diff --git a/docs/material_clip.lua b/docs/material_clip.lua
new file mode 100644
index 0000000..06e0fc5
--- /dev/null
+++ b/docs/material_clip.lua
@@ -0,0 +1,27 @@
+---@meta soluna.material.clip
+
+---clip material 模块。
+---Clip material module.
+---
+---`rect(width, height)` 打开一个矩形裁剪范围，`rect()` 关闭最近一次打开的裁剪范围。
+---裁剪矩形位于屏幕空间，是轴对齐矩形；它不是 layer-local clip，也不为旋转 layer
+---提供精确裁剪。
+---
+---`rect(width, height)` opens a rectangular clipping region, and `rect()`
+---closes the latest opened clipping region. The clipping rectangle is
+---screen-space and axis-aligned. It is not a layer-local clip and does not
+---provide exact clipping for rotated layers.
+---@class soluna.material.clip
+local matclip = {}
+
+---打开或关闭矩形裁剪范围。
+---Opens or closes a rectangular clipping region.
+---@overload fun(): string
+---@overload fun(width: number, height: number): string
+---@param width number 逻辑像素宽度 / Width in logical pixels.
+---@param height number 逻辑像素高度 / Height in logical pixels.
+---@return string stream 打包后的 clip 命令流 / Packed clip command stream.
+function matclip.rect(width, height)
+end
+
+return matclip
diff --git a/docs/material_text.lua b/docs/material_text.lua
index 4ecfb00..b3ed081 100644
--- a/docs/material_text.lua
+++ b/docs/material_text.lua
@@ -1,27 +1,133 @@
 ---@meta soluna.material.text
 
----文本块创建函数
+---text style 配置。
+---Text style configuration.
+---@class soluna.material.text.Style
+---@field font integer `font.name()` 返回的字体 id / Font id returned by `font.name()`
+---@field size? integer 字体像素大小，默认 24 / Font pixel size, default 24
+---@field color? integer ARGB 颜色，默认 `0xff000000` / ARGB color, default `0xff000000`
+---@field line_height? integer 行高；小于字体自然高度时使用自然高度 / Line height; clamped to the natural font height
+
+---text style set。
+---Text style set.
+---@class soluna.material.text.Styles: userdata
+
+---文本行信息。
+---Text line information.
+---
+---`start` 和 `finish` 是 0-based visible position，`finish` 为 exclusive。
+---`start` and `finish` are 0-based visible positions. `finish` is exclusive.
+---@class soluna.material.text.Line
+---@field start integer 行起始 visible position / First visible position on the line
+---@field finish integer 行结束 visible position，exclusive / End visible position, exclusive
+---@field x integer 行矩形 X / Line rectangle X
+---@field y integer 行矩形 Y / Line rectangle Y
+---@field width integer 行矩形宽度 / Line rectangle width
+---@field height integer 行矩形高度 / Line rectangle height
+
+---文本布局查询对象。
+---Text layout query object.
+---@class soluna.material.text.Layout
+local Layout = {}
+
+---返回文本实际高度。
+---Returns text content height.
+---@return integer height 文本实际高度 / Text content height
+function Layout:height()
+end
+
+---返回最大行高。
+---Returns maximum line height.
+---@return integer height 最大行高 / Maximum line height
+function Layout:line_height()
+end
+
+---返回行数。
+---Returns line count.
+---@return integer count 行数 / Line count
+function Layout:line_count()
+end
+
+---返回 cursor position 数量。
+---Returns cursor position count.
+---@return integer count cursor position 数量 / Cursor position count
+function Layout:cursor_count()
+end
+
+---返回 1-based 行信息。
+---Returns 1-based line information.
+---@param index integer 1-based 行号 / 1-based line index
+---@return soluna.material.text.Line? line 行信息 / Line information
+function Layout:line(index)
+end
+
+---查询 cursor 矩形。
+---Queries cursor rectangle.
+---@param position integer 0-based cursor position / 0-based cursor position
+---@return integer x cursor X / Cursor X
+---@return integer y cursor Y / Cursor Y
+---@return integer width cursor 宽度 / Cursor width
+---@return integer height cursor 高度 / Cursor height
+---@return integer position clamp 后的 cursor position / Clamped cursor position
+---@return integer decent 字体 descent / Font descent
+function Layout:cursor(position)
+end
+
+---命中测试，返回 0-based cursor position。
+---Hit-tests and returns a 0-based cursor position.
+---@param x number 本地 X / Local X
+---@param y number 本地 Y / Local Y
+---@return integer position cursor position / Cursor position
+---@return boolean out_of_box 是否在布局盒外 / Whether the point is outside the layout box
+function Layout:hit_test(x, y)
+end
+
+---返回 visible position 使用的 0-based style id。
+---Returns the 0-based style id at a visible position.
+---@param position integer 0-based visible position / 0-based visible position
+---@return integer? style style id；无效 position 返回 nil / Style id; nil for invalid position
+function Layout:style(position)
+end
+
+---文本块创建函数。
 ---Text block builder function.
 ---@alias soluna.material.text.Block fun(text: string, width?: integer, height?: integer): string, integer
 
----光标位置查询函数
----Text cursor query function.
----@alias soluna.material.text.Cursor fun(text: string, position: integer, width?: integer, height?: integer): integer, integer, integer, integer, integer, integer
+---文本布局创建函数。
+---Text layout builder function.
+---@alias soluna.material.text.LayoutBuilder fun(text: string, width?: integer, height?: integer): soluna.material.text.Layout
 
----text material 模块
+---text material 模块。
 ---Text material module.
+---
+---Tagged text stream 支持 `[i42]` icon、`[hex]` 临时颜色、`[sN]` style 切换、
+---`[s]` 回到 style 0，以及 `[[` 输出字面量 `[`。`[sN]` 中的 `N` 是
+---0-based style id，Lua style 数组第一项对应 style 0。
+---
+---Tagged text streams support `[i42]` icons, `[hex]` temporary colors, `[sN]`
+---style switching, `[s]` reset to style 0, and `[[` for a literal `[`.
+---`N` in `[sN]` is a 0-based style id. The first Lua style entry is style 0.
 ---@class soluna.material.text
 local mattext = {}
 
