Warning, /plasma/qqc2-breeze-style/style/qtquickcontrols/TabButton.qml is written in an unsupported language. File is not indexed.

 /* SPDX-FileCopyrightText: 2020 Noah Davis <noahadvs@gmail.com>
  * SPDX-License-Identifier: LGPL-2.1-only OR LGPL-3.0-only OR LicenseRef-KDE-Accepted-LGPL
  */
 
 import QtQuick
 import QtQuick.Templates as T
 import org.kde.kirigami as Kirigami
 import org.kde.breeze
 import org.kde.breeze.impl as Impl
 
 T.TabButton {
     id: control
 
     readonly property bool __inTabBar: T.TabBar.tabBar != null
     readonly property bool __hasLeftSeparator: background && background.hasOwnProperty("leftSeparatorLine")
     readonly property bool __hasRightSeparator: background && background.hasOwnProperty("rightSeparatorLine")
     readonly property bool __inHeader: T.TabBar.position === T.TabBar.Header
     readonly property bool __inFooter: T.TabBar.position === T.TabBar.Footer
 
     implicitWidth: Math.max(implicitBackgroundWidth + leftInset + rightInset,
                             implicitContentWidth + leftPadding + rightPadding,
                             implicitIndicatorWidth + leftPadding + rightPadding)
     implicitHeight: Math.max(implicitBackgroundHeight + topInset + bottomInset,
                              implicitContentHeight + topPadding + bottomPadding,
                              implicitIndicatorHeight + topPadding + bottomPadding)
 
     padding: Kirigami.Units.mediumSpacing
     leftPadding: {
         if ((!contentItem.hasIcon && contentItem.textBesideIcon) // False if contentItem has been replaced
             || display == T.AbstractButton.TextOnly
             || display == T.AbstractButton.TextUnderIcon) {
             return Impl.Units.mediumHorizontalPadding
         } else {
             return control.horizontalPadding
         }
     }
     rightPadding: {
         if (contentItem.hasLabel && display != T.AbstractButton.IconOnly) { // False if contentItem has been replaced
             return Impl.Units.mediumHorizontalPadding
         } else {
             return control.horizontalPadding
         }
     }
 
     leftInset: {
         if (!mirrored && __hasLeftSeparator && background.leftSeparatorLine.visible) {
             return background.leftSeparatorLine.width
         } else if (mirrored && __hasRightSeparator && background.rightSeparatorLine.visible) {
             return background.rightSeparatorLine.width
         } else {
             return 0
         }
     }
     rightInset: {
         if (!mirrored && __hasRightSeparator && background.leftSeparatorLine.visible) {
             return background.rightSeparatorLine.width
         } else if (mirrored && __hasLeftSeparator && background.rightSeparatorLine.visible) {
             return background.leftSeparatorLine.width
         } else {
             return 0
         }
     }
 
     spacing: Kirigami.Units.mediumSpacing
 
     icon.width: Kirigami.Units.iconSizes.sizeForLabels
     icon.height: Kirigami.Units.iconSizes.sizeForLabels
 
     Kirigami.Theme.colorSet: {
         if (control.__inTabBar && !(control.checked)) {
             return T.TabBar.tabBar.Kirigami.Theme.colorSet
         } else {
             return Kirigami.Theme.Button
         }
     }
     Kirigami.Theme.inherit: !(background && background.visible)
 
     contentItem:Impl.IconLabelContent {
         control: control
     }
 
     //TODO: tweak the appearance. This is just to have something usable and reasonably close to what we want.
     background: Rectangle {
         implicitHeight: Impl.Units.mediumControlHeight + (Kirigami.Units.smallSpacing * 2) // fill TabBar
         implicitWidth: implicitHeight
         color: control.checked ? Kirigami.Theme.backgroundColor : "transparent"
 
         property Rectangle leftSeparatorLine: Rectangle {
             parent: control.background
             visible: control.T.TabBar.index != 0 && control.checked
             Kirigami.Theme.colorSet: Kirigami.Theme.Button
             Kirigami.Theme.inherit: false
             anchors.left: parent.left
             anchors.leftMargin: -control.leftInset
             anchors.verticalCenter: parent.verticalCenter
             width: 1
             height: control.checked ? parent.height : Math.min(parent.height, Kirigami.Units.gridUnit)
             color: Impl.Theme.separatorColor()
             Behavior on height {
                 NumberAnimation {
                     easing.type: Easing.InOutQuad
                     duration: Kirigami.Units.longDuration
                 }
             }
         }
 
         property Rectangle rightSeparatorLine: Rectangle {
             parent: control.background
             visible: control.__inTabBar && control.T.TabBar.index != control.T.TabBar.tabBar.count - 1 && control.checked
             Kirigami.Theme.colorSet: Kirigami.Theme.Button
             Kirigami.Theme.inherit: false
             anchors.right: parent.right
             anchors.rightMargin: -control.rightInset
             anchors.verticalCenter: parent.verticalCenter
             width: 1
             height: parent.leftSeparatorLine.height
             color: Impl.Theme.separatorColor()
         }
 
         Rectangle {
             id: thickHighlightLine
             anchors.left: parent.left
             anchors.right: parent.right
             anchors.leftMargin: -control.leftInset
             anchors.rightMargin: -control.rightInset
             y: control.__inHeader ? 0 : parent.height - height
             height: Impl.Units.highlightLineThickness
             opacity: control.visualFocus || control.checked || control.hovered || control.down ? 1 : 0
             Kirigami.Theme.colorSet: Kirigami.Theme.Button
             Kirigami.Theme.inherit: false
             color: {
                 if (control.visualFocus) {
                     Kirigami.Theme.alternateBackgroundColor
                 } else if (control.checked || control.down) {
                     Kirigami.Theme.focusColor
                 } else {
                     Impl.Theme.separatorColor()
                 }
             }
             Behavior on opacity {
                 OpacityAnimator {
                     easing.type: Easing.OutCubic
                     duration: Kirigami.Units.shortDuration
                 }
             }
             Behavior on color {
                 ColorAnimation {
                     easing.type: Easing.InOutQuad
                     duration: Kirigami.Units.longDuration
                 }
             }
         }
 
         Rectangle {
             id: thinHighlightLine
             anchors.left: parent.left
             anchors.right: parent.right
             anchors.leftMargin: -control.leftInset
             anchors.rightMargin: -control.rightInset
             y: control.__inHeader ? 0 : parent.height - height
             height: 1
             opacity: control.visualFocus ? 1 : 0
             Kirigami.Theme.colorSet: Kirigami.Theme.Button
             Kirigami.Theme.inherit: false
             color: Kirigami.Theme.focusColor
             Behavior on opacity {
                 OpacityAnimator {
                     easing.type: Easing.OutCubic
                     duration: Kirigami.Units.shortDuration
                 }
             }
         }
     }
 }