writing [ or ] into a sign breaks the form for some users

the exact effect varies with client behavior and the particular text contents.
(characters erased, disappering formspec elements, loss of text)

.gitignore

@@ -1,7 +0,0 @@
-# temporary files
-*~
-
-# eclipse project files
-.project
-.settings
-.buildpath

API.md

@@ -78,17 +78,11 @@ In this text, common terms such as `pos`, `node`, or `placer`/`digger` will not
 
     Default: `signs_lib.after_place_node`
 
-  * `on_rightclick = function(pos)`
+  * `on_rightclick = function(pos, node, player, itemstack, pointed_thing)`
 
     See below under "Main functions".
 
-    Default: `signs_lib.construct_sign`
-
-  * `on_construct = function(pos)`
-
-    See below under "Main functions".
-
-    Default: `signs_lib.construct_sign`
+    Default: `signs_lib.rightclick_sign`
 
   * `on_destruct = function(pos)`
 
@@ -96,12 +90,6 @@ In this text, common terms such as `pos`, `node`, or `placer`/`digger` will not
 
     Default: `signs_lib.destruct_sign`
 
-  * `on_receive_fields = function(pos, formname, fields, sender)`
-
-    See below under "Main functions".
-
-    Default: `signs_lib.receive_fields`
-
   * `on_punch = function(pos)`
 
     See below under "Main functions".
@@ -258,18 +246,14 @@ signs_lib.register_sign("basic_signs:sign_wall_glass", {
 
   * `locked`: if set to **true**, the sign's meta will be tweaked to indicate its ownership by the `placer`.
 
-* `signs_lib.construct_sign(pos)`
+* `signs_lib.rightclick_sign(pos, node, player, itemstack, pointed_thing)`
 
-  Sets up the sign's formspec and infotext overlay.
+  Open the default sign formspec, if the player has the `signslib_edit` privilege.
 
 * `signs_lib.destruct_sign(pos)`
 
   Deletes the sign's entity, if any, when the sign is dug.
 
-* `signs_lib.receive_fields(pos, formname, fields, sender)`
-
-  This handles the text input and wide font on/off switch, logging any actions the user takes.  Bails-out silently if the user is not allowed to edit the sign.  See the standard Minetest lua_api.txt for details.
-
 * `signs_lib.update_sign(pos, fields)`
 
   If the sign's writable, this deletes any sign-related entities in the sign's node space, spawns a new one, and renders whatever text is in the sign's meta.
@@ -352,7 +336,7 @@ Supplying one or both of the following in the pole/post node's definition will c
     If supplied, this function will be run when the mod is looking for a normal vertical pole/post.  Useful if the target node's orientation and/or shape determine what sides a sign can attach to.  For example, [Pipeworks](https://forum.minetest.net/viewtopic.php?pid=27794) uses this to figure out if a sign can be attached to a tube or pipe, depending on the tube's/pipe's number of junctions, and on its orientation and that of the placed sign.
 
     * `def`: the placed sign's node defintion
-    * `pole_pos`: the target node's position 
+    * `pole_pos`: the target node's position
     * `pole_node`: the target node itself
     * `pole_def`: its node definition
 

README.md

@@ -24,19 +24,17 @@ That said, there are some basic text formatting options:
 
 * A color may be specified in the sign text by using "#" followed by a single hexadcimal digit (0-9 or a-f).  These colors come from the standard Linux/IRC/CGA color set, and are shown in the sign's formspec.  Any color change will remain in effect until changed again, or until the next line break.  Any number of color changes in any arbitrary arrangement is allowed.
 
+* Most writable signs can display double-wide text by flipping a switch in the sign's formspec.
+
 ## Sign placement and rotation notes
 
 * Pointing at a wall while placing will, of course, place the sign on the wall.
 
-* For most signs, pointing at the ground while placing puts the sign flat on the ground.
+* For most signs that use the standard sign model, pointing at the ground while placing creates an upright standalone yard sign.  Others not using the standard model will most often end up flat on the ground.
 
-  Exception: if you have [basic_signs](https://forum.minetest.net/viewtopic.php?f=11&t=23289) installed, placing a default wooden sign on the ground will instead create a "yard" sign (basically a regular wooden sign mounted upright on a small stick).
+* For most standard signs, pointing at the ceiling while placing will hang the sign from the ceiling by a pair of chains.  Others not using the standard model will usually end up flat on the ceiling.
 
