ludic.ui: a new component instance's first build is declared - a first show mid-play is not a frame's keep

Master's windowed fog profile failed the fence at walk t 35 s: +512 B from value_new / value_put /
value_slot / value_lists under bd_class and cmp_keycap_model - a KeyCap first shown mid-walk.

It is a first build, bounded, not a per-show leak: an unmounted instance goes to in_free and the next
show of its class reuses it (in_reuse, `renew`), its props and model objects kept and filled in place.
Only a NEW instance makes them - bounded by how many of that class are up at once, and the ones
unmounted less than two builds ago. in_reuse already declared the record; the props and model objects
and their first fill, made afterwards in bd_class, were not. They are now: in_reuse marks a new record
`fresh`, and bd_class's first fill of it goes through bd_first_fill (@alloc_ok) - a reused instance's
fill stays judged, so a real per-show leak would still fail.

Golden ui_first_show: a component first shown at frame 700, once the fence is judging, then hidden and
shown twice more: bad 0 (the toolchain before this fails frame 701: +464 B value_new from value_slot
under cmp_cell_model, value_put grow - the profile's failure). The 37 ui examples pass.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

examples/library/ui_first_show.ludic

@@ -0,0 +1,27 @@
+# ui_first_show.ludic - a component shown for the first time once the fence is judging (a prompt's key
+# hint mid-walk) makes its instance's props and model: declared, once per instance, and the failing
+# fence lets it through; hidden and shown again, the instance is reused and nothing more is made:
+#   bad 0 shown 3
+import "ludic.ui"
+import "ui_first_show_parts/Cell.ludic"
+import "ui_first_show_parts/Host.ludic"
+program UiFirstShow {
+  numbers float
+  function frame(ui_st: mut UiState) -> UiNode {
+    let root: UiNode = ui_nodes(ui_st, "Host", null)
+    ui_place(ui_st, root, 0.0, 0.0, 400.0, 400.0)
+    return root
+  }
+  entry (ui_st: mut UiState) {
+    var shown = 0
+    for f in 0 .. 1400 {
+      let root = frame(ui_st)
+      if f == 700 or f == 900 or f == 1000 or f == 1100 or f == 1200 {
+        ui_press(ui_st, root.children[0].children[0])
+        if f != 900 and f != 1100 { shown += 1 }
+      }
+      Mem.frame()
+    }
+    print(`bad {Mem.bad_frames()} shown {shown}`)
+  }
+}

examples/library/ui_first_show_parts/Cell.lss

@@ -0,0 +1 @@
+.cell { width: 100px; height: 40px }

examples/library/ui_first_show_parts/Cell.ludic

@@ -0,0 +1,3 @@
+component Cell {
+  prop caption: string = ""
+}

examples/library/ui_first_show_parts/Cell.xml

@@ -0,0 +1,3 @@
+<div class="item">
+  <button class="cell" on-click="emit click"><p>{caption}</p></button>
+</div>

examples/library/ui_first_show_parts/Host.lss

@@ -0,0 +1 @@
+.t { width: 60px; height: 30px }

examples/library/ui_first_show_parts/Host.ludic

@@ -0,0 +1,4 @@
+component Host {
+  state on: bool = false
+  on flip() { on = not on }
+}

examples/library/ui_first_show_parts/Host.xml

@@ -0,0 +1,4 @@
+<div>
+  <button class="t" on-click="flip()">t</button>
+  <if test="{on}"><Cell caption="a"/></if>
+</div>

