Zero-cost table(view)

.github/actions/install-deps/action.yaml

@@ -90,10 +90,17 @@ runs:
           shell: bash
           run: echo "CMAKE_GENERATOR=Ninja" >> "$GITHUB_ENV"
 
+        - name: Use Node.js ${{ matrix.node-version }}
+          uses: actions/setup-node@v4
+          with:
+              node-version: ${{ matrix.node-version }}
+
         - name: Install pnpm
-          uses: pnpm/action-setup@v3
+          uses: pnpm/action-setup@v6
           with:
-              version: 9
+              version: 12
+              cache: true
+              cache_dependency_path: pnpm-lock.yaml
 
         # emsdk installs to `<workspace>/.emsdk` (`install_emsdk.mjs`), and
         # the emscripten sysroot libraries generated during the first build
@@ -166,13 +173,6 @@ runs:
         #       pip debug --verbose
         #   shell: bash
 
-        - name: Use Node.js ${{ matrix.node-version }}
-          uses: actions/setup-node@v4
-          with:
-              node-version: ${{ matrix.node-version }}
-              cache: "pnpm"
-              cache-dependency-path: pnpm-lock.yaml
-
         - name: Install rust
           uses: dtolnay/rust-toolchain@nightly
           if: ${{ inputs.rust == 'true' && inputs.arch != 'aarch64' }}

.github/workflows/build.yaml

@@ -559,7 +559,7 @@ jobs:
                   path: rust/perspective-python/perspective/widget/static
 
             - name: Python Build Pyodide
-              run: pnpm install && pnpm run build
+              run: pnpm install && node tools/scripts/install_emsdk.mjs && pnpm run build
               env:
                   PSP_PYODIDE: 1
                   PACKAGE: "python"

DEVELOPMENT.md

@@ -138,10 +138,10 @@ Deviating from this specific version of Emscripten specified in the project's
 `package.json` can introduce various errors that are extremely difficult to
 debug.
 
-To install a specific version of Emscripten (e.g. `4.0.9`):
+To install a specific version of Emscripten (e.g. `5.0.3`):
 
 ```bash
-./emsdk install 4.0.9
+./emsdk install 5.0.3
 ```
 
 Set `PSP_SKIP_EMSDK_INSTALL=1` to prevent `pnpm install` from downloading the
@@ -168,8 +168,7 @@ this within a virtual environment.
 
 To build for [Pyodide](https://pyodide.org/), select
 `perspective-python (pyodide)` in `pnpm run setup` and install the pinned
-Pyodide distribution with `pnpm run install_pyodide`. Pyodide builds use the
-separate `pyodide_emscripten` version pinned in `package.json`.
+Pyodide distribution with `pnpm run install_pyodide`.
 
 ### `perspective-jupyterlab`
 
@@ -288,9 +287,9 @@ tests are run with `PACKAGE=jupyterlab pnpm run test --jupyter`.
 
 Many UI tests compare against screenshot and DOM snapshots, which live in
 `tools/test/dist/snapshots` and are not checked in to this repository. CI
-fetches them from a separate snapshots repository. To regenerate
-snapshots locally after an intentional rendering change, or to generate them
-for the first time from a known-passing (in CI) build you've checked out:
+fetches them from a separate snapshots repository. To regenerate snapshots
+locally after an intentional rendering change, or to generate them for the first
+time from a known-passing (in CI) build you've checked out:
 
 ```bash
 pnpm run test --update-snapshots
@@ -310,6 +309,10 @@ are forwarded to `pytest`.
 With `rust` selected, `pnpm run test` runs `cargo test` for the `perspective`
 and `perspective-client` crates.
 
+`perspective-viewer` and `perspective-js` deliberately carry no Rust unit tests;
+their behavior is tested through the Playwright suites, against the public
+JavaScript API.
+
 ## Lint
 
 ```bash

docs/build.collage.mjs

@@ -24,7 +24,7 @@ const COLLAGE_GAP = 2;
 
 const COLLAGE_BG = { light: "#ffffff", dark: "#242526" };
 
-const COLLAGE_SEED = 0x5eed;
+const COLLAGE_SEED = 0xdeadbeef;
 
 function shuffled(items, seed) {
     let state = seed;
@@ -55,27 +55,33 @@ function pngSize(file) {
     }
 }
 
