feat: çift tıklama fill/fit toggle + ok tuşları ile gezinme

lib/widgets/image_canvas.dart

@@ -14,12 +14,30 @@ class ImageCanvas extends StatefulWidget {
 class _ImageCanvasState extends State<ImageCanvas> {
   late TransformationController _controller;
   double _currentScale = 1.0;
+  bool _isFilled = false; // false = fit, true = fill screen
+  Size? _imageSize;
+  Size? _viewportSize;
 
   @override
   void initState() {
     super.initState();
     _controller = TransformationController();
     _controller.addListener(_onTransformChanged);
+    _loadImageSize();
+  }
+
+  void _loadImageSize() {
+    final image = Image.file(File(widget.filePath));
+    image.image.resolve(const ImageConfiguration()).addListener(
+      ImageStreamListener((info, _) {
+        setState(() {
+          _imageSize = Size(
+            info.image.width.toDouble(),
+            info.image.height.toDouble(),
+          );
+        });
+      }),
+    );
   }
 
   @override
@@ -27,22 +45,58 @@ class _ImageCanvasState extends State<ImageCanvas> {
     super.didUpdateWidget(oldWidget);
     if (oldWidget.filePath != widget.filePath) {
       _resetView();
+      _loadImageSize();
     }
   }
 
   void _resetView() {
     _controller.value = Matrix4.identity();
     _currentScale = 1.0;
+    _isFilled = false;
   }
 
   void _onTransformChanged() {
     _currentScale = _controller.value.getMaxScaleOnAxis();
   }
 
+  void _toggleFillFit() {
+    if (_imageSize == null || _viewportSize == null) return;
+
+    if (_isFilled) {
+      // Go to fit mode — reset transform
+      _controller.value = Matrix4.identity();
+      _currentScale = 1.0;
+      _isFilled = false;
+    } else {
+      // Go to fill mode — scale to cover viewport
+      final scaleX = _viewportSize!.width / _imageSize!.width;
+      final scaleY = _viewportSize!.height / _imageSize!.height;
+      final fillScale = scaleX > scaleY ? scaleX : scaleY;
+
+      // Center the image
+      final offsetX = (_viewportSize!.width - _imageSize!.width * fillScale) / 2;
+      final offsetY = (_viewportSize!.height - _imageSize!.height * fillScale) / 2;
+
+      _controller.value = Matrix4.identity()
+        // ignore: deprecated_member_use
+        ..translate(offsetX, offsetY)
+        // ignore: deprecated_member_use
+        ..scale(fillScale);
+      _currentScale = fillScale;
+      _isFilled = true;
+    }
+  }
+
+  void _handleDoubleTap() {
+    _toggleFillFit();
+  }
+
   void _handleScroll(PointerScrollEvent event) {
     final renderBox = context.findRenderObject() as RenderBox?;
     if (renderBox == null) return;
 
+    _viewportSize = renderBox.size;
+
     final localPosition = renderBox.globalToLocal(event.position);
 
     final delta = event.scrollDelta.dy;
@@ -53,8 +107,6 @@ class _ImageCanvasState extends State<ImageCanvas> {
 
     final actualScale = newScale / _currentScale;
 
-    // Decompose current matrix: widget_point = scale * child_point + translation
-    // So: child_point = (widget_point - translation) / scale
     final matrix = _controller.value;
     final tx = matrix.getTranslation().x;
     final ty = matrix.getTranslation().y;
@@ -62,7 +114,6 @@ class _ImageCanvasState extends State<ImageCanvas> {
     final childX = (localPosition.dx - tx) / _currentScale;
     final childY = (localPosition.dy - ty) / _currentScale;
 
-    // Build new matrix: zoom around child_point, then re-apply
     final newMatrix = Matrix4.identity()
       // ignore: deprecated_member_use
       ..translate(childX, childY)
@@ -84,12 +135,17 @@ class _ImageCanvasState extends State<ImageCanvas> {
 
   @override
   Widget build(BuildContext context) {
+    return LayoutBuilder(
+      builder: (context, constraints) {
+        _viewportSize = Size(constraints.maxWidth, constraints.maxHeight);
         return Listener(
           onPointerSignal: (event) {
             if (event is PointerScrollEvent) {
               _handleScroll(event);
             }
           },
+          child: GestureDetector(
+            onDoubleTap: _handleDoubleTap,
             child: InteractiveViewer(
               transformationController: _controller,
               boundaryMargin: const EdgeInsets.all(double.infinity),
@@ -120,6 +176,9 @@ class _ImageCanvasState extends State<ImageCanvas> {
                 ),
               ),
             ),
+          ),
+        );
+      },
     );
   }
 }