v0.2.0

A minor version rather than a patch: new components, new parameters on the
sheet, the tab bar and the controls, and a declared backdrop. Existing code
builds unchanged; the one layout change is in the ripple shader's uniforms
(see Performance). Three defaults behave differently: a pressed GlassButton
swells (GlassPress.none turns it off), a sheet stands on the keyboard
instead of under it, and a switch, slider or segmented control inside a
horizontal scrollable takes a horizontal drag from the page.

A backdrop the application declares:

• GlassBackdrop declares what is behind the glass in a subtree, and that
  glass samples a texture made from the declaration instead of a capture of
  the screen: GlassBackdrop.color, .image (an ImageProvider, placed by
  fit and alignment), .texture (a ui.Image the application holds) and
  .gradient and .painter (any GlassProxyPainter). The texture is
  made once per finish blur and size, through the same shader and the same
  blur arithmetic as a captured slot, and the host leaves those surfaces out
  of its capture: a screen whose glass is all declared takes no snapshot.
  Over a declared colour the glass draws what it draws over a captured screen
  of that colour, to 2 code values.
• Scoped to the subtree, innermost first: GlassBackdrop.live hands a part
  back to the capture, so a page can declare its wallpaper and still let the
  bar over its list refract the list. The widget paints what it declares under
  its child unless paintBackdrop: false, and an image that has not loaded
  leaves the glass on the capture until it has; so does a replaced image,
  with the old one still painted until the new one arrives.
• Glass over a declared backdrop is ordinary content for the capture of other
  glass, as a cheap surface is: a captured bar over declared cards shows them.
  Fused groups sample the declaration too, and a fused member is left out of
  the capture exactly when its group is, whatever GlassBackdrop sits between
  them. A draw holds the texture it was recorded with, so glass that moves
  without repainting keeps drawing while other glass under the same
  declaration asks for new blurs, and no texture is made while a frame is
  composited. Adaptive glass does not read a
  declared backdrop yet, and falls back to its declarations.
• RenderGlassSurface.paintsWithDeclaredBackdrop,
  RenderGlassGroup.paintsWithDeclaredBackdrop,
  RenderGlassSurface.readsDeclaredBackdrop and
  GlassBackdropDeclaration.renders say what was sampled and how many
  textures were made; GlassSurfaceRecord.declared and readsCapture say
  what the ledger priced.

Components:

• GlassStepper: a minus and a plus in one glass capsule, as UIStepper. A
  press steps at once; held, a half repeats after
  kGlassStepperRepeatDelay (500 ms) every kGlassStepperRepeatInterval
  (100 ms), and the half that would pass a limit is disabled unless wraps.
  One surface: a press, the repeat and a glyph dimming are drawn inside the
  glass and are no capture. A screen reader hears one adjustable control.
  Under right to left it is mirrored, with the minus at the end.
• GlassPageControl: page dots on a glass capsule, as UIPageControl on its
  platter. It follows a PageController without a build and turns it; a tap
  moves one page toward the side tapped, as iOS's does, and a drag scrubs.
  One surface. A PageView beside it is retaken while it scrolls (43 captures
  a swipe in the package's tests), which belongs to the view: the same 43 with
  dots that stay put. Under right to left the first dot is at the right, and
  a count that shrinks below the current page clamps it.
• GlassSearchBar: the glass search field with a clear button while there is
  text, and a Cancel that slides in while it has the focus. One surface, the
  field's; typing and the clear button are no capture. Cancel's slide narrows
  the glass, and that is a capture a frame for cancelDuration (16 over
  250 ms at 60 Hz, each way), one frame under reduced motion.
• GlassBadge: a count, a label or a dot on the corner of an icon or a tab,
  as an opaque systemRed capsule. Not glass, as iOS 26's badge is not; it
  costs no surface, and a count changing on glass is a repaint inside the
  glass.
• Their sizes (kGlassStepperSize, kGlassPageDot, kGlassPageDotGap,
  kGlassPageControlHeight, kGlassBadgeHeight, kGlassBadgeDot) are
  layout, not Apple measurements: none of the four was among the controls
  measured. The stepper, the page control and the search bar are laid
  out at least kGlassMinTapTarget tall.

iOS 26 behaviours:

• Sheet detents: showGlassSheet(detents:, initialDetent:, onDetentChanged:) with GlassSheetDetent.medium (the content's height, as
  before; Apple's is half the window) and GlassSheetDetent.large (the whole
  height below the top safe area less 8, edge to edge). A drag between them
  follows the finger and settles at the nearer, or where a flick was heading;
  a tap on a settling sheet, or on a button in it, leaves the settle alone.
• A large sheet is largeFinish, by default the finish with its tint at full
  alpha. Once it is all the way up it is drawn on GlassTier.cheap and reads
  no backdrop: headless, with a glass bar under it, one surface of two
  captured instead of two, and 20,608 px² of capture against 337,408. The
  other way: the sheet is then content to the capture of the glass around it,
  so a change inside it is a retake (1 against 0). A translucent
  largeFinish keeps it glass.
• GlassTabBar(minimizeBehavior: GlassTabBarMinimizeBehavior.onScrollDown)
  collapses the bar to a circle of the selected tab's icon when the content
  scrolls down, and expands it on a scroll up or a tap on the circle, which
  selects nothing. The scroll is read by a GlassTabBarMinimizer above both
  the scroll view and the bar; GlassScaffold is one. The collapse moves
  inside a declared travel region: no record over 60 frames, against 60
  without the declaration. Collapsed, a screen reader hears one button named
  for the selected tab. GlassTabBarMinimizer.notificationPredicate (and
  GlassScaffold.minimizeNotificationPredicate) lets a list one level down,
  in a PageView, TabBarView or NestedScrollView, collapse it, and the
  direction is read on the screen, so a reverse: true list collapses it as
  any list does.
• GlassTabBar.bottomAccessory: a glass capsule kGlassTabAccessoryHeight
  (48) tall above the bar, which moves down beside the collapsed circle. The
  bar's box keeps its height, so the body is not laid out again for it.
• The gap above a large sheet, its radius, the circle's size, the accessory's
  height and gaps, kGlassTabMinimizeScroll (12) and the springs are layout
  taste: none was measured on Apple's devices.

