diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5cbbab7..3a83d32 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -76,7 +76,7 @@ dmod_add_library(${DMOD_MODULE_NAME} ${DMOD_MODULE_VERSION}
 )
 
 dmod_link_modules(${DMOD_MODULE_NAME}
-    dmvsi@>=0.5
+    dmvsi@>=0.6
     dmvs_js@>=0.1
 )
 
diff --git a/README.md b/README.md
index ab3e939..a929ef0 100644
--- a/README.md
+++ b/README.md
@@ -141,6 +141,16 @@ What's reported and left out:
 A class changes only the look of its element; what it moves around it
 stays.
 
+**Talking to the application.** A page is shown by an application on
+dmodOS; `dmod` (dmvs_js) is the channel between them -
+`dmod.prop()`, `get()`, `set()`, `onchange()`, `emit()`. One thing more is
+said in HTML: `data-dmod-width="name"` makes an element as wide as the
+integer property `name` says - its laid out width times the property over
+`data-dmod-scale` (1000: per mille; `data-dmod-value` its initial value when
+no script makes the property). What is in the element is painted at its
+whole width and cut at the property's end: a progress bar the application
+moves. In a browser the page's own `dmod.js` does it.
+
 ## Resources
 
 Style sheets, fonts and images are files next to the page; a URL is read
diff --git a/src/layout.c b/src/layout.c
index ae1e9d6..bec9604 100644
--- a/src/layout.c
+++ b/src/layout.c
@@ -701,10 +701,14 @@ static int32_t place_line(conv_t* c, node_t* block, item_t* items, uint32_t from
 static int32_t layout_inline(conv_t* c, node_t* block, node_t* first, node_t* stop, int32_t x0, int32_t y0, int32_t avail,
                              int32_t cb_h, bool* first_baseline_set)
 {
-    item_t* storage = arena_alloc(&c->arena, MAX_ITEMS * sizeof(item_t));
+    /* (on the heap, not the arena: a page lays out its inline content many times - flex measures) */
+    item_t* storage = Dmod_Malloc(MAX_ITEMS * sizeof(item_t));
     items_t it = { c, storage, 0, true };
     if (storage == NULL)
+    {
+        c->arena.failed = true;
         return 0;
+    }
     /* The children from `first` up to `stop`, as if they were all of a parent */
     node_t holder;
     memset(&holder, 0, sizeof(holder));
@@ -741,6 +745,7 @@ static int32_t layout_inline(conv_t* c, node_t* block, node_t* first, node_t* st
                 it.items[i].node->box.container = block;
             }
         }
+        Dmod_Free(storage);
         return 0;
     }
 
@@ -784,6 +789,7 @@ static int32_t layout_inline(conv_t* c, node_t* block, node_t* first, node_t* st
         if (end == it.count)
             break;
     }
+    Dmod_Free(storage);
     return y - y0;
 }
 
@@ -868,10 +874,13 @@ static bool replaced_size(conv_t* c, node_t* n, int32_t* w, int32_t* h)
 
 static int32_t intrinsic_items(conv_t* c, node_t* n, bool max_content)
 {
-    item_t* storage = arena_alloc(&c->arena, MAX_ITEMS * sizeof(item_t));
+    item_t* storage = Dmod_Malloc(MAX_ITEMS * sizeof(item_t));     /* (on the heap: see layout_inline()) */
     items_t it = { c, storage, 0, true };
     if (storage == NULL)
+    {
+        c->arena.failed = true;
         return 0;
+    }
     inline_items(&it, n, 0, AUTO_SIZE, true, max_content, 0);
     int32_t best = 0, line = 0, word = 0;
     for (uint32_t i = 0; i < it.count; i++)
@@ -899,6 +908,7 @@ static int32_t intrinsic_items(conv_t* c, node_t* n, bool max_content)
             word = 0;
         }
     }
+    Dmod_Free(storage);
     return max32(best, max_content ? line : word);
 }
 
@@ -1087,10 +1097,13 @@ static int32_t layout_flex(conv_t* c, node_t* n, int32_t x0, int32_t y0, int32_t
     int32_t main_avail = row ? cw : ch;
     len_t gap_len = row ? st->column_gap : st->row_gap;
     int32_t gap = (gap_len.kind == LEN_SET) ? len_resolve(gap_len, max32(main_avail, 0)) : 0;
-    flex_item_t* items = arena_alloc(&c->arena, MAX_FLEX * sizeof(flex_item_t));
+    flex_item_t* items = Dmod_Malloc(MAX_FLEX * sizeof(flex_item_t));     /* (on the heap: see layout_inline()) */
     uint32_t count = 0;
     if (items == NULL)
+    {
+        c->arena.failed = true;
         return 0;
+    }
 
     for (node_t* k = n->first; k != NULL; k = k->next)
     {
@@ -1334,6 +1347,7 @@ static int32_t layout_flex(conv_t* c, node_t* n, int32_t x0, int32_t y0, int32_t
             baseline_set = true;
         }
     }
+    Dmod_Free(items);
     if (row)
         return (ch != AUTO_SIZE) ? ch : line_cross;
     return (ch != AUTO_SIZE) ? ch : used;
diff --git a/src/script.c b/src/script.c
index 72b419d..1c9cd0d 100644
--- a/src/script.c
+++ b/src/script.c
@@ -1125,7 +1125,7 @@ static bool has_class(const node_t* n, const char* name)
 }
 
