imajviewer/lib/widgets/image_canvas.dart

import 'dart:io';
import 'package:flutter/material.dart';
import 'package:flutter/gestures.dart';

class ImageCanvas extends StatefulWidget {
  final String filePath;
  const ImageCanvas({super.key, required this.filePath});
  @override
  State<ImageCanvas> createState() => _ImageCanvasState();
}

class _ImageCanvasState extends State<ImageCanvas> {
  bool _isFilled = true;
  final GlobalKey _imageKey = GlobalKey();
  double _tx = 0, _ty = 0, _sc = 1.0;
  Size _vpSize = Size.zero;

  void _clamp() {
    if (_vpSize.width <= 0 || _vpSize.height <= 0) return;
    if (_isFilled) {
      // Fill mode: viewport tabanli clamp
      final double w = _vpSize.width * _sc;
      final double h = _vpSize.height * _sc;
      if (w >= _vpSize.width) {
        if (_tx > 0) _tx = 0;
        else if (_tx + w < _vpSize.width) _tx = _vpSize.width - w;
      } else { if (_tx != 0) _tx = 0; }
      if (h >= _vpSize.height) {
        if (_ty > 0) _ty = 0;
        else if (_ty + h < _vpSize.height) _ty = _vpSize.height - h;
      } else { if (_ty != 0) _ty = 0; }
      return;
    }
    // Fit mode: resmin gercek boyutuna gore clamp (letterbox dahil)
    double m = 0, n = 0;
    double w = _vpSize.width * _sc;
    double h = _vpSize.height * _sc;
    final box = _imageKey.currentContext?.findRenderObject() as RenderBox?;
    if (box != null && box.hasSize && box.size.width > 0) {
      final Size img = box.size;
      m = (_vpSize.width - img.width) / 2;
      n = (_vpSize.height - img.height) / 2;
      w = img.width * _sc;
      h = img.height * _sc;
    }
    if (w >= _vpSize.width) {
      final double lo = -m * _sc;
      final double hi = _vpSize.width - m * _sc - w;
      if (lo <= hi) {
        if (_tx < lo) _tx = lo;
        if (_tx > hi) _tx = hi;
      } else {
        if (_tx < hi) _tx = hi;
        if (_tx > lo) _tx = lo;
      }
    } else {
      final double lo = -m * _sc;
      final double hi = _vpSize.width - m * _sc - w;
      if (_tx < lo) _tx = lo;
      if (_tx > hi) _tx = hi;
    }
    if (h >= _vpSize.height) {
      final double lo = -n * _sc;
      final double hi = _vpSize.height - n * _sc - h;
      if (lo <= hi) {
        if (_ty < lo) _ty = lo;
        if (_ty > hi) _ty = hi;
      } else {
        if (_ty < hi) _ty = hi;
        if (_ty > lo) _ty = lo;
      }
    } else {
      final double lo = -n * _sc;
      final double hi = _vpSize.height - n * _sc - h;
      if (_ty < lo) _ty = lo;
      if (_ty > hi) _ty = hi;
    }
  }

  @override
  void didUpdateWidget(ImageCanvas old) {
    super.didUpdateWidget(old);
    if (old.filePath != widget.filePath) _resetView();
  }
  void _resetView() {
    setState(() { _tx = 0; _ty = 0; _sc = 1.0; _isFilled = true; _vpSize = Size.zero; });
  }
  void _toggleFillFit() {
    setState(() { _isFilled = !_isFilled; _tx = 0; _ty = 0; _sc = 1.0; _vpSize = Size.zero; });
  }
  void _handleDoubleTap() => _toggleFillFit();

  void _handleScroll(PointerScrollEvent e) {
    if (_vpSize.width <= 0 || _vpSize.height <= 0) return;
    final double vx = e.localPosition.dx;
    final double vy = e.localPosition.dy;
    final double cx = (vx - _tx) / _sc;
    final double cy = (vy - _ty) / _sc;
    const double factor = 1.1;
    final double rawSc = _sc * (e.scrollDelta.dy < 0 ? factor : 1.0 / factor);
    final double newSc = rawSc.clamp(1.0, 10.0);
    _tx = _tx + cx * _sc - cx * newSc;
    _ty = _ty + cy * _sc - cy * newSc;
    _sc = newSc;
    _clamp();
    setState(() {});
  }

  void _onPanUpdate(DragUpdateDetails d) {
    _tx += d.delta.dx;
    _ty += d.delta.dy;
    _clamp();
    setState(() {});
  }

  Widget _buildImage() {
    return Image.file(
      key: _imageKey,
      File(widget.filePath),
      fit: _isFilled ? BoxFit.cover : BoxFit.contain,
      filterQuality: FilterQuality.high,
      errorBuilder: (_, _, _) => _errorWidget(),
    );
  }

  @override
  Widget build(BuildContext context) {
    return LayoutBuilder(
      builder: (context, constraints) {
        _vpSize = constraints.biggest;
        _clamp();
        return SizedBox.expand(
          child: Stack(
            children: [
              ClipRect(
                child: GestureDetector(
                  onDoubleTap: _handleDoubleTap,
                  onPanUpdate: _onPanUpdate,
                  child: Listener(
                    onPointerSignal: (event) {
                      if (event is PointerScrollEvent) _handleScroll(event);
                    },
                    child: Transform(
                      alignment: Alignment.topLeft,
                      transform: Matrix4.identity()
                        ..translate(_tx, _ty)
                        ..scale(_sc),
                      child: _isFilled
                          ? SizedBox.expand(child: _buildImage())
                          : Center(child: _buildImage()),
                    ),
                  ),
                ),
              ),
            ],
          ),
        );
      },
    );
  }

  Widget _errorWidget() {
    return const Center(
      child: Column(
        mainAxisSize: MainAxisSize.min,
        children: [
          Icon(Icons.broken_image, size: 48, color: Colors.white38),
          SizedBox(height: 8),
          Text('Resim yüklenemedi', style: TextStyle(color: Colors.white38)),
        ],
      ),
    );
  }
}