158e3285951d366b40211320fb30826a76cb7a0da6400"
+checksum = "8f7b6f3f7f4f0b3ec5c5039aaa9e8c3cef97a7a480a400fd62944841314f293d"
 dependencies = [
  "bitflags",
  "block",
@@ -167,9 +167,9 @@ dependencies = [
 
 [[package]]
 name = "core-foundation"
-version = "0.6.4"
+version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "25b9e03f145fd4f2bf705e07b900cd41fc636598fe5dc452fd0db1441c3f496d"
+checksum = "57d24c7a13c43e870e37c1556b74555437870a04514f7685f5b354e090567171"
 dependencies = [
  "core-foundation-sys",
  "libc",
@@ -177,15 +177,15 @@ dependencies = [
 
 [[package]]
 name = "core-foundation-sys"
-version = "0.6.2"
+version = "0.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e7ca8a5221364ef15ce201e8ed2f609fc312682a8f4e0e3d4aa5879764e0fa3b"
+checksum = "b3a71ab494c0b5b860bdc8407ae08978052417070c2ced38573a9157ad75b8ac"
 
 [[package]]
 name = "core-graphics"
-version = "0.17.3"
+version = "0.19.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "56790968ab1c8a1202a102e6de05fc6e1ec87da99e4e93e9a7d13efbfc1e95a9"
+checksum = "59e78b2e0aaf43f08e7ae0d6bc96895ef72ff0921c7d4ff4762201b2dba376dd"
 dependencies = [
  "bitflags",
  "core-foundation",
@@ -195,9 +195,9 @@ dependencies = [
 
 [[package]]
 name = "core-video-sys"
-version = "0.1.3"
+version = "0.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8dc065219542086f72d1e9f7aadbbab0989e980263695d129d502082d063a9d0"
+checksum = "34ecad23610ad9757664d644e369246edde1803fcb43ed72876565098a5d3828"
 dependencies = [
  "cfg-if",
  "core-foundation-sys",
@@ -225,6 +225,17 @@ dependencies = [
  "byteorder",
 ]
 
+[[package]]
+name = "derivative"
+version = "2.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cb582b60359da160a9477ee80f15c8d784c477e69c217ef2cdd4169c24ea380f"
+dependencies = [
+ "proc-macro2 1.0.18",
+ "quote 1.0.7",
+ "syn",
+]
+
 [[package]]
 name = "dispatch"
 version = "0.2.0"
@@ -233,11 +244,11 @@ checksum = "bd0c93bb4b0c6d9b77f4435b0ae98c24d17f1c45b2ff844c6151a07256ca923b"
 
 [[package]]
 name = "dlib"
-version = "0.4.1"
+version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "77e51249a9d823a4cb79e3eca6dcd756153e8ed0157b6c04775d04bf1b13b76a"
+checksum = "b11f15d1e3268f140f68d390637d5e76d849782d971ae7063e0da69fe9709a76"
 dependencies = [
- "libloading",
+ "libloading 0.6.2",
 ]
 
 [[package]]
@@ -290,9 +301,9 @@ dependencies = [
 
 [[package]]
 name = "half"
-version = "1.5.0"
+version = "1.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f36b5f248235f45773d4944f555f83ea61fe07b18b561ccf99d7483d7381e54d"
+checksum = "d36fab90f82edc3c747f9d438e06cf0a491055896f2a279638bb5beed6c40177"
 
 [[package]]
 name = "hermit-abi"
@@ -314,9 +325,9 @@ dependencies = [
 
 [[package]]
 name = "instant"
-version = "0.1.3"
+version = "0.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f7152d2aed88aa566e7a342250f21ba2222c1ae230ad577499dbfa3c18475b80"
+checksum = "7777a24a1ce5de49fcdde84ec46efa487c3af49d5b6e6e0a50367cc5c1096182"
 
 [[package]]
 name = "iovec"
@@ -327,6 +338,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "jni-sys"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8eaf4bc02d17cbdd7ff4c7438cafcdf7fb9a4613313ad11b4f8fefe7d3fa0130"
+
 [[package]]
 name = "kernel32-sys"
 version = "0.2.2"
@@ -339,9 +356,9 @@ dependencies = [
 
 [[package]]
 name = "kurbo"
-version = "0.6.0"
+version = "0.6.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5657aca5a36917d389d717f1a0c24d5ebcee5551fda8c1f555af597565d408e4"
+checksum = "2520c9c9010461ec2b4573599bca458272319a314fd0b9476cacfcb9b6e5adc8"
 dependencies = [
  "arrayvec",
 ]
@@ -360,9 +377,9 @@ checksum = "b294d6fa9ee409a054354afc4352b0b9ef7ca222c69b8812cbea9e7d2bf3783f"
 
 [[package]]
 name = "libc"
-version = "0.2.69"
+version = "0.2.71"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "99e85c08494b21a9054e7fe1374a732aeadaff3980b6990b94bfd3a70f690005"
+checksum = "9457b06509d27052635f90d6466700c65095fdf75409b3fbdd903e988b886f49"
 
