diff --git a/nur_src/v/v.php b/nur_src/v/v.php
index a657974..db94d17 100644
--- a/nur_src/v/v.php
+++ b/nur_src/v/v.php
@@ -261,7 +261,7 @@ class v {
     return $pieces;
   }
 
-  private static function _list(?iterable $values, ?string $sep=", ", ?string $prefix=null, ?string $suffix=null, ?callable $function): array {
+  private static function _list(?iterable $values, ?string $sep=", ", ?string $prefix=null, ?string $suffix=null, ?callable $function=null): array {
     $vs = [];
     if ($values !== null) {
       $functx = $function !== null? func::_prepare($function): null;
@@ -285,7 +285,7 @@ class v {
   }
 
   static final function simple_list(?iterable $values, ?string $sep=", ", ?string $prefix=null, ?string $suffix=null): array {
-    return self::_list($values, $sep, $prefix, $suffix, null);
+    return self::_list($values, $sep, $prefix, $suffix);
   }
 
   const LIST_SCHEMA = [
diff --git a/src/web/content/BlockTag.php b/src/web/content/BlockTag.php
new file mode 100644
index 0000000..ad5c04a
--- /dev/null
+++ b/src/web/content/BlockTag.php
@@ -0,0 +1,33 @@
+<?php
+namespace nulib\web\content;
+
+class BlockTag extends Tag {
+  const START_PREFIX = null;
+  const START_SUFFIX = null;
+
+  const END_PREFIX = null;
+  const END_SUFFIX = "\n";
+
+  protected ?string $startPrefix;
+  protected ?string $startSuffix;
+
+  protected ?string $endPrefix;
+  protected ?string $endSuffix;
+
+  function reset(string $tag, ?array $params=null, $content=null): self {
+    parent::reset($tag, $params, $content);
+    $this->startPrefix = $params["start_prefix"] ?? self::START_PREFIX;
+    $this->startSuffix = $params["start_suffix"] ?? self::START_SUFFIX;
+    $this->endPrefix = $params["end_prefix"] ?? self::END_PREFIX;
+    $this->endSuffix = $params["end_suffix"] ?? self::END_SUFFIX;
+    return $this;
+  }
+
+  function getStart(): array {
+    return [$this->startPrefix, ...parent::getStart(), $this->startSuffix];
+  }
+
+  function getEnd(): array {
+    return [$this->endPrefix, ...parent::getEnd(), $this->endSuffix];
+  }
+}
diff --git a/src/web/content/EmptyTag.php b/src/web/content/EmptyTag.php
new file mode 100644
index 0000000..2e60179
--- /dev/null
+++ b/src/web/content/EmptyTag.php
@@ -0,0 +1,6 @@
+<?php
+namespace nulib\web\content;
+
+class EmptyTag extends Tag {
+  const ALLOW_EMPTY = true;
+}
diff --git a/src/web/content/Tag.php b/src/web/content/Tag.php
index e50da56..6703ff9 100644
--- a/src/web/content/Tag.php
+++ b/src/web/content/Tag.php
@@ -2,35 +2,179 @@
 namespace nulib\web\content;
 
 
+use Closure;
 use nulib\A;
+use nulib\cl;
 use nulib\php\content\c;
 use nulib\php\content\IContent;
+use nulib\php\content\IPrintable;
+use nulib\php\func;
+use nur\str;
 
-class Tag implements IContent {
-  function __construct(string $tag, $content=null) {
-    $this->tag = $tag;
-    $content = c::q($content);
-    $this->content = $content;
+class Tag implements IContent, IPrintable {
+  const ALLOW_EMPTY = false;
+
+  const REQUIRE_CONTENT = false;
+
+  function __construct(string $tag, ?array $params=null, $content=null) {
+    $this->reset($tag, $params, $content);
   }
 
-  protected string $tag;
-  protected iterable $content;
+  protected bool $allowEmpty;
 