Interaction:

• GlassPress: a pressed GlassButton swells by 12 px on its longest side
  and leans up to 3 px toward a dragging finger, then springs back. Declared
  on GlassHost.press, GlassThemeData.press or GlassButton.press;
  GlassPress.none turns it off, and so do reduced motion and a disabled
  button. A feel rather than a measurement: Apple's press was not measured,
  and 17 px, another package's number, would be 1.39× a 44 px button. It
  costs two captures a press (touch-down and settle) and nothing at rest,
  because the region it grows in is declared only while it moves; declared
  always, it doubled a 44 px button's captured area (3,600 to 7,056 px²).
  Toolbar cells take the focus but do not swell: the group is one surface.
• GlassSlider.divisions: every input, a drag, a tap, a key or a screen
  reader, lands on a stop, and onChanged is called only when the stop
  changes.
• The switch, the slider and the segmented control drag from touch-down.
  Inside a horizontal scrollable such as a PageView a horizontal drag that
  starts on them moves the control and not the page, and a vertical swipe
  still scrolls the vertical list around them, a carousel row's included.
• The keyboard: the button, switch, slider, segmented control, stepper, page
  control and toolbar cells take the focus (focusNode, autofocus); Space
  and Enter activate, and the arrows step the slider, the segmented control,
  the stepper and the page control. The ring
  (kGlassFocusRingColor, kGlassFocusRingWidth, kGlassFocusRingGap) is
  drawn inside the glass's own subtree, which no capture sees; a switch's or a
  segmented control's ring under other glass costs one capture as the focus
  changes.
• Right to left: the switch is on at the left, the slider fills from the
  right, the segmented control's first segment is at the right, the toolbar's
  first item is at the right, the stepper's minus and the page control's first
  dot are at the right, and the arrow keys follow.
  SliderGeometry.fillEnd takes a textDirection.
• GlassConcentric: Apple's concentric corners as arithmetic, a shape's
  radius as its container's less the inset, with a floor. The segmented
  control's capsule (pixel for pixel what it was) and the focus rings use it.

Fixes:

• A dismissible sheet follows the finger: a 116 px drag moved it about
  4.5 px. It closes past a third of its height or on a flick, and while it
  moves it declares where it travels: one retake a drag instead of 16.
• Under right to left, the segmented control's capsule sat under the wrong
  label, and GlassButtonGroup brightened the wrong cell.
• A sheet stands on the keyboard, as an iOS sheet does: 8 px above it at
  medium, on it at large. Its content sees no bottom viewInsets, so content
  already padded by them is not padded twice.
• A sheet popped while a finger drags it no longer pops the page under it when
  the finger lifts, and a drag down from large after the content or the window
  changed no longer jumps.
• GlassSlider sends one onChangeStart before its changes and one
  onChangeEnd after, carrying the last value it sent, for a tap, a hold, a
  drag, a cancelled pointer and a slider disabled mid-gesture: a tap used to
  end before it started, and a hold then a drag started twice.
• A segmented control in a vertical list no longer selects a segment after the
  list scrolled away under the finger.
• GlassButtonGroup threw, or kept its ring on a cell that was gone, when the
  focused or held item was removed.

Performance:

• The shaders' uniforms are packed into vec4s: 19 slots to 9 for a surface
  and a group, 24 to 12 for the ripple. Metal binds each declared float
  uniform on its own every draw, where Vulkan binds one struct. The pixels are
  byte-identical; the raster thread spends 0.9 to 1.4 µs less a surface draw
  and 1.0 to 1.8 µs less a group draw, on macOS under Impeller/Metal. The ripple's
  count, reach and light moved after its arrays, which matters only to
  code that writes the uniforms by hand. Every flutter test run checks the
  lane order against an unpacked copy of each shader, with a lane swap as the
  control that it fails.

Platforms:

• The floor is Flutter 3.47.0 (Dart 3.13.0): sdk: ^3.13.1 shut 3.47.0 out
  although the package runs on it unchanged, and CI now tests that exact
  version rather than the newest 3.47 patch. Below 3.47 the package would need
  code changes, and on Apple hosts that opt into SDF rendering it would draw
  differently, so the floor stays there.

Documentation:

• "Misuse and common errors", in the README and on the site: each mistake
  with what it looks like, the error text where there is one, the cause and
  the fix.
• The site has a page with a live demo for the stepper, the page control, the
  search bar and the badge, and the sheet, tab bar, button, slider and
  segmented control pages show detents, the collapse, the press, divisions,
  the keyboard and right to left. The README has a pattern for a tab bar that
  collapses on scroll, and the agent skill has the same pages and rules.

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https://pub.dev/packages/g1455/versions/0.2.0