M1: write grid track sizes in .fig export (#465)

The import has read `gridColumnsSizing` / `gridRowsSizing` since #630, but the
export wrote only equal tracks and warned about it, so a grid with a fixed
column beside two weighted ones came back equal after a save and reload.

Write the sizing map next to the order map, keyed by the same track ids: fixed
px, fractional fill and content-sized tracks keep their sizes. A track the
format has no name for (negative or out-of-range size, or a document track the
frame doesn't list) keeps its id and reads back equal, with the existing
warning.

Co-authored-by: xiaou61 <113765024+xiaou61@users.noreply.github.com>

crates/format/src/fig/export.rs

@@ -25,10 +25,10 @@ use figcraft_doc::proto::{
     Action, Direction, Easing, GAMEPAD_BUTTONS, Interaction, KeyMods, Overflow, OverlayPosition, ScrollPosition, Transition, Trigger,
 };
 use figcraft_doc::{
-    AutoLayout, BoolOp, ContentAlign, CrossAlign, Document, EffectKind, ExportSize, GridAlign, GridKind, HConstraint, LayoutMode, LetterSpacing,
-    LineHeight, ListStyle, MainAlign, MaskType, Node, NodeId, NodeKind, NoiseMode, PropDef, Sizing, StrokeAlign, StrokeCap, StrokeJoin, StyleKind,
-    TextAlignH, TextAlignV, TextAutoResize, TextCase, TextData, TextDecoration, TextStyle, VConstraint, VariableType, VariableValue, VectorNetwork,
-    WindingRule,
+    AutoLayout, BoolOp, ContentAlign, CrossAlign, Document, EffectKind, ExportSize, GridAlign, GridKind, GridTrack, HConstraint, LayoutMode,
+    LetterSpacing, LineHeight, ListStyle, MainAlign, MaskType, Node, NodeId, NodeKind, NoiseMode, PropDef, Sizing, StrokeAlign, StrokeCap,
+    StrokeJoin, StyleKind, TextAlignH, TextAlignV, TextAutoResize, TextCase, TextData, TextDecoration, TextStyle, VConstraint, VariableType,
+    VariableValue, VectorNetwork, WindingRule,
 };
 use serde_json::Value;
 