-  function add($content): self {
-    if (!is_array($this->content)) {
-      # si c'est un itérable, l'inclure avec un merge statique, afin de pouvoir
-      # rajouter des éléments
-      $this->content = [[[], $this->content]];
-    }
-    A::merge($this->content, c::q($content));
+  protected bool $requireContent;
+
+  protected string $tag;
+
+  protected iterable $contents;
+
+  protected ?array $attrs = null;
+
+  protected ?array $children = null;
+
+  protected bool $empty = false;
+
+  function reset(string $tag, ?array $params=null, $content=null): self {
+    $this->allowEmpty = $params["allow_empty"] ?? self::ALLOW_EMPTY;
+    $this->requireContent = $params["require_content"] ?? self::REQUIRE_CONTENT;
+    $this->tag = $tag;
+    $this->contents = c::q($content);
+    $this->attrs = null;
+    $this->children = null;
+    $this->empty = false;
     return $this;
   }
 
-  function getContent($object_or_class=null): iterable {
+  function add($content): self {
+    if (!is_array($this->contents)) {
+      # si c'est un itérable, l'inclure avec un merge statique, afin de pouvoir
+      # rajouter des éléments
+      $contents = $this->contents;
+      $this->contents = [static function() use ($contents) {
+        return $contents;
+      }];
+    }
+    A::merge($this->contents, c::q($content));
+    $this->attrs = null;
+    $this->children = null;
+    $this->empty = false;
+    return $this;
+  }
+
+  private function add_contents(iterable $source, array &$contents, array &$attrs): void {
+    $index = 0;
+    foreach ($source as $key => $content) {
+      if ($content instanceof Closure) {
+        # les closure sont appelés dès la résolution
+        $content = func::with($content)->invoke([$this]);
+        if ($key === $index) {
+          $index++;
+          # le résultat est inséré tels quels dans le flux
+          if (is_iterable($content)) {
+            $contents[] = $content;
+          } else {
+            A::merge($contents, cl::with($content));
+          }
+        } else {
+          # le résultat est la valeur de l'attribut
+          A::merge($attrs[$key], [$content]);
+        }
+      } elseif (is_array($content)) {
+        if ($key === $index) {
+          $index++;
+          $this->add_contents($content, $contents, $attrs);
+        } else {
+          foreach ($content as &$value) {
+            if ($value instanceof Closure) {
+              $value = func::with($value)->invoke([$this]);
+            }
+          }; unset($value);
+          A::merge($attrs[$key], $content);
+        }
+      } elseif ($key === $index) {
+        $index++;
+        A::merge($contents, cl::with($content));
+      } else {
+        A::merge($attrs[$key], [$content]);
+      }
+    }
+  }
+
+  function resolve($objectOrClass=null): self {
+    if ($this->attrs === null) {
+      $attrs = [];
+      $contents = [];
+      $this->add_contents($this->contents, $contents, $attrs);
+      $this->attrs = $attrs;
+      $this->children = c::resolve($contents, $objectOrClass);
+      $this->empty = $this->allowEmpty && !$this->children;
+    }
+    return $this;
+  }
+
+  function getStart(): array {
+    $parts = ["<{$this->tag}"];
+    foreach ($this->attrs as $key => $value) {
+      if ($value === null || $value === false) continue;
+      if ($value === true || $value === [true]) {
+        $value = $key;
+      } elseif (is_array($value)) {
+        $value = str::join3($value);
+        if (!$value) continue;
+      }
+      $parts[] = " ";
+      $parts[] = $key;
+      $parts[] = "=\"";
+      $parts[] = htmlspecialchars($value);
+      $parts[] = "\"";
+    }
+    $parts[] = $this->empty? "/>": ">";
+    return $parts;
+  }
+
+  function getChildren(): array {
+    return $this->children;
+  }
+
+  function getEnd(): array {
+    if ($this->empty) return [];
+    else return ["</{$this->tag}>"];
+  }
+
+  function getContent($objectOrClass=null): iterable {
