From a1b79a55d2d70660aa156da460ee2e55ebc99183 Mon Sep 17 00:00:00 2001
From: Přemysl Janouch <p.janouch@gmail.com>
Date: Sun, 12 Aug 2012 06:10:27 +0200
Subject: Change how Cairo is presented to Lua scripts.

Makes the whole thing a bit more stable and less weird.
---
 liblogdiag/ld-lua.c                   | 185 ++++++++++++++++++----------------
 share/library/Active/bipolar.lua      |  50 ++++-----
 share/library/Active/igfet.lua        |  54 +++++-----
 share/library/Active/jfet.lua         |  38 +++----
 share/library/Logical/and.lua         |  24 ++---
 share/library/Logical/not.lua         |  22 ++--
 share/library/Logical/or.lua          |  46 ++++-----
 share/library/Misc/cell.lua           |  18 ++--
 share/library/Misc/ground.lua         |  18 ++--
 share/library/Misc/junction.lua       |   4 +-
 share/library/Misc/lamp.lua           |  30 +++---
 share/library/Misc/meters.lua         |  44 ++++----
 share/library/Misc/signs.lua          |  16 +--
 share/library/Misc/switch.lua         |  14 +--
 share/library/Misc/terminal.lua       |   8 +-
 share/library/Misc/voltage-source.lua |  24 ++---
 share/library/Passive/capacitor.lua   |  18 ++--
 share/library/Passive/diode.lua       |  68 ++++++-------
 share/library/Passive/inductor.lua    |  16 +--
 share/library/Passive/resistor.lua    |  64 ++++++------
 20 files changed, 386 insertions(+), 375 deletions(-)

diff --git a/liblogdiag/ld-lua.c b/liblogdiag/ld-lua.c
index d16f327..18bf9ce 100644
--- a/liblogdiag/ld-lua.c
+++ b/liblogdiag/ld-lua.c
@@ -2,7 +2,7 @@
  * ld-lua.c
  *
  * This file is a part of logdiag.
- * Copyright Přemysl Janouch 2010 - 2011. All rights reserved.
+ * Copyright Přemysl Janouch 2010, 2011, 2012. All rights reserved.
  *
  * See the file LICENSE for licensing information.
  *
@@ -44,9 +44,10 @@ struct _LdLuaPrivate
  *   -> The rendering function
  */
 
-#define LD_LUA_LIBRARY_NAME "logdiag"
-#define LD_LUA_DATA_INDEX LD_LUA_LIBRARY_NAME "_data"
-#define LD_LUA_SYMBOLS_INDEX LD_LUA_LIBRARY_NAME "_symbols"
+#define LD_LUA_LIBRARY_NAME   "logdiag"
+#define LD_LUA_DATA_INDEX     LD_LUA_LIBRARY_NAME "_data"
+#define LD_LUA_SYMBOLS_INDEX  LD_LUA_LIBRARY_NAME "_symbols"
+#define LD_LUA_META_INDEX     LD_LUA_LIBRARY_NAME "_meta"
 
 /*
  * LdLuaData:
@@ -88,7 +89,6 @@ static gboolean read_symbol_area (lua_State *L, int index, LdRectangle *area);
 static gboolean read_terminals (lua_State *L, int index,
 	LdPointArray **terminals);
 
-static void push_cairo_object (lua_State *L, LdLuaDrawData *draw_data);
 static gdouble get_cairo_scale (cairo_t *cr);
 static int ld_lua_cairo_save (lua_State *L);
 static int ld_lua_cairo_restore (lua_State *L);
@@ -163,6 +163,24 @@ ld_lua_class_init (LdLuaClass *klass)
 	g_type_class_add_private (klass, sizeof (LdLuaPrivate));
 }
 
+static void
+push_cairo_metatable (lua_State *L)
+{
+	luaL_Reg *fn;
+
+	luaL_newmetatable (L, LD_LUA_META_INDEX);
+
+	/* Create a method table. */
+	lua_newtable (L);
+	for (fn = ld_lua_cairo_table; fn->name; fn++)
+	{
+		lua_pushcfunction (L, fn->func);
+		lua_setfield (L, -2, fn->name);
+	}
+
+	lua_setfield (L, -2, "__index");
+}
+
 static void
 ld_lua_init (LdLua *self)
 {
@@ -175,7 +193,7 @@ ld_lua_init (LdLua *self)
 	L = self->priv->L = lua_newstate (ld_lua_alloc, NULL);
 	g_return_if_fail (L != NULL);
 
-	/* TODO: lua_atpanic () */
+	/* XXX: Might not be a bad idea to use lua_atpanic(). */
 
 	/* Load some safe libraries. */
 	lua_pushcfunction (L, luaopen_string);
@@ -191,7 +209,7 @@ ld_lua_init (LdLua *self)
 	luaL_register (L, LD_LUA_LIBRARY_NAME, ld_lua_logdiag_lib);
 
 	/* Store user data to the registry. */
-	ud = lua_newuserdata (L, sizeof (LdLuaData));
+	ud = lua_newuserdata (L, sizeof *ud);
 	ud->self = self;
 	ud->load_callback = NULL;
 	ud->load_user_data = NULL;
@@ -201,6 +219,8 @@ ld_lua_init (LdLua *self)
 	/* Create an empty symbol table. */
 	lua_newtable (L);
 	lua_setfield (L, LUA_REGISTRYINDEX, LD_LUA_SYMBOLS_INDEX);
+
+	push_cairo_metatable (L);
 }
 
 static void
@@ -278,7 +298,7 @@ ld_lua_load_file (LdLua *self, const gchar *filename,
 	g_return_val_if_fail (filename != NULL, FALSE);
 	g_return_val_if_fail (callback != NULL, FALSE);
 
-	/* XXX: If something from the following fails, Lua will call exit(). */
+	/* XXX: If something from the following fails, Lua will panic. */
 	lua_getfield (self->priv->L, LUA_REGISTRYINDEX, LD_LUA_DATA_INDEX);
 	ud = lua_touserdata (self->priv->L, -1);
 	lua_pop (self->priv->L, 1);
@@ -344,7 +364,7 @@ ld_lua_private_draw (LdLua *self, LdLuaSymbol *symbol, cairo_t *cr)
 static int
 ld_lua_private_draw_cb (lua_State *L)
 {
-	LdLuaDrawData *data;
+	LdLuaDrawData *data, *luadata;
 
 	data = lua_touserdata (L, -1);
 