@@ -168,7 +168,12 @@ message PrototypeStartingPoint string name=1, string position=3
 message OverlayBackgroundAppearance OverlayBackgroundType backgroundType=1, Color backgroundColor=2
 message GUIDPositionMapEntry GUID id=1, string position=2
 message GUIDPositionMap GUIDPositionMapEntry[] entries=1
-message NodeChange GUID guid=1, NodePhase phase=2, ParentIndex parentIndex=3, NodeType type=4, string name=5, bool visible=6, bool locked=7, float opacity=8, BlendMode blendMode=9, Vector size=11, Matrix transform=12, bool mask=16, MaskType maskType=317, float backgroundOpacity=19, bool backgroundEnabled=15, bool internalOnly=142, string description=318, StyleType styleType=163, string sortPosition=320, StyleId styleIdForFill=332, StyleId styleIdForStrokeFill=333, StyleId styleIdForText=334, StyleId styleIdForEffect=335, StyleId styleIdForGrid=336, VariableDataMap variableConsumptionMap=307, VariableModeBySetMap variableModeBySetMap=316, VariableSetMode[] variableSetModes=312, VariableSetID variableSetID=313, VariableResolvedDataType variableResolvedType=314, VariableDataValues variableDataValues=315, VariableScope[] variableScopes=353, DocumentColorProfile documentColorProfile=349, Paint[] fillPaints=38, Paint[] strokePaints=39, float strokeWeight=26, StrokeAlign strokeAlign=29, StrokeJoin strokeJoin=31, StrokeCap strokeCap=30, float[] dashPattern=13, float miterLimit=25, bool borderStrokeWeightsIndependent=299, float borderTopWeight=295, float borderRightWeight=298, float borderBottomWeight=296, float borderLeftWeight=297, Effect[] effects=43, float cornerRadius=20, float cornerSmoothing=160, bool rectangleCornerRadiiIndependent=149, float rectangleTopLeftCornerRadius=145, float rectangleTopRightCornerRadius=146, float rectangleBottomRightCornerRadius=148, float rectangleBottomLeftCornerRadius=147, ConstraintType horizontalConstraint=28, ConstraintType verticalConstraint=37, bool frameMaskDisabled=115, bool resizeToFit=117, bool isStateGroup=225, bool sectionContentsHidden=283, Color backgroundColor=50, StackMode stackMode=105, float stackSpacing=107, float stackCounterSpacing=324, StackWrap stackWrap=323, StackCounterAlignContent stackCounterAlignContent=343, float stackHorizontalPadding=209, float stackVerticalPadding=210, float stackPaddingRight=233, float stackPaddingBottom=234, StackJustify stackPrimaryAlignItems=230, StackAlign stackCounterAlignItems=231, StackSize stackPrimarySizing=229, StackSize stackCounterSizing=221, bool bordersTakeSpace=294, bool stackReverseZIndex=271, float gridColumnGap=438, float gridRowGap=437, GUIDPositionMap gridColumns=436, GUIDPositionMap gridRows=435, float stackChildPrimaryGrow=232, StackCounterAlign stackChildAlignSelf=236, StackPositioning stackPositioning=269, OptionalVector minSize=325, OptionalVector maxSize=326, GUID gridColumnAnchor=440, GUID gridRowAnchor=439, uint gridColumnSpan=442, uint gridRowSpan=441, LayoutGrid[] layoutGrids=47, ExportSettings[] exportSettings=45, TextData textData=42, FontName fontName=41, float fontSize=21, Number lineHeight=40, Number letterSpacing=165, TextCase textCase=34, TextDecoration textDecoration=35, TextAlignHorizontal textAlignHorizontal=32, TextAlignVertical textAlignVertical=33, TextAutoResize textAutoResize=46, TextTruncation textTruncation=280, int maxLines=351, float paragraphSpacing=23, float paragraphIndent=22, Hyperlink hyperlink=223, bool autoRename=14, bool fontVariantCommonLigatures=127, bool fontVariantContextualLigatures=128, string fontVersion=202, uint textUserLayoutVersion=203, uint textExplicitLayoutVersion=396, uint textBidiVersion=279, float textTracking=27, bool textDecorationSkipInk=412, EmojiImageSet emojiImageSet=391, uint styleID=49, Path[] fillGeometry=51, Path[] strokeGeometry=52, VectorData vectorData=48, VectorMirror handleMirroring=44, uint count=10, float starInnerScale=24, ArcData arcData=195, BooleanOperation booleanOperation=36, string symbolDescription=144, VariableWidthPoint[] variableWidthPoints=447, PluginData[] pluginData=204, SymbolData symbolData=113, NodeChange[] derivedSymbolData=125, GUID overriddenSymbolID=143, ComponentPropDef[] componentPropDefs=266, ComponentPropAssignment[] componentPropAssignments=268, VariableDataMap parameterConsumptionMap=445, GUIDPath guidPath=111, PrototypeInteraction[] prototypeInteractions=226, PrototypeStartingPoint prototypeStartingPoint=249, ScrollDirection scrollDirection=159, ScrollBehavior scrollBehavior=186, OverlayPositionType overlayPositionType=198, OverlayBackgroundInteraction overlayBackgroundInteraction=200, OverlayBackgroundAppearance overlayBackgroundAppearance=201
+enum GridTrackSizingType FLEX=0 FIXED=1 HUG=2 UNKNOWN=3
+message GridTrackSizeFunction GridTrackSizingType type=1, float value=2
+message GridTrackSize GridTrackSizeFunction minSizing=1, GridTrackSizeFunction maxSizing=2
+message GridTrackSizeEntry GUID id=1, GridTrackSize trackSize=2
+message GridTrackSizeMap GridTrackSizeEntry[] entries=1
+message NodeChange GUID guid=1, NodePhase phase=2, ParentIndex parentIndex=3, NodeType type=4, string name=5, bool visible=6, bool locked=7, float opacity=8, BlendMode blendMode=9, Vector size=11, Matrix transform=12, bool mask=16, MaskType maskType=317, float backgroundOpacity=19, bool backgroundEnabled=15, bool internalOnly=142, string description=318, StyleType styleType=163, string sortPosition=320, StyleId styleIdForFill=332, StyleId styleIdForStrokeFill=333, StyleId styleIdForText=334, StyleId styleIdForEffect=335, StyleId styleIdForGrid=336, VariableDataMap variableConsumptionMap=307, VariableModeBySetMap variableModeBySetMap=316, VariableSetMode[] variableSetModes=312, VariableSetID variableSetID=313, VariableResolvedDataType variableResolvedType=314, VariableDataValues variableDataValues=315, VariableScope[] variableScopes=353, DocumentColorProfile documentColorProfile=349, Paint[] fillPaints=38, Paint[] strokePaints=39, float strokeWeight=26, StrokeAlign strokeAlign=29, StrokeJoin strokeJoin=31, StrokeCap strokeCap=30, float[] dashPattern=13, float miterLimit=25, bool borderStrokeWeightsIndependent=299, float borderTopWeight=295, float