+    $this->resolve($objectOrClass);
+    if ($this->requireContent && !$this->children) return [];
     return [
-      "<$this->tag>",
-      ...c::resolve($this->content, $object_or_class),
-      "</$this->tag>",
+      ...$this->getStart(),
+      ...$this->getChildren(),
+      ...$this->getEnd(),
     ];
   }
+
+  /** afficher le tag ouvrant. */
+  function printStart(): void {
+    $this->resolve();
+    c::write($this->getStart());
+  }
+
+  /** afficher le contenu enfant */
+  function printChildren(): void {
+    $this->resolve();
+    c::write($this->getChildren());
+  }
+
+  /** afficher le tag fermant */
+  function printEnd(): void {
+    $this->resolve();
+    c::write($this->getEnd());
+  }
+
+  /** afficher le tag et le contenu enfant */
+  function print(): void {
+    $this->resolve();
+    if ($this->requireContent && !$this->children) return;
+    c::write($this->getStart());
+    c::write($this->getChildren());
+    c::write($this->getEnd());
+  }
 }
diff --git a/src/web/content/v.php b/src/web/content/v.php
index e6d7fbb..1d57970 100644
--- a/src/web/content/v.php
+++ b/src/web/content/v.php
@@ -5,6 +5,65 @@ namespace nulib\web\content;
  * Class v: classe outil pour gérer du contenu pour le web
  */
 class v {
-  static function h1($content): iterable { return (new Tag("h1", $content))->getContent(); }
-  const h1 = [Tag::class, null, "h1"];
+  private const require_content = ["require_content" => true];
+  private const start_nl = ["start_suffix" => "\n"];
+
+  private static function h(string $tag, $content): BlockTag {
+    return new BlockTag($tag, self::require_content, $content);
+  }
+  static function h1($content): BlockTag { return self::h("h1", $content); }
+  const H1 = [BlockTag::class, false, "h1", self::require_content];
+  static function h2($content): BlockTag { return self::h("h2", $content); }
+  const H2 = [BlockTag::class, false, "h2", self::require_content];
+  static function h3($content): BlockTag { return self::h("h3", $content); }
+  const H3 = [BlockTag::class, false, "h3", self::require_content];
+  static function h4($content): BlockTag { return self::h("h4", $content); }
+  const H4 = [BlockTag::class, false, "h4", self::require_content];
+  static function h5($content): BlockTag { return self::h("h5", $content); }
+  const H5 = [BlockTag::class, false, "h5", self::require_content];
+  static function h6($content): BlockTag { return self::h("h6", $content); }
+  const H6 = [BlockTag::class, false, "h6", self::require_content];
+
+  static function hr($content): EmptyTag { return (new EmptyTag("hr", null, $content)); }
+  const HR = [EmptyTag::class, false, "hr", null];
+  static function br($content): EmptyTag { return (new EmptyTag("br", null, $content)); }
+  const BR = [EmptyTag::class, false, "br", null];
+
+  static function div($content): Tag { return (new Tag("div", null, $content)); }
+  const DIV = [Tag::class, false, "div", null];
+  static function p($content): Tag { return (new Tag("p", self::require_content, $content)); }
+  const P = [Tag::class, false, "p", self::require_content];
+  static function pre($content): Tag { return (new Tag("pre", self::require_content, $content)); }
+  const PRE = [Tag::class, false, "pre", self::require_content];
+
+  static function span($content): Tag { return (new Tag("span", null, $content)); }
+  const SPAN = [Tag::class, false, "span", null];
+  static function b($content): Tag { return (new Tag("b", null, $content)); }
+  const B = [Tag::class, false, "b", null];
+  static function i($content): Tag { return (new Tag("i", null, $content)); }
+  const I = [Tag::class, false, "i", null];
+  static function em($content): Tag { return (new Tag("em", null, $content)); }
+  const EM = [Tag::class, false, "em", null];
+  static function strong($content): Tag { return (new Tag("strong", null, $content)); }
+  const STRONG = [Tag::class, false, "strong", null];