----创建文本块和光标查询函数
----Creates text block and cursor query functions.
+---创建 style set。
+---Creates a style set.
+---@param fontcobj lightuserdata `font.cobj()` 返回的字体管理器指针 / Font manager pointer returned by `font.cobj()`
+---@param styles soluna.material.text.Style[] style 数组，第一项是 style 0 / Style array; first entry is style 0
+---@return soluna.material.text.Styles styles style set / Style set
+function mattext.styles(fontcobj, styles)
+end
+
+---创建文本块和布局查询函数。
+---Creates text block and layout query functions.
+---@overload fun(styles: soluna.material.text.Styles, alignment?: string): soluna.material.text.Block, soluna.material.text.LayoutBuilder
 ---@param fontcobj lightuserdata `font.cobj()` 返回的字体管理器指针 / Font manager pointer returned by `font.cobj()`
 ---@param fontid integer `font.name()` 返回的字体 id / Font id returned by `font.name()`
----@param size? integer 字体像素大小，默认 16 / Font pixel size, default 16
+---@param size? integer 字体像素大小，默认 24 / Font pixel size, default 24
 ---@param color? integer ARGB 颜色，默认 `0xff000000` / ARGB color, default `0xff000000`
 ---@param alignment? string 对齐代码，如 `"LT"`、`"CV"`、`"RB"` / Alignment code such as `"LT"`, `"CV"`, `"RB"`
 ---@return soluna.material.text.Block block 创建 packed text stream / Creates packed text stream
----@return soluna.material.text.Cursor cursor 查询光标矩形 / Queries cursor rectangle
+---@return soluna.material.text.LayoutBuilder layout 创建布局查询对象 / Creates layout query object
 function mattext.block(fontcobj, fontid, size, color, alignment)
 end
 
diff --git a/src/embedlua.c b/src/embedlua.c
index d9fe9c9..2469089 100644
--- a/src/embedlua.c
+++ b/src/embedlua.c
@@ -26,6 +26,7 @@
 #include "mattext.lua.h"
 #include "matquad.lua.h"
 #include "matmask.lua.h"
+#include "matclip.lua.h"
 
 #include "lua.h"
 #include "lauxlib.h"
@@ -102,6 +103,7 @@ luaopen_embedsource(lua_State *L) {
 			REG_MATERIAL(mattext)
 			REG_MATERIAL(matquad)
 			REG_MATERIAL(matmask)
+			REG_MATERIAL(matclip)
 		lua_setfield(L, -2, "material");
 
 		lua_newtable(L);	// data list
diff --git a/src/luamods.c b/src/luamods.c
index 764c2f5..af3d965 100644
--- a/src/luamods.c
+++ b/src/luamods.c
@@ -21,6 +21,7 @@ int luaopen_material_default(lua_State *L);
 int luaopen_material_text(lua_State *L);
 int luaopen_material_quad(lua_State *L);
 int luaopen_material_mask(lua_State *L);
+int luaopen_material_clip(lua_State *L);
 int luaopen_material_blit(lua_State *L);
 int luaopen_material_external(lua_State *L);
 int luaopen_soluna_app(lua_State *L);
@@ -53,6 +54,7 @@ void soluna_embed(lua_State* L) {
 		{ "soluna.material.text", luaopen_material_text },
 		{ "soluna.material.quad", luaopen_material_quad },
 		{ "soluna.material.mask", luaopen_material_mask },
+		{ "soluna.material.clip", luaopen_material_clip },
 		{ "soluna.material.blit", luaopen_material_blit },
 		{ "soluna.material.ext", luaopen_material_external },
 		{ "soluna.datalist", luaopen_datalist },
diff --git a/src/luayoga.c b/src/luayoga.c
index c39e598..aace2ce 100644
--- a/src/luayoga.c
+++ b/src/luayoga.c
@@ -12,6 +12,7 @@
 #define Wrap 8
 #define Display 16
 #define PositionType 32
+#define Overflow 64
 
 #define ENUM(x, what) { YG##x##ToString(YG##x##what), (x) << 16 | (YG##x##what) },
 
@@ -512,6 +513,11 @@ lsetPosition(lua_State *L, YGNodeRef node) {
 	YGNodeStyleSetPositionType(node, getEnum(L, PositionType, "position"));
 }
 
