[foxnne]

Part of fizzyedit/work#21 (step 4 of plans/WORKSPACES_PLAN.md). Stacked on #462, which is stacked on #461.

What changes

Behind FIZZY_WORKSPACES=1, a saved layout comes back whole.

• An old panes.zon becomes the app's splits. The first time fizzy runs with the flag, the workbench's saved tree is laid out split for split from the place the first workspace is in (Main). Each pane's workspace goes in its half, at the share it had. Then panes.zon is deleted: the arrangement is layout.zon's from then on. A subtree whose panes didn't come back is skipped, so its sibling takes the room.
• A place whose workspace didn't come back closes. A workspace that held no document at quit, or none that could open, isn't restored. Its place used to come back empty; now it closes, as it would have had it emptied.
• Region.splitOnSized: splitOn for a place that hasn't been drawn yet, with a share for the new half. A nested tree splits a half made in the same frame. splitOn now calls it with the drawn size and half.

What's already kept and needed no change: which place holds which workspace and each workspace's documents in order (layout.zon, since #461), and each workspace's selected tab (the session, KeptDocuments.applySelections).

Older fizzy reads the same layout.zon it always did; nothing new is written. With the flag off, nothing changes. (The workbench still reads panes.zon as it did; only the carry-over deletes it.)

SDK impact

• None (test-sdk-version passes).

Verified

• macOS: in a sandbox profile:
  • ran without the flag and split Main (Pane 0 | Pane 4);
  • hand-edited the saved panes.zon into a nested tree (horizontal 0.6: Pane 0 | vertical 0.5 of Pane 4, Pane 5) and gave Pane 5 a document in layout.zon;
  • relaunched with FIZZY_WORKSPACES=1: Main came back as Main | (Main/r1 over Main/r1/b1), each half showing its workspace's document, the horizontal share 60/40, and panes.zon gone.
  • zig build, zig build test, zig build test-integration (53/53 steps), zig build check-web, zig build test-sdk-version, scripts/check-fmt.sh.
• Windows:
• Linux:
• Web: builds; no panes.zon there, and the flag is never on.

Follow-ups

• A split of a split's new half comes out uneven. The vertical 0.5 above settled at about 1:3, and splitting a nested half by hand came out uneven the same way. A branch sizes itself in its parent by its origin's extent (Region, .branch), the same name its kept half reads its own size from along the other axis. That's the app's split code with or without this flag, so it's a separate fix.
• Step 5: tear a tab off into a float holding a new workspace (State.documents with a float), and back.

🤖 Generated with Claude Code

[foxnne]

The 1:3 in the follow-up comes from this PR's carry-over, not from the .branch arm.

I reproduced it on this head (f927a7f) with the recipe above: a panes.zon of Pane 0 | (Pane 4 over Pane 5, vertical 0.5), relaunched with FIZZY_WORKSPACES=1. Main/r1 came out at 248 px over Main/r1/b1 at 708 px (2×). The extent layout.zon stored for Main/r1/b1 is 354 pt:

• (718 − handle_size 10) × 0.5 = 354, and
• 718 pt is Main's content height without the Panel: (976 + 20 + 472) px / 2 − 2 × 8 pt card padding.

With the Panel there, Main is 472 pt tall inside, and its half would be 231 pt. So settle reads placeSize(Main) on a frame before the Panel has taken its 236 pt, and carryOver passes that height to splitOnSized. The width is right (Main/r1's 341.6 = (864 − 10) × 0.4) because nothing beside Main changes width on that frame.

Why it isn't the shared name. The kept origin is always the leftover half of its own branch (resize = false), so it never writes an extent under that name. Within a tree, extent("Main/r1") only ever means Main/r1's reach along its parent's axis, before and after it is split again. Splitting a nested half by hand on main comes out even apart from the card padding, which a restart keeps.

The uneven split by hand was a separate, smaller bug: every split of a carded place came out short by the card padding on both sides (494 / 462 px). #465 fixes it: a place's recorded size is now its border box, and splitOnSized here picks that up as it is.

Suggested fix here: carry over once the layout under Main has settled, for example on a later frame, or once the Panel has registered its size. Another option is to store each new half's share of the place and turn it into an extent when the half is first drawn. Measuring on the first frame settle runs will keep picking up whatever hasn't been laid out yet.

🤖 Generated with Claude Code