1 files changed, 57 insertions, 0 deletions
diff --git a/src/surface.zig b/src/surface.zig
index eef787b4..b19c24c7 100644
--- a/src/surface.zig
+++ b/src/surface.zig
@@ -324,6 +324,51 @@ test "pixel attachment fit and pan do not invalidate cached pixels" {
     try std.testing.expect(key.eql(place.cacheKey()));
 }
 
+/// One part of the frame and where it is, placed once by `draw.place`
+/// before anything is painted: every painter and every shell reads the
+/// geometry here instead of working it out again. `rect` is in grid cells
+/// and is the hit-test geometry.
+pub const Region = struct {
+    pub const Kind = enum(u8) {
+        /// The frame-wide border fill every other part is painted over.
+        page,
+        /// A pane's grip: the mode mark at the head of its tag rows.
+        grip,
+        /// A pane's tag rows, right of its grip.
+        tag,
+        /// A pane's body, right of its rail: absent while it is collapsed.
+        body,
+        /// The scroll rail down a pane's left edge, beside its body.
+        rail,
+        /// A transient band over the body's top rows (a message, a prompt).
+        notice,
+        column_grip,
+        column_tag,
+        workspace_tag,
+    };
+    pub const none = std.math.maxInt(u8);
+
+    kind: Kind,
+    /// The pane slot, or the column, the part belongs to; `none` for the
+    /// page and the workspace tag.
+    owner: u8 = none,
+    serial: u32 = 0,
+    rect: layout.Rect,
+    /// The pane or column has the keyboard's focus.
+    active: bool = false,
+    /// A rail's thumb: rows from the rail's top, and how many. Zero rows is
+    /// a rail with no thumb (an image).
+    thumb_y: u16 = 0,
+    thumb_h: u16 = 0,
+    /// A notice's index in its pane's `notices`.
+    notice: u8 = 0,
+    /// Cells the column-move rail takes off the right edge while it runs
+    /// there: layers and pixel shells stop short of them, the grid does not.
+    clip: u16 = 0,
+};
+
+pub const MAX_REGIONS = 1 + MAX_PANES * (4 + panes.Pane.Notices.max) + pardes.MAX_COLS * 2 + 1;
+
 /// The canonical interface: what a frame of pardes IS. The tty shell writes
 /// these cells to vaxis one-to-one; the SDL shells rasterize them.
 pub const Surface = struct {
@@ -337,6 +382,8 @@ pub const Surface = struct {
     tag_layers: [MAX_TAG_LAYERS]TagLayer = @splat(.{}),
     cols: u16 = 0,
     rows: u16 = 0,
+    regions: [MAX_REGIONS]Region = undefined,
+    nregions: u16 = 0,
     cells: []Cell = &.{},
     /// bar: draw an insert-style thin cursor instead of the block
     cursor: ?struct { x: u16, y: u16, bar: bool = false } = null,
@@ -357,6 +404,16 @@ pub const Surface = struct {
         return &s.body_layers;
     }
 
+    pub fn regionList(s: *const Surface) []const Region {
+        return s.regions[0..s.nregions];
+    }
+
+    /// The first part of `kind` that `owner` has: its tag, its rail.
+    pub fn region(s: *Surface, kind: Region.Kind, owner: usize) ?*Region {
+        for (s.regions[0..s.nregions]) |*r| if (r.kind == kind and r.owner == owner) return r;
+        return null;
+    }
+
     pub fn panelTracks(s: *const Surface) []const animation.Track {
         return s.panel_tracks[0..s.npanel_tracks];
     }