Authors CurseForge

I was wondering about this too a few days ago so I took a look at Grid and SecureTemplates.lua. To create and configure a header in Lua only you'd do:

local header = CreateFrame("Frame","Header",UIParent,"SecureGroupHeaderTemplate")

Then you set the attributes, which are all documented in SecureTemplates.lua

showRaid = [BOOLEAN] -- true if the header should be shown while in a raid
showParty = [BOOLEAN] -- true if the header should be shown while in a party and not in a raid
showPlayer = [BOOLEAN] -- true if the header should show the player when not in a raid
showSolo = [BOOLEAN] -- true if the header should be shown while not in a group (implies showPlayer)
nameList = [STRING] -- a comma separated list of player names (not used if 'groupFilter' is set)
groupFilter = [1-8, STRING] -- a comma seperated list of raid group numbers and/or uppercase class names and/or uppercase roles
strictFiltering = [BOOLEAN] - if true, then characters must match both a group and a class from the groupFilter list
point = [STRING] -- a valid XML anchoring point (Default: "TOP")
xOffset = [NUMBER] -- the x-Offset to use when anchoring the unit buttons (Default: 0)
yOffset = [NUMBER] -- the y-Offset to use when anchoring the unit buttons (Default: 0)
sortMethod = ["INDEX", "NAME"] -- defines how the group is sorted (Default: "INDEX")
sortDir = ["ASC", "DESC"] -- defines the sort order (Default: "ASC")
template = [STRING] -- the XML template to use for the unit buttons
templateType = [STRING] - specifies the frame type of the managed subframes (Default: "Button")
groupBy = [nil, "GROUP", "CLASS", "ROLE"] - specifies a "grouping" type to apply before regular sorting (Default: nil)
groupingOrder = [STRING] - specifies the order of the groupings (ie. "1,2,3,4,5,6,7,8")
maxColumns = [NUMBER] - maximum number of columns the header will create (Default: 1)
unitsPerColumn = [NUMBER or nil] - maximum units that will be displayed in a singe column, nil is infinate (Default: nil)
startingIndex = [NUMBER] - the index in the final sorted unit list at which to start displaying units (Default: 1)
columnSpacing = [NUMBER] - the ammount of space between the rows/columns (Default: 0)
columnAnchorPoint = [STRING] - the anchor point of each new column (ie. use LEFT for the columns to grow to the right)

Now you have to specify how the children are configured. You add a 'initialConfigFunction' field to the header

header:SetAttribute("template","SecureUnitButtonTemplate")
local initialConfigFunction(child)
...
-- manipulate child here
...
end
header.initialConfigFunction = initialConfigFunction

Also, you'll have to register all the events you want (health, power..etc.) for each child in the function. You get the unitd by calling child:GetAttribute("unit").

The rest (set pointing, creation, ..etc.) is automatically done by SecureTemplates.lua. I'd recommend looking at GridFrame.lua and GridLayout.lua.