Name: preOpenControl

Type: message

Syntax: preOpenControl

Summary: Sent to a <group> when you go to the <card> that contains it and to a <background group> when going from a card which it is not placed on to one where it is.

Introduced: 3.5

OS: mac,windows,linux,ios,android

Platforms: desktop,server,web,mobile

Example:
on preOpenControl
  resizeMyObjects
  put empty into field "Customer Address" of me
end preOpenControl

Description:
Handle the <preOpenControl> message to update a group's appearance before it appears on screen.

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For groups with their <backgroundBehavior property> set to true, the <preOpenControl> message is sent immediately after the <preOpenBackground message> is sent to the <card(object)> being opened. For non-background groups, it is sent after the <preOpenCard message>.

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For nested groups, the <preOpenControl> message is sent to the parent group first, if it is passed or not handled by the parent group, then it passes through each child group in reverse layer order (i.e from highest to lowest).

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The actual navigation is not triggered by the <preOpenControl> <message>, so blocking the <message> and not allowing it to pass does not prevent the <card(keyword)> with the <group> from opening.

References: card (keyword), background group (property), backgroundBehavior property (property), preOpenBackground message (message), openControl (message), preOpenCard message (message), dispatch (command), group (command), card (object), message (glossary)