@@ -357,9 +377,28 @@ ld_lua_private_draw_cb (lua_State *L)
 	lua_getfield (L, -1, "render");
 	luaL_checktype (L, -1, LUA_TFUNCTION);
 
-	/* Call the function do draw the symbol. */
-	push_cairo_object (L, data);
-	lua_pcall (L, 1, 0, 0);
+	/* Create a Cairo wrapper object. */
+	luadata = lua_newuserdata (L, sizeof *data);
+	memcpy (luadata, data, sizeof *data);
+	lua_getfield (L, LUA_REGISTRYINDEX, LD_LUA_META_INDEX);
+	lua_setmetatable (L, -2);
+
+	/* Force it to stay alive for a bit longer. */
+	lua_pushvalue (L, -1);
+	lua_insert (L, 1);
+
+	/* Draw the symbol. */
+	if (lua_pcall (L, 1, 0, 0))
+	{
+		g_warning ("Lua error: %s", lua_tostring (L, -1));
+		lua_pop (L, 1);
+	}
+
+	/* Copy the userdata back and invalidate it, so that malicious Lua
+	 * scripts won't succeed at drawing onto a long invalid Cairo context.
+	 */
+	memcpy (data, luadata, sizeof *data);
+	memset (luadata, 0, sizeof *data);
 	return 0;
 }
 
@@ -562,7 +601,7 @@ read_symbol_area (lua_State *L, int index, LdRectangle *area)
 
 	area->x = MIN (x1, x2);
 	area->y = MIN (y1, y2);
-	area->width = ABS (x2 - x1);
+	area->width  = ABS (x2 - x1);
 	area->height = ABS (y2 - y1);
 
 	lua_pop (L, 4);
@@ -622,32 +661,6 @@ read_terminals_fail:
 
 /* ===== Cairo ============================================================= */
 
-static void
-push_cairo_object (lua_State *L, LdLuaDrawData *draw_data)
-{
-	luaL_Reg *fn;
-
-	/* Create a table. */
-	lua_newtable (L);
-
-	/* Add methods. */
-	/* XXX: The light user data pointer gets invalid after the end of
-	 *      "render" function invocation. If the script stores the "cr" object
-	 *      in some global variable and then tries to reuse it the next time,
-	 *      the application may go SIGSEGV.
-	 *
-	 *      The solution is creating a full user data instead, referencing
-	 *      the cairo object and dereferencing it upon garbage collection
-	 *      of the user data object.
-	 */
-	for (fn = ld_lua_cairo_table; fn->name; fn++)
-	{
-		lua_pushlightuserdata (L, draw_data);
-		lua_pushcclosure (L, fn->func, 1);
-		lua_setfield (L, -2, fn->name);
-	}
-}
-
 static gdouble
 get_cairo_scale (cairo_t *cr)
 {
@@ -657,6 +670,11 @@ get_cairo_scale (cairo_t *cr)
 	return dx;
 }
 
+#define LD_LUA_CAIRO_GET_DATA \
+	data = luaL_checkudata (L, 1, LD_LUA_META_INDEX); \
+	if (!data->cr) \
+		return luaL_error (L, "Tried to use an invalid Cairo object");
+
 #define LD_LUA_CAIRO_BEGIN(name) \
 static int \
 ld_lua_cairo_ ## name (lua_State *L) \
@@ -669,7 +687,7 @@ ld_lua_cairo_ ## name (lua_State *L) \
 
 #define LD_LUA_CAIRO_TRIVIAL(name) \
 LD_LUA_CAIRO_BEGIN (name) \
-	data = lua_touserdata (L, lua_upvalueindex (1)); \
+	LD_LUA_CAIRO_GET_DATA \
 	cairo_ ## name (data->cr); \
 LD_LUA_CAIRO_END (0)
 
@@ -685,7 +703,7 @@ LD_LUA_CAIRO_TRIVIAL (clip)
 LD_LUA_CAIRO_TRIVIAL (clip_preserve)
 
 LD_LUA_CAIRO_BEGIN (save)
-	data = lua_touserdata (L, lua_upvalueindex (1));
+	LD_LUA_CAIRO_GET_DATA
 	if (data->save_count + 1)
 	{
 		data->save_count++;
@@ -694,7 +712,7 @@ LD_LUA_CAIRO_BEGIN (save)
 LD_LUA_CAIRO_END (0)
 
 LD_LUA_CAIRO_BEGIN (restore)
-	data = lua_touserdata (L, lua_upvalueindex (1));
+	LD_LUA_CAIRO_GET_DATA
 	if (data->save_count)
 	{
 		data->save_count--;
@@ -703,24 +721,23 @@ LD_LUA_CAIRO_BEGIN (restore)
 LD_LUA_CAIRO_END (0)
 
 LD_LUA_CAIRO_BEGIN (get_line_width)
-	data = lua_touserdata (L, lua_upvalueindex (1));
+	LD_LUA_CAIRO_GET_DATA
 	lua_pushnumber (L, cairo_get_line_width (data->cr)
 		* get_cairo_scale (data->cr));
 LD_LUA_CAIRO_END (1)
 
 LD_LUA_CAIRO_BEGIN (set_line_width)
-	data = lua_touserdata (L, lua_upvalueindex (1));
-	cairo_set_line_width (data->cr, luaL_checknumber (L, 1)
+	LD_LUA_CAIRO_GET_DATA
+	cairo_set_line_width (data->cr, luaL_checknumber (L, 2)
 		/ get_cairo_scale (data->cr));
 LD_LUA_CAIRO_END (0)
 
 LD_LUA_CAIRO_BEGIN (translate)
 	lua_Number x, y;
 
-	data = lua_touserdata (L, lua_upvalueindex (1));
-
-	x = luaL_checknumber (L, 1);
-	y = luaL_checknumber (L, 2);
+	LD_LUA_CAIRO_GET_DATA
+	x = luaL_checknumber (L, 2);
+	y = luaL_checknumber (L, 3);
 
 	cairo_translate (data->cr, x, y);
 LD_LUA_CAIRO_END (0)
@@ -728,10 +745,9 @@ LD_LUA_CAIRO_END (0)
 LD_LUA_CAIRO_BEGIN (scale)
 	lua_Number sx, sy;
 
