fix: grid algorithm — 4:3 breakpoint, 16:9 cap, uniform tile sizes

- Lower landscape breakpoint from width>height to width/height>=4:3
- fitTile helper caps tiles at 16:9 and shrinks to fit both dimensions,
  preventing overflow on ultrawide containers
- Mixed candidate uses uniform tile sizes for all rows; partial rows
  are centered with the same tile dimensions as full rows

src/app/call.ts

@@ -62,13 +62,12 @@ export type TileRow = {
 }
 
 /**
- * Adaptive tile grid: rows can have different tile sizes, allowing
- * a Jitsi-style layout where tiles flex between 3:4 and 16:9 and
- * partial rows use wider tiles to fill whitespace.
+ * Adaptive tile grid: all tiles share the same dimensions. Full rows
+ * fill the container width; partial rows are centered.
  *
  * Example (3 tiles, 2 columns):
  *   row 0: [ square ] [ square ]
- *   row 1: [   16:9     ]   (centered)
+ *   row 1: [    square    ]   (centered, same size)
  */
 export type AdaptiveTileGrid = {
   rows: TileRow[]
@@ -112,10 +111,26 @@ const compareScores = (a: LayoutScore, b: LayoutScore): number => {
   return 0
 }
 
+/**
+ * Compute the largest tile size that fits within a given width and height,
+ * bounded by [minAspect, TILE_ASPECT_LANDSCAPE]. The tile is shrunk to fit
+ * whichever dimension is more constraining, so it never overflows.
+ */
+const fitTile = (availWidth: number, availHeight: number, minAspect: number) => {
+  const fillAspect = availWidth / availHeight
+  const aspectRatio = Math.max(minAspect, Math.min(TILE_ASPECT_LANDSCAPE, fillAspect))
+  if (fillAspect >= aspectRatio) {
+    const tileWidth = availHeight * aspectRatio
+    return {tileWidth, tileHeight: availHeight, aspectRatio}
+  }
+  const tileHeight = availWidth / aspectRatio
+  return {tileWidth: availWidth, tileHeight, aspectRatio}
+}
+
 /**
  * Build a single-row TileRow for the uniform case where all rows
- * have the same number of tiles. No upper-bound clamping on aspect
- * ratio — tiles can be wider than 16:9 to avoid overflow.
+ * have the same number of tiles. Tiles are centered within the row
+ * and capped at 16:9 to avoid overflow on ultrawide containers.
  */
 const buildUniformRow = (
   columnCount: number,
@@ -125,26 +140,16 @@ const buildUniformRow = (
   minAspect: number,
 ): TileRow => {
   const gap = TILE_GAP
-  const availableHeight = containerHeight - (rowCount - 1) * gap
-  const rowHeight = availableHeight / rowCount
-  const tileWidth = (containerWidth - (columnCount - 1) * gap) / columnCount
-  const fillAspect = tileWidth / rowHeight
-  const aspectRatio = Math.max(minAspect, Math.min(TILE_ASPECT_LANDSCAPE, fillAspect))
-  const tileHeight = tileWidth / aspectRatio
+  const availHeight = (containerHeight - (rowCount - 1) * gap) / rowCount
+  const availWidth = (containerWidth - (columnCount - 1) * gap) / columnCount
+  const {tileWidth, tileHeight, aspectRatio} = fitTile(availWidth, availHeight, minAspect)
   return {columnCount, tileWidth, tileHeight, aspectRatio}
 }
 
 /**
  * Build a mixed-size layout candidate for a given column count.
- * Uses a "match heights" approach: the last (partial) row is at 16:9
- * (per review #1: "single centered 16:9 tile") and full-row tiles
- * match that same height. This creates a cohesive Jitsi-style look
- * where all tiles in all rows are the same height, with different
- * widths per row (full-row tiles are narrower/squarer, last-row
- * tiles are wider).
- *
- * If the full-row aspect would go below the portrait bound (3:4),
- * the height diverges: full rows clamp to 3:4 portrait.
+ * All tiles share the same dimensions — full rows fill the width,
+ * and the partial last row is centered with the same tile size.
  */
 const buildMixedCandidate = (
   tileCount: number,
@@ -158,48 +163,18 @@ const buildMixedCandidate = (
   const remainder = tileCount % columnCount
   const totalRowCount = fullRowCount + 1
 