 [[package]]
 name = "libloading"
@@ -374,6 +391,15 @@ dependencies = [
  "winapi 0.3.8",
 ]
 
+[[package]]
+name = "libloading"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2cadb8e769f070c45df05c78c7520eb4cd17061d4ab262e43cfc68b4d00ac71c"
+dependencies = [
+ "winapi 0.3.8",
+]
+
 [[package]]
 name = "line_drawing"
 version = "0.7.0"
@@ -469,6 +495,37 @@ dependencies = [
  "ws2_32-sys",
 ]
 
+[[package]]
+name = "ndk"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "95a356cafe20aee088789830bfea3a61336e84ded9e545e00d3869ce95dcb80c"
+dependencies = [
+ "jni-sys",
+ "ndk-sys",
+ "num_enum",
+]
+
+[[package]]
+name = "ndk-glue"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d1730ee2e3de41c3321160a6da815f008c4006d71b095880ea50e17cf52332b8"
+dependencies = [
+ "android_log-sys",
+ "lazy_static",
+ "libc",
+ "log",
+ "ndk",
+ "ndk-sys",
+]
+
+[[package]]
+name = "ndk-sys"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2b2820aca934aba5ed91c79acc72b6a44048ceacc5d36c035ed4e051f12d887d"
+
 [[package]]
 name = "net2"
 version = "0.2.34"
@@ -502,6 +559,28 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "num_enum"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ca565a7df06f3d4b485494f25ba05da1435950f4dc263440eda7a6fa9b8e36e4"
+dependencies = [
+ "derivative",
+ "num_enum_derive",
+]
+
+[[package]]
+name = "num_enum_derive"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ffa5a33ddddfee04c0283a7653987d634e880347e96b5b2ed64de07efb59db9d"
+dependencies = [
+ "proc-macro-crate",
+ "proc-macro2 1.0.18",
+ "quote 1.0.7",
+ "syn",
+]
+
 [[package]]
 name = "objc"
 version = "0.2.7"
@@ -513,9 +592,9 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.3.1"
+version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b1c601810575c99596d4afc46f78a678c80105117c379eb3650cf99b8a21ce5b"
+checksum = "0b631f7e854af39a1739f401cf34a8a013dfe09eac4fa4dba91e9768bd28168d"
 
 [[package]]
 name = "ordered-float"
@@ -583,8 +662,8 @@ dependencies = [
 name = "piet-gpu-derive"
 version = "0.0.0"
 dependencies = [
- "proc-macro2 1.0.10",
- "quote 1.0.3",
+ "proc-macro2 1.0.18",
+ "quote 1.0.7",
  "syn",
 ]
 
@@ -614,9 +693,9 @@ checksum = "05da548ad6865900e60eaba7f589cc0783590a92e940c26953ff81ddbab2d677"
 
 [[package]]
 name = "png"
-version = "0.16.2"
+version = "0.16.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "910f09135b1ed14bb16be445a8c23ddf0777eca485fbfc7cee00d81fecab158a"
+checksum = "12faa637ed9ae3d3c881332e54b5ae2dba81cda9fc4bbce0faa1ba53abcead50"
 dependencies = [
  "bitflags",
  "crc32fast",
@@ -626,9 +705,18 @@ dependencies = [
 
 [[package]]
 name = "ppv-lite86"
-version = "0.2.6"
+version = "0.2.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "74490b50b9fbe561ac330df47c08f3f33073d2d00c150f719147d7c54522fa1b"
+checksum = "237a5ed80e274dbc66f86bd59c1e25edc039660be53194b5fe0a482e0f2612ea"
+
+[[package]]
+name = "proc-macro-crate"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e10d4b51f154c8a7fb96fd6dad097cb74b863943ec010ac94b9fd1be8861fe1e"
+dependencies = [
+ "toml",
+]
 
 [[package]]
 name = "proc-macro2"
@@ -641,9 +729,9 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.10"
+version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "df246d292ff63439fea9bc8c0a270bed0e390d5ebd4db4ba15aba81111b5abe3"
+checksum = "beae6331a816b1f65d04c45b078fd8e6c93e8071771f41b8163255bbd8d7c8fa"
 dependencies = [
  "unicode-xid 0.2.0",
 ]
@@ -659,11 +747,11 @@ dependencies = [
 
 [[package]]
 name = "quote"
-version = "1.0.3"
+version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2bdc6c187c65bca4260c9011c9e3132efe4909da44726bad24cf7572ae338d7f"
+checksum = "aa563d17ecb180e500da1cfd2b028310ac758de548efdd203e18f283af693f37"
 dependencies = [
- "proc-macro2 1.0.10",
+ "proc-macro2 1.0.18",
 ]
 
 [[package]]
@@ -766,6 +854,12 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
 
+[[package]]
+name = "serde"
+version = "1.0.111"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c9124df5b40cbd380080b2cc6ab894c040a3070d995f5c9dc77e18c34a8ae37d"
+
 [[package]]
 name = "slab"
 version = "0.4.2"
@@ -811,12 +905,12 @@ checksum = "8ea5119cdb4c55b55d432abb513a0429384878c15dde60cc77b1c99de1a95a6a"
 
