MediaAttachmentGrid: correct but slow layout

src/timelines/MediaAttachmentGrid.tsx

@@ -2,29 +2,52 @@ import type { mastodon } from "masto";
 import {
   type Component,
   For,
-  createEffect,
+  createMemo,
   createRenderEffect,
   createSignal,
   onCleanup,
-  onMount,
 } from "solid-js";
 import { css } from "solid-styled";
 import tootStyle from "./toot.module.css";
 import MediaViewer from "./MediaViewer";
 import { render } from "solid-js/web";
-import { useWindowSize } from "@solid-primitives/resize-observer";
+import {
+  createElementSize,
+  useWindowSize,
+} from "@solid-primitives/resize-observer";
 import { useStore } from "@nanostores/solid";
 import { $settings } from "../settings/stores";
 
+type ElementSize = { width: number; height: number };
+
+function constraintedSize(
+  { width: owidth, height: oheight }: Readonly<ElementSize>, // originalSize
+  { width: mwidth, height: mheight }: Readonly<Partial<ElementSize>>, // modifier
+  { width: maxWidth, height: maxHeight }: Readonly<ElementSize>, // maxSize
+) {
+  const ySize = owidth + (mwidth ?? 0);
+  const yScale = ySize > maxWidth ? ySize / maxWidth : 1;
+  const xSize = oheight + (mheight ?? 0);
+  const xScale = xSize > maxHeight ? xSize / maxHeight : 1;
+
+  const maxScale = Math.max(yScale, xScale);
+  const scaledWidth = owidth / maxScale;
+  const scaledHeight = oheight / maxScale;
+
+  return {
+    width: scaledWidth,
+    height: scaledHeight,
+  };
+}
+
 const MediaAttachmentGrid: Component<{
   attachments: mastodon.v1.MediaAttachment[];
 }> = (props) => {
-  let rootRef: HTMLElement;
+  const [rootRef, setRootRef] = createSignal<HTMLElement>();
   const [viewerIndex, setViewerIndex] = createSignal<number>();
   const viewerOpened = () => typeof viewerIndex() !== "undefined";
-  const windowSize = useWindowSize();
-  const vh35 = () => Math.floor(windowSize.height * 0.35);
   const settings = useStore($settings);
+  const windowSize = useWindowSize();
 
   createRenderEffect((lastDispose?: () => void) => {
     lastDispose?.();
@@ -64,6 +87,22 @@ const MediaAttachmentGrid: Component<{
     }
   };
 
+  const rawElementSize = createElementSize(rootRef);
+
+  const elementWidth = () => rawElementSize.width;
+
+  const itemMaxSize = createMemo(() => {
+    const ewidth = elementWidth();
+    const width = ewidth
+      ? (ewidth - (columnCount() - 1) * 4) / columnCount()
+      : 1;
+
+    return {
+      height: windowSize.height * 0.35,
+      width,
+    };
+  });
+
   css`
     .attachments {
       column-count: ${columnCount().toString()};
@@ -71,7 +110,7 @@ const MediaAttachmentGrid: Component<{
   `;
   return (
     <section
-      ref={rootRef!}
+      ref={setRootRef}
       class={[tootStyle.tootAttachmentGrp, "attachments"].join(" ")}
       onClick={(e) => {
         if (e.target !== e.currentTarget) {
@@ -89,19 +128,33 @@ const MediaAttachmentGrid: Component<{
           // before using this. See #37.
           // TODO: use fast average color to extract accent color
           const accentColor = item.meta?.colors?.accent;
+          const { width, height } = item.meta?.small || {};
+
+          const size = () => {
+            return constraintedSize(
+              item.meta?.small || { width: 1, height: 1 },
+              { width: 2, height: 2 },
+              itemMaxSize(),
+            );
+          };
+
           switch (item.type) {
             case "image":
               return (
                 <img
                   src={item.previewUrl}
-                  width={item.meta?.small?.width}
-                  height={item.meta?.small?.height}
+                  width={width}
+                  height={height}
                   alt={item.description || undefined}
                   onClick={[openViewerFor, index()]}
                   loading="lazy"
-                  style={
-                    accentColor ? { "--media-color-accent": accentColor } : {}
-                  }
+                  style={Object.assign(
+                    {
+                      width: `${size().width}px`,
+                      height: `${size().height}px`,
+                    },
+                    accentColor ? { "--media-color-accent": accentColor } : {},
+                  )}
                 ></img>
               );
             case "video":
@@ -112,8 +165,8 @@ const MediaAttachmentGrid: Component<{
                   playsinline={settings().autoPlayVideos ? true : undefined}
                   controls
                   poster={item.previewUrl}
-                  width={item.meta?.small?.width}
-                  height={item.meta?.small?.height}
+                  width={width}
+                  height={height}
                 />
               );
             case "gifv":
@@ -125,8 +178,8 @@ const MediaAttachmentGrid: Component<{
                   playsinline /* or safari on iOS will play in full-screen */
                   loop
                   poster={item.previewUrl}
-                  width={item.meta?.small?.width}
-                  height={item.meta?.small?.height}
+                  width={width}
+                  height={height}
                 />
               );