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libghostty: simplify Wasm allocation API

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Replace a bunch of type-specific Wasm allocation functions with a generic
byte allocator and reusable opaque out-parameters for pointers. This
makes it a lot more ergonomic (relatively) to use the Wasm interface
and removes a dozen or so exports.

This also updates the `ghostty_type_json` `abi` field with a maximum
alignment value that host sides can use to keep every allocation aligned
properly, easily, without hardcoding numbers.

This adds a test to verify this all works as intended and runs in CI.
This commit is contained in:
Mitchell Hashimoto
2026-08-16 12:37:16 -07:00
parent 0ba6250388
commit a8e9b413f1
17 changed files with 481 additions and 243 deletions
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62
example/wasm-sgr/index.html
View File

@@ -106,6 +106,7 @@
<script>
let wasmInstance = null;
let wasmMemory = null;
let typeLayout = null;
async function loadWasm() {
try {
@@ -124,6 +125,12 @@
wasmInstance = wasmModule.instance;
wasmMemory = wasmInstance.exports.memory;
const jsonPtr = wasmInstance.exports.ghostty_type_json();
const jsonStr = new TextDecoder().decode(
new Uint8Array(wasmMemory.buffer, jsonPtr, wasmMemory.buffer.byteLength - jsonPtr)
).split('\0')[0];
typeLayout = JSON.parse(jsonStr);
return true;
} catch (e) {
@@ -252,18 +259,22 @@
throw new Error(`ghostty_sgr_new failed with result ${result}`);
}
const parserPtr = new DataView(getBuffer()).getUint32(parserPtrPtr, true);
const parserPtr = wasmInstance.exports.ghostty_wasm_take_opaque(parserPtrPtr);
wasmInstance.exports.ghostty_wasm_free_opaque(parserPtrPtr);
// Allocate and set parameters
const paramsPtr = wasmInstance.exports.ghostty_wasm_alloc_u16_array(params.length);
const paramsByteLength = params.length * Uint16Array.BYTES_PER_ELEMENT;
const paramsPtr = wasmInstance.exports.ghostty_wasm_alloc(paramsByteLength);
const paramsView = new Uint16Array(getBuffer(), paramsPtr, params.length);
params.forEach((p, i) => paramsView[i] = p);
// Allocate and set separators (or use null if empty)
let sepsPtr = 0;
const sepsByteLength = separators.length > 0 ? params.length : 0;
if (separators.length > 0) {
sepsPtr = wasmInstance.exports.ghostty_wasm_alloc_u8_array(separators.length);
const sepsView = new Uint8Array(getBuffer(), sepsPtr, separators.length);
sepsPtr = wasmInstance.exports.ghostty_wasm_alloc(sepsByteLength);
const sepsView = new Uint8Array(getBuffer(), sepsPtr, sepsByteLength);
sepsView.fill(0);
separators.forEach((s, i) => sepsView[i] = s.charCodeAt(0));
}
@@ -289,7 +300,8 @@
output += 'm\n\n';
// Iterate through attributes
const attrPtr = wasmInstance.exports.ghostty_wasm_alloc_sgr_attribute();
const attrSize = typeLayout.types.GhosttySgrAttribute.size;
const attrPtr = wasmInstance.exports.ghostty_wasm_alloc(attrSize);
let count = 0;
while (wasmInstance.exports.ghostty_sgr_next(parserPtr, attrPtr)) {
@@ -313,9 +325,9 @@
case SGR_ATTR_TAGS.DIRECT_COLOR_FG: {