packages/ludic.ui/build_class.ludic

@@ -5,17 +5,8 @@ function bd_class(ui_st: mut UiState, k: UiTpl, e: UiEnv, key: string, out: []Ui
   let cls = k.cls
   uc_load(ui_st, cls)
   let it = in_get(ui_st, key, cls)
-  if it.props == null { it.props = Value.object() }
-  let props = it.props
-  Value.clear(props)
-  for i in 0 .. len(k.keys) {
-    let a = k.keys[i]
-    if a != "class" and a != "style" and a != "id" { Value.put(props, a, ui_eval(ui_st, k.vals[i], e)) }
-  }
-  cls.props(it.ptr, props)
   let ce = env_new(ui_st, null)
-  if it.model == null { it.model = Value.object() }
-  ce.model = cls.model(it.ptr, it.model)
+  if it.fresh { ce.model = bd_first_fill(ui_st, it, k, e) } else { ce.model = bd_fill(ui_st, it, k, e) }
   ce.inst = it
   ce.ctx = e.ctx
   ce.slot = k
@@ -34,6 +25,26 @@ function bd_class(ui_st: mut UiState, k: UiTpl, e: UiEnv, key: string, out: []Ui
   bd_kids(ui_st, root, ce, key, out)
   if len(out) > at { bd_pass_down(ui_st, out[at], k, e) }
 }
+# an instance's props and model, filled in place into the objects it keeps (a reused one's are kept)
+function bd_fill(ui_st: mut UiState, it: UiInst, k: UiTpl, e: UiEnv) -> Val {
+  if it.props == null { it.props = Value.object() }
+  let props = it.props
+  Value.clear(props)
+  for i in 0 .. len(k.keys) {
+    let a = k.keys[i]
+    if a != "class" and a != "style" and a != "id" { Value.put(props, a, ui_eval(ui_st, k.vals[i], e)) }
+  }
+  it.cls.props(it.ptr, props)
+  if it.model == null { it.model = Value.object() }
+  return it.cls.model(it.ptr, it.model)
+}
+# a new instance's first fill makes its props and model objects and every Value in them - once per
+# instance, which in_reuse bounds (a prompt's key hint first shown mid-walk was judged as a frame's keep)
+@alloc_ok("a new component instance's first build: its props and model, then kept or reused")
+function bd_first_fill(ui_st: mut UiState, it: UiInst, k: UiTpl, e: UiEnv) -> Val {
+  it.fresh = false
+  return bd_fill(ui_st, it, k, e)
+}
 # <Card class="wide" style="margin: 4px" id="c"> puts those on the card's own root element; when that
 # root is itself a component, each user in turn adds theirs (the outermost's id wins)
 function bd_pass_down(ui_st: mut UiState, n: UiNode, k: UiTpl, e: UiEnv) -> void {

packages/ludic.ui/instance.ludic

@@ -7,6 +7,7 @@ property UiInst {
   seen: int = 0
   props: Val = null             # its props, filled again each frame into the same object
   model: Val = null             # and its model, filled in place by the class's model()
+  fresh: bool = false           # made, not reused: its first build makes its props and model
 }
 # builds before an unmounted instance is mounted again: the tree that last named it is good for two
 const IN_SPARE_AFTER: int = 2
@@ -41,6 +42,7 @@ function in_reuse(ui_st: mut UiState, k: UiClass) -> UiInst {
   let it = new UiInst
   it.cls = k
   it.ptr = k.make()
+  it.fresh = true
   return it
 }
 # after a build of `screen`: its instances the build did not reach are unmounted

tools/ludic-cli/test.ludic

@@ -1248,6 +1248,7 @@ function cmd_dev_test() -> int {
   controller_case("library/ui_emit_click", "", "got 2 | pressed: got 1", "ui_emit_click.ludic (L11: a component's `emit click` reaches its user's on-click, by the mouse and by a press)")
   controller_case("library/ui_select_arrows", "", "prev 0 next next 2", "ui_select_arrows.ludic (L11: a select's < steps back and its > forward)")
   controller_case("library/ui_pointer_through", "", "pressed 1, hovered #4a5058; > hovered 1", "ui_pointer_through.ludic (L11: the pointer looks through a root with no size to a positioned panel's button; a select's > answers :hover)")
+  controller_case("library/ui_first_show", "", "bad 0 shown 3", "ui_first_show.ludic (L11: a component first shown once the fence is judging makes its props and model declared, once per instance; shown again, it is reused)")
   controller_case("library/ui_submit", "", "[hi] chat '' | [hi][yo][Ada] chat '' name 'Ada'", "ui_submit.ludic (L11: on-submit on a text field by Enter or A, clear-on-submit, the focus kept)")
   controller_case("library/ui_zoom", "", "plain 100 pad 10 text 16 h 20 | half 50 pad 5 text 8 h 10 | half of twice 100 | fit 50 em 16", "ui_zoom.ludic (L11: zoom scales a subtree's lengths, text and layout, multiplies, and takes min() and a length over a length)")
   controller_case("library/ui_hold", "", "31 frames 500 ms t 500 | 121 frames 500 ms t 500 | pad 16 frames 250 ms t 250 | dududu", "ui_hold.ludic (L11: on-hold every frame a button is held, by the pointer or A, with dt and t on the clock at any rate)")