Fix bug in input.lua, make 0.9-ready, add utf8 editing

1) [input.lua] Pressing backspace while the cursor was at the beggining
   of the text removed the first character. Fixed thanks to riidom.
2) [LÖVE 0.9] Use setLine(Width|Style) instead of setLine. Split
   keyboard.pressed() into keyboard.pressed() and keyboard.textinput().
   (see readme)
3) [utf8.lua] Add support for UTF-8 text editing. May still fail
   spectacurlarly with invalid UTF-8 strings.

6 files changed, 116 insertions, 21 deletions

diff --git a/README.md b/README.md
index bb76e4c..734202c 100644
--- a/README.md
+++ b/README.md
@@ -135,7 +135,16 @@ Quickie is an [immediate mode gui][IMGUI] library for [LÖVE][LOVE]. Initial
 	end
 
 	function love.keypressed(key, code)
-		gui.keyboard.pressed(key, code)
+		gui.keyboard.pressed(key)
+		-- LÖVE 0.8: see if this code can be converted in a character
+		if pcall(string.char, code) code > 0 then
+			gui.keyboard.textinput(string.char(code))
+		end
+	end
+
+	-- LÖVE 0.9
+	function love.textinput(str)
+		gui.keyboard.textinput(str)
 	end
 
 # Documentation
diff --git a/core.lua b/core.lua
index cbccbae..42b1ae1 100644
--- a/core.lua
+++ b/core.lua
@@ -99,7 +99,8 @@ local function draw()
 	for i = 1,draw_items.n do draw_items[i]() end
 
 	-- restore graphics state
-	love.graphics.setLine(lw, ls)
+	love.graphics.setLineWidth(lw)
+	love.graphics.setLineStyle(ls)
 	if f then love.graphics.setFont(f) end
 	love.graphics.setColor(c)
 
diff --git a/input.lua b/input.lua
index ad0683f..b161993 100644
--- a/input.lua
+++ b/input.lua
@@ -29,6 +29,7 @@ local core     = require(BASE .. 'core')
 local group    = require(BASE .. 'group')
 local mouse    = require(BASE .. 'mouse')
 local keyboard = require(BASE .. 'keyboard')
+local utf8     = require(BASE .. 'utf8')
 
 -- {info = {text = "", cursor = text:len()}, pos = {x, y}, size={w, h}, widgetHit=widgetHit, draw=draw}
 return function(w)
@@ -45,11 +46,13 @@ return function(w)
 	if not keyboard.hasFocus(id) then
 		--[[nothing]]
 	-- editing
-	elseif keyboard.key == 'backspace' then
-		w.info.text = w.info.text:sub(1,w.info.cursor-1) .. w.info.text:sub(w.info.cursor+1)
+	elseif keyboard.key == 'backspace' and w.info.cursor > 0 then
 		w.info.cursor = math.max(0, w.info.cursor-1)
+		local left, right = utf8.split(w.info.text, w.info.cursor)
+		w.info.text = left .. utf8.sub(right, 2)
 	elseif keyboard.key == 'delete' then
-		w.info.text = w.info.text:sub(1,w.info.cursor) .. w.info.text:sub(w.info.cursor+2)
+		local left, right = utf8.split(w.info.text, w.info.cursor)
+		w.info.text = left .. utf8.sub(right, 2)
 		w.info.cursor = math.min(w.info.text:len(), w.info.cursor)
 	-- movement
 	elseif keyboard.key == 'left' then
@@ -64,10 +67,9 @@ return function(w)
 	elseif keyboard.key == 'return' then
 		keyboard.clearFocus()
 		keyboard.pressed('', -1)
-	elseif keyboard.code >= 32 and keyboard.code < 127 then
-		local left = w.info.text:sub(1,w.info.cursor)
-		local right =  w.info.text:sub(w.info.cursor+1)
-		w.info.text = table.concat{left, string.char(keyboard.code), right}
+	elseif keyboard.str then
+		local left, right = utf8.split(w.info.text, w.info.cursor)
+		w.info.text = left .. keyboard.str .. right
 		w.info.cursor = w.info.cursor + 1
 	end
 
diff --git a/keyboard.lua b/keyboard.lua
index 4850df3..0e52eb3 100644
--- a/keyboard.lua
+++ b/keyboard.lua
@@ -24,7 +24,7 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 ]]--
 
-local key,code = nil, -1
+local key,str = nil, nil
 local focus, lastwidget
 local NO_WIDGET = {}
 
@@ -34,11 +34,16 @@ local cycle = {
 	next = {key = 'tab'},
 }
 
-local function pressed(...)
-	key, code = ...
-	assert(type(key) == 'string', 'Invalid argument `key`. Expected string, got ' .. type(key))
-	assert(type(code) == 'number', 'Invalid argument `code`. Expected number, got ' .. type(code))
+local function pressed(k)
+	assert(type(k) == 'string', 'Invalid argument `key`. Expected string, got ' .. type(k))
+	key = k
 end
+
+local function textinput(s)
+	assert(type(s) == 'string', 'Invalid argument `key`. Expected string, got ' .. type(s))
+	str = s
+end
+
 local function setFocus(id) focus = id end
 local function disable()    focus = NO_WIDGET end
 local function clearFocus() focus = nil end
@@ -79,12 +84,13 @@ local function beginFrame()
 end
 
 local function endFrame()
-	key, code = nil, -1
+	key, str = nil, nil
 end
 
 return setmetatable({
 	cycle         = cycle,
 	pressed       = pressed,
+	textinput     = textinput,
 	tryGrab       = tryGrab,
 	isBindingDown = isBindingDown,
 	setFocus      = setFocus,
@@ -99,4 +105,4 @@ return setmetatable({
 
 	beginFrame   = beginFrame,
 	endFrame     = endFrame,
-}, {__index = function(_,k) return ({key = key, code = code})[k] end})
+}, {__index = function(_,k) return ({key = key, str = str})[k] end})
diff --git a/style-default.lua b/style-default.lua
index e970d7a..71f412a 100644
--- a/style-default.lua
+++ b/style-default.lua
@@ -24,6 +24,9 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 ]]--
 