// Use ghostty_color_rgb_get to extract RGB components
const rPtr = wasmInstance.exports.ghostty_wasm_alloc_u8();
const gPtr = wasmInstance.exports.ghostty_wasm_alloc_u8();
const bPtr = wasmInstance.exports.ghostty_wasm_alloc_u8();
const rPtr = wasmInstance.exports.ghostty_wasm_alloc(1);
const gPtr = wasmInstance.exports.ghostty_wasm_alloc(1);
const bPtr = wasmInstance.exports.ghostty_wasm_alloc(1);
wasmInstance.exports.ghostty_color_rgb_get(valuePtr, rPtr, gPtr, bPtr);
@@ -325,17 +337,17 @@
output += `Foreground RGB = (${r}, ${g}, ${b})\n`;
wasmInstance.exports.ghostty_wasm_free_u8(rPtr);
wasmInstance.exports.ghostty_wasm_free_u8(gPtr);
wasmInstance.exports.ghostty_wasm_free_u8(bPtr);
wasmInstance.exports.ghostty_wasm_free(rPtr, 1);
wasmInstance.exports.ghostty_wasm_free(gPtr, 1);
wasmInstance.exports.ghostty_wasm_free(bPtr, 1);
break;
}
case SGR_ATTR_TAGS.DIRECT_COLOR_BG: {
// Use ghostty_color_rgb_get to extract RGB components
const rPtr = wasmInstance.exports.ghostty_wasm_alloc_u8();
const gPtr = wasmInstance.exports.ghostty_wasm_alloc_u8();
const bPtr = wasmInstance.exports.ghostty_wasm_alloc_u8();
const rPtr = wasmInstance.exports.ghostty_wasm_alloc(1);
const gPtr = wasmInstance.exports.ghostty_wasm_alloc(1);
const bPtr = wasmInstance.exports.ghostty_wasm_alloc(1);
wasmInstance.exports.ghostty_color_rgb_get(valuePtr, rPtr, gPtr, bPtr);
@@ -345,17 +357,17 @@
output += `Background RGB = (${r}, ${g}, ${b})\n`;
wasmInstance.exports.ghostty_wasm_free_u8(rPtr);
wasmInstance.exports.ghostty_wasm_free_u8(gPtr);
wasmInstance.exports.ghostty_wasm_free_u8(bPtr);
wasmInstance.exports.ghostty_wasm_free(rPtr, 1);
wasmInstance.exports.ghostty_wasm_free(gPtr, 1);
wasmInstance.exports.ghostty_wasm_free(bPtr, 1);
break;
}
case SGR_ATTR_TAGS.UNDERLINE_COLOR: {
// Use ghostty_color_rgb_get to extract RGB components
const rPtr = wasmInstance.exports.ghostty_wasm_alloc_u8();
const gPtr = wasmInstance.exports.ghostty_wasm_alloc_u8();
const bPtr = wasmInstance.exports.ghostty_wasm_alloc_u8();
const rPtr = wasmInstance.exports.ghostty_wasm_alloc(1);
const gPtr = wasmInstance.exports.ghostty_wasm_alloc(1);
const bPtr = wasmInstance.exports.ghostty_wasm_alloc(1);
wasmInstance.exports.ghostty_color_rgb_get(valuePtr, rPtr, gPtr, bPtr);
@@ -365,9 +377,9 @@
output += `Underline color RGB = (${r}, ${g}, ${b})\n`;
wasmInstance.exports.ghostty_wasm_free_u8(rPtr);
wasmInstance.exports.ghostty_wasm_free_u8(gPtr);
wasmInstance.exports.ghostty_wasm_free_u8(bPtr);
wasmInstance.exports.ghostty_wasm_free(rPtr, 1);
wasmInstance.exports.ghostty_wasm_free(gPtr, 1);
wasmInstance.exports.ghostty_wasm_free(bPtr, 1);
break;
}
@@ -415,7 +427,9 @@
outputDiv.textContent = output;
// Cleanup
wasmInstance.exports.ghostty_wasm_free_sgr_attribute(attrPtr);
wasmInstance.exports.ghostty_wasm_free(attrPtr, attrSize);
wasmInstance.exports.ghostty_wasm_free(paramsPtr, paramsByteLength);
wasmInstance.exports.ghostty_wasm_free(sepsPtr, sepsByteLength);
wasmInstance.exports.ghostty_sgr_free(parserPtr);
} catch (e) {