Overriding image width with updateExportSettings - plugins

Question

I have cross posted on the Adobe Forums.
Writing my first lightroom plugin, I have created a minimal example which should set the photo width here and included below. However I can not get the image to be the 400 x 400 specified.
ExportFilterProvider400.lua:
local LrView = import 'LrView'
local bind = LrView.bind
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-- This function will create the section displayed on the export dialog
-- when this filter is added to the export session.
local function sectionForFilterInDialog( f, propertyTable )
return {
title = LOC "$$$/SDK/MetaExportFilter/SectionTitle=400x400 Filter",
}
end
--------------------------------------------------------------------------------
-- Example on updating export settings
local function updateExportSettings( exportSettings )
exportSettings.LR_size_maxHeight = 400
exportSettings.LR_size_maxWidth = 400
exportSettings.LR_size_doConstrain = true
end
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return {
sectionForFilterInDialog = sectionForFilterInDialog,
updateExportSettings = updateExportSettings , --Does this work
}
Info.lua:
return {
LrSdkVersion = 3.0,
LrSdkMinimumVersion = 1.3,
LrPluginName = "400x400 Export",
LrToolkitIdentifier = 'sample.export400x400',
LrExportFilterProvider = {
title = LOC "$$$/SDK/MetaExportFilter/Sample=400x400 Size", -- the string that appears in the export filter section of the export dialog in LR
file = 'ExportFilterProvider400.lua', -- name of the file containing the filter definition script
id = "metadata1", -- unique identifier for export filter
},
VERSION = { major=5, minor=0, revision=0, build=907681, },
}
Adobe Lightroom can load the plugin, and add it to the export session, but the updateExportSettings do not seem to take effect. Tested in Lightroom 5.3.

Answer 1

Rob Cole on the Adobe SDK forum has pointed out that updateExportSettings is used by 'Export Service providers' to preset export settings.
'Export Filter providers' should use renditionOptions as part of postProcessRenderedPhotos.
After some trial and error I have this minimal example,
Info.lua (no change):
return {
LrSdkVersion = 3.0,
LrSdkMinimumVersion = 1.3, -- minimum SDK version required by this plugin
LrPluginName = "400x400 Export",
LrToolkitIdentifier = 'sample.export400x400',
LrExportFilterProvider = {
title = LOC "$$$/SDK/MetaExportFilter/Sample=400x400 Size",
file = 'ExportFilterProvider400.lua',
id = "metadata1", -- unique identifier for export filter
},
VERSION = { major=5, minor=0, revision=0, build=907681, },
}
ExportFilterProvider400.lua:
local LrView = import 'LrView'
local bind = LrView.bind
local function sectionForFilterInDialog( f, propertyTable )
logger:info('Called sectionForFilterInDialog')
return {
title = LOC "$$$/SDK/MetaExportFilter/SectionTitle=400x400 Filter",
}
end
local function postProcessRenderedPhotos( functionContext, filterContext )
local renditionOptions = {
filterSettings = function( renditionToSatisfy, exportSettings )
exportSettings.LR_size_maxHeight = 400
exportSettings.LR_size_maxWidth = 400
exportSettings.LR_size_doConstrain = true
end
}
for sourceRendition, renditionToSatisfy in filterContext:renditions( renditionOptions ) do
-- Wait for the upstream task to finish its work on this photo.
local success, pathOrMessage = sourceRendition:waitForRender()
end
end
--------------------------------------------------------------------------------
return {
sectionForFilterInDialog = sectionForFilterInDialog,
postProcessRenderedPhotos = postProcessRenderedPhotos,
}