-  const tileWidthFull = (containerWidth - (columnCount - 1) * gap) / columnCount
-  if (tileWidthFull <= 0) return undefined
-
-  const tileWidthLast = (containerWidth - (remainder - 1) * gap) / remainder
-  if (tileWidthLast <= 0) return undefined
-
-  const maxPossibleHeight = Math.min(
-    tileWidthFull / minAspect,
-    tileWidthLast / minAspect,
-    (containerHeight - (totalRowCount - 1) * gap) / totalRowCount,
-  )
-
-  // Target 16:9 for the last row if possible
-  const targetHeight = tileWidthLast / TILE_ASPECT_LANDSCAPE
-  const commonHeight = Math.min(maxPossibleHeight, targetHeight)
-
-  const tileHeightFull = commonHeight
-  const tileHeightLast = commonHeight
-  const fullRowAspectRatio = tileWidthFull / commonHeight
-  const lastRowAspectRatio = tileWidthLast / commonHeight
-
-  const totalHeight = fullRowCount * tileHeightFull + tileHeightLast + (totalRowCount - 1) * gap
-  const totalWidth = Math.max(
-    columnCount * tileWidthFull + (columnCount - 1) * gap,
-    remainder * tileWidthLast + (remainder - 1) * gap,
-  )
+  const availHeight = (containerHeight - (totalRowCount - 1) * gap) / totalRowCount
+  const availWidth = (containerWidth - (columnCount - 1) * gap) / columnCount
+  const {tileWidth, tileHeight, aspectRatio} = fitTile(availWidth, availHeight, minAspect)
 
   const rows: TileRow[] = []
   for (let r = 0; r < fullRowCount; r++) {
-    rows.push({
-      columnCount,
-      tileWidth: tileWidthFull,
-      tileHeight: tileHeightFull,
-      aspectRatio: fullRowAspectRatio,
-    })
+    rows.push({columnCount, tileWidth, tileHeight, aspectRatio})
   }
-  rows.push({
-    columnCount: remainder,
-    tileWidth: tileWidthLast,
-    tileHeight: tileHeightLast,
-    aspectRatio: lastRowAspectRatio,
-  })
+  rows.push({columnCount: remainder, tileWidth, tileHeight, aspectRatio})
+
+  const totalHeight = totalRowCount * tileHeight + (totalRowCount - 1) * gap
+  const totalWidth = columnCount * tileWidth + (columnCount - 1) * gap
 
   return {
     rows,
@@ -214,12 +189,12 @@ const buildMixedCandidate = (
  *
  * - Tiles flex between 3:4 (portrait) and wider than 16:9 if needed
  *   to avoid overflow. No upper bound on aspect ratio — tiles can
- *   be wider than 16:9 when the container is very wide.
- * - When the last row is partial (fewer tiles than a full row),
- *   those tiles are wider (16:9) while full rows use square-ish
- *   tiles, filling whitespace per review #1.
- * - Only allows overflow (scroll) when tiles would be below
- *   MIN_TILE_HEIGHT (review #2: ~6-8 tiles on portrait phone).
+ * Tiles flex between a minimum aspect (1:1 on landscape, 3:4 on portrait)
+ * and 16:9, capped so they never overflow the container. Partial rows
+ * use the same tile size as full rows, centered.
+ *
+ * Only allows overflow (scroll) when tiles would be below
+ * MIN_TILE_HEIGHT (review #2: ~6-8 tiles on portrait phone).
  *
  * Prioritises:
  *  1. No overflow (tiles shrink to fit within aspect bounds)
@@ -234,10 +209,10 @@ export const computeAdaptiveGrid = (
 ): AdaptiveTileGrid | undefined => {
   if (tileCount <= 0 || containerWidth <= 0 || containerHeight <= 0) return undefined
 
-  // On landscape viewports, bound tiles at 1:1 (square) so they don't
-  // become tall and narrow. On portrait viewports, allow 3:4 so more
-  // tiles fit on a phone screen.
-  const minAspect = containerWidth > containerHeight ? 1 : TILE_ASPECT_PORTRAIT
+  // When the container is at least 4:3 landscape, bound tiles at 1:1 (square)
+  // so they don't become tall and narrow. On narrower/portrait viewports,
+  // allow 3:4 so more tiles fit on a phone screen.
+  const minAspect = containerWidth / containerHeight >= 4 / 3 ? 1 : TILE_ASPECT_PORTRAIT
 
   let best: AdaptiveTileGrid | undefined
   let bestScore: LayoutScore | undefined