+local BASE = (...):match("(.-)[^%.]+$")
+local utf8 = require(BASE .. 'utf8')
+
 -- default style
 local color = {
 	normal = {bg = {78,78,78}, fg = {200,200,200}, border={20,20,20}},
@@ -43,7 +46,8 @@ end
 gradient:set(200,255)
 
 local function box(x,y,w,h, bg, border, flip)
-	love.graphics.setLine(1, 'rough')
+	love.graphics.setLineWidth(1)
+	love.graphics.setLineStyle('rough')
 
 	love.graphics.setColor(bg)
 	local sy = flip and -h/2 or h/2
@@ -82,7 +86,8 @@ end
 local function Slider(state, fraction, vertical, x,y,w,h)
 	local c = color[state]
 	
-	love.graphics.setLine(1, 'rough')
+	love.graphics.setLineWidth(1)
+	love.graphics.setLineStyle('rough')
 	love.graphics.setColor(c.bg)
 	if vertical then
 		love.graphics.rectangle('fill', x+w/2-2,y,4,h)
@@ -105,7 +110,8 @@ local function Slider2D(state, fraction, x,y,w,h)
 	box(x,y,w,h, c.bg, c.border)
 
 	-- draw quadrants
-	love.graphics.setLine(1, 'rough')
+	love.graphics.setLineWidth(1)
+	love.graphics.setLineStyle('rough')
 	love.graphics.setColor(c.fg[1], c.fg[2], c.fg[3], math.min(127,c.fg[4] or 255))
 	love.graphics.line(x+w/2,y, x+w/2,y+h)
 	love.graphics.line(x,y+h/2, x+w,y+h/2)
@@ -124,7 +130,7 @@ local function Input(state, text, cursor, x,y,w,h)
 
 	local f = love.graphics.getFont()
 	local th = f:getHeight(text)
-	local cursorPos = x + 2 + f:getWidth(text:sub(1,cursor))
+	local cursorPos = x + 2 + f:getWidth(utf8.sub(text, 1,cursor))
 	local offset = 2 - math.floor((cursorPos-x) / (w-4)) * (w-4)
 
 	local tsx,tsy,tsw,tsh = x+1, y, w-2, h
@@ -139,7 +145,8 @@ local function Input(state, text, cursor, x,y,w,h)
 	end
 
 	love.graphics.setScissor(tsx, tsy, tsw, tsh)
-	love.graphics.setLine(1, 'rough')
+	love.graphics.setLineWidth(1)
+	love.graphics.setLineStyle('rough')
 	love.graphics.setColor(color.normal.fg)
 	love.graphics.print(text, x+offset,y+(h-th)/2)
 	if state ~= 'normal' then
diff --git a/utf8.lua b/utf8.lua
new file mode 100644
index 0000000..f661b1b
--- /dev/null
+++ b/utf8.lua
@@ -0,0 +1,70 @@
+local function iter(s, i)
+	if i >= #s then return end
+	local b, nbytes = s:byte(i+1,i+1), 1
+
+	-- determine width of the codepoint by counting the number of set bits in the first byte
+	-- warning: there is no validation of the following bytes!
+	if     b >= 0xc0 and b <= 0xdf then nbytes = 2 -- 1100 0000 to 1101 1111
+	elseif b >= 0xe0 and b <= 0xef then nbytes = 3 -- 1110 0000 to 1110 1111
+	elseif b >= 0xf0 and b <= 0xf7 then nbytes = 4 -- 1111 0000 to 1111 0111
+	elseif b >= 0xf8 and b <= 0xfb then nbytes = 5 -- 1111 1000 to 1111 1011
+	elseif b >= 0xfc and b <= 0xfd then nbytes = 6 -- 1111 1100 to 1111 1101
+	elseif b <  0x00 or  b >  0x7f then error(("Invalid codepoint: 0x%02x"):format(b))
+	end
+	return i+nbytes, s:sub(i+1,i+nbytes), nbytes
+end
+
+local function chars(s)
+	return iter, s, 0
+end
+
+local function len(s)
+	-- assumes sane utf8 string: count the number of bytes that is *not* 10xxxxxx
+	local _, c = s:gsub('[^\128-\191]', '')
+	return c
+end
+
+local function sub(s, i, j)
+	local l = len(s)
+	j = j or l
+	if i < 0 then i = l + i + 1 end
+	if j < 0 then j = l + j + 1 end
+	if j < i then return '' end
+
+	local k, t = 1, {}
+	for _, c in chars(s) do
+		if k >= i then t[#t+1] = c end
+		if k >= j then break end
+		k = k + 1
+	end
+	return table.concat(t)
+end
+
+local function split(s, i)
+	local l = len(s)
+	if i < 0 then i = l + i + 1 end
+
+	local k, pos = 1, 0
+	for byte in chars(s) do
+		if k > i then break end
+		pos, k = byte, k + 1
+	end
+	return s:sub(1, pos), s:sub(pos+1, -1)
+end
+
+local function reverse(s)
+	local t = {}
+	for _, c in chars(s) do
+		table.insert(t, 1, c)
+	end
+	return table.concat(t)
+end
+
+return {
+	iter    = iter,
+	chars   = chars,
+	len     = len,
+	sub     = sub,
+	split   = split,
+	reverse = reverse,
+}