Add header on limit to extruder

1 files changed, 11 insertions, 1 deletions

diff --git a/docs/profiles/getting_a_setting_value.md b/docs/profiles/getting_a_setting_value.md
index d9d1dc1b8d..beb8c38783 100644
--- a/docs/profiles/getting_a_setting_value.md
+++ b/docs/profiles/getting_a_setting_value.md
@@ -6,4 +6,14 @@ This page explains all possible cases for a setting, but not all of them may app
 
 Per Object Settings
 ----
-Per-object settings, which are added to an object using the per-object settings tool, will always prevail over other setting values. They are not evaluated with the rest of the settings system because Cura's front-end doesn't need to send all setting values for all objects to CuraEngine separately. It only sends over the per-object settings that get overridden. CuraEngine then evaluates settings that can be changed per-object using the list of settings for that object but if the object doesn't have the setting attached falls back on the settings in the object's extruder. Refer to the [CuraEngine](#CuraEngine) chapter to see how this works.
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+Per-object settings, which are added to an object using the per-object settings tool, will always prevail over other setting values. They are not evaluated with the rest of the settings system because Cura's front-end doesn't need to send all setting values for all objects to CuraEngine separately. It only sends over the per-object settings that get overridden. CuraEngine then evaluates settings that can be changed per-object using the list of settings for that object but if the object doesn't have the setting attached falls back on the settings in the object's extruder. Refer to the [CuraEngine](#CuraEngine) chapter to see how this works.
+
+Settings where the `settable_per_mesh` property is false will not be shown in Cura's interface in the list of available settings in the per-object settings panel. They cannot be adjusted per object then. CuraEngine will also not evaluate those settings for each object separately. There is (or should always be) a good reason why each of these settings are not evaluated per object: Simply because CuraEngine is not processing one particular mesh at that moment. For instance, when writing the move to change to the next layer, CuraEngine hasn't processed any of the meshes on that layer yet and so the layer change movement speed, or indeed the layer height, can't change for each object.
+
+The per-object settings are stored in a separate container stack that is particular to the object. The container stack is added to the object via a scene decorator. It has just a single container in it, which contains all of the settings that the user changed.
+
+Limit To Extruder
+----
+If the setting is not listed in the per-object settings, it needs to be evaluated from the extruder that the object is assigned to. However there are some exceptions. Some groups of settings belong to a particular "extruder setting", like the Infill Extruder setting, or the Support Extruder setting. Which extruder a setting belongs to is stored in the `limit_to_extruder` property. Settings which have their `limit_to_extruder` property set to `adhesion_extruder_nr`, for instance, belong to the build plate adhesion settings.
+
+If the `limit_to_extruder` property evaluates to a positive number, instead of getting the setting from the object's extruder it will be obtained from the extruder written in the `limit_to_extruder` property. So even if an object is set to be printed with extruder 0, if the infill extruder is set to extruder 1 any infill setting will be obtained from extruder 1. If `limit_to_extruder` is negative (in particular -1, which is the default), then the setting will be obtained from the object's own extruder.
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