-* For most signs, pointing at the ceiling while placing will put the sign flat against the ceiling.
-
-  Exception: default wood and steel signs will instead be hung from the ceiling by a pair of chains.  If you have [basic_signs](https://forum.minetest.net/viewtopic.php?f=11&t=23289), all standard signs created by it will do the same.
-
-* Pointing at an X or Z side of something that's detected as a pole/post will mount the sign onto that pole.  Note that the sign actually occupies the node space in front of the pole, since they're still separate nodes.  But, I figure, no one's going to want to use the space in front of the sign anyway, because doing so would of course obscure the sign, so it doesn't matter if the sign logically occupies that node space.
+* Pointing at an X or Z side of something that's detected as a pole/post will mount the sign onto that pole, if possible.  Note that the sign actually occupies the node space in front of the pole, since they're still separate nodes.  But, I figure, no one's going to want to use the space in front of the sign anyway, because doing so would of course obscure the sign, so it doesn't matter if the sign logically occupies that node space.
 
 * If you're holding the "Sneak" key (usually `Shift`) while placing, the on-pole/hanging/yard checks are skipped, allowing you to just place a sign flat onto the ground, ceiling, or top/bottom of a pole/post, like they used to work before `signs_lib` was a thing.
 
@@ -57,3 +55,9 @@ At present, only one command is defined:
 This will read through the list of currently-loaded blocks known to contain one or more signs, delete all entities found in each sign's node space, and respawn and re-render each from scratch.
 
 The list of loaded, sign-bearing blocks is created/populated by an LBM (and trimmed by this command if any listed blocks are found to have been unloaded).
+
+## Privileges
+
+* `signslib_edit`
+
+Allows to rotate signs and to open (and consequently edit) any default sign formspec.

api.lua

@@ -2,6 +2,8 @@
 
 local S = signs_lib.gettext
 
+local function get_sign_formspec() end
+
 signs_lib.lbm_restore_nodes = {}
 signs_lib.old_fenceposts = {}
 signs_lib.old_fenceposts_replacement_signs = {}
@@ -159,9 +161,9 @@ local ctexcache = {}
 minetest.register_entity("signs_lib:text", {
 	collisionbox = { 0, 0, 0, 0, 0, 0 },
 	visual = "mesh",
-	mesh = "signs_lib_standard_wall_sign_entity.obj",
+	mesh = "signs_lib_standard_sign_entity_wall.obj",
 	textures = {},
-	static_save = false,
+	static_save = true,
 	backface_culling = false
 })
 
@@ -345,10 +347,10 @@ local function file_exists(name, return_handle, mode)
 		if (return_handle) then
 			return f
 		end
-		io.close(f) 
-		return true 
-	else 
-		return false 
+		io.close(f)
+		return true
+	else
+		return false
 	end
 end
 
@@ -552,7 +554,7 @@ local function make_line_texture(line, lineno, pos, line_width, line_height, cwi
 			table.insert(texture, (":%d,%d=%s"):format(xpos + ch.off, ypos, ch.tex))
 		end
 		table.insert(
-			texture, 
+			texture,
 			(":%d,%d="):format(xpos + word.w, ypos) .. char_tex(font_name, " ")
 		)
 		xpos = xpos + word.w + cwidth_tab[" "]
@@ -619,31 +621,12 @@ function signs_lib.split_lines_and_words(text)
 	return lines
 end
 
-function signs_lib.construct_sign(pos)
-	local form = "size[6,4]"..
-		"textarea[0,-0.3;6.5,3;text;;${text}]"..
-		"background[-0.5,-0.5;7,5;signs_lib_sign_bg.jpg]"
-	local node = minetest.get_node(pos)
-	local def = minetest.registered_items[node.name]
-	local meta = minetest.get_meta(pos)
+function signs_lib.rightclick_sign(pos, node, player, itemstack, pointed_thing)
 
-	if def.allow_widefont then
-		local state = "off"
-		if meta:get_int("widefont") == 1 then state = "on" end
-		form = form.."label[1,3.4;Use wide font]"..
-			"image_button[1.1,3.7;1,0.6;signs_lib_switch_"..
-			state..".png;"..
-			state..";;;false;signs_lib_switch_interm.png]"..
-			"button_exit[3,3.4;2,1;ok;"..S("Write").."]"
-	else
-		form = form.."button_exit[2,3.4;2,1;ok;"..S("Write").."]"
-	end
+	if not signs_lib.can_modify(pos, player) then return end
 