-	data = lua_touserdata (L, lua_upvalueindex (1));
-
-	sx = luaL_checknumber (L, 1);
-	sy = luaL_checknumber (L, 2);
+	LD_LUA_CAIRO_GET_DATA
+	sx = luaL_checknumber (L, 2);
+	sy = luaL_checknumber (L, 3);
 
 	cairo_scale (data->cr, sx, sy);
 LD_LUA_CAIRO_END (0)
@@ -739,18 +755,17 @@ LD_LUA_CAIRO_END (0)
 LD_LUA_CAIRO_BEGIN (rotate)
 	lua_Number angle;
 
-	data = lua_touserdata (L, lua_upvalueindex (1));
-	angle = luaL_checknumber (L, 1);
+	LD_LUA_CAIRO_GET_DATA
+	angle = luaL_checknumber (L, 2);
 	cairo_rotate (data->cr, angle);
 LD_LUA_CAIRO_END (0)
 
 LD_LUA_CAIRO_BEGIN (move_to)
 	lua_Number x, y;
 
-	data = lua_touserdata (L, lua_upvalueindex (1));
-
-	x = luaL_checknumber (L, 1);
-	y = luaL_checknumber (L, 2);
+	LD_LUA_CAIRO_GET_DATA
+	x = luaL_checknumber (L, 2);
+	y = luaL_checknumber (L, 3);
 
 	cairo_move_to (data->cr, x, y);
 LD_LUA_CAIRO_END (0)
@@ -758,10 +773,9 @@ LD_LUA_CAIRO_END (0)
 LD_LUA_CAIRO_BEGIN (line_to)
 	lua_Number x, y;
 
-	data = lua_touserdata (L, lua_upvalueindex (1));
-
-	x = luaL_checknumber (L, 1);
-	y = luaL_checknumber (L, 2);
+	LD_LUA_CAIRO_GET_DATA
+	x = luaL_checknumber (L, 2);
+	y = luaL_checknumber (L, 3);
 
 	cairo_line_to (data->cr, x, y);
 LD_LUA_CAIRO_END (0)
@@ -769,14 +783,13 @@ LD_LUA_CAIRO_END (0)
 LD_LUA_CAIRO_BEGIN (curve_to)
 	lua_Number x1, y1, x2, y2, x3, y3;
 
-	data = lua_touserdata (L, lua_upvalueindex (1));
-
-	x1 = luaL_checknumber (L, 1);
-	y1 = luaL_checknumber (L, 2);
-	x2 = luaL_checknumber (L, 3);
-	y2 = luaL_checknumber (L, 4);
-	x3 = luaL_checknumber (L, 5);
-	y3 = luaL_checknumber (L, 6);
+	LD_LUA_CAIRO_GET_DATA
+	x1 = luaL_checknumber (L, 2);
+	y1 = luaL_checknumber (L, 3);
+	x2 = luaL_checknumber (L, 4);
+	y2 = luaL_checknumber (L, 5);
+	x3 = luaL_checknumber (L, 6);
+	y3 = luaL_checknumber (L, 7);
 
 	cairo_curve_to (data->cr, x1, y1, x2, y2, x3, y3);
 LD_LUA_CAIRO_END (0)
@@ -784,13 +797,12 @@ LD_LUA_CAIRO_END (0)
 LD_LUA_CAIRO_BEGIN (arc)
 	lua_Number xc, yc, radius, angle1, angle2;
 
-	data = lua_touserdata (L, lua_upvalueindex (1));
-
-	xc = luaL_checknumber (L, 1);
-	yc = luaL_checknumber (L, 2);
-	radius = luaL_checknumber (L, 3);
-	angle1 = luaL_checknumber (L, 4);
-	angle2 = luaL_checknumber (L, 5);
+	LD_LUA_CAIRO_GET_DATA
+	xc = luaL_checknumber (L, 2);
+	yc = luaL_checknumber (L, 3);
+	radius = luaL_checknumber (L, 4);
+	angle1 = luaL_checknumber (L, 5);
+	angle2 = luaL_checknumber (L, 6);
 
 	cairo_arc (data->cr, xc, yc, radius, angle1, angle2);
 LD_LUA_CAIRO_END (0)
@@ -798,13 +810,12 @@ LD_LUA_CAIRO_END (0)
 LD_LUA_CAIRO_BEGIN (arc_negative)
 	lua_Number xc, yc, radius, angle1, angle2;
 
-	data = lua_touserdata (L, lua_upvalueindex (1));
-
-	xc = luaL_checknumber (L, 1);
-	yc = luaL_checknumber (L, 2);
-	radius = luaL_checknumber (L, 3);
-	angle1 = luaL_checknumber (L, 4);
-	angle2 = luaL_checknumber (L, 5);
+	LD_LUA_CAIRO_GET_DATA
+	xc = luaL_checknumber (L, 2);
+	yc = luaL_checknumber (L, 3);
+	radius = luaL_checknumber (L, 4);
+	angle1 = luaL_checknumber (L, 5);
+	angle2 = luaL_checknumber (L, 6);
 
 	cairo_arc_negative (data->cr, xc, yc, radius, angle1, angle2);
 LD_LUA_CAIRO_END (0)
@@ -816,8 +827,8 @@ LD_LUA_CAIRO_BEGIN (show_text)
 	int width, height;
 	double x, y;
 
-	data = lua_touserdata (L, lua_upvalueindex (1));
-	text = luaL_checkstring (L, 1);
+	LD_LUA_CAIRO_GET_DATA
+	text = luaL_checkstring (L, 2);
 
 	layout = pango_cairo_create_layout (data->cr);
 	pango_layout_set_text (layout, text, -1);
diff --git a/share/library/Active/bipolar.lua b/share/library/Active/bipolar.lua
index 921772c..bac8786 100644
--- a/share/library/Active/bipolar.lua
+++ b/share/library/Active/bipolar.lua
@@ -26,50 +26,50 @@ local terminals = {{-2, 0}, {2, 2}, {2, -2}}
 -- Rendering
 local render = function (cr)
 	-- The terminals
-	cr.move_to (-2, 0)
-	cr.line_to (0, 0)
+	cr:move_to (-2, 0)
+	cr:line_to (0, 0)
 
-	cr.move_to (0, 0.5)
-	cr.line_to (2, 2)
+	cr:move_to (0, 0.5)
+	cr:line_to (2, 2)
 
-	cr.move_to (0, -0.5)
-	cr.line_to (2, -2)
+	cr:move_to (0, -0.5)
+	cr:line_to (2, -2)
 
