Comment 0 for bug 1560458

r1886

Header should not update (or stop updating) Flickable content margins in case either one of its sides have null size or it's !visible.
This is to be consistent with how QtQuick layout components already behave -> they ignore children whose size is null or that are !visible.

NOTE: opacity should not affect this logic. If opacity is 0, the items should NOT be ignored (this allows opacity animations).

TestCase: you can verify that flickable.topMargin is equal to editHeader's height even when the header it's not visible and standardHeader is the visible one instead.

            MainView {
                id: mainView_movingHeaderTest
                width: units.gu(50)
                height: units.gu(80)
                clip: true

                property alias page: pageItem
                property alias standardHeader: standardHeaderItem
                property alias editHeader: editHeaderItem

                Page {
                    id: pageItem
                    header: standardHeaderItem

                    Flickable {
                        id: flickable_movingHeaderTest
                        anchors.fill: parent
                        //just make sure the scrollbar is scrollable
                        contentHeight: mainView_movingHeaderTest.height * 2
                        contentWidth: mainView_movingHeaderTest.width * 2
                        Label {
                            text: "Use the icons in the header."
                            visible: standardHeaderItem.visible
                        }
                    }
                    Scrollbar {
                        id: scrollbar_movingHeaderTest
                        flickableItem: flickable_movingHeaderTest
                    }

                    PageHeader {
                        id: standardHeaderItem
                        visible: pageItem.header === standardHeaderItem
                        title: "Default title"
                        flickable: flickable_movingHeaderTest
                        trailingActionBar.actions: [
                            Action {
                                iconName: "edit"
                                text: "Edit"
                                onTriggered: pageItem.header = editHeaderItem
                            }
                        ]
                    }
                    PageHeader {
                        id: editHeaderItem
                        visible: pageItem.header === editHeaderItem
                        flickable: flickable_movingHeaderTest
                        property Component delegate: Component {
                            AbstractButton {
                                id: button
                                action: modelData
                                width: label.width + units.gu(4)
                                height: parent.height
                                Rectangle {
                                    color: UbuntuColors.slate
                                    opacity: 0.1
                                    anchors.fill: parent
                                    visible: button.pressed
                                }
                                Label {
                                    anchors.centerIn: parent
                                    id: label
                                    text: action.text
                                    font.weight: text === "Confirm"
                                                 ? Font.Normal
                                                 : Font.Light
                                }
                            }
                        }
                        leadingActionBar {
                            anchors.leftMargin: 0
                            actions: Action {
                                text: "Cancel"
                                iconName: "close"
                                onTriggered: pageItem.header = standardHeaderItem
                            }
                            delegate: editHeaderItem.delegate
                        }
                        trailingActionBar {
                            anchors.rightMargin: 0
                            actions: Action {
                                text: "Confirm"
                                iconName: "tick"
                                onTriggered: pageItem.header = standardHeaderItem
                            }
                            delegate: editHeaderItem.delegate
                        }
                        extension: Toolbar {
                            anchors {
                                left: parent.left
                                right: parent.right
                                bottom: parent.bottom
                            }
                            trailingActionBar.actions: [
                                Action { iconName: "bookmark-new" },
                                Action { iconName: "add" },
                                Action { iconName: "edit-select-all" },
                                Action { iconName: "edit-copy" },
                                Action { iconName: "select" }
                            ]
                            leadingActionBar.actions: Action {
                                iconName: "delete"
                                text: "delete"
                                onTriggered: print("Delete action triggered")
                            }
                        }
                    }
                }
            }