Feature/progress (#17)

* improve example gui. Add simple pages

* return old progress bar with example

* base progress with steps, there is bug with step? 1 ~= 1, small delta?

* polish progress, check float error case

* add callback on end of "to" function, value check

* start of green/red in progress

* add first version of rich progress bar

* make green bar darker

* rich bar fixes

* add delay, before filling in rich progress

* PR fixes

* remove dublicate of 'progress_rich'

druid/helper.lua

@@ -0,0 +1,71 @@
+local M = {}
+
+function M.centrate_text_with_icon(text_node, icon_node, offset_x)
+	offset_x = offset_x or 0
+	local metr = gui.get_text_metrics_from_node(text_node)
+	local scl = gui.get_scale(text_node).x
+	local pos = gui.get_position(text_node)
+	local scl_i = gui.get_scale(icon_node).x
+	local pos_i = gui.get_position(icon_node)
+	local w = metr.width * scl -- text width
+	local icon_w = gui.get_size(icon_node).x * scl_i -- icon width
+	local width = w + icon_w
+
+	pos.x = -width/2 + w + offset_x
+	gui.set_position(text_node, pos)
+	pos_i.x = width/2 - icon_w + offset_x
+	gui.set_position(icon_node, pos_i)
+end
+
+
+local STRING = "string"
+function M.get_node(node_or_name)
+	if type(node_or_name) == STRING then
+		return gui.get_node(node_or_name)
+	end
+	return node_or_name
+end
+
+
+function M.step(current, target, step)
+	if current < target then
+		return math.min(current + step, target)
+	else
+		return math.max(target, current - step)
+	end
+end
+
+
+function M.clamp(a, min, max)
+	if min > max then
+		min, max = max, min
+	end
+
+	if a >= min and a <= max then
+		return a
+	elseif a < min then
+		return min
+	else
+		return max
+	end
+end
+
+
+function M.round(num, numDecimalPlaces)
+	local mult = 10^(numDecimalPlaces or 0)
+	return math.floor(num * mult + 0.5) / mult
+end
+
+
+function M.is_enabled(node)
+	local is_enabled = gui.is_enabled(node)
+	local parent = gui.get_parent(node)
+	while parent and is_enabled do
+		is_enabled = is_enabled and gui.is_enabled(parent)
+		parent = gui.get_parent(parent)
+	end
+	return is_enabled
+end
+
+
+return M