+static void
+lsetOverflow(lua_State *L, YGNodeRef node) {
+	YGNodeStyleSetOverflow(node, getEnum(L, Overflow, "overflow"));
+}
+
 static void
 setPosition(lua_State *L, YGNodeRef node, YGEdge edge) {
 	static const struct set_edge_number setter = {
@@ -636,6 +642,7 @@ luaopen_layout_yoga(lua_State *L) {
 		{ "display", lsetDisplay },
 		{ "flex", lsetFlex },
 		{ "position", lsetPosition },
+		{ "overflow", lsetOverflow },
 		{ "top", lsetTop },
 		{ "bottom", lsetBottom },
 		{ "left", lsetLeft },
@@ -678,6 +685,9 @@ luaopen_layout_yoga(lua_State *L) {
 		ENUM(PositionType, Static)
 		ENUM(PositionType, Relative)
 		ENUM(PositionType, Absolute)
+		ENUM(Overflow, Visible)
+		ENUM(Overflow, Hidden)
+		ENUM(Overflow, Scroll)
 	};
 	n = sizeof(estr) / sizeof(estr[0]);
 	lua_createtable(L, n, 0);
diff --git a/src/material/matclip.lua b/src/material/matclip.lua
new file mode 100644
index 0000000..a61137f
--- /dev/null
+++ b/src/material/matclip.lua
@@ -0,0 +1,25 @@
+local clipmat = require "soluna.material.clip"
+
+local ctx = ...
+local state = ctx.state
+clipmat.set_material_id(ctx.id)
+
+state.material_clip = clipmat.new {
+	uniform = state.uniform,
+}
+
+local material = {}
+
+function material.reset()
+	state.material_clip:reset()
+end
+
+function material.submit(ptr, n)
+	state.material_clip:submit(ptr, n)
+end
+
+function material.draw(ptr, n)
+	state.material_clip:draw(ptr, n)
+end
+
+return material
diff --git a/src/material_clip.c b/src/material_clip.c
new file mode 100644
index 0000000..e3146f7
--- /dev/null
+++ b/src/material_clip.c
@@ -0,0 +1,275 @@
+#include <lua.h>
+#include <lauxlib.h>
+#include <assert.h>
+#include <math.h>
+#include <stdint.h>
+#include <string.h>
+
+#include "sokol/sokol_app.h"
+#include "sokol/sokol_gfx.h"
+#include "batch.h"
+#include "material_util.h"
+
+#define PIXEL_SCALE 256.0f
+#define CLIP_STACK_MAX 64
+
+enum scissor_command {
+	SCISSOR_PUSH = 1,
+	SCISSOR_POP = 2,
+};
+
+struct scissor_rect {
+	int x;
+	int y;
+	int w;
+	int h;
+};
+
+struct scissor_payload {
+	struct draw_primitive_external header;
+	int command;
+	float w;
+	float h;
+};
+
+struct scissor_primitive {
+	struct draw_primitive pos;
+	union {
+		struct draw_primitive dummy;
+		struct scissor_payload scissor;
+	} u;
+};
+
+struct material_clip {
+	float *uniform;
+	int stack_n;
+	struct scissor_rect stack[CLIP_STACK_MAX];
+};
+
+static int material_id = 0;
+
+static struct scissor_rect
+full_scissor(struct material_clip *m) {
+	float sx = m->uniform[0];
+	float sy = m->uniform[1];
+	int w = sx == 0.0f ? 0 : (int)floorf(2.0f / sx + 0.5f);
+	int h = sy == 0.0f ? 0 : (int)floorf(-2.0f / sy + 0.5f);
+	struct scissor_rect r = { 0, 0, w, h };
+	return r;
+}
+
+static struct scissor_rect
+intersect_scissor(struct scissor_rect a, struct scissor_rect b) {
+	int x0 = a.x > b.x ? a.x : b.x;
+	int y0 = a.y > b.y ? a.y : b.y;
+	int x1 = a.x + a.w < b.x + b.w ? a.x + a.w : b.x + b.w;
+	int y1 = a.y + a.h < b.y + b.h ? a.y + a.h : b.y + b.h;
+	struct scissor_rect r = {
+		x0,
+		y0,
+		x1 > x0 ? x1 - x0 : 0,
+		y1 > y0 ? y1 - y0 : 0,
+	};
+	return r;
+}
+
+static void
+apply_scissor(struct scissor_rect r) {
+	float scale = sapp_dpi_scale();
+	if (scale <= 0.0f)
+		scale = 1.0f;
+	int x0 = (int)floorf((float)r.x * scale);
+	int y0 = (int)floorf((float)r.y * scale);
+	int x1 = (int)ceilf((float)(r.x + r.w) * scale);
+	int y1 = (int)ceilf((float)(r.y + r.h) * scale);
+	sg_apply_scissor_rect(x0, y0, x1 > x0 ? x1 - x0 : 0, y1 > y0 ? y1 - y0 : 0, true);
+}
+
+static void
+sr_matrix(uint32_t sr, float m[4]) {
+	uint32_t scale_fix = sr >> 12;
+	float scale = 1.0f;
+	if (scale_fix != 0) {
+		if (scale_fix >= 0xff000) {
+			scale = (float)(scale_fix & 0xfff) * (1.0f / 4096.0f);
+		} else {
+			scale = (float)scale_fix * (1.0f / 256.0f) + 1.0f;
+		}
+	}
+	uint32_t rot_fix = sr & 0xfff;
+	if (rot_fix == 0) {
+		m[0] = scale;
+		m[1] = 0.0f;
+		m[2] = 0.0f;
+		m[3] = scale;
+	} else {
+		const float pi = 3.1415927f;
+		float rot = (float)rot_fix * (pi / 2048.0f);
+		float cosr = cosf(rot) * scale;
+		float sinr = sinf(rot) * scale;
+		m[0] = cosr;
+		m[1] = -sinr;
+		m[2] = sinr;
+		m[3] = cosr;
+	}
+}
+
+static void
+point_bounds(float base_x, float base_y, const float m[4], float x, float y, float *min_x, float *min_y, float *max_x, float *max_y) {
+	float tx = base_x + x * m[0] + y * m[1];
+	float ty = base_y + x * m[2] + y * m[3];
+	if (tx < *min_x)
+		*min_x = tx;
+	if (tx > *max_x)
+		*max_x = tx;
+	if (ty < *min_y)
+		*min_y = ty;
+	if (ty > *max_y)
+		*max_y = ty;
+}
+
+static struct scissor_rect
+primitive_scissor(struct draw_primitive *pos, struct scissor_payload *payload) {
+	float base_x = (float)pos->x / PIXEL_SCALE;
+	float base_y = (float)pos->y / PIXEL_SCALE;
+	float m[4];
+	sr_matrix(pos->sr, m);
+	float min_x = base_x;
+	float min_y = base_y;
+	float max_x = base_x;
+	float max_y = base_y;
+	point_bounds(base_x, base_y, m, payload->w, 0.0f, &min_x, &min_y, &max_x, &max_y);
+	point_bounds(base_x, base_y, m, 0.0f, payload->h, &min_x, &min_y, &max_x, &max_y);
+	point_bounds(base_x, base_y, m, payload->w, payload->h, &min_x, &min_y, &max_x, &max_y);
+	struct scissor_rect r = {
+		(int)floorf(min_x),
+		(int)floorf(min_y),
+		(int)ceilf(max_x) - (int)floorf(min_x),
+		(int)ceilf(max_y) - (int)floorf(min_y),
+	};
+	return r;
+}
+
+static int
+lmaterial_clip_reset(lua_State *L) {
+	struct material_clip *m = (struct material_clip *)luaL_checkudata(L, 1, "SOLUNA_MATERIAL_CLIP");
+	m->stack_n = 0;
+	return 0;
+}
+
+static int
+lmaterial_clip_submit(lua_State *L) {
+	return 0;
+}
+
+static int
+lmaterial_clip_draw(lua_State *L) {
+	struct material_clip *m = (struct material_clip *)luaL_checkudata(L, 1, "SOLUNA_MATERIAL_CLIP");
+	struct draw_primitive *prim = lua_touserdata(L, 2);
+	int prim_n = luaL_checkinteger(L, 3);
+	int i;
+	for (i=0;i<prim_n;i++) {
+		struct draw_primitive *pos = &prim[i*2];
+		assert(pos->sprite == -material_id);
+		struct scissor_payload *payload = (struct scissor_payload *)&prim[i*2+1];
+		switch (payload->command) {
+		case SCISSOR_PUSH: {
+			if (m->stack_n >= CLIP_STACK_MAX)
+				return luaL_error(L, "Too many nested clip commands");
+			struct scissor_rect current = m->stack_n > 0 ? m->stack[m->stack_n - 1] : full_scissor(m);
+			struct scissor_rect next = intersect_scissor(current, primitive_scissor(pos, payload));
+			m->stack[m->stack_n++] = next;
+			apply_scissor(next);
+			break;
+		}
+		case SCISSOR_POP:
+			if (m->stack_n <= 0)
+				return luaL_error(L, "Clip close without open");
+			--m->stack_n;
+			apply_scissor(m->stack_n > 0 ? m->stack[m->stack_n - 1] : full_scissor(m));
+			break;
+		default:
+			return luaL_error(L, "Invalid clip command %d", payload->command);
+		}
+	}
+	return 0;
+}
+
+static int
+lnew_material_clip(lua_State *L) {
+	luaL_checktype(L, 1, LUA_TTABLE);
+	struct material_clip *m = (struct material_clip *)lua_newuserdatauv(L, sizeof(*m), 1);
+	memset(m, 0, sizeof(*m));
+	util_ref_object(L, &m->uniform, 1, "uniform", "SOKOL_UNIFORM", 1);
+
+	if (luaL_newmetatable(L, "SOLUNA_MATERIAL_CLIP")) {
+		luaL_Reg l[] = {
+			{ "__index", NULL },
+			{ "reset", lmaterial_clip_reset },
+			{ "submit", lmaterial_clip_submit },
+			{ "draw", lmaterial_clip_draw },
+			{ NULL, NULL },
+		};
+		luaL_setfuncs(L, l, 0);
+
+		lua_pushvalue(L, -1);
+		lua_setfield(L, -2, "__index");
+	}
+	lua_setmetatable(L, -2);
+	return 1;
+}
+
+static int
+lset_material_id(lua_State *L) {
+	int id = luaL_checkinteger(L, 1);
+	if (id <= 0) {
+		return luaL_error(L, "Invalid clip material id %d", id);
+	}
+	material_id = id;
+	return 0;
+}
+
+static void
+push_command(lua_State *L, int command, float w, float h) {
+	if (material_id <= 0) {
+		luaL_error(L, "Clip material is not registered");
+	}
+	struct scissor_primitive prim;
+	memset(&prim, 0, sizeof(prim));
+	prim.pos.sprite = -material_id;
+	prim.u.scissor.header.sprite = -1;
+	prim.u.scissor.command = command;
+	prim.u.scissor.w = w;
+	prim.u.scissor.h = h;
+	lua_pushlstring(L, (const char *)&prim, sizeof(prim));
+}
+
+static int
+lrect(lua_State *L) {
+	int n = lua_gettop(L);
+	if (n == 0) {
+		push_command(L, SCISSOR_POP, 0.0f, 0.0f);
+		return 1;
+	}
+	if (n != 2)
+		return luaL_error(L, "Invalid clip rect arguments");
+	float w = luaL_checknumber(L, 1);
+	float h = luaL_checknumber(L, 2);
+	if (w < 0 || h < 0)
+		return luaL_error(L, "Invalid clip rect size %f x %f", w, h);
+	push_command(L, SCISSOR_PUSH, w, h);
+	return 1;
+}
+
+int
+luaopen_material_clip(lua_State *L) {
+	luaL_checkversion(L);
+	luaL_Reg l[] = {
+		{ "set_material_id", lset_material_id },
+		{ "new", lnew_material_clip },
+		{ "rect", lrect },
+		{ NULL, NULL },
+	};
+	luaL_newlib(L, l);
+	return 1;
+}
diff --git a/src/material_text.c b/src/material_text.c
index af285c7..ee96b3c 100644
--- a/src/material_text.c
+++ b/src/material_text.c
@@ -307,7 +307,10 @@ count_string(const char *str) {
 	while ((str = utf8_decode(str, &val))) {
 		if (val == 0)
 			break;
-		if (val > 32) {
+		if (val <= 32) {
+			if (val != '\n')
+				++n;
+		} else {
 			if (val == '[') {
 				char c = *str;
 				if (c == '[') {
@@ -367,6 +370,7 @@ static int
 get_field(lua_State *L, const char *key, int def) {
 	int t = lua_getfield(L, -1, key);
 	if (t == LUA_TNIL) {
+		lua_pop(L, 1);
 		return def;
 	} else if (t != LUA_TNUMBER) {
 		return luaL_error(L, ".%s should be integer", key);
@@ -379,9 +383,34 @@ get_field(lua_State *L, const char *key, int def) {
 	return v;
 }
 