-	meta:set_string("formspec", form)
-	local i = meta:get_string("infotext")
-	if i == "" then -- it wasn't even set, so set it.
-		meta:set_string("infotext", "")
-	end
+	player:get_meta():set_string("signslib:pos", minetest.pos_to_string(pos))
+	minetest.show_formspec(player:get_player_name(), "signs_lib:sign", get_sign_formspec(pos, node.name))
 end
 
 function signs_lib.destruct_sign(pos)
@@ -663,6 +646,11 @@ end
 function signs_lib.update_sign(pos, fields)
 	local meta = minetest.get_meta(pos)
 
+	-- legacy udpate
+	if meta:get_string("formspec") ~= "" then
+		meta:set_string("formspec", "")
+	end
+
 	local text = fields and fields.text or meta:get_string("text")
 	text = trim_input(text)
 
@@ -675,54 +663,19 @@ function signs_lib.update_sign(pos, fields)
 	signs_lib.set_obj_text(pos, text)
 end
 
-function signs_lib.receive_fields(pos, formname, fields, sender)
-
-	if not fields or not signs_lib.can_modify(pos, sender) then return end
-
-	if fields.text and fields.ok then
-		minetest.log("action", S("@1 wrote \"@2\" to sign at @3",
-			(sender:get_player_name() or ""),
-			fields.text:gsub('\\', '\\\\'):gsub("\n", "\\n"),
-			minetest.pos_to_string(pos)
-		))
-		signs_lib.update_sign(pos, fields)
-	elseif fields.on or fields.off then
-		local node = minetest.get_node(pos)
-		local meta = minetest.get_meta(pos)
-		local change
-
-		if fields.on and meta:get_int("widefont") == 1 then
-			meta:set_int("widefont", 0)
-			change = true
-		elseif fields.off and meta:get_int("widefont") == 0 then
-			meta:set_int("widefont", 1)
-			change = true
-		end
-		if change then
-			minetest.log("action", S("@1 flipped the wide-font switch to \"@2\" at @3",
-				(sender:get_player_name() or ""),
-				(fields.on and "off" or "on"),
-				minetest.pos_to_string(pos)
-			))
-			signs_lib.construct_sign(pos)
-			signs_lib.update_sign(pos, fields)
-		end
-	end
-end
-
 function signs_lib.can_modify(pos, player)
 	local meta = minetest.get_meta(pos)
 	local owner = meta:get_string("owner")
 	local playername = player:get_player_name()
 
-	if minetest.is_protected(pos, playername) then 
+	if minetest.is_protected(pos, playername) then
 		minetest.record_protection_violation(pos, playername)
 		return false
 	end
 
 	if owner == ""
 	  or playername == owner
-	  or (minetest.check_player_privs(playername, {sign_editor=true}))
+	  or (minetest.check_player_privs(playername, {signslib_edit=true}))
 	  or (playername == minetest.settings:get("name")) then
 		return true
 	end
@@ -887,10 +840,8 @@ function signs_lib.register_sign(name, raw_def)
 	def.after_place_node = raw_def.after_place_node or signs_lib.after_place_node
 