 /* The states laid out, kept for painting their looks (c->states) */
-#define MAX_STATES      48u
+#define MAX_STATES      96u
 
 typedef struct
 {
@@ -1831,6 +1831,86 @@ static void texts(script_t* sc, node_t* n, uint32_t depth)
     }
 }
 
+/*
+ * data-dmod-width="name": the element's width follows the property `name`
+ * of the view (dmod.prop(), or made here) - the width it is laid out at
+ * times the property over data-dmod-scale (1000: per mille). What is in it
+ * is painted at its whole width and cut where the property puts its end
+ * (a progress bar). The application that shows the view sets the property.
+ */
+
+/* The integer property `name`: one the scripts made, else a new one at `initial` */
+static dmvsi_var_t prop_var(conv_t* c, const char* name, int32_t initial)
+{
+    dmvsi_var_info_t info;
+    for (dmvsi_var_t v = 1; dmvsi_var_info(c->doc, v, &info) == 0; v++)
+    {
+        const char* prop = dmvsi_var_prop(c->doc, v);
+        if (prop != NULL && strcmp(prop, name) == 0)
+            return (info.kind == DMVSI_VAR_INT) ? v : 0;
+    }
+    dmvsi_var_t v = dmvsi_add_var(c->doc, name, initial);
+    if (v != 0 && dmvsi_set_prop(c->doc, v, name) != 0)
+        return 0;
+    return v;
+}
+
+static int32_t attr_number(const node_t* e, const char* name, int32_t otherwise)
+{
+    const char* a = node_attr(e, name);
+    if (a == NULL || *a == '\0')
+        return otherwise;
+    int32_t v = 0;
+    bool negative = *a == '-';
+    for (a += negative ? 1 : 0; *a >= '0' && *a <= '9'; a++)
+        v = v * 10 + (*a - '0');
+    return negative ? -v : v;
+}
+
+static int bind_widths(conv_t* c, node_t* n, uint32_t depth)
+{
+    for (node_t* e = n->first; e != NULL && depth < 200U; e = e->next)
+    {
+        if (e->kind != NODE_ELEMENT)
+            continue;
+        const char* name = node_attr(e, "data-dmod-width");
+        if (name != NULL && *name != '\0' && e->box.placed)
+        {
+            int32_t scale = attr_number(e, "data-dmod-scale", 1000);
+            int32_t w = e->box.w / DMVSI_UNIT;
+            dmvsi_var_t prop = prop_var(c, name, attr_number(e, "data-dmod-value", 0));
+            dmvsi_var_info_t info;
+            if (prop == 0 || scale <= 0 || dmvsi_var_info(c->doc, prop, &info) != 0)
+            {
+                WARN(c, "data-dmod-width of #%s: \"%s\" is no integer property - not converted\n", label_of(e), name);
+                continue;
+            }
+            if (e->dynamic == NULL && (e->dynamic = arena_alloc(&c->arena, sizeof(dynamic_t))) == NULL)
+                return -ENOMEM;
+            char label[48];
+            Dmod_SnPrintf(label, sizeof(label), "%s_w", label_of(e));
+            int64_t now = (int64_t)info.initial * w / scale;
+            dmvsi_var_t px = dmvsi_add_var(c->doc, label, (int32_t)((now < 0) ? 0 : (now > w) ? w : now));
+            /* On a change: px = clamp(prop, 0, scale) * w / scale */
+            dmvsi_action_t a[5];
+            memset(a, 0, sizeof(a));
+            a[0].kind = DMVSI_ACT_SET; a[0].var = px; a[0].operand = prop;
+            a[1].kind = DMVSI_ACT_MAX; a[1].var = px; a[1].value = 0;
+            a[2].kind = DMVSI_ACT_MIN; a[2].var = px; a[2].value = scale;
+            a[3].kind = DMVSI_ACT_MUL; a[3].var = px; a[3].value = w;
+            a[4].kind = DMVSI_ACT_DIV; a[4].var = px; a[4].value = scale;
+            dmvsi_handler_t h = (px != 0) ? dmvsi_add_handler(c->doc, a, 5) : 0;
+            if (h == 0 || dmvsi_on_change(c->doc, prop, h) != 0)
+                return -ENOMEM;
+            e->dynamic->bind[DMVSI_BIND_W] = px;
+        }
+        int ret = bind_widths(c, e, depth + 1U);
+        if (ret != 0)
+            return ret;
+    }
+    return 0;
+}
+
 int script_compile(conv_t* c)
 {
     script_t* sc = Dmod_Malloc(sizeof(*sc));
@@ -1847,7 +1927,10 @@ int script_compile(conv_t* c)
     find_scripts(sc, c->document, programs, 0);
     int status = 0;
     if (programs->count == 0)
+    {
+        status = bind_widths(c, c->document, 0);     /* (no scripts: only what the application sets) */
         goto done;
+    }
 
     dmvs_js_host_t host;
     memset(&host, 0, sizeof(host));
@@ -1891,6 +1974,8 @@ int script_compile(conv_t* c)
         status = expand_held(sc);
     if (status == 0)
         status = lay_out_changes(sc);
+    if (status == 0)
+        status = bind_widths(c, c->document, 0);
     if (status == 0)
         status = make_src_variants(sc);
     if (status == 0)
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index ecc20bd..1511c6e 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -10,7 +10,7 @@ dmod_add_test(${DMOD_MODULE_NAME} ${DMOD_MODULE_VERSION}
 
 # dmvs_js: dmvs_html needs it loaded to convert a page's scripts
 dmod_link_modules(${DMOD_MODULE_NAME}
-    dmvsi@>=0.5
+    dmvsi@>=0.6
     dmvs_js@>=0.1
 )