1 files changed, 143 insertions, 0 deletions
diff --git a/group.lua b/group.lua
new file mode 100644
index 0000000..50e413e
--- /dev/null
+++ b/group.lua
@@ -0,0 +1,143 @@
+--[[
+Copyright (c) 2012 Matthias Richter
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+Except as contained in this notice, the name(s) of the above copyright holders
+shall not be used in advertising or otherwise to promote the sale, use or
+other dealings in this Software without prior written authorization.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+]]--
+
+local stack = {n = 0}
+local default = {
+	pos = {0,0},
+	grow = {0,0},
+	spacing = 2,
+	size = {100, 30},
+	upper_left  = {0,0},
+	lower_right = {0,0},
+}
+local current = default
+
+local Grow = {
+	none  = { 0,  0},
+	up    = { 0, -1},
+	down  = { 0,  1},
+	left  = {-1,  0},
+	right = { 1,  0}
+}
+
+-- {grow = grow, spacing = spacing, size = size, pos = pos}
+local function push(info)
+	local grow    = info.grow    or "none"
+	local spacing = info.spacing or default.spacing
+
+	local size = {
+		info.size and info.size[1] or current.size[1],
+		info.size and info.size[2] or current.size[2]
+	}
+
+	local pos = {current.pos[1], current.pos[2]}
+	if info.pos then
+		pos[1] = pos[1] + (info.pos[1] or 0)
+		pos[2] = pos[2] + (info.pos[2] or 0)
+	end
+
+	assert(size, "Size neither specified nor derivable from parent group.")
+	assert(pos, "Position neither specified nor derivable from parent group.")
+	grow = assert(Grow[grow], "Invalid grow: " .. tostring(grow))
+
+	current = {
+		pos         = pos,
+		grow        = grow,
+		size        = size,
+		spacing     = spacing,
+		upper_left  = { math.huge,  math.huge},
+		lower_right = {-math.huge, -math.huge},
+	}
+	stack.n = stack.n + 1
+	stack[stack.n] = current
+end
+
+local function advance(pos, size)
+	current.upper_left[1]  = math.min(current.upper_left[1], pos[1])
+	current.upper_left[2]  = math.min(current.upper_left[2], pos[2])
+	current.lower_right[1] = math.max(current.lower_right[1], pos[1] + size[1])
+	current.lower_right[2] = math.max(current.lower_right[2], pos[2] + size[2])
+
+	if current.grow[1] ~= 0 then
+		current.pos[1] = pos[1] + current.grow[1] * (size[1] + current.spacing)
+	end
+	if current.grow[2] ~= 0 then
+		current.pos[2] = pos[2] + current.grow[2] * (size[2] + current.spacing)
+	end
+	return pos, size
+end
+
+local function getRect(pos, size)
+	pos  = {pos  and pos[1]  or 0,               pos  and pos[2]  or 0}
+	size = {size and size[1] or current.size[1], size and size[2] or current.size[2]}
+
+	-- growing left/up: update current position to account for differnt size
+	if current.grow[1] < 0 and current.size[1] ~= size[1] then
+		current.pos[1] = current.pos[1] + (current.size[1] - size[1])
+	end
+	if current.grow[2] < 0 and current.size[2] ~= size[2] then
+		current.pos[2] = current.pos[2] - (current.size[2] - size[2])
+	end
+
+	pos[1] = pos[1] + current.pos[1]
+	pos[2] = pos[2] + current.pos[2]
+
+	return advance(pos, size)
+end
+
+local function pop()
+	assert(stack.n > 0, "Group stack is empty.")
+	stack.n = stack.n - 1
+	local child = current
+	current = stack[stack.n] or default
+
+	local size = {
+		child.lower_right[1] - math.max(child.upper_left[1], current.pos[1]),
+		child.lower_right[2] - math.max(child.upper_left[2], current.pos[2])
+	}
+	advance(current.pos, size)
+end
+
+local function beginFrame()
+	current = default
+	stack.n = 0
+end
+
+local function endFrame()
+	-- future use?
+end
+
+return setmetatable({
+	push       = push,
+	pop        = pop,
+	getRect    = getRect,
+	advance    = advance,
+	beginFrame = beginFrame,
+	endFrame   = endFrame,
+	default    = default,
+}, {__index = function(_,k) 
+	return ({size = current.size, pos = current.pos})[k]
+end})