+static void
+style_getinfo(struct font_manager *mgr, struct font_style *fs, int line_height) {
+	int ascent, decent, gap;
+	font_manager_fontheight(mgr, fs->fontid, fs->size, &ascent, &decent, &gap);
+	if (gap == 0)
+		gap = 1;
+	int natural_decent = -decent;
+	int natural_height = ascent + natural_decent;
+	if (line_height > 0) {
+		if (line_height < natural_height) {
+			line_height = natural_height;
+		}
+		int leading = line_height - natural_height;
+		int leading_top = leading / 2;
+		fs->ascent = ascent + leading_top;
+		fs->decent = natural_decent + leading - leading_top;
+		fs->gap = 0;
+	} else {
+		fs->ascent = ascent;
+		fs->decent = natural_decent + gap;
+		fs->gap = gap;
+	}
+}
+
 static void
 read_style(lua_State *L, int index, struct styles *s, int i) {
 	struct font_style *fs = &s->s[i];
+	int line_height;
 	if (lua_geti(L, index, i+1) != LUA_TTABLE) {
 		luaL_error(L, "Invalid style at %d, need a table", i+1);
 	}
@@ -392,25 +421,11 @@ read_style(lua_State *L, int index, struct styles *s, int i) {
 	if (!(fs->color & 0xff000000))
 		fs->color |= 0xff000000;
 	fs->size = get_field(L, "size", DEFAULT_FONTSIZE);
+	line_height = get_field(L, "line_height", 0);
+	style_getinfo(s->font, fs, line_height);
 	lua_pop(L, 1);
 }
 
-static void
-style_getinfo(struct styles *s) {
-	struct font_manager *mgr = s->font;
-	int i;
-	for (i=0;i<s->n;i++) {
-		int ascent, decent, gap;
-		struct font_style *fs = &s->s[i];
-		font_manager_fontheight(mgr, fs->fontid, fs->size, &ascent, &decent, &gap);
-		if (gap == 0)
-			gap = 1;
-		fs->ascent = ascent;
-		fs->decent = -decent + gap;
-		fs->gap = gap;
-	}
-}
-
 static int
 ltext_styles(lua_State *L) {
 	luaL_checktype(L, 1, LUA_TLIGHTUSERDATA);
@@ -429,7 +444,11 @@ ltext_styles(lua_State *L) {
 	for (i=0;i<n;i++) {
 		read_style(L, 2, s, i);
 	}
-	style_getinfo(s);
+	if (luaL_newmetatable(L, "SOLUNA_TEXT_STYLES")) {
+		lua_pushvalue(L, -1);
+		lua_setfield(L, -2, "__index");
+	}
+	lua_setmetatable(L, -2);
 	return 1;
 }
 
@@ -449,29 +468,84 @@ struct block_context {
 	int alignment;
 };
 
+struct line_info {
+	int y;
+	int h;
+};
+
 struct position {
 	int x;
-	int y;
 	int w;
-	int h;
-	int gap;
-	int ascent;
-	int decent;
+	int style;
+	int line;
 };
 
 struct layout {
 	int n;
+	int cap;
 	int width;
 	int height;
 	int top;
 	int text_height;
-	struct position pos[];
+	int line_count;
+	struct font_style *styles;
+	struct font_style style;
 };
 