 	-- The ohmic connection
-	cr.move_to (0, -1)
-	cr.line_to (0, 1)
+	cr:move_to (0, -1)
+	cr:line_to (0, 1)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 local render_npn = function (cr)
 	render (cr)
 
-	cr.save ()
-	cr.translate (0, 0.5)
-	cr.rotate (math.atan2 (-2, 1.5))
+	cr:save ()
+	cr:translate (0, 0.5)
+	cr:rotate (math.atan2 (-2, 1.5))
 
-	cr.move_to (-0.4, 0.8)
-	cr.line_to (0, 1.4)
-	cr.line_to (0.4, 0.8)
+	cr:move_to (-0.4, 0.8)
+	cr:line_to (0, 1.4)
+	cr:line_to (0.4, 0.8)
 
-	cr.stroke ()
-	cr.restore ()
+	cr:stroke ()
+	cr:restore ()
 end
 
 local render_pnp = function (cr)
 	render (cr)
 
-	cr.save ()
-	cr.translate (2, -2)
-	cr.rotate (math.atan2 (2, 1.5))
+	cr:save ()
+	cr:translate (2, -2)
+	cr:rotate (math.atan2 (2, 1.5))
 
-	cr.move_to (-0.4, 1.3)
-	cr.line_to (0, 1.9)
-	cr.line_to (0.4, 1.3)
+	cr:move_to (-0.4, 1.3)
+	cr:line_to (0, 1.9)
+	cr:line_to (0.4, 1.3)
 
-	cr.stroke ()
-	cr.restore ()
+	cr:stroke ()
+	cr:restore ()
 end
 
 -- Register the symbols
diff --git a/share/library/Active/igfet.lua b/share/library/Active/igfet.lua
index 8b5796d..3e17183 100644
--- a/share/library/Active/igfet.lua
+++ b/share/library/Active/igfet.lua
@@ -27,59 +27,59 @@ local terminals_p = {{-2, -1}, {2, 1}, {2, 0}, {2, -1}}
 -- Rendering
 local render = function (cr)
 	-- The terminals
-	cr.move_to (-0.3, 1)
-	cr.line_to (-0.3, -1)
+	cr:move_to (-0.3, 1)
+	cr:line_to (-0.3, -1)
 
-	cr.move_to (0, 1)
-	cr.line_to (2, 1)
+	cr:move_to (0, 1)
+	cr:line_to (2, 1)
 
-	cr.move_to (0, 0)
-	cr.line_to (2, 0)
+	cr:move_to (0, 0)
+	cr:line_to (2, 0)
 
-	cr.move_to (0, -1)
-	cr.line_to (2, -1)
+	cr:move_to (0, -1)
+	cr:line_to (2, -1)
 
 	-- Source, gate, drain
-	cr.move_to (0, -1.5)
-	cr.line_to (0, -0.5)
+	cr:move_to (0, -1.5)
+	cr:line_to (0, -0.5)
 
-	cr.move_to (0, -0.3)
-	cr.line_to (0, 0.3)
+	cr:move_to (0, -0.3)
+	cr:line_to (0, 0.3)
 
-	cr.move_to (0, 0.5)
-	cr.line_to (0, 1.5)
+	cr:move_to (0, 0.5)
+	cr:line_to (0, 1.5)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 local render_n = function (cr)
 	render (cr)
 
 	-- The left-side terminal
-	cr.move_to (-2, 1)
-	cr.line_to (-0.3, 1)
+	cr:move_to (-2, 1)
+	cr:line_to (-0.3, 1)
 
 	-- The arrow
-	cr.move_to (0.9, -0.4)
-	cr.line_to (0.4, 0)
-	cr.line_to (0.9, 0.4)
+	cr:move_to (0.9, -0.4)
+	cr:line_to (0.4, 0)
+	cr:line_to (0.9, 0.4)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 local render_p = function (cr)
 	render (cr)
 
 	-- The left-side terminal
-	cr.move_to (-2, -1)
-	cr.line_to (-0.3, -1)
+	cr:move_to (-2, -1)
+	cr:line_to (-0.3, -1)
 
 	-- The arrow
-	cr.move_to (0.4, -0.4)
-	cr.line_to (0.9, 0)
-	cr.line_to (0.4, 0.4)
+	cr:move_to (0.4, -0.4)
+	cr:line_to (0.9, 0)
+	cr:line_to (0.4, 0.4)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 -- Register the symbols
diff --git a/share/library/Active/jfet.lua b/share/library/Active/jfet.lua
index ebe917a..5fb9d47 100644
--- a/share/library/Active/jfet.lua
+++ b/share/library/Active/jfet.lua
@@ -27,47 +27,47 @@ local terminals_p = {{-2, -1}, {2, 1}, {2, -1}}
 -- Rendering
 local render = function (cr)
 	-- The terminals
-	cr.move_to (0, 1)
-	cr.line_to (2, 1)
+	cr:move_to (0, 1)
+	cr:line_to (2, 1)
 
-	cr.move_to (0, -1)
-	cr.line_to (2, -1)
+	cr:move_to (0, -1)
+	cr:line_to (2, -1)
 
 	-- The ohmic connection
-	cr.move_to (0, -1.5)
-	cr.line_to (0, 1.5)
+	cr:move_to (0, -1.5)
+	cr:line_to (0, 1.5)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 local render_n = function (cr)
 	render (cr)
 
 	-- The left-side terminal
-	cr.move_to (-2, 1)
-	cr.line_to (0, 1)
+	cr:move_to (-2, 1)
+	cr:line_to (0, 1)
 
 	-- The arrow
-	cr.move_to (-1, 0.6)
-	cr.line_to (-0.5, 1)
-	cr.line_to (-1, 1.4)
+	cr:move_to (-1, 0.6)
+	cr:line_to (-0.5, 1)
+	cr:line_to (-1, 1.4)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 local render_p = function (cr)
 	render (cr)
 
 	-- The left-side terminal
-	cr.move_to (-2, -1)
-	cr.line_to (0, -1)
+	cr:move_to (-2, -1)
+	cr:line_to (0, -1)
 