borderRightWeight=298, float borderBottomWeight=296, float borderLeftWeight=297, Effect[] effects=43, float cornerRadius=20, float cornerSmoothing=160, bool rectangleCornerRadiiIndependent=149, float rectangleTopLeftCornerRadius=145, float rectangleTopRightCornerRadius=146, float rectangleBottomRightCornerRadius=148, float rectangleBottomLeftCornerRadius=147, ConstraintType horizontalConstraint=28, ConstraintType verticalConstraint=37, bool frameMaskDisabled=115, bool resizeToFit=117, bool isStateGroup=225, bool sectionContentsHidden=283, Color backgroundColor=50, StackMode stackMode=105, float stackSpacing=107, float stackCounterSpacing=324, StackWrap stackWrap=323, StackCounterAlignContent stackCounterAlignContent=343, float stackHorizontalPadding=209, float stackVerticalPadding=210, float stackPaddingRight=233, float stackPaddingBottom=234, StackJustify stackPrimaryAlignItems=230, StackAlign stackCounterAlignItems=231, StackSize stackPrimarySizing=229, StackSize stackCounterSizing=221, bool bordersTakeSpace=294, bool stackReverseZIndex=271, float gridColumnGap=438, float gridRowGap=437, GUIDPositionMap gridColumns=436, GUIDPositionMap gridRows=435, GridTrackSizeMap gridColumnsSizing=443, GridTrackSizeMap gridRowsSizing=444, float stackChildPrimaryGrow=232, StackCounterAlign stackChildAlignSelf=236, StackPositioning stackPositioning=269, OptionalVector minSize=325, OptionalVector maxSize=326, GUID gridColumnAnchor=440, GUID gridRowAnchor=439, uint gridColumnSpan=442, uint gridRowSpan=441, LayoutGrid[] layoutGrids=47, ExportSettings[] exportSettings=45, TextData textData=42, FontName fontName=41, float fontSize=21, Number lineHeight=40, Number letterSpacing=165, TextCase textCase=34, TextDecoration textDecoration=35, TextAlignHorizontal textAlignHorizontal=32, TextAlignVertical textAlignVertical=33, TextAutoResize textAutoResize=46, TextTruncation textTruncation=280, int maxLines=351, float paragraphSpacing=23, float paragraphIndent=22, Hyperlink hyperlink=223, bool autoRename=14, bool fontVariantCommonLigatures=127, bool fontVariantContextualLigatures=128, string fontVersion=202, uint textUserLayoutVersion=203, uint textExplicitLayoutVersion=396, uint textBidiVersion=279, float textTracking=27, bool textDecorationSkipInk=412, EmojiImageSet emojiImageSet=391, uint styleID=49, Path[] fillGeometry=51, Path[] strokeGeometry=52, VectorData vectorData=48, VectorMirror handleMirroring=44, uint count=10, float starInnerScale=24, ArcData arcData=195, BooleanOperation booleanOperation=36, string symbolDescription=144, VariableWidthPoint[] variableWidthPoints=447, PluginData[] pluginData=204, SymbolData symbolData=113, NodeChange[] derivedSymbolData=125, GUID overriddenSymbolID=143, ComponentPropDef[] componentPropDefs=266, ComponentPropAssignment[] componentPropAssignments=268, VariableDataMap parameterConsumptionMap=445, GUIDPath guidPath=111, PrototypeInteraction[] prototypeInteractions=226, PrototypeStartingPoint prototypeStartingPoint=249, ScrollDirection scrollDirection=159, ScrollBehavior scrollBehavior=186, OverlayPositionType overlayPositionType=198, OverlayBackgroundInteraction overlayBackgroundInteraction=200, OverlayBackgroundAppearance overlayBackgroundAppearance=201
 struct Blob byte[] bytes
 message Message MessageType type=1, uint sessionID=2, NodeChange[] nodeChanges=4, Blob[] blobs=6
 ";
@@ -277,6 +282,20 @@ fn s(x: &str) -> Kv<'static> {
 fn b(x: bool) -> Kv<'static> {
     Kv::Bool(x)
 }
+
+/// A track's size as the format's enum name and value, when both sizing functions agree (the
+/// importer keeps only those). `None`: the format has no name for it, so an equal track stands in.
+fn grid_track_size(track: &GridTrack) -> Option<(&'static str, f64)> {
+    let value = track.value;
+    let fits = value.is_finite() && (0.0..=crate::fig::map::MAX_GRID_TRACK_VALUE).contains(&value);
+    match track.sizing {
+        Sizing::Fixed if fits => Some(("FIXED", value)),
+        Sizing::Fill if fits && value > 0.0 => Some(("FLEX", value)),
+        Sizing::Hug => Some(("HUG", 0.0)),
+        _ => None,
+    }
+}
+
 fn guid(session: u32, local: u32) -> Kv<'static> {
     o(vec![("sessionID", u(session)), ("localID", u(local))])
 }
@@ -1415,9 +1434,28 @@ impl<'d> Exporter<'d> {
                 )])
             };
             f.extend([("gridColumnGap", fl(l.gap)), ("gridRowGap", fl(l.cross_gap)), ("gridColumns", map(&cols)), ("gridRows", map(&rows))]);
-            if l.column_tracks.iter().chain(&l.row_tracks).any(|t| t.sizing != Sizing::Fill) {
+            // Sizing is keyed by track id like the order map. A track the document doesn't set is
+            // left out, and one the format can't hold keeps its id (the import equalises it).
+            let sizing = |tracks: &[GridTrack], ids: &[u32]| -> Option<Kv<'static>> {
+                let mut entries = Vec::new();
+                for (i, id) in ids.iter().enumerate() {
+                    let Some(track) = tracks.get(i) else { continue };
+                    if let Some((kind, value)) = grid_track_size(track) {
+                        let size = || o(vec![("type", e(kind)), ("value", fl(value))]);
+                        entries.push(o(vec![("id", guid(AUX, *id)), ("trackSize", o(vec![("minSizing", size()), ("maxSizing", size())]))]));
+                    }
+                }
+                (!entries.is_empty()).then(|| o(vec![("entries", arr(entries))]))
+            };
+            let (column_sizing, row_sizing) = (sizing(&l.column_tracks, &cols), sizing(&l.row_tracks, &rows));
+            if l.column_tracks.iter().chain(&l.row_tracks).any(|t| grid_track_size(t).is_none()) {
                 self.warn("grid tracks of fixed or content size were written as equal tracks");
             }
+            for (name, sizing) in [("gridColumnsSizing", column_sizing), ("gridRowsSizing", row_sizing)] {
+                if let Some(v) = sizing {
+                    f.push((name, v));
+                }
+            }
             self.tracks.insert(key, (cols, rows));
         } else {
             let spread = l.content_align == ContentAlign::SpaceBetween;