+static inline int
+newline(struct block_context *ctx, struct text_primitive * prim, int n, struct layout *pos);
+
+static inline struct position *
+layout_positions(struct layout *pos) {
+	return (struct position *)(pos + 1);
+}
+
+static inline struct line_info *
+layout_lines(struct layout *pos) {
+	return (struct line_info *)(layout_positions(pos) + pos->cap);
+}
+
+static inline size_t
+layout_size(int cap) {
+	return sizeof(struct layout)
+		+ (size_t)cap * sizeof(struct position)
+		+ (size_t)cap * sizeof(struct line_info);
+}
+
+static inline int
+layout_line_bottom(struct layout *pos, struct line_info *lines, int line) {
+	if (line + 1 < pos->line_count) {
+		return lines[line + 1].y;
+	}
+	return pos->top + pos->text_height;
+}
+
+static void
+set_layout_styles(lua_State *L, struct layout *pos, struct styles *styles, int external) {
+	if (external) {
+		pos->styles = styles->s;
+		lua_pushvalue(L, lua_upvalueindex(1));
+		lua_setiuservalue(L, -2, 1);
+	} else {
+		pos->style = styles->s[0];
+		pos->styles = &pos->style;
+	}
+}
+
+static inline void
+set_position(struct layout *pos, int n, struct block_context *ctx) {
+	struct position *p = &layout_positions(pos)[n];
+	p->x = ctx->x;
+	p->w = 0;
+	p->style = (int)(ctx->fs - ctx->s->s);
+	p->line = 0;
+	pos->n = n + 1;
+}
+
 static inline int
 advance(struct layout *pos, struct block_context *ctx, int x) {
 	if (pos && pos->n > 0) {
-		pos->pos[pos->n-1].w = x;
+		layout_positions(pos)[pos->n-1].w = x;
 	}
 	if (x + ctx->x > ctx->width)
 		return 1;
@@ -488,6 +562,25 @@ advance(struct layout *pos, struct block_context *ctx, int x) {
 	return 0;
 }
 
+static inline int
+advance_space(struct block_context *ctx, struct text_primitive *prim, struct layout *pos, int *n, int advance_x) {
+	if (pos) {
+		set_position(pos, *n, ctx);
+	}
+	if (advance(pos, ctx, advance_x)) {
+		if (newline(ctx, prim, *n, pos))
+			return 1;
+		if (pos) {
+			set_position(pos, *n, ctx);
+		}
+		advance(pos, ctx, advance_x);
+	}
+	if (pos) {
+		++*n;
+	}
+	return 0;
+}
+
 static inline int
 newline(struct block_context *ctx, struct text_primitive * prim, int n, struct layout *pos) {
 	int from = ctx->line_prim;
@@ -496,7 +589,6 @@ newline(struct block_context *ctx, struct text_primitive * prim, int n, struct l
 	int line_ascent = ctx->line_ascent;
 	int line_decent = ctx->line_decent;
 	int line_height = ctx->line_height;
-	int line_gap = line_ascent + line_decent - line_height;
 	ctx->line_width = 0;
 	ctx->line_height = 0;
 	ctx->line_ascent = 0;
@@ -528,16 +620,20 @@ newline(struct block_context *ctx, struct text_primitive * prim, int n, struct l
 		}
 	}
 	if (pos != NULL) {
-		if (offx > 0) {
+		if (n > from) {
+			struct position *positions = layout_positions(pos);
+			struct line_info *lines = layout_lines(pos);
+			int line = pos->line_count++;
+			lines[line].y = ctx->y;
+			lines[line].h = line_height;
 			for (i=from;i<n;i++) {
-				pos->pos[i].x += offx;
-				pos->pos[i].h = line_height;
-				pos->pos[i].gap = line_gap;
+				positions[i].line = line;
 			}
-		} else {
+		}
+		if (offx > 0) {
+			struct position *positions = layout_positions(pos);
 			for (i=from;i<n;i++) {
-				pos->pos[i].h = line_height;
-				pos->pos[i].gap = line_gap;
+				positions[i].x += offx;
 			}
 		}
 	}
@@ -608,7 +704,7 @@ parse_bracket(struct block_context *ctx, const char *str, int *icon) {
 }
 
 static int
-ltext_(lua_State *L, struct styles *s, int gen_layout) {
+ltext_(lua_State *L, struct styles *s, int gen_layout, int external) {
 	const char * str = luaL_checkstring(L, 1);
 	int count = count_string(str);
 	struct block_context ctx;
@@ -632,21 +728,26 @@ ltext_(lua_State *L, struct styles *s, int gen_layout) {
 	struct text_primitive * prim = NULL;
 	struct layout * pos = NULL;
 	if (gen_layout) {
-		pos = (struct layout *)lua_newuserdatauv(L, sizeof(struct layout) + (count+1) * sizeof(struct position), 0);
+		int cap = count + 1;
+		pos = (struct layout *)lua_newuserdatauv(L, layout_size(cap), external ? 1 : 0);
 		pos->n = 0;
+		pos->cap = cap;
 		pos->width = ctx.width;
 		pos->height = ctx.height;
 		pos->text_height = 0;
 		pos->top = 0;
+		pos->line_count = 0;
+		set_layout_styles(L, pos, s, external);
 	} else {
 		buffer = (char *)malloc(count * sizeof(struct text_primitive)+1);
 		prim = (struct text_primitive *)buffer;
 	}
-	int i;
 	int n = 0;
-	for (i=0;i<count;) {
+	for (;;) {
 		uint32_t val = 0;
 		str = utf8_decode(str, &val);
+		if (str == NULL || val == 0)
+			break;
 		if (val <= 32) {
 			if (val == '\n') {
 				if (ctx.x > ctx.line_width)
@@ -658,11 +759,8 @@ ltext_(lua_State *L, struct styles *s, int gen_layout) {
 				if (font_manager_glyph(mgr, ctx.fs->fontid, ' ', ctx.fs->size, &g, &og) == NULL) {
 					if (ctx.x > ctx.line_width)
 						ctx.line_width = ctx.x;
-					if (advance(pos, &ctx, g.advance_x)) {
-						if (newline(&ctx, prim, n, pos))
-							break;
-						advance(pos, &ctx, g.advance_x);
-					}
+					if (advance_space(&ctx, prim, pos, &n, g.advance_x))
+						break;
 				}
 			}
 		} else {
@@ -695,15 +793,7 @@ ltext_(lua_State *L, struct styles *s, int gen_layout) {
 				prim[n].pos.sprite = -material_id;
 			} else {
 				// assert(pos != NULL)
-				struct position *p = &pos->pos[n];
-				p->x = ctx.x;
-				p->y = ctx.y;
-				p->w = 0;
-				p->h = 0;
-				p->gap = 0;
-				p->ascent = ctx.fs->ascent;
-				p->decent = ctx.fs->decent;
-				pos->n = n + 1;
+				set_position(pos, n, &ctx);
 			}
 			