 	-- The arrow
-	cr.move_to (-0.4, -0.6)
-	cr.line_to (-1, -1)
-	cr.line_to (-0.4, -1.4)
+	cr:move_to (-0.4, -0.6)
+	cr:line_to (-1, -1)
+	cr:line_to (-0.4, -1.4)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 -- Register the symbols
diff --git a/share/library/Logical/and.lua b/share/library/Logical/and.lua
index da09cfe..8c4477f 100644
--- a/share/library/Logical/and.lua
+++ b/share/library/Logical/and.lua
@@ -17,23 +17,23 @@ local terminals = {{-4, -1}, {-4, 1}, {5, 0}}
 -- Rendering
 local render = function (cr)
 	-- The main shape
-	cr.move_to (-2, -2)
-	cr.line_to (1, -2)
-	cr.arc (1, 0, 2, math.pi * 1.5, math.pi * 0.5)
-	cr.line_to (-2, 2)
-	cr.close_path ()
+	cr:move_to (-2, -2)
+	cr:line_to (1, -2)
+	cr:arc (1, 0, 2, math.pi * 1.5, math.pi * 0.5)
+	cr:line_to (-2, 2)
+	cr:close_path ()
 
 	-- The terminals
-	cr.move_to (-4, -1)
-	cr.line_to (-2, -1)
+	cr:move_to (-4, -1)
+	cr:line_to (-2, -1)
 
-	cr.move_to (-4, 1)
-	cr.line_to (-2, 1)
+	cr:move_to (-4, 1)
+	cr:line_to (-2, 1)
 
-	cr.move_to (3, 0)
-	cr.line_to (5, 0)
+	cr:move_to (3, 0)
+	cr:line_to (5, 0)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 -- Register the symbol
diff --git a/share/library/Logical/not.lua b/share/library/Logical/not.lua
index 8153e4a..44e4cc3 100644
--- a/share/library/Logical/not.lua
+++ b/share/library/Logical/not.lua
@@ -17,23 +17,23 @@ local terminals = {{-4, 0}, {4, 0}}
 -- Rendering
 local render = function (cr)
 	-- The triangle
-	cr.move_to (-2, -2)
-	cr.line_to (2, 0)
-	cr.line_to (-2, 2)
-	cr.close_path ()
+	cr:move_to (-2, -2)
+	cr:line_to (2, 0)
+	cr:line_to (-2, 2)
+	cr:close_path ()
 
 	-- The circle
-	cr.new_sub_path ()
-	cr.arc (2.25, 0, 0.25, 0, 2 * math.pi)
+	cr:new_sub_path ()
+	cr:arc (2.25, 0, 0.25, 0, 2 * math.pi)
 
 	-- The terminals
-	cr.move_to (-4, 0)
-	cr.line_to (-2, 0)
+	cr:move_to (-4, 0)
+	cr:line_to (-2, 0)
 
-	cr.move_to (2.5, 0)
-	cr.line_to (4, 0)
+	cr:move_to (2.5, 0)
+	cr:line_to (4, 0)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 -- Register the symbol
diff --git a/share/library/Logical/or.lua b/share/library/Logical/or.lua
index a7ff4bf..18aabab 100644
--- a/share/library/Logical/or.lua
+++ b/share/library/Logical/or.lua
@@ -17,38 +17,38 @@ local terminals = {{-4, -1}, {-4, 1}, {5, 0}}
 -- Rendering
 local render = function (cr)
 	-- The main shape
-	cr.move_to (-2, -2)
-	cr.line_to (0, -2)
-	cr.curve_to (2, -2, 3, 0, 3, 0)
-	cr.curve_to (3, 0, 2, 2, 0, 2)
-	cr.line_to (-2, 2)
-	cr.curve_to (-1, 1, -1, -1, -2, -2)
-	cr.stroke ()
+	cr:move_to (-2, -2)
+	cr:line_to (0, -2)
+	cr:curve_to (2, -2, 3, 0, 3, 0)
+	cr:curve_to (3, 0, 2, 2, 0, 2)
+	cr:line_to (-2, 2)
+	cr:curve_to (-1, 1, -1, -1, -2, -2)
+	cr:stroke ()
 
 	-- The terminals
-	cr.save ()
+	cr:save ()
 
 	-- Crop the contacts according to
 	-- the left side of the main shape
-	cr.move_to (-4, 2)
-	cr.line_to (-2, 2)
-	cr.curve_to (-1, 1, -1, -1, -2, -2)
-	cr.line_to (-4, -2)
-	cr.close_path ()
-	cr.clip ()
+	cr:move_to (-4, 2)
+	cr:line_to (-2, 2)
+	cr:curve_to (-1, 1, -1, -1, -2, -2)
+	cr:line_to (-4, -2)
+	cr:close_path ()
+	cr:clip ()
 
-	cr.move_to (-4, -1)
-	cr.line_to (-1, -1)
+	cr:move_to (-4, -1)
+	cr:line_to (-1, -1)
 
-	cr.move_to (-4, 1)
-	cr.line_to (-1, 1)
+	cr:move_to (-4, 1)
+	cr:line_to (-1, 1)
 
-	cr.stroke ()
-	cr.restore ()
+	cr:stroke ()
+	cr:restore ()
 
-	cr.move_to (3, 0)
-	cr.line_to (5, 0)
-	cr.stroke ()
+	cr:move_to (3, 0)
+	cr:line_to (5, 0)
+	cr:stroke ()
 end
 
 -- Register the symbol
diff --git a/share/library/Misc/cell.lua b/share/library/Misc/cell.lua
index 8a6a575..541e44c 100644
--- a/share/library/Misc/cell.lua
+++ b/share/library/Misc/cell.lua
@@ -17,20 +17,20 @@ local terminals = {{-1, 0}, {1, 0}}
 -- Rendering
 local render = function (cr)
 	-- The vertical lines
-	cr.move_to (-0.2, -1)
-	cr.line_to (-0.2, 1)
+	cr:move_to (-0.2, -1)
+	cr:line_to (-0.2, 1)
 
-	cr.move_to (0.2, -2)
-	cr.line_to (0.2, 2)
+	cr:move_to (0.2, -2)
+	cr:line_to (0.2, 2)
 
 	-- The terminals
-	cr.move_to (-1, 0)
-	cr.line_to (-0.2, 0)
+	cr:move_to (-1, 0)
+	cr:line_to (-0.2, 0)
 
