access typst brand yaml logo in templates/partials

[gordonwoodhull]

From #11616 (reply in thread)_

We do not currently have any general facilities for accessing brand metadata in templates.

Given that templates are the same level of abstraction as brands, it would make sense to expose brand metadata directly to templates.

But currently you can only access the entire brand metadata from Lua or via the brand shortcode, neither of which help you with templates.

The background logo with positioning that we currently support in Typst

https://quarto.org/docs/authoring/brand.html#document-logo-customization

is implemented in this Lua filter:

quarto-cli/src/resources/filters/quarto-post/typst-brand-yaml.lua

Lines 217 to 305 in bf03850

	local logo = param('logo')
	local logoOptions = {}
	local foundLogo = null
	if logo then
	if type(logo) == 'string' then
	foundLogo = _quarto.modules.brand.get_logo(brandMode, logo) or {path=logo}
	elseif type(logo) == 'table' then
	for k, v in pairs(logo) do
	logoOptions[k] = v
	end
	if logo.path then
	foundLogo = _quarto.modules.brand.get_logo(brandMode, logo.path) or {path=logo}
	end
	end
	end
	if not foundLogo and brand.processedData.logo then
	local tries = {'large', 'small', 'medium'} -- low to high priority
	foundLogo = _quarto.modules.brand.get_logo(brandMode, 'medium')
	or _quarto.modules.brand.get_logo(brandMode, 'small')
	or _quarto.modules.brand.get_logo(brandMode, 'large')
	end
	if foundLogo then
	logoOptions.path = foundLogo.path
	logoOptions.alt = foundLogo.alt
	local pads = {}
	for k, v in _quarto.utils.table.sortedPairs(logoOptions) do
	if k == 'padding' then
	local widths = {}
	_quarto.modules.typst.css.parse_multiple(v, 5, function(s, start)
	local width, newstart = _quarto.modules.typst.css.consume_width(s, start)
	table.insert(widths, width)
	return newstart
	end)
	local sides = _quarto.modules.typst.css.expand_side_shorthand(
	widths,
	'widths in padding list: ' .. v)
	pads.top = sides.top
	pads.right = sides.right
	pads.bottom = sides.bottom
	pads.left = sides.left
	elseif k:find '^padding-' then
	local _, ndash = k:gsub('-', '')
	if ndash == 1 then
	local side = k:match('^padding--(%a+)')
	local padding_sides = {'left', 'top', 'right', 'bottom'}
	if tcontains(padding_sides, side) then
	pads[side] = _quarto.modules.typst.css.translate_length(v)
	else
	quarto.log.warning('invalid padding key ' .. k)
	end
	else
	quarto.log.warning('invalid padding key ' .. k)
	end
	end
	end
	local inset = nil
	if next(pads) then
	if pads.top == pads.right and
	pads.right == pads.bottom and
	pads.bottom == pads.left
	then
	inset = pads.top
	elseif pads.top == pads.bottom and pads.left == pads.right then
	inset = _quarto.modules.typst.as_typst_dictionary({x = pads.left, y = pads.top})
	else
	inset = _quarto.modules.typst.as_typst_dictionary(pads)
	end
	else
	inset = '0.75in'
	end
	logoOptions.width = _quarto.modules.typst.css.translate_length(logoOptions.width or '1.5in')
	logoOptions.location = logoOptions.location and
	location_to_typst_align(logoOptions.location) or 'left+top'
	quarto.log.debug('logo options', logoOptions)
	local altProp = logoOptions.alt and (', alt: "' .. logoOptions.alt .. '"') or ''
	local imageFilename = logoOptions.path
	if _quarto.modules.mediabag.should_mediabag(imageFilename) then
	imageFilename = _quarto.modules.mediabag.resolved_url_cache[logoOptions.path] or _quarto.modules.mediabag.fetch_and_store_image(logoOptions.path)
	imageFilename = _quarto.modules.mediabag.write_mediabag_entry(imageFilename) or imageFilename
	else
	-- backslashes need to be doubled for Windows
	imageFilename = string.gsub(imageFilename, '\\', '\\\\')
	end
	quarto.doc.include_text('in-header',
	'#set page(background: align(' .. logoOptions.location .. ', box(inset: ' .. inset .. ', image("' .. imageFilename .. '", width: ' .. logoOptions.width .. altProp .. '))))')
	end
	end
	end,

We have discussed separately that the logo should be implemented as a partial instead of this Lua filter directly generating the

#set page(background: ...)

Exposing brand metadata to templates would be a similar effort, but more general, because it would expose all of the brand logos to the template, not just the chosen one.

It could be done either through definition of more constants in Typst as is done for colors, or through more metadata exposed to the template as the Typst brand.typography metadata discussed here.

[gordonwoodhull]

Fixed by #13119 and #13120