 			struct font_glyph g, og;
@@ -717,14 +807,7 @@ ltext_(lua_State *L, struct styles *s, int gen_layout) {
 						prim[n].pos.x = ctx.x * PIXEL_SCALE;
 						prim[n].pos.y = ( ctx.y + dy ) * PIXEL_SCALE;
 					} else {
-						struct position *p = &pos->pos[n];
-						p->x = ctx.x;
-						p->y = ctx.y;
-						p->w = 0;
-						p->h = 0;
-						p->gap = 0;
-						p->ascent = ctx.fs->ascent;
-						p->decent = ctx.fs->decent;
+						set_position(pos, n, &ctx);
 					}
 					advance(pos, &ctx, g.advance_x);
 				}
@@ -737,7 +820,6 @@ ltext_(lua_State *L, struct styles *s, int gen_layout) {
 				}
 				++n;
 			}
-			++i;
 		}
 	}
 	if (ctx.x > ctx.line_width)
@@ -746,14 +828,7 @@ ltext_(lua_State *L, struct styles *s, int gen_layout) {
 	if (n == 0 && pos) {
 		// no text, set one
 		if (pos) {
-			struct position *p = &pos->pos[0];
-			p->x = 0;
-			p->y = 0;
-			p->w = 0;
-			p->h = 0;
-			p->gap = 0;
-			p->ascent = ctx.fs->ascent;
-			p->decent = ctx.fs->decent;
+			set_position(pos, 0, &ctx);
 			ctx.line_ascent = ctx.fs->ascent;
 			ctx.line_decent = ctx.fs->decent;
 			ctx.line_height = ctx.fs->ascent + ctx.fs->decent - ctx.fs->gap;
@@ -764,12 +839,14 @@ ltext_(lua_State *L, struct styles *s, int gen_layout) {
 		newline(&ctx, prim, n, pos);
 	}
 	if (pos && n>0) {
-		pos->pos[n] = pos->pos[n-1];
-		pos->pos[n].x = pos->pos[n-1].x + pos->pos[n-1].w;
-		pos->pos[n].w = 0;
+		struct position *positions = layout_positions(pos);
+		positions[n] = positions[n-1];
+		positions[n].x = positions[n-1].x + positions[n-1].w;
+		positions[n].w = 0;
 	}
 	int offy;
 	int valign = ctx.alignment & VALIGNMENT_MASK;
+	int i;
 	switch (valign) {
 	case VALIGNMENT_CENTER:
 		offy = (ctx.height - height) / 2 * PIXEL_SCALE;
@@ -795,8 +872,9 @@ ltext_(lua_State *L, struct styles *s, int gen_layout) {
 		pos->n = n;
 		if (offy != 0) {
 			int offset = offy / PIXEL_SCALE;
-			for (i=0;i<=n;i++) {
-				pos->pos[i].y += offset;
+			struct line_info *lines = layout_lines(pos);
+			for (i=0;i<pos->line_count;i++) {
+				lines[i].y += offset;
 			}
 			pos->top = offset;
 		}
@@ -818,20 +896,21 @@ get_styles(lua_State *L, struct styles *tmp) {
 	fs->size = lua_tointeger(L, lua_upvalueindex(3));
 	fs->color = lua_tointeger(L, lua_upvalueindex(4));
 
-	style_getinfo(tmp);
+	style_getinfo(tmp->font, fs, 0);
 	return tmp;
 }
 
 static int
 ltext(lua_State *L) {
 	struct styles tmp;
-	return ltext_(L, get_styles(L, &tmp), 0);
+	return ltext_(L, get_styles(L, &tmp), 0, 0);
 }
 
 static int
 ltext_layout(lua_State *L) {
 	struct styles tmp;
-	ltext_(L, get_styles(L, &tmp), 1);
+	int external = luaL_testudata(L, lua_upvalueindex(1), "SOLUNA_TEXT_STYLES") != NULL;
+	ltext_(L, get_styles(L, &tmp), 1, external);
 	lua_pushvalue(L, lua_upvalueindex(6));
 	lua_setmetatable(L, -2);
 	return 1;
@@ -846,17 +925,171 @@ ltext_cursor(lua_State *L) {
 	} else if (n > pos->n ) {
 		n = pos->n;
 	}
-	struct position *p = &pos->pos[n];
-	int height = p->ascent + p->decent - p->gap;
+	struct position *p = &layout_positions(pos)[n];
+	struct font_style *style = &pos->styles[p->style];
+	struct line_info *line = &layout_lines(pos)[p->line];
+	int height = style->ascent + style->decent - style->gap;
 	lua_pushinteger(L, p->x);
-	lua_pushinteger(L, p->y + p->h - height);
+	lua_pushinteger(L, line->y + line->h - height);
 	lua_pushinteger(L, 2);
 	lua_pushinteger(L, height);
 	lua_pushinteger(L, n);
-	lua_pushinteger(L, p->decent);
+	lua_pushinteger(L, style->decent);
 	return 6;
 }
 