+
+  static function ul($content): BlockTag { return (new BlockTag("ul", self::start_nl, $content)); }
+  const UL = [BlockTag::class, false, "ul", self::start_nl];
+  static function ol($content): BlockTag { return (new BlockTag("ol", self::start_nl, $content)); }
+  const OL = [BlockTag::class, false, "ol", self::start_nl];
+  static function li($content): BlockTag { return (new BlockTag("li", null, $content)); }
+  const LI = [BlockTag::class, false, "li", null];
+
+  static function table($content): BlockTag { return (new BlockTag("table", self::start_nl, $content)); }
+  const TABLE = [BlockTag::class, false, "table", self::start_nl];
+  static function thead($content): BlockTag { return (new BlockTag("thead", self::start_nl, $content)); }
+  const THEAD = [BlockTag::class, false, "thead", self::start_nl];
+  static function tbody($content): BlockTag { return (new BlockTag("tbody", self::start_nl, $content)); }
+  const TBODY = [BlockTag::class, false, "tbody", self::start_nl];
+  static function tr($content): BlockTag { return (new BlockTag("tr", null, $content)); }
+  const TR = [BlockTag::class, false, "tr", null];
+  static function th($content): Tag { return (new Tag("th", null, $content)); }
+  const TH = [Tag::class, false, "th", null];
+  static function td($content): Tag { return (new Tag("td", null, $content)); }
+  const TD = [Tag::class, false, "td", null];
 }
diff --git a/src/web/layout/README.md b/src/web/layout/README.md
new file mode 100644
index 0000000..515c0a0
--- /dev/null
+++ b/src/web/layout/README.md
@@ -0,0 +1,78 @@
+# nulib\web\layout
+
+faire le layout d'avance, e.g
+~~~php
+ly::prepare([
+  ["row", "class" => "row-gap",
+    ["col", 2, "content" => "a"],
+    ["col", 10, "content" => "b"],
+  ],
+  ["row",
+    ["col", 6, "content" => "c"],
+    ["col", 6, "content" => "d"],
+  ],
+]);
+~~~
+dans cet exemple, il y a 4 sections de contenu appelées "a", "b", "c" et "d"
+
+désactiver le contenu dans un colonne ou un row avec `"content" => false`
+
+faut-il prévoir d'autres types que "row" et "col", par exemple "panel"?
+
+une fois que le layout est fait, on sélectionne les sections avant de les remplir
+~~~php
+ly::start("a");
+//... contenu de la section "a"
+ly::start("b");
+//... contenu de la section "b"
+ly::end();
+~~~
+tant que les sections sont mentionnées dans l'ordre, l'affichage se fait au fur
+et à mesure
+
+*éventuellement*, supporter un mode où les sections sont remplies dans un ordre
+quelconque. dans ce cas, le contenu est enregistré dans un fichier temporaire
+mémoire avec `ob_start()` et `ob_end()` puis il est affiché à la fin lors de
+ly::end()
+exemple:
+~~~php
+ly::prepare([["row",
+  ["col", 3, "content" => "menu"],
+  ["col", 9, "content" => "details"],
+]]);
+foreach ($items as $item) {
+  ly::start("menu");
+  write(link);
+  ly::start("details");
+  write(details);
+}
+~~~
+
+## alternatives
+
+les ids de contenu sont des clés
+~~~php
+ly::prepare([["row",
+  "menu" => ["col", 3],
+  "details" => ["col", 9],
+]]);
+~~~
+conflit possible avec `"class" => xxx` et autres attributs?
+
+`ly::start($id, $func)` permet de basculer temporairement dans une section
+~~~php
+ly::start("details");
+foreach ($items as $item) {
+  ly::start("menu", function() {
+    write(link);  
+  });
+  write(details);
+}
+~~~
+
+le comportement d'enregistrer le contenu devrait être demandé explicitement
+* true
+* false: exception si une section n'est pas remplie avant de passer à la suivante
+* auto: activé si les sections sont accédées dans un ordre différent du naturel
+
+-*- coding: utf-8 mode: markdown -*- vim:sw=4:sts=4:et:ai:si:sta:fenc=utf-8:noeol:binary
\ No newline at end of file
diff --git a/tests/php/content/cTest.php b/tests/php/content/cTest.php
index 64875e4..f6d0cf3 100644
--- a/tests/php/content/cTest.php
+++ b/tests/php/content/cTest.php
@@ -1,9 +1,10 @@
 <?php
 namespace nulib\php\content;
 
