[infra_ui][overlay] (WIP) Add overlay declearations

app_flowy/packages/flowy_infra_ui/example/pubspec.yaml

@@ -12,6 +12,7 @@ dependencies:
     sdk: flutter
 
   cupertino_icons: ^1.0.2
+
   flowy_infra_ui:
     path: ../
 
@@ -19,51 +20,7 @@ dev_dependencies:
   flutter_test:
     sdk: flutter
 
-  # The "flutter_lints" package below contains a set of recommended lints to
-  # encourage good coding practices. The lint set provided by the package is
-  # activated in the `analysis_options.yaml` file located at the root of your
-  # package. See that file for information about deactivating specific lint
-  # rules and activating additional ones.
   flutter_lints: ^1.0.0
 
-# For information on the generic Dart part of this file, see the
-# following page: https://dart.dev/tools/pub/pubspec
-
-# The following section is specific to Flutter.
 flutter:
-
-  # The following line ensures that the Material Icons font is
-  # included with your application, so that you can use the icons in
-  # the material Icons class.
   uses-material-design: true
-
-  # To add assets to your application, add an assets section, like this:
-  # assets:
-  #   - images/a_dot_burr.jpeg
-  #   - images/a_dot_ham.jpeg
-
-  # An image asset can refer to one or more resolution-specific "variants", see
-  # https://flutter.dev/assets-and-images/#resolution-aware.
-
-  # For details regarding adding assets from package dependencies, see
-  # https://flutter.dev/assets-and-images/#from-packages
-
-  # To add custom fonts to your application, add a fonts section here,
-  # in this "flutter" section. Each entry in this list should have a
-  # "family" key with the font family name, and a "fonts" key with a
-  # list giving the asset and other descriptors for the font. For
-  # example:
-  # fonts:
-  #   - family: Schyler
-  #     fonts:
-  #       - asset: fonts/Schyler-Regular.ttf
-  #       - asset: fonts/Schyler-Italic.ttf
-  #         style: italic
-  #   - family: Trajan Pro
-  #     fonts:
-  #       - asset: fonts/TrajanPro.ttf
-  #       - asset: fonts/TrajanPro_Bold.ttf
-  #         weight: 700
-  #
-  # For details regarding fonts from package dependencies,
-  # see https://flutter.dev/custom-fonts/#from-packages

app_flowy/packages/flowy_infra_ui/lib/src/overlay/overlay_basis.dart

@@ -0,0 +1,42 @@
+import 'package:flutter/material.dart';
+
+/// Specifies how overlay are anchored to the SourceWidget
+enum AnchorDirection {
+  // Corner aligned with a corner of the SourceWidget
+  topLeft,
+  topRight,
+  bottomLeft,
+  bottomRight,
+
+  // Edge aligned with a edge of the SourceWidget
+  topWithLeftAligned,
+  topWithCenterAligned,
+  topWithRightAligned,
+  rightWithTopAligned,
+  rightWithCenterAligned,
+  rightWithBottomAligned,
+  bottomWithLeftAligned,
+  bottomWithCenterAligned,
+  bottomWithRightAligned,
+  leftWithTopAligned,
+  leftWithCenterAligned,
+  leftWithBottomAligned,
+
+  // Custom position
+  custom,
+}
+
+/// The behavior of overlay when user tapping system back button
+enum OnBackBehavior {
+  /// Won't handle the back action
+  none,
+
+  /// Animate to get the user's attention
+  alert,
+
+  /// Intercept the back action and abort directly
+  abort,
+
+  /// Intercept the back action and dismiss overlay
+  dismiss,
+}

app_flowy/packages/flowy_infra_ui/lib/src/overlay/overlay_pannel.dart

@@ -0,0 +1,43 @@
+import 'dart:ui';
+
+import 'package:flutter/material.dart';
+import 'overlay_basis.dart';
+
+class OverlayPannel extends SingleChildLayoutDelegate {
+  OverlayPannel({
+    required this.targetRect,
+    this.anchorDirection = AnchorDirection.topRight,
+    this.safeAreaEnabled = false,
+    this.insets = EdgeInsets.zero,
+  });
+
+  final AnchorDirection anchorDirection;
+  final bool safeAreaEnabled;
+  final EdgeInsets insets;
+  final Rect targetRect;
+
+  @override
+  bool shouldRelayout(OverlayPannel oldDelegate) {
+    return targetRect != oldDelegate.targetRect ||
+        insets != oldDelegate.insets ||
+        safeAreaEnabled != oldDelegate.safeAreaEnabled ||
+        anchorDirection != oldDelegate.anchorDirection;
+  }
+
+  @override
+  Offset getPositionForChild(Size size, Size childSize) {
+    var pannelRect = targetRect;
+    if (safeAreaEnabled) {
+      final safeArea = MediaQueryData.fromWindow(window).padding;
+      pannelRect = safeArea.deflateRect(pannelRect);
+    }
+
+    // TODO: junlin - calculate child position
+    return Offset.zero;
+  }
+
+  @override
+  BoxConstraints getConstraintsForChild(BoxConstraints constraints) {
+    return constraints.loosen();
+  }
+}