+static int
+ltext_height(lua_State *L) {
+	struct layout * pos = (struct layout *)lua_touserdata(L, 1);
+	lua_pushinteger(L, pos->text_height);
+	return 1;
+}
+
+static int
+ltext_line_height(lua_State *L) {
+	struct layout * pos = (struct layout *)lua_touserdata(L, 1);
+	int n = pos->n;
+	if (n <= 0) {
+		lua_pushinteger(L, pos->text_height);
+		return 1;
+	}
+	int height = 0;
+	int i;
+	struct line_info *lines = layout_lines(pos);
+	for (i=0;i<pos->line_count;i++) {
+		struct line_info *line = &lines[i];
+		int line_height = layout_line_bottom(pos, lines, i) - line->y;
+		if (line_height > height) {
+			height = line_height;
+		}
+	}
+	lua_pushinteger(L, height);
+	return 1;
+}
+
+static int
+ltext_line_count(lua_State *L) {
+	struct layout * pos = (struct layout *)lua_touserdata(L, 1);
+	int n = pos->n;
+	if (n <= 0) {
+		lua_pushinteger(L, pos->text_height > 0 ? 1 : 0);
+		return 1;
+	}
+	lua_pushinteger(L, pos->line_count);
+	return 1;
+}
+
+static int
+ltext_cursor_count(lua_State *L) {
+	struct layout * pos = (struct layout *)lua_touserdata(L, 1);
+	lua_pushinteger(L, pos->n + 1);
+	return 1;
+}
+
+static void
+set_integer_field(lua_State *L, const char *key, int value) {
+	lua_pushinteger(L, value);
+	lua_setfield(L, -2, key);
+}
+
+static void
+push_line(lua_State *L, struct layout *pos, int start, int finish) {
+	struct position *positions = layout_positions(pos);
+	struct line_info *lines = layout_lines(pos);
+	int x0 = positions[start].x;
+	int x1 = x0;
+	int y = lines[positions[start].line].y;
+	int y1 = y;
+	int text_bottom = pos->top + pos->text_height;
+	int i;
+	for (i=start;i<finish;i++) {
+		struct position *p = &positions[i];
+		if (p->x < x0) {
+			x0 = p->x;
+		}
+		int right = p->x + p->w;
+		if (right > x1) {
+			x1 = right;
+		}
+		int bottom = layout_line_bottom(pos, lines, p->line);
+		if (bottom > y1) {
+			y1 = bottom;
+		}
+	}
+	if (y1 > text_bottom) {
+		y1 = text_bottom;
+	}
+	lua_createtable(L, 0, 6);
+	set_integer_field(L, "start", start);
+	set_integer_field(L, "finish", finish);
+	set_integer_field(L, "x", x0);
+	set_integer_field(L, "y", y);
+	set_integer_field(L, "width", x1 - x0);
+	set_integer_field(L, "height", y1 > y ? y1 - y : 0);
+}
+
+static int
+ltext_line(lua_State *L) {
+	struct layout * pos = (struct layout *)lua_touserdata(L, 1);
+	int line = luaL_checkinteger(L, 2);
+	if (line <= 0) {
+		lua_pushnil(L);
+		return 1;
+	}
+	int n = pos->n;
+	if (n <= 0) {
+		if (line != 1) {
+			lua_pushnil(L);
+			return 1;
+		}
+		lua_createtable(L, 0, 6);
+		set_integer_field(L, "start", 0);
+		set_integer_field(L, "finish", 0);
+		set_integer_field(L, "x", 0);
+		set_integer_field(L, "y", pos->top);
+		set_integer_field(L, "width", 0);
+		set_integer_field(L, "height", pos->text_height);
+		return 1;
+	}
+	int target = line - 1;
+	if (target >= pos->line_count) {
+		lua_pushnil(L);
+		return 1;
+	}
+	int start = -1;
+	int finish = -1;
+	struct position *positions = layout_positions(pos);
+	int i;
+	for (i=0;i<n;i++) {
+		if (positions[i].line == target) {
+			if (start < 0) {
+				start = i;
+			}
+			finish = i + 1;
+		} else if (start >= 0) {
+			break;
+		}
+	}
+	if (start >= 0) {
+		push_line(L, pos, start, finish);
+		return 1;
+	}
+	lua_pushnil(L);
+	return 1;
+}
+
+static int
+ltext_style(lua_State *L) {
+	struct layout * pos = (struct layout *)lua_touserdata(L, 1);
+	int n = luaL_checkinteger(L, 2);
+	if (n < 0 || n >= pos->n) {
+		lua_pushnil(L);
+		return 1;
+	}
+	lua_pushinteger(L, layout_positions(pos)[n].style);
+	return 1;
+}
+
 static int
 get_pos(lua_State *L, int index) {
 	int isnum;
@@ -871,12 +1104,15 @@ static int
 bsearch_pos(struct layout * pos, int x, int y) {
 	int from = 0;
 	int to = pos->n;
+	struct position *positions = layout_positions(pos);
+	struct line_info *lines = layout_lines(pos);
 	while (from < to) {
 		int mid = from + (to - from) / 2;
-		struct position *p = &pos->pos[mid];
-		if (y < p->y) {
+		struct position *p = &positions[mid];
+		struct line_info *line = &lines[p->line];
+		if (y < line->y) {
 			to = mid;
-		} else if (y >= p->y + p->h + p->gap) {
+		} else if (y >= layout_line_bottom(pos, lines, p->line)) {
 			from = mid + 1;
 		} else if (x < p->x) {
 			to = mid;
@@ -901,7 +1137,7 @@ ltext_hit_test(lua_State *L) {
 		return 2;
 	}
 	if (y - top >= pos->text_height) {
-		lua_pushinteger(L, pos->n-1);
+		lua_pushinteger(L, pos->n);
 		lua_pushboolean(L, y >= pos->height);	// out of box
 		return 2;
 	}
@@ -953,18 +1189,24 @@ ltext_block(lua_State *L) {
 	if (material_id <= 0) {
 		return luaL_error(L, "Text material is not registered");
 	}
-	void * font_mgr = lua_touserdata(L, 1);
+	void * font_mgr = NULL;
+	int styles_arg = 0;
 	int fontid = 0;
 	int fontsize = 0;
 	uint32_t color = 0;
 	uint32_t alignment = 0;
-	
-	if (lua_type(L, 2) == LUA_TSTRING) {
-		// font_mgr is struct styles
-		luaL_checktype(L, 1, LUA_TUSERDATA);
-		alignment = parse_alignment(L, 2);
+
+	if (luaL_testudata(L, 1, "SOLUNA_TEXT_STYLES")) {
+		font_mgr = lua_touserdata(L, 1);
+		styles_arg = 1;
+		if (lua_type(L, 2) == LUA_TSTRING) {
+			alignment = parse_alignment(L, 2);
+		} else {
+			luaL_opt(L, luaL_checkstring, 2, NULL);
+		}
 	} else {
 		luaL_checktype(L, 1, LUA_TLIGHTUSERDATA);
+		font_mgr = lua_touserdata(L, 1);
 		fontid = luaL_checkinteger(L, 2);
 		fontsize = luaL_optinteger(L, 3, DEFAULT_FONTSIZE);
 		color = luaL_optinteger(L, 4, 0xff000000);
@@ -976,13 +1218,21 @@ ltext_block(lua_State *L) {
 			color |= 0xff000000;
 	}
 