-use nulib\php\content\impl\html;
+use nulib\php\content\impl\AContent;
+use nulib\php\content\impl\APrintable;
+use nulib\tests\TestCase;
 use nulib\web\content\v;
-use PHPUnit\Framework\TestCase;
 
 class cTest extends TestCase {
   function testTo_string() {
@@ -20,21 +21,24 @@ class cTest extends TestCase {
     self::assertSame("hello. world", c::to_string(["hello.", "world"]));
     self::assertSame("hello.<world>", c::to_string(["hello.", "<world>"]));
 
-    self::assertSame(
-      "<h1>title&lt;q/&gt;</h1><p>hello<nq/><span>brave&lt;q/&gt;</span><span>world<nq/></span></p>",
-      c::to_string([
-        [html::H1, "title<q/>"],
-        [html::P, [
-          "hello<nq/>",
-          [html::SPAN, "brave<q/>"],
-          [html::SPAN, ["world<nq/>"]],
-        ]],
-      ]));
-  }
+    self::assertSame(<<<EOT
+<h1>title&lt;q/&gt;</h1>
+<p>hello<nq/><span>brave&lt;q/&gt;</span><span>world<nq/></span></p>
+EOT, c::to_string([
+      [v::H1, "title<q/>"],
+      [v::P, [
+        "hello<nq/>",
+        [v::SPAN, "brave<q/>"],
+        [v::SPAN, ["world<nq/>"]],
+      ]],
+    ]));
 
-  function testXxx() {
-    $content = [[v::h1, "hello"]];
-    self::assertSame("<h1>hello</h1>", c::to_string($content));
+    self::assertSame(<<<EOT
+<span>content</span><p>printable</p>
+EOT, c::to_string([
+      new AContent(),
+      new APrintable(),
+    ]));
   }
 }
 