-	cr.move_to (0.2, 0)
-	cr.line_to (1, 0)
+	cr:move_to (0.2, 0)
+	cr:line_to (1, 0)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 -- Register the symbol
diff --git a/share/library/Misc/ground.lua b/share/library/Misc/ground.lua
index 6d20b57..2209718 100644
--- a/share/library/Misc/ground.lua
+++ b/share/library/Misc/ground.lua
@@ -17,20 +17,20 @@ local terminals = {{0, -1}}
 -- Rendering
 local render = function (cr)
 	-- The vertical line
-	cr.move_to (0, -1)
-	cr.line_to (0, 0.5)
+	cr:move_to (0, -1)
+	cr:line_to (0, 0.5)
 
 	-- The horizontal lines
-	cr.move_to (-1, 0.5)
-	cr.line_to (1, 0.5)
+	cr:move_to (-1, 0.5)
+	cr:line_to (1, 0.5)
 
-	cr.move_to (-0.75, 1.1)
-	cr.line_to (0.75, 1.1)
+	cr:move_to (-0.75, 1.1)
+	cr:line_to (0.75, 1.1)
 
-	cr.move_to (-0.5, 1.7)
-	cr.line_to (0.5, 1.7)
+	cr:move_to (-0.5, 1.7)
+	cr:line_to (0.5, 1.7)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 -- Register the symbol
diff --git a/share/library/Misc/junction.lua b/share/library/Misc/junction.lua
index 75fbafb..c7c399b 100644
--- a/share/library/Misc/junction.lua
+++ b/share/library/Misc/junction.lua
@@ -17,8 +17,8 @@ local terminals = {}
 -- Rendering
 local render = function (cr)
 	-- The disk
-	cr.arc (0, 0, 0.3, 0, math.pi * 2)
-	cr.fill ()
+	cr:arc (0, 0, 0.3, 0, math.pi * 2)
+	cr:fill ()
 end
 
 -- Register the symbol
diff --git a/share/library/Misc/lamp.lua b/share/library/Misc/lamp.lua
index f543bde..d6dd411 100644
--- a/share/library/Misc/lamp.lua
+++ b/share/library/Misc/lamp.lua
@@ -17,29 +17,29 @@ local terminals = {{-2, 0}, {2, 0}}
 -- Rendering
 local render = function (cr)
 	-- The circle
-	cr.save ()
+	cr:save ()
 
-	cr.arc (0, 0, 1, 0, 2 * math.pi)
-	cr.stroke_preserve ()
-	cr.clip ()
+	cr:arc (0, 0, 1, 0, 2 * math.pi)
+	cr:stroke_preserve ()
+	cr:clip ()
 
-	cr.move_to (-1, -1)
-	cr.line_to (1, 1)
+	cr:move_to (-1, -1)
+	cr:line_to (1, 1)
 
-	cr.move_to (1, -1)
-	cr.line_to (-1, 1)
+	cr:move_to (1, -1)
+	cr:line_to (-1, 1)
 
-	cr.stroke ()
-	cr.restore ()
+	cr:stroke ()
+	cr:restore ()
 
 	-- The terminals
-	cr.move_to (-2, 0)
-	cr.line_to (-1, 0)
+	cr:move_to (-2, 0)
+	cr:line_to (-1, 0)
 
-	cr.move_to (1, 0)
-	cr.line_to (2, 0)
+	cr:move_to (1, 0)
+	cr:line_to (2, 0)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 -- Register the symbol
diff --git a/share/library/Misc/meters.lua b/share/library/Misc/meters.lua
index 55b6e28..1fb0394 100644
--- a/share/library/Misc/meters.lua
+++ b/share/library/Misc/meters.lua
@@ -35,45 +35,45 @@ local terminals = {{-2, 0}, {2, 0}, {0, -2}, {0, 2}}
 -- Rendering
 local render_A = function (cr)
 	-- The circle
-	cr.arc (0, 0, 2, 0, math.pi * 2)
+	cr:arc (0, 0, 2, 0, math.pi * 2)
 
 	-- The letter A
-	cr.move_to (-0.4, 0.5)
-	cr.line_to (0, -0.5)
-	cr.line_to (0.4, 0.5)
+	cr:move_to (-0.4, 0.5)
+	cr:line_to (0, -0.5)
+	cr:line_to (0.4, 0.5)
 
-	cr.move_to (-0.3, 0.25)
-	cr.line_to (0.3, 0.25)
+	cr:move_to (-0.3, 0.25)
+	cr:line_to (0.3, 0.25)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 local render_V = function (cr)
 	-- The circle
-	cr.arc (0, 0, 2, 0, math.pi * 2)
+	cr:arc (0, 0, 2, 0, math.pi * 2)
 
 	-- The letter V
-	cr.move_to (-0.4, -0.5)
-	cr.line_to (0, 0.5)
-	cr.line_to (0.4, -0.5)
+	cr:move_to (-0.4, -0.5)
+	cr:line_to (0, 0.5)
+	cr:line_to (0.4, -0.5)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 local render_ohm = function (cr)
 	-- The circle
-	cr.arc (0, 0, 2, 0, math.pi * 2)
+	cr:arc (0, 0, 2, 0, math.pi * 2)
 
 	-- The capital letter omega
-	cr.move_to (-0.5, 0.5)
-	cr.line_to (-0.15, 0.5)
-	cr.curve_to (-0.15, 0.5, -0.4, 0.3, -0.4, 0)
-	cr.curve_to (-0.4, -0.25, -0.25, -0.5, 0, -0.5)
-	cr.curve_to (0.25, -0.5, 0.4, -0.25, 0.4, 0)
-	cr.curve_to (0.4, 0.3, 0.15, 0.5, 0.15, 0.5)
-	cr.line_to (0.5, 0.5)
-
-	cr.stroke ()
+	cr:move_to (-0.5, 0.5)
+	cr:line_to (-0.15, 0.5)
+	cr:curve_to (-0.15, 0.5, -0.4, 0.3, -0.4, 0)
+	cr:curve_to (-0.4, -0.25, -0.25, -0.5, 0, -0.5)
+	cr:curve_to (0.25, -0.5, 0.4, -0.25, 0.4, 0)
+	cr:curve_to (0.4, 0.3, 0.15, 0.5, 0.15, 0.5)
+	cr:line_to (0.5, 0.5)
+
+	cr:stroke ()
 end
 
 -- Register the symbols
diff --git a/share/library/Misc/signs.lua b/share/library/Misc/signs.lua
index d2efe45..158d9b2 100644
--- a/share/library/Misc/signs.lua
+++ b/share/library/Misc/signs.lua
@@ -26,21 +26,21 @@ local terminals = {}
 -- Rendering
 local render_plus = function (cr)
 	-- The plus sign
-	cr.move_to (0, -0.4)
-	cr.line_to (0, 0.4)
+	cr:move_to (0, -0.4)
+	cr:line_to (0, 0.4)
 
