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.

README.md

@@ -55,3 +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
 })
 
@@ -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)
 
@@ -675,41 +663,6 @@ 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")
@@ -722,7 +675,7 @@ function signs_lib.can_modify(pos, player)
 
 	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