feat: Add dragRegionBuilder to TabView for Borderless Window Dragging

[uiYzzi]

This PR introduces a new dragRegionBuilder property to the TabView component, allowing developers to easily implement window dragging functionality in borderless window applications.

Changes Made

Core Implementation:

• Added dragRegionBuilder property to TabView class in lib/src/controls/navigation/tab_view/tab_view.dart
• Modified build logic to wrap the entire tab strip with the drag region builder
• Maintained full backward compatibility with existing stripBuilder functionality
• Added comprehensive debug information for the new property

Documentation & Examples:

• Updated example app in example/lib/screens/navigation/tab_view.dart with practical usage demonstration
• Added dedicated showcase for borderless window dragging with window_manager integration
• Included clear usage patterns for developers

Testing:

• Added comprehensive test coverage in test/tab_view_test.dart
• Tests verify both dragRegionBuilder functionality and null handling
• All existing tests continue to pass

Related Issue

#1239

Usage Example

TabView(
  currentIndex: currentIndex,
  tabs: tabs,
  dragRegionBuilder: (context, child) {
    return GestureDetector(
      behavior: HitTestBehavior.translucent,
      onPanStart: (details) => windowManager.startDragging(),
      child: child,
    );
  },
)

Pre-launch Checklist

• I have updated CHANGELOG.md with my changes
• I have run "dart format ." on the project
• I have added/updated relevant documentation
• All tests pass successfully
• Example app demonstrates the new functionality

[Copilot]

Pull Request Overview

This PR adds a new dragRegionBuilder property to the TabView component to enable borderless window dragging functionality, allowing the entire tab strip area to serve as a drag region for window management.

• Added dragRegionBuilder property to TabView with appropriate documentation and debug information
• Modified the build logic to apply the drag region builder to the entire tab strip while maintaining compatibility with existing stripBuilder
• Updated example app to demonstrate the new functionality with DragToMoveArea integration

Reviewed Changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
lib/src/controls/navigation/tab_view/tab_view.dart	Core implementation adding dragRegionBuilder property and build logic
test/tab_view_test.dart	Added comprehensive tests for the new functionality and null handling
example/lib/screens/navigation/tab_view.dart	Updated example to showcase borderless window dragging with practical usage
example/macos/Runner/AppDelegate.swift	Updated macOS configuration for modern Swift conventions
example/macos/Runner.xcodeproj/project.pbxproj	Xcode project version updates
example/macos/Runner.xcodeproj/xcshareddata/xcschemes/Runner.xcscheme	Xcode scheme configuration updates

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[WinXaito]

LGTM to me (only look at the code, didn't try it).

However, I wonder how it looks when the tabbar is full of tabs ?

For example, Firefox keep a minimum width for us to grab the window:

I just tried on my app, but it is a modified version of TabView, so do not know of far I am from reality:

So I don't know if it is possible to set a BoxConstraint inside the dragBuilder or when a dragBuilder is passed we automatically defined a zone that will always be free to grab the window.

[aefmind]

TabView already includes the stripBuilder and reservedStripWidth properties to serve this purpose.

Example:

TabView(
    tabs: tabs,
    stripBuilder: (context, strip) => DragToMoveArea(child: strip),
    reservedStripWidth: 34,
    ...
);

[uiYzzi]

TabView already includes the stripBuilder and reservedStripWidth properties to serve this purpose.

Example:

TabView(
    tabs: tabs,
    stripBuilder: (context, strip) => DragToMoveArea(child: strip),
    reservedStripWidth: 34,
    ...
);

Using stripBuilder: (context, strip) => DragToMoveArea(child: strip), will it prevent the tabs in the tab bar from being dragged?