+/// Pick the column count whose natural tile aspect lands closest to filling the
+/// frame, then stretch the rows so the grid covers it exactly.
 function bestFitGrid(count, aspect, width, height) {
     let best;
     for (let cols = 1; cols <= count; cols++) {
         const rows = Math.ceil(count / cols);
         const tileWidth = Math.floor((width - (cols - 1) * COLLAGE_GAP) / cols);
+        if (tileWidth <= 0) {
+            break;
+        }
+
+        const natural =
+            rows * Math.round(tileWidth / aspect) + (rows - 1) * COLLAGE_GAP;
 
-        const tileHeight = Math.round(tileWidth / aspect);
-        const contentHeight = rows * tileHeight + (rows - 1) * COLLAGE_GAP;
-        if (contentHeight <= height && tileHeight > (best?.tileHeight ?? 0)) {
-            best = { cols, rows, tileWidth, tileHeight };
+        const drift = Math.abs(natural - height);
+        if (best === undefined || drift < best.drift) {
+            best = { cols, rows, tileWidth, drift };
         }
     }
 
-    return (
-        best ?? {
-            cols: count,
-            rows: 1,
-            tileWidth: Math.floor(height * aspect),
-            tileHeight: height,
-        }
-    );
+    const { cols, rows, tileWidth } = best;
+    return {
+        cols,
+        rows,
+        tileWidth,
+        tileHeight: Math.ceil((height - (rows - 1) * COLLAGE_GAP) / rows),
+    };
 }
 
 export async function collage(page, ids, theme, { out, port }) {
@@ -99,12 +105,12 @@ export async function collage(page, ids, theme, { out, port }) {
         height,
     );
 
-    const tiles = present
-        .map(
-            (id) =>
-                `<img src="http://localhost:${port}/projects/${theme}/${id}.png" />`,
-        )
-        .join("");
+    const cells = cols * rows;
+    const tiles = Array.from(
+        { length: cells },
+        (_, i) =>
+            `<img src="http://localhost:${port}/projects/${theme}/${present[i % present.length]}.png" />`,
+    ).join("");
 
     await page.setViewport({ width: COLLAGE_WIDTH, height });
     await page.setContent(
@@ -113,18 +119,17 @@ export async function collage(page, ids, theme, { out, port }) {
             .collage {
                 width: ${COLLAGE_WIDTH}px;
                 height: ${height}px;
-                display: flex;
-                flex-wrap: wrap;
-                align-content: center;
-                justify-content: center;
+                display: grid;
+                grid-template-columns: repeat(${cols}, 1fr);
+                grid-auto-rows: ${tileHeight}px;
                 gap: ${COLLAGE_GAP}px;
                 overflow: hidden;
             }
             .collage img {
-                width: ${tileWidth}px;
+                width: 100%;
                 height: ${tileHeight}px;
-                /* The tile box shares the screenshots' aspect, so \`cover\`
-                   only absorbs the sub-pixel rounding — no visible crop. */
+                /* Rows are stretched to fill the frame exactly, so \`cover\`
+                   absorbs the difference from the screenshots' own aspect. */
                 object-fit: cover;
                 display: block;
             }
@@ -134,9 +139,9 @@ export async function collage(page, ids, theme, { out, port }) {
     );
 
     const tiles_found = await page.$$eval(".collage img", (x) => x.length);
-    if (tiles_found !== present.length) {
+    if (tiles_found !== cells) {
         throw new Error(
-            `collage page has ${tiles_found} tiles, expected ${present.length}`,
+            `collage page has ${tiles_found} tiles, expected ${cells}`,
         );
     }
 
@@ -159,8 +164,8 @@ export async function collage(page, ids, theme, { out, port }) {
 
     fs.writeFileSync(path.join(dir, COLLAGE), await page.screenshot());
     console.log(
-        `Collage (${theme}): ${present.length} thumbnails, ${cols}×${rows} ` +
-            `grid of ${tileWidth}×${tileHeight} tiles, ` +
+        `Collage (${theme}): ${present.length} thumbnails in ${cells} cells, ` +
+            `${cols}×${rows} grid of ${tileWidth}×${tileHeight} tiles, ` +
             `${COLLAGE_WIDTH}×${height}.`,
     );
 }

docs/md/SUMMARY.md

@@ -35,6 +35,7 @@
         - [`expressions`](./explanation/view/config/expressions.md)
         - [Window Columns](./explanation/view/config/windows.md)
     - [Advanced View Operations](./explanation/view/advanced.md)
+- [Derived `Table`s](./explanation/derived_table.md)
 - [`Join`](./explanation/join.md)
     - [Join Types](./explanation/join/join_types.md)
     - [Join Options](./explanation/join/options.md)