-	lua_pushlightuserdata(L, font_mgr);	// 1
+	if (styles_arg) {
+		lua_pushvalue(L, 1);
+	} else {
+		lua_pushlightuserdata(L, font_mgr);
+	}
 	lua_pushinteger(L, fontid);	// 2
 	lua_pushinteger(L, fontsize);	// 3
 	lua_pushinteger(L, color);	// 4
 	lua_pushinteger(L, alignment);	// 5
 	lua_pushcclosure(L, ltext, 5);
-	lua_pushlightuserdata(L, font_mgr);	// 1
+	if (styles_arg) {
+		lua_pushvalue(L, 1);
+	} else {
+		lua_pushlightuserdata(L, font_mgr);
+	}
 	lua_pushinteger(L, fontid);	// 2
 	lua_pushinteger(L, fontsize);	// 3
 	lua_pushinteger(L, color);	// 4
@@ -1008,8 +1258,14 @@ luaopen_material_text(lua_State *L) {
 	
 	if (luaL_newmetatable(L, "SOLUNA_TEXT_LAYOUT")) {
 		luaL_Reg meta[] = {
+			{ "height", ltext_height },
+			{ "line_height", ltext_line_height },
+			{ "line_count", ltext_line_count },
+			{ "cursor_count", ltext_cursor_count },
+			{ "line", ltext_line },
 			{ "cursor", ltext_cursor },
 			{ "hit_test", ltext_hit_test },
+			{ "style", ltext_style },
 			{ NULL, NULL },
 		};
 		luaL_setfuncs(L, meta, 0);
diff --git a/test/text.lua b/test/text.lua
index 8e3cbd5..aa2b7cf 100644
--- a/test/text.lua
+++ b/test/text.lua
@@ -2,6 +2,7 @@ local soluna = require "soluna"
 local ltask = require "ltask"
 local mattext = require "soluna.material.text"
 local matquad = require "soluna.material.quad"
+local matclip = require "soluna.material.clip"
 local font = require "soluna.font"
 local file = require "soluna.file"
 
@@ -48,6 +49,9 @@ local fontcobj = font.cobj()
 local callback = {}
 local WIDTH <const> = 200
 local HEIGHT <const> = 200
+local VIEWPORT_MIN <const> = 48
+local VIEWPORT_MAX <const> = HEIGHT
+local CLIP_BLEED <const> = 8
 local screen_w = args.width
 local screen_h = args.height
 
@@ -59,16 +63,30 @@ end
 local TEXT <const> = "[004000]Hello[n], 这个句子中有[s1]大字[n]，也有[s2]小字[n]。这句话会在文本区居中。"
 -- size 32; color 0; alignment center
 -- local block, layout = mattext.block(fontcobj, fontid, 32, 0, "CV")
-local styles = mattext.styles(fontcobj, {
-	{ font = fontid, size = 24, color = 0 },
-	{ font = fontid, size = 32, color = 0x800000 },
-	{ font = fontid, size = 16, color = 0x000080 },
-})
-local block, layout = mattext.block(styles, "CV")
+local function text_block()
+	local styles = mattext.styles(fontcobj, {
+		{ font = fontid, size = 24, color = 0 },
+		{ font = fontid, size = 32, color = 0x800000 },
+		{ font = fontid, size = 16, color = 0x000080 },
+	})
+	return mattext.block(styles, "CV")
+end
+
+local block, layout = text_block()
+-- Verify block closures keep the local styles object alive.
+collectgarbage "collect"
 local label = block(TEXT, WIDTH, HEIGHT)
 local label_layout = layout(TEXT, WIDTH, HEIGHT)
 
-local CURSOR_N = 0
+local cursor_pos = 0
+local selection_anchor = nil
+local selection_focus = nil
+local dragging = false
+
+local function viewport_height(count)
+	local t = (math.sin(count * 0.025) + 1) * 0.5
+	return math.floor(VIEWPORT_MIN + (VIEWPORT_MAX - VIEWPORT_MIN) * t)
+end
 
 local function position()
 	local x = (screen_w - WIDTH) / 2
@@ -76,22 +94,73 @@ local function position()
 	return x, y
 end
 
+local function ordered_selection()
+	if not selection_anchor or not selection_focus then
+		return nil
+	end
+	local from = selection_anchor
+	local to = selection_focus
+	if to < from then
+		from, to = to, from
+	end
+	if from == to then
+		return nil
+	end
+	return from, to
+end
+
+local function draw_selection(x, y)
+	local from, to = ordered_selection()
+	if not from then
+		return
+	end
+	for i = 1, label_layout:line_count() do
+		local line = label_layout:line(i)
+		if line then
+			local a = math.max(from, line.start)
+			local b = math.min(to, line.finish)
+			if a < b then
+				local sx
+				if a <= line.start then
+					sx = line.x
+				else
+					sx = label_layout:cursor(a)
+				end
+				local ex
+				if b >= line.finish then
+					ex = line.x + line.width
+				else
+					ex = label_layout:cursor(b)
+				end
+				local w = math.floor(ex - sx + 0.5)
+				if w > 0 then
+					batch:add(matquad.quad(w, line.height, 0x664f7dff), x + sx, y + line.y)
+				end
+			end
+		end
+	end
+end
+
 function callback.frame(count)
 	local x, y = position()
-	batch:add(matquad.quad(WIDTH, HEIGHT, 0x400000ff), x, y)
+	local clip_h = viewport_height(count)
+	batch:add(matquad.quad(WIDTH, clip_h, 0x400000ff), x, y)
+	batch:add(matclip.rect(WIDTH + CLIP_BLEED * 2, clip_h), x - CLIP_BLEED, y)
+	draw_selection(x, y)
 	batch:add(label, x, y)
 	-- cursor
-	local cx, cy, cw, ch, n = label_layout:cursor(CURSOR_N)
-	CURSOR_N = n
+	local cx, cy, cw, ch, n = label_layout:cursor(cursor_pos)
+	cursor_pos = n
 	batch:add(matquad.quad(cw, ch, 0xffffff), cx + x, cy + y)
+	batch:add(matclip.rect())
 end
 
 function callback.key(keycode, state)
 	if state == 1 then         -- press
 		if keycode == 262 then -- right
-			CURSOR_N = CURSOR_N + 1
+			cursor_pos = cursor_pos + 1
 		elseif keycode == 263 then -- left
-			CURSOR_N = CURSOR_N - 1
+			cursor_pos = cursor_pos - 1
 		else
 			print(keycode)
 		end
@@ -102,22 +171,37 @@ end
 local mouse_x = 0
 local mouse_y = 0
 
+local function hit_text(x, y)
+	local ox, oy = position()
+	return label_layout:hit_test(x - ox, y - oy)
+end
+
 function callback.mouse_move(x, y)
 	mouse_x = x
 	mouse_y = y
+	if dragging then
+		selection_focus = hit_text(x, y)
+		cursor_pos = selection_focus
+	end
 end
 
 local MOUSE_LEFT <const> = 0
+local MOUSE_RELEASE <const> = 0
 local MOUSE_PRESS <const> = 1
 
 function callback.mouse_button(button, state)
-	if button ~= MOUSE_LEFT or state ~= MOUSE_PRESS then
+	if button ~= MOUSE_LEFT then
 		return
 	end
-	local x, y = position()
-	x = mouse_x - x
-	y = mouse_y - y
-	CURSOR_N = label_layout:hit_test(x, y)
+	if state == MOUSE_PRESS then
+		local hit = hit_text(mouse_x, mouse_y)
+		selection_anchor = hit
+		selection_focus = hit
+		cursor_pos = hit
+		dragging = true
+	elseif state == MOUSE_RELEASE then
+		dragging = false
+	end
 end
 
 return callback