-	cr.move_to (-0.4, 0)
-	cr.line_to (0.4, 0)
+	cr:move_to (-0.4, 0)
+	cr:line_to (0.4, 0)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 local render_minus = function (cr)
 	-- The minus sign
-	cr.move_to (-0.4, 0)
-	cr.line_to (0.4, 0)
+	cr:move_to (-0.4, 0)
+	cr:line_to (0.4, 0)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 -- Register the symbols
diff --git a/share/library/Misc/switch.lua b/share/library/Misc/switch.lua
index 2cae086..2d95b6b 100644
--- a/share/library/Misc/switch.lua
+++ b/share/library/Misc/switch.lua
@@ -17,17 +17,17 @@ local terminals = {{-2, 0}, {2, 0}}
 -- Rendering
 local render = function (cr)
 	-- The switch contact
-	cr.move_to (1.3, -1.3)
-	cr.line_to (-1, 0)
+	cr:move_to (1.3, -1.3)
+	cr:line_to (-1, 0)
 
 	-- The terminals
-	cr.move_to (-2, 0)
-	cr.line_to (-1, 0)
+	cr:move_to (-2, 0)
+	cr:line_to (-1, 0)
 
-	cr.move_to (1, 0)
-	cr.line_to (2, 0)
+	cr:move_to (1, 0)
+	cr:line_to (2, 0)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 -- Register the symbol
diff --git a/share/library/Misc/terminal.lua b/share/library/Misc/terminal.lua
index 3d31537..4bc2f2f 100644
--- a/share/library/Misc/terminal.lua
+++ b/share/library/Misc/terminal.lua
@@ -17,13 +17,13 @@ local terminals = {{-1, 0}}
 -- Rendering
 local render = function (cr)
 	-- The circle
-	cr.arc (0, 0, 0.3, 0, math.pi * 2)
+	cr:arc (0, 0, 0.3, 0, math.pi * 2)
 
 	-- The contact
-	cr.move_to (-1, 0)
-	cr.line_to (-0.3, 0)
+	cr:move_to (-1, 0)
+	cr:line_to (-0.3, 0)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 -- Register the symbol
diff --git a/share/library/Misc/voltage-source.lua b/share/library/Misc/voltage-source.lua
index 456310b..9003364 100644
--- a/share/library/Misc/voltage-source.lua
+++ b/share/library/Misc/voltage-source.lua
@@ -26,35 +26,35 @@ local terminals = {{-2, 0}, {2, 0}, {0, -2}, {0, 2}}
 -- Rendering
 local render = function (cr)
 	-- The circle
-	cr.arc (0, 0, 2, 0, math.pi * 2)
+	cr:arc (0, 0, 2, 0, math.pi * 2)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 local render_ac = function (cr)
 	render (cr)
 
 	-- The AC symbol
-	cr.move_to (-1, 0.25)
-	cr.curve_to (-0.4, -1.5, 0.4, 1.5, 1, -0.25)
+	cr:move_to (-1, 0.25)
+	cr:curve_to (-0.4, -1.5, 0.4, 1.5, 1, -0.25)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 local render_dc = function (cr)
 	render (cr)
 
 	-- The DC symbol
-	cr.move_to (-1, -0.25)
-	cr.line_to (1, -0.25)
+	cr:move_to (-1, -0.25)
+	cr:line_to (1, -0.25)
 
-	cr.move_to (-1, 0.25)
-	cr.line_to (-0.2, 0.25)
+	cr:move_to (-1, 0.25)
+	cr:line_to (-0.2, 0.25)
 
-	cr.move_to (0.2, 0.25)
-	cr.line_to (1, 0.25)
+	cr:move_to (0.2, 0.25)
+	cr:line_to (1, 0.25)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 -- Register the symbols
diff --git a/share/library/Passive/capacitor.lua b/share/library/Passive/capacitor.lua
index 121b01d..bd8c408 100644
--- a/share/library/Passive/capacitor.lua
+++ b/share/library/Passive/capacitor.lua
@@ -17,20 +17,20 @@ local terminals = {{-2, 0}, {2, 0}}
 -- Rendering
 local render = function (cr)
 	-- The vertical lines
-	cr.move_to (-0.2, -1)
-	cr.line_to (-0.2, 1)
+	cr:move_to (-0.2, -1)
+	cr:line_to (-0.2, 1)
 
-	cr.move_to (0.2, -1)
-	cr.line_to (0.2, 1)
+	cr:move_to (0.2, -1)
+	cr:line_to (0.2, 1)
 
 	-- The terminals
-	cr.move_to (-2, 0)
-	cr.line_to (-0.2, 0)
+	cr:move_to (-2, 0)
+	cr:line_to (-0.2, 0)
 
-	cr.move_to (0.2, 0)
-	cr.line_to (2, 0)
+	cr:move_to (0.2, 0)
+	cr:line_to (2, 0)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 -- Register the symbol
diff --git a/share/library/Passive/diode.lua b/share/library/Passive/diode.lua
index d480b46..46bfa99 100644
--- a/share/library/Passive/diode.lua
+++ b/share/library/Passive/diode.lua
@@ -45,79 +45,79 @@ local terminals = {{-2, 0}, {2, 0}}
 -- Rendering
 local render = function (cr)
 	-- The triangle
-	cr.move_to (-1, -1)
-	cr.line_to (1, 0)
-	cr.line_to (-1, 1)
-	cr.line_to (-1, -1)
+	cr:move_to (-1, -1)
+	cr:line_to (1, 0)
+	cr:line_to (-1, 1)
+	cr:line_to (-1, -1)
 
 	-- The vertical line
-	cr.move_to (1, 1)
-	cr.line_to (1, -1)
+	cr:move_to (1, 1)
+	cr:line_to (1, -1)
 
 	-- The terminals
-	cr.move_to (-2, 0)
-	cr.line_to (2, 0)
+	cr:move_to (-2, 0)
+	cr:line_to (2, 0)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 local render_zener = function (cr)
 	render (cr)
 
-	cr.move_to (1, 1)
-	cr.line_to (0.5, 1)
+	cr:move_to (1, 1)
+	cr:line_to (0.5, 1)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 local render_arrow = function (cr)
-	cr.move_to (0, 0)
-	cr.line_to (0, -1.5)
+	cr:move_to (0, 0)
+	cr:line_to (0, -1.5)
 
