ionic-framework/ionic/components/app/structure.scss

// Z-Index
// --------------------------------------------------
// Grouped by elements which would be siblings

$z-index-menu-overlay:           80;
$z-index-menu-backdrop:          79;
$z-index-overlay:                1000;
$z-index-click-block:            9999;

$z-index-navbar-section:         10;

$z-index-toolbar:                10;
$z-index-toolbar-background:     -1;

$z-index-toolbar-border:         20;
$z-index-list-border:            50;

$z-index-backdrop:               1;
$z-index-overlay-wrapper:        10;

$z-index-item-options:           1;


// Flex Order
// --------------------------------------------------

$flex-order-toolbar-top:         -10;
$flex-order-toolbar-bottom:      10;

$flex-order-tab-bar-navbar:      -30;
$flex-order-tab-bar-top:         -20;
$flex-order-tab-bar-bottom:      20;



// App Structure
// --------------------------------------------------

* {
  box-sizing: border-box;
  -webkit-tap-highlight-color: rgba(0, 0, 0, 0);
  -webkit-tap-highlight-color: transparent;
  -webkit-touch-callout: none;
}

html {
  width: 100%;
  height: 100%;
  -ms-text-size-adjust: 100%; // 1
  -webkit-text-size-adjust: 100%; // 1
}

body {
  position: fixed;
  overflow: hidden;
  width: 100%;
  height: 100%;
  max-width: 100%;
  max-height: 100%;
  margin: 0;
  padding: 0;
  word-wrap: break-word;

  touch-action: manipulation;
  -webkit-user-drag: none;
  -ms-content-zooming: none;

  -webkit-font-smoothing: antialiased;
  font-smoothing: antialiased;
  text-rendering: optimizeLegibility;

  -webkit-text-size-adjust: none;
  -moz-text-size-adjust: none;
  text-size-adjust: none;

  @include user-select-none();
  background-color: $background-color;
}

ion-app,
ion-nav,
ion-tabs {
  display: flex;
  flex-direction: column;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
}

ion-navbar-section {
  display: block;
  width: 100%;
  min-height: 50px;
}

ion-content-section {
  display: block;
  flex: 1;
  position: relative;
  width: 100%;
  height: 100%;
}

ion-page {
  display: flex;
  flex-direction: column;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  transform: translateZ(0);
}

ion-content {
  position: relative;
  display: block;
  width: 100%;
  height: 100%;
  flex: 1;
  background-color: $background-color;
}

scroll-content {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  display: block;
  overflow-y: scroll;
  overflow-x: hidden;
  -webkit-overflow-scrolling: touch;
  will-change: scroll-position;
}

ion-tab-bar {
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  min-height: 50px;
}

ion-tab-section {
  display: block;
  position: relative;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  overflow: hidden;
}

ion-page.tab-subpage {
  position: fixed;
  z-index: 10;
}

ion-navbar {
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  min-height: 50px;
  z-index: $z-index-navbar-section;
}

ion-navbar-section ion-navbar.toolbar {
  position: absolute;
}

ion-toolbar {
  display: block;
  width: 100%;
  height: 50px;
}

ion-toolbar[position=bottom] {
  bottom: 0;
  z-index: $z-index-toolbar;
}