 	if raw_def.entity_info then
-		def.on_rightclick       = raw_def.on_rightclick       or signs_lib.construct_sign
-		def.on_construct        = raw_def.on_construct        or signs_lib.construct_sign
+		def.on_rightclick       = raw_def.on_rightclick       or signs_lib.rightclick_sign
 		def.on_destruct         = raw_def.on_destruct         or signs_lib.destruct_sign
-		def.on_receive_fields   = raw_def.on_receive_fields   or signs_lib.receive_fields
 		def.on_punch            = raw_def.on_punch            or signs_lib.update_sign
 		def.number_of_lines     = raw_def.number_of_lines     or signs_lib.standard_lines
 		def.horiz_scaling       = raw_def.horiz_scaling       or signs_lib.standard_hscale
@@ -1184,3 +1135,75 @@ minetest.register_chatcommand("regen_signs", {
 		minetest.chat_send_player(player_name, "Finished.")
 	end
 })
+
+minetest.register_privilege("signslib_edit", {})
+
+
+
+--
+-- local functions
+--
+
+function get_sign_formspec(pos, nodename)
+
+	local meta = minetest.get_meta(pos)
+	local txt = meta:get_string("text")
+
+	local formspec = {
+		"size[6,4]",
+		"textarea[0,-0.3;6.5,3;text;;" .. minetest.formspec_escape(txt) .. "]",
+		"background[-0.5,-0.5;7,5;signs_lib_sign_bg.jpg]",
+		"button_exit[2,3.4;2,1;ok;" .. S("Write") .. "]"
+	}
+
+	if minetest.registered_nodes[nodename].allow_widefont then
+		local state = "off"
+		if meta:get_int("widefont") == 1 then state = "on" end
+		formspec[5] = "label[0.5,3.4;Use wide font]"
+		formspec[6] = "image_button[0.6,3.7;1,0.6;signs_lib_switch_" .. state .. ".png;"
+				.. state .. ";;;false;signs_lib_switch_interm.png]"
+	end
+
+	return table.concat(formspec, "")
+end
+
+
+minetest.register_on_player_receive_fields(function(player, formname, fields)
+
+	if formname ~= "signs_lib:sign" then return end
+
+	local pos_string = player:get_meta():get_string("signslib:pos")
+	local pos = minetest.string_to_pos(pos_string)
+	local playername = player:get_player_name()
+
+	if fields.text and fields.ok then
+		minetest.log("action", S("@1 wrote \"@2\" to sign at @3",
+			(playername or ""),
+			fields.text:gsub('\\', '\\\\'):gsub("\n", "\\n"),
+			pos_string
+		))
+		signs_lib.update_sign(pos, fields)
+	elseif fields.on or fields.off then
+		local node = minetest.get_node(pos)
+		local meta = minetest.get_meta(pos)
+		local change
+
+		if fields.on and meta:get_int("widefont") == 1 then
+			meta:set_int("widefont", 0)
+			change = true
+		elseif fields.off and meta:get_int("widefont") == 0 then
+			meta:set_int("widefont", 1)
+			change = true
+		end
+
+		if change then
+			minetest.log("action", S("@1 flipped the wide-font switch to \"@2\" at @3",
+				(playername or ""),
+				(fields.on and "off" or "on"),
+				minetest.pos_to_string(pos)
+			))
+			signs_lib.update_sign(pos, fields)
+			minetest.show_formspec(playername, "signs_lib:sign", get_sign_formspec(pos, node.name))
+		end
+	end
+end)

depends.txt

@@ -4,3 +4,4 @@ screwdriver?
 streetspoles?
 streetlamps?
 cottages?
+prefab_redo?

mod.conf

@@ -1 +1,2 @@
 name = signs_lib
+min_minetest_version = 5.2.0

standard_signs.lua

@@ -38,16 +38,21 @@ signs_lib.register_sign("default:sign_wall_steel", {
 	allow_yard = true
 })
 
+minetest.register_alias("signs:sign_hanging",                   "default:sign_wood_hanging")
+minetest.register_alias("basic_signs:hanging_sign",             "default:sign_wood_hanging")
+minetest.register_alias("signs:sign_yard",                      "default:sign_wood_yard")
+minetest.register_alias("basic_signs:yard_sign",                "default:sign_wood_yard")
 
-minetest.register_alias("default:sign_wall_wood_onpole",  "default:sign_wood_onpole")
+minetest.register_alias("default:sign_wall_wood_onpole",        "default:sign_wood_onpole")
+minetest.register_alias("default:sign_wall_wood_onpole_horiz",  "default:sign_wood_onpole_horiz")
+minetest.register_alias("default:sign_wall_wood_hanging",       "default:sign_wood_hanging")
+minetest.register_alias("default:sign_wall_wood_yard",          "default:sign_wood_yard")
 
-minetest.register_alias("default:sign_wall_wood_hanging", "default:sign_wood_hanging")
-minetest.register_alias("signs:sign_hanging",             "default:sign_wood_hanging")
-minetest.register_alias("basic_signs:hanging_sign",       "default:sign_wood_hanging")
+minetest.register_alias("default:sign_wall_steel_onpole",       "default:sign_steel_onpole")
+minetest.register_alias("default:sign_wall_steel_onpole_horiz", "default:sign_steel_onpole_horiz")
+minetest.register_alias("default:sign_wall_steel_hanging",      "default:sign_steel_hanging")
+minetest.register_alias("default:sign_wall_steel_yard",         "default:sign_steel_yard")
 
-minetest.register_alias("default:sign_wall_wood_yard",    "default:sign_wood_yard")
-minetest.register_alias("signs:sign_yard",                "default:sign_wood_yard")
-minetest.register_alias("basic_signs:yard_sign",          "default:sign_wood_yard")
 
 table.insert(signs_lib.lbm_restore_nodes, "signs:sign_hanging")
 table.insert(signs_lib.lbm_restore_nodes, "basic_signs:hanging_sign")