-	cr.stroke ()
+	cr:stroke ()
 
-	cr.move_to (-0.3, -0.7)
-	cr.line_to (0, -1.5)
-	cr.line_to (0.3, -0.7)
-	cr.close_path ()
+	cr:move_to (-0.3, -0.7)
+	cr:line_to (0, -1.5)
+	cr:line_to (0.3, -0.7)
+	cr:close_path ()
 
-	cr.fill ()
+	cr:fill ()
 end
 
 local render_radiation = function (cr)
-	cr.save ()
-	cr.translate (-0.4, 0)
+	cr:save ()
+	cr:translate (-0.4, 0)
 	render_arrow (cr)
-	cr.restore ()
+	cr:restore ()
 
-	cr.save ()
-	cr.translate (0.4, 0)
+	cr:save ()
+	cr:translate (0.4, 0)
 	render_arrow (cr)
-	cr.restore ()
+	cr:restore ()
 end
 
 local render_led = function (cr)
 	render (cr)
 
-	cr.save ()
-	cr.translate (-0.3, -1.0)
-	cr.rotate (math.atan2 (1, 1))
+	cr:save ()
+	cr:translate (-0.3, -1.0)
+	cr:rotate (math.atan2 (1, 1))
 
 	render_radiation (cr)
 
-	cr.restore ()
+	cr:restore ()
 end
 
 local render_photo = function (cr)
 	render (cr)
 
-	cr.save ()
-	cr.translate (0.75, -2.05)
-	cr.rotate (math.atan2 (-1, -1))
+	cr:save ()
+	cr:translate (0.75, -2.05)
+	cr:rotate (math.atan2 (-1, -1))
 
 	render_radiation (cr)
 
-	cr.restore ()
+	cr:restore ()
 end
 
 -- Register the symbol
diff --git a/share/library/Passive/inductor.lua b/share/library/Passive/inductor.lua
index b63a8f5..34a1cda 100644
--- a/share/library/Passive/inductor.lua
+++ b/share/library/Passive/inductor.lua
@@ -26,22 +26,22 @@ local terminals = {{-2, 0}, {2, 0}}
 -- Rendering
 local render = function (cr)
 	-- The arcs
-	cr.arc (-1.5, 0, 0.5, math.pi, 0)
-	cr.arc (-0.5, 0, 0.5, math.pi, 0)
-	cr.arc (0.5, 0, 0.5, math.pi, 0)
-	cr.arc (1.5, 0, 0.5, math.pi, 0)
+	cr:arc (-1.5, 0, 0.5, math.pi, 0)
+	cr:arc (-0.5, 0, 0.5, math.pi, 0)
+	cr:arc (0.5, 0, 0.5, math.pi, 0)
+	cr:arc (1.5, 0, 0.5, math.pi, 0)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 local render_core = function (cr)
 	render (cr)
 
 	-- The core
-	cr.move_to (-2, -1)
-	cr.line_to (2, -1)
+	cr:move_to (-2, -1)
+	cr:line_to (2, -1)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 -- Register the symbols
diff --git a/share/library/Passive/resistor.lua b/share/library/Passive/resistor.lua
index fdb1642..7c0b222 100644
--- a/share/library/Passive/resistor.lua
+++ b/share/library/Passive/resistor.lua
@@ -38,63 +38,63 @@ local terminals_pot = {{-2, 0}, {2, 0}, {2, -2}}
 -- Rendering
 local render = function (cr)
 	-- The rectangle
-	cr.move_to (-1.5, -0.5)
-	cr.line_to (1.5, -0.5)
-	cr.line_to (1.5, 0.5)
-	cr.line_to (-1.5, 0.5)
-	cr.line_to (-1.5, -0.5)
+	cr:move_to (-1.5, -0.5)
+	cr:line_to (1.5, -0.5)
+	cr:line_to (1.5, 0.5)
+	cr:line_to (-1.5, 0.5)
+	cr:line_to (-1.5, -0.5)
 
 	-- The terminals
-	cr.move_to (-2, 0)
-	cr.line_to (-1.5, 0)
+	cr:move_to (-2, 0)
+	cr:line_to (-1.5, 0)
 
-	cr.move_to (1.5, 0)
-	cr.line_to (2, 0)
+	cr:move_to (1.5, 0)
+	cr:line_to (2, 0)
 
-	cr.stroke ()
+	cr:stroke ()
 end
 
 local render_adj = function (cr)
 	render (cr)
 
 	-- The arrow
-	cr.move_to (-1, 1)
-	cr.line_to (1, -1)
+	cr:move_to (-1, 1)
+	cr:line_to (1, -1)
 
-	cr.stroke ()
+	cr:stroke ()
 
-	cr.save ()
-	cr.translate (1.5, -1.5)
-	cr.rotate (math.atan2 (1, 1))
+	cr:save ()
+	cr:translate (1.5, -1.5)
+	cr:rotate (math.atan2 (1, 1))
 
-	cr.move_to (0, 0)
-	cr.line_to (0.3, 0.8)
-	cr.line_to (-0.3, 0.8)
-	cr.close_path ()
+	cr:move_to (0, 0)
+	cr:line_to (0.3, 0.8)
+	cr:line_to (-0.3, 0.8)
+	cr:close_path ()
 
-	cr.fill ()
-	cr.restore ()
+	cr:fill ()
+	cr:restore ()
 end
 
 local render_pot = function (cr)
 	render (cr)
 
 	-- The contact
-	cr.move_to (0, -2)
-	cr.line_to (2, -2)
+	cr:move_to (0, -2)
+	cr:line_to (2, -2)
 
 	-- The arrow
-	cr.move_to (0, -2)
-	cr.line_to (0, -1)
+	cr:move_to (0, -2)
+	cr:line_to (0, -1)
 
-	cr.stroke ()
+	cr:stroke ()
 
-	cr.move_to (0, -0.5)
-	cr.line_to (0.3, -1.3)
-	cr.line_to (-0.3, -1.3)
-	cr.close_path ()
+	cr:move_to (0, -0.5)
+	cr:line_to (0.3, -1.3)
+	cr:line_to (-0.3, -1.3)
+	cr:close_path ()
 
-	cr.fill ()
+	cr:fill ()
 end
 
 -- Register the symbol
-- 
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