diff --git a/tests/php/content/impl/ATag.php b/tests/php/content/impl/ATag.php
deleted file mode 100644
index b4cc2ed..0000000
--- a/tests/php/content/impl/ATag.php
+++ /dev/null
@@ -1,23 +0,0 @@
-<?php
-namespace nulib\php\content\impl;
-
-use nulib\php\content\c;
-use nulib\php\content\IContent;
-
-class ATag implements IContent {
-  function __construct(string $tag, $content=null) {
-    $this->tag = $tag;
-    $this->content = $content;
-  }
-
-  protected $tag;
-  protected $content;
-
-  function getContent(): iterable {
-    return [
-      "<$this->tag>",
-      ...c::q($this->content),
-      "</$this->tag>",
-    ];
-  }
-}
diff --git a/tests/php/content/impl/html.php b/tests/php/content/impl/html.php
deleted file mode 100644
index 3567b2e..0000000
--- a/tests/php/content/impl/html.php
+++ /dev/null
@@ -1,14 +0,0 @@
-<?php
-namespace nulib\php\content\impl;
-
-class html {
-  const H1 = [self::class, "h1"];
-  const DIV = [self::class, "div"];
-  const P = [self::class, "p"];
-  const SPAN = [self::class, "span"];
-
-  static function h1($content) { return new ATag("h1", $content); }
-  static function div($content) { return new ATag("div", $content); }
-  static function p($content) { return new ATag("p", $content); }
-  static function span($content) { return new ATag("span", $content); }
-}
diff --git a/tests/web/content/TagTest.php b/tests/web/content/TagTest.php
new file mode 100644
index 0000000..550fc06
--- /dev/null
+++ b/tests/web/content/TagTest.php
@@ -0,0 +1,86 @@
+<?php
+namespace nulib\web\content;
+
+use nulib\php\content\c;
+use nulib\tests\TestCase;
+
+class TagTest extends TestCase {
+  function testTag() {
+    $tag = new Tag("tag", null, [
+      "before",
+      "class" => "first",
+      ["class" => "second"],
+      function () {
+        return 42;
+      },
+      "attr" => [
+        "static",
+        "true" => true,
+        "false" => false,
+      ],
+      "after",
+    ]);
+
+    self::assertSame([
+      null,
+      "<tag",
+      " ", "class", "=\"", "first second", "\"",
+      " ", "attr", "=\"", "static true", "\"",
+      ">",
+      "before",
+      42,
+      "after",
+      "</tag>",
+      null,
+    ], $tag->getContent());
+
+    self::assertSame('<tag class="first second" attr="static true">before 42 after</tag>', c::to_string($tag));
+  }
+
+  function testMerge() {
+    $tag = new Tag("tag", null, [
+      "class" => "first",
+      ["class" => "second"],
+      ["class" => function () {
+        return "third";
+      }],
+      "cond" => [
+        "base",
+        "ok" => true,
+        "ko" => false,
+        "dynok" => function () {
+          return true;
+        },
+        "dynko" => function () {
+          return false;
+        },
+      ],
+      ["plouf" => "base"],
+      ["plouf" => [
+        "ok" => true,
+        "ko" => false,
+      ]],
+      ["plouf" => [
+        "dynok" => function () {
+          return true;
+        },
+        "dynko" => function () {
+          return false;
+        },
+      ]],
+    ]);
+
+    self::assertSame([
+      null,
+      "<tag",
+      " ", "class", "=\"", "first second third", "\"",
+      " ", "cond", "=\"", "base ok dynok", "\"",
+      " ", "plouf", "=\"", "base ok dynok", "\"",
+      ">",
+      "</tag>",
+      null,
+    ], $tag->getContent());
+
+    self::assertSame('<tag class="first second third" cond="base ok dynok" plouf="base ok dynok"></tag>', c::to_string($tag));
+  }
+}
diff --git a/tests/web/content/vTest.php b/tests/web/content/vTest.php
new file mode 100644
index 0000000..5d972ae
--- /dev/null
+++ b/tests/web/content/vTest.php
@@ -0,0 +1,96 @@
+<?php
+namespace nulib\web\content;
+
+use nulib\cl;
+use nulib\php\content\c;
+use nulib\tests\TestCase;
+
+class vTest extends TestCase {
+  function testStatic() {
+    $static = [
+      [v::H1, "title"],
+      [v::P, "text"],
+    ];
+    self::assertSame(<<<EOT
+<h1>title</h1>
+<p>text</p>
+EOT, c::to_string($static));
+
+    $static = [
+      [v::DIV, [
+        "before",
+        "class" => "div",
+        [v::SPAN, "spanned"],
+        "disabled" => false,
+        "checked" => true,
+        "after",
+      ]],
+    ];
+    self::assertSame(<<<EOT
+<div class="div" checked="checked">before<span>spanned</span>after</div>
+EOT, c::to_string($static));
+  }
+
+  function testDynamic() {
+    $dynamic = [
+      v::h1("title"),
+      v::p("text"),
+    ];
+    self::assertSame(<<<EOT
+<h1>title</h1>
+<p>text</p>
+EOT, c::to_string($dynamic));
+
+    $dynamic = [
+      v::div([
+        "before",
+        "class" => "div",
+        v::span("spanned"),
+        "disabled" => false,
+        "checked" => true,
+        "after",
+      ]),
+    ];
+    self::assertSame(<<<EOT
+<div class="div" checked="checked">before<span>spanned</span>after</div>
+EOT, c::to_string($dynamic));
+  }
+
+  function testDynamic2() {
+    $rows = [
+      ["a" => 1, "b" => 2, "c" => 3],
+      ["a" => "un", "b" => "deux", "c" => "trois"],
+      ["a" => "one", "b" => "two", "c" => "three"],
+    ];
+    $dynamic = v::table([
+      v::thead(v::tr(function() use ($rows) {
+        $headers = array_keys(cl::first($rows));
+        foreach ($headers as $header) {
+          yield v::th($header);
+        }
+      })),
+      v::tbody(function() use ($rows) {
+        foreach ($rows as $row) {
+          yield v::tr(function () use ($row) {
+            foreach ($row as $col) {
+              yield v::td($col);
+            }
+          });
+        }
+      }),
+    ]);
+    self::assertSame(<<<EOT
+<table>
+<thead>
+<tr><th>a</th><th>b</th><th>c</th></tr>
+</thead>
+<tbody>
+<tr><td>1</td><td>2</td><td>3</td></tr>
+<tr><td>un</td><td>deux</td><td>trois</td></tr>
+<tr><td>one</td><td>two</td><td>three</td></tr>
+</tbody>
+</table>
+
+EOT, c::to_string($dynamic));
+  }
+}