 [[package]]
 name = "syn"
-version = "1.0.17"
+version = "1.0.31"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0df0eb663f387145cab623dea85b09c2c5b4b0aef44e945d928e682fce71bb03"
+checksum = "b5304cfdf27365b7585c25d4af91b35016ed21ef88f17ced89c7093b43dba8b6"
 dependencies = [
- "proc-macro2 1.0.10",
- "quote 1.0.3",
+ "proc-macro2 1.0.18",
+ "quote 1.0.7",
  "unicode-xid 0.2.0",
 ]
 
@@ -829,6 +923,15 @@ dependencies = [
  "unicode-width",
 ]
 
+[[package]]
+name = "toml"
+version = "0.5.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ffc92d160b1eef40665be3a05630d003936a3bc7da7421277846c2613e92c71a"
+dependencies = [
+ "serde",
+]
+
 [[package]]
 name = "unicode-width"
 version = "0.1.7"
@@ -981,11 +1084,10 @@ checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
 
 [[package]]
 name = "winit"
-version = "0.22.1"
+version = "0.22.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fc53342d3d1a3d57f3949e0692d93d5a8adb7814d8683cef4a09c2b550e94246"
+checksum = "1e4ccbf7ddb6627828eace16cacde80fc6bf4dbb3469f88487262a02cf8e7862"
 dependencies = [
- "android_glue",
  "bitflags",
  "cocoa",
  "core-foundation",
@@ -998,6 +1100,9 @@ dependencies = [
  "log",
  "mio",
  "mio-extras",
+ "ndk",
+ "ndk-glue",
+ "ndk-sys",
  "objc",
  "parking_lot",
  "percent-encoding",
diff --git a/piet-gpu-hal/src/vulkan.rs b/piet-gpu-hal/src/vulkan.rs
index 29d4fd3..2fac015 100644
--- a/piet-gpu-hal/src/vulkan.rs
+++ b/piet-gpu-hal/src/vulkan.rs
@@ -1016,7 +1016,7 @@ unsafe fn choose_compute_device(
     devices: &[vk::PhysicalDevice],
     surface: Option<&VkSurface>,
 ) -> Option<(vk::PhysicalDevice, u32)> {
-    for pdevice in &devices[0..] {
+    for pdevice in devices {
         let props = instance.get_physical_device_queue_family_properties(*pdevice);
         for (ix, info) in props.iter().enumerate() {
             // Check for surface presentation support
diff --git a/piet-gpu/src/lib.rs b/piet-gpu/src/lib.rs
index 1e839d2..5813ed3 100644
--- a/piet-gpu/src/lib.rs
+++ b/piet-gpu/src/lib.rs
@@ -20,20 +20,12 @@ pub const HEIGHT: usize = TILE_H * HEIGHT_IN_TILES;
 const TILE_W: usize = 16;
 const TILE_H: usize = 16;
 
-const WIDTH_IN_TILEGROUPS: usize = 4;
-const HEIGHT_IN_TILEGROUPS: usize = 96;
-const TILEGROUP_STRIDE: usize = 2048;
-
 const WIDTH_IN_TILES: usize = 128;
 const HEIGHT_IN_TILES: usize = 96;
 const PTCL_INITIAL_ALLOC: usize = 1024;
 
-const K2_PER_TILE_SIZE: usize = 8;
-
 const N_CIRCLES: usize = 0;
 
-const N_WG: u32 = 16;
-
 pub fn render_svg(rc: &mut impl RenderContext, filename: &str, scale: f64) {
     let xml_str = std::fs::read_to_string(filename).unwrap();
     let start = std::time::Instant::now();
@@ -57,8 +49,8 @@ pub fn render_scene(rc: &mut impl RenderContext) {
         let circle = Circle::new(center, radius);
         rc.fill(circle, &color);
     }
-    let mut path = BezPath::new();
     /*
+    let mut path = BezPath::new();
     path.move_to((100.0, 1150.0));
     path.line_to((200.0, 1200.0));
     path.line_to((150.0, 1250.0));
diff --git a/piet-gpu/src/render_ctx.rs b/piet-gpu/src/render_ctx.rs
index f914a2e..c3e1dd7 100644
--- a/piet-gpu/src/render_ctx.rs
+++ b/piet-gpu/src/render_ctx.rs
@@ -1,10 +1,6 @@
 use std::borrow::Cow;
 
-use piet_gpu_types::encoder::{Encode, Encoder, Ref};
-use piet_gpu_types::scene;
-use piet_gpu_types::scene::{
-    Bbox, PietCircle, PietFill, PietItem, PietStrokePolyLine, SimpleGroup,
-};
+use piet_gpu_types::encoder::{Encode, Encoder};
 
 use piet_gpu_types::scene::{CubicSeg, Element, Fill, LineSeg, QuadSeg, SetLineWidth, Stroke};