crates/format/src/fig/export_tests.rs

@@ -1022,6 +1022,45 @@ fn junk_documents_never_panic() {
     }
 }
 
+/// Grid track sizes reach the file and come back: fixed px, fractional fill and hug tracks, and a
+/// track the format has no name for leaves an equal track behind instead of failing the write.
+#[test]
+fn grid_track_sizes_round_trip() {
+    let mut doc = Document::new("File");
+    let page = doc.first_page().unwrap();
+    let grid = doc.create(page, NodeKind::Frame, "Grid", 0.0, 0.0, 400.0, 200.0).unwrap();
+    {
+        let node = doc.node_mut(grid).unwrap();
+        node.layout = Some(AutoLayout {
+            mode: LayoutMode::Grid,
+            grid_columns: 3,
+            grid_rows: 2,
+            column_tracks: vec![GridTrack::fixed(120.0), GridTrack::fill(2.0), GridTrack::hug()],
+            row_tracks: vec![GridTrack::fill(1.0), GridTrack::fixed(50.0)],
+            ..AutoLayout::default()
+        });
+    }
+    let (bytes, warnings) = export(&doc, None).unwrap();
+    assert!(warnings.is_empty(), "{warnings:?}");
+    let (back, iw) = import(&bytes, "File").unwrap();
+    assert!(iw.is_empty(), "{iw:?}");
+    let l = back.node(back.pages[0]).and_then(|p| p.children.first()).and_then(|c| back.node(*c)).and_then(|n| n.layout.clone()).unwrap();
+    assert_eq!(l.column_tracks, vec![GridTrack::fixed(120.0), GridTrack::fill(2.0), GridTrack::hug()]);
+    assert_eq!(l.row_tracks, vec![GridTrack::fill(1.0), GridTrack::fixed(50.0)]);
+
+    // A negative fixed track is no size the format can name: the write still succeeds, the track
+    // falls back to an equal one, and the warning says so.
+    let mut odd = doc.clone();
+    if let Some(l) = odd.node_mut(grid).and_then(|n| n.layout.as_mut()) {
+        l.column_tracks[0] = GridTrack::fixed(-5.0);
+    }
+    let (bytes, warnings) = export(&odd, None).unwrap();
+    assert_eq!(warnings, vec!["grid tracks of fixed or content size were written as equal tracks".to_string()]);
+    let (back, _) = import(&bytes, "File").unwrap();
+    let l = back.node(back.pages[0]).and_then(|p| p.children.first()).and_then(|c| back.node(*c)).and_then(|n| n.layout.clone()).unwrap();
+    assert_eq!(l.column_tracks[0], GridTrack::fill(1.0), "an unwritable track reads back equal");
+}
+
 /// A frame's own min/max size survives whatever its parent is, not only under auto layout.
 #[test]
 fn frame_size_limits_survive_without_auto_layout_parent() {

crates/format/src/fig/map.rs

@@ -24,7 +24,7 @@ const MAX_DEPTH: usize = 256;
 /// Most path commands read from one geometry blob.
 const MAX_COMMANDS: usize = 200_000;
 const MAX_GRID_TRACKS: usize = 1_000;
-const MAX_GRID_TRACK_VALUE: f64 = 1e6;
+pub(super) const MAX_GRID_TRACK_VALUE: f64 = 1e6;
 /// Id of "no style".
 const NO_STYLE: &str = "4294967295:4294967295";
 /// Longest asset `key` or `version` kept for resolving references given as assets.

docs/file-format-parity.md

@@ -122,10 +122,10 @@ each.
   image adjustments, glass settings other than frost, springs other than Gentle (written as ease
   out), set-variable, set-variable-mode and conditional actions, scroll-to offsets, text decoration
   looks, variable font axes, text on a path, nested list levels, list spacing, hanging punctuation,
-  leading trim, OpenType features, per-layer operations inside boolean groups, grid tracks of fixed
-  or content size, different stroke ends on lines. Not written at all: stroke outlines of dashed and
-  per-side strokes and of inside or outside strokes on polygons, stars and vectors, glyph outlines
-  of text (a reader lays text out with its own fonts), version history and branches.
+  leading trim, OpenType features, per-layer operations inside boolean groups, different stroke ends
+  on lines. Not written at all: stroke outlines of dashed and per-side strokes and of inside or
+  outside strokes on polygons, stars and vectors, glyph outlines of text (a reader lays text out
+  with its own fonts), version history and branches.
 - **Checked by opening written files in other software:** the example documents and a small test
   file open there, and layers, fills, gradients, strokes, shadows, vectors, components and text draw
   as in FigCraft. A file saved again there and read back keeps the layer tree and properties; two
@@ -165,6 +165,7 @@ each.
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-10-20 | minor | `.fig` export writes grid track sizes (`gridColumnsSizing` / `gridRowsSizing`): fixed px, fractional fill and content-sized tracks keep their sizes and come back through our own importer (#465). Tracks whose sizing the format has no name for (a negative or out-of-range size, a constrained min/max) keep their id and read back equal, with the existing warning. Numbers unchanged |
 | 2026-10-18 | minor | REST file JSON import keeps `SLOT` layers (#792): they were dropped with everything placed in them, which emptied every instance's slot. A slot in a main component becomes a slot frame bound to its `SLOT` property (the one it references, else the one named like it, else the only one left), and an instance's slot holds the instance's own content, kept across syncs, moves of the mains and saving, unless the instance's property value is the main's default content (without values, a slot that holds layers keeps them). Instances in slot content link to their own mains. Slot content limits, preferred-only and preferred components are warnings. Synthetic files only. Numbers unchanged |
 | 2026-10-17 | minor | REST file JSON import reads grid track sizes from the CSS track strings `gridColumnsSizing` / `gridRowsSizing` (fixed px, fill fr, hug `auto`, `minmax(0, 1fr)`, `repeat()`; other tracks stay equal) (#465). Numbers unchanged |
 | 2026-10-17 | minor | The community batches #727 and #728 in the `.fig` row: instance identity and cached library components, overrides by key, text style precedence, grid track sizes, slot content, labels of connectors saved with their path, skip ink, paragraph options, list start numbers, vertical trim, per-point stroke joins, text on a path, image adjustments (also REST), images in the message; budgets from the file's size; the journal keeps no file bytes; the import report. Not read cut to what's left. A `.fig` copy from Save as. Pasted content: layers copied from another design app, best effort (tested only with clipboard HTML made from our own export), and images under Wayland (not run there). All on synthetic files: summary and hours unchanged |