locked x axis if zoomed out

white page background
dont allow drawing out of page

lib/canvas/drawing_page.dart

@@ -1,9 +1,7 @@
-import 'dart:math';
 import 'dart:ui';
-
-import 'package:equations/equations.dart';
 import 'package:flutter/material.dart';
 import 'package:notes/canvas/my_painter.dart';
+import 'package:notes/canvas/screen_document_mapping.dart';
 
 import 'document_types.dart';
 
@@ -18,8 +16,9 @@ class _DrawingPageState extends State<DrawingPage> {
   List<Stroke> _strokes = [];
   bool allowDrawWithFinger = false;
 
-  double zoom = .5;
+  double zoom = .75;
-  Offset scrollPos = const Offset(.0, .0);
+  double basezoom = 1.0;
+  Offset offset = const Offset(.0, .0);
 
   @override
   Widget build(BuildContext context) {
@@ -37,57 +36,102 @@ class _DrawingPageState extends State<DrawingPage> {
     return basetickness;
 
     // todo do correct linear interpolation and extimate angle
-    final lininterpol = PolynomialInterpolation(
+    // final lininterpol = PolynomialInterpolation(
-        nodes: pts
+    //     nodes: pts
-            .map((e) => InterpolationNode(x: e.point.dx, y: e.point.dy))
+    //         .map((e) => InterpolationNode(x: e.point.dx, y: e.point.dy))
-            .toList(growable: false));
+    //         .toList(growable: false));
-    lininterpol.compute(1.0);
+    // lininterpol.compute(1.0);
-    print(lininterpol.buildPolynomial().toString());
+    // print(lininterpol.buildPolynomial().toString());
-
+    //
-    // double angle = atan((pt2.dy - pt1.dy)/(pt2.dx - pt1.dx));
+    // // double angle = atan((pt2.dy - pt1.dy)/(pt2.dx - pt1.dx));
-
+    //
-    final angle = 5 / (2 * pi);
+    // final angle = 5 / (2 * pi);
-    // print("pt1: ${pt1}, pt2: ${pt2}, angle: ${angle}");
+    // // print("pt1: ${pt1}, pt2: ${pt2}, angle: ${angle}");
-
+    //
-    return basetickness * (angle / .5 + .5);
+    // return basetickness * (angle / .5 + .5);
   }
 
   Widget _buildCanvas() {
     final width = MediaQuery.of(context).size.width;
-
+    final height = MediaQuery.of(context).size.height;
-    final zoomedwidth = width * zoom;
 
     return Scaffold(
       body: Listener(
+        behavior: HitTestBehavior.opaque,
         onPointerMove: (event) {
-          // print(event.tilt);
+          Offset pos = event.localPosition;
-          final pos = event.localPosition;
+          final scale =
-          final pts = _strokes.last.points;
+              calcPageDependentScale(zoom, a4Page, Size(width, height));
+          pos = translateScreenToDocumentPoint(pos, scale, offset);
 
-          if(pts.last.point == pos) return;
+          if (!a4Page.contains(pos)) {
+            return;
+          }
 
           if (allowDrawWithFinger || event.kind != PointerDeviceKind.touch) {
+            final pts = _strokes.last.points;
+
+            if (pts.last.point == pos) return;
+
             double newWidth = _calcTiltedWidth(3.0, event.tilt);
 
-            if(_strokes.last.points.length > 1){
+            if (_strokes.last.points.length > 1) {
               // todo current point not in list
-              newWidth = _calcAngleDependentWidth(pts.getRange(pts.length - 10 >= 0 ? pts.length -10 : 0, pts.length).toList(growable: false), event.tilt);
+              newWidth = _calcAngleDependentWidth(
+                  pts
+                      .getRange(pts.length - 10 >= 0 ? pts.length - 10 : 0,
+                          pts.length)
+                      .toList(growable: false),
+                  event.tilt);
             }
             setState(() {
               _strokes = List.from(_strokes, growable: false)
                 ..last.points.add(Point(pos, newWidth));
             });
+          } else {
+            if (zoom > 1.0) {
+              Offset newOffset = offset + event.delta;
+              // don't allow navigating out of page if zoomed in
+              if (newOffset.dx > .0) {
+                setState(() {
+                  offset = Offset(.0, newOffset.dy);
+                });
+              } else if (newOffset.dx < (-width * zoom) + width) {
+                setState(() {
+                  offset = Offset((-width * zoom) + width, newOffset.dy);
+                });
+                print(offset);
+              } else {
+                setState(() {
+                  offset = offset + event.delta;
+                });
+              }
+            } else {
+              setState(() {
+                // keep page x centered if zoomed out
+                offset = Offset(
+                    (width - (width * zoom)) / 2, offset.dy + event.delta.dy);
+              });
+            }
           }
         },
         onPointerDown: (event) {
           if (allowDrawWithFinger || event.kind != PointerDeviceKind.touch) {
+            Offset pos = event.localPosition;
+            final scale =
+                calcPageDependentScale(zoom, a4Page, Size(width, height));
+            pos = translateScreenToDocumentPoint(pos, scale, offset);
+
+            // todo line drawn on edge where line left page
+            if (!a4Page.contains(pos)) return;
+
             setState(() {
               _strokes = List.from(_strokes)
-                ..add(Stroke.fromPoints([Point(event.localPosition, _calcTiltedWidth(3.0, event.tilt))]));
+                ..add(Stroke.fromPoints(
+                    [Point(pos, _calcTiltedWidth(3.0, event.tilt))]));
             });
           }
         },
-
         onPointerUp: (event) {
           if (allowDrawWithFinger || event.kind != PointerDeviceKind.touch) {
             if (_strokes.last.points.length <= 1) {
@@ -106,15 +150,21 @@ class _DrawingPageState extends State<DrawingPage> {
           }
         },
         child: GestureDetector(
-        onScaleUpdate: (details) {
+          onScaleUpdate: (details) {
-          setState(() {
+            if (details.scale == 1.0) return;
-            zoom = details.scale;
+
-          });
+            print('scale; ${details.scale}');
-        },
+            setState(() {
-        child: CustomPaint(
+              zoom = (basezoom * details.scale).clamp(0.25, 5.0);
-          painter: MyPainter(strokes: _strokes,offset: scrollPos, zoom: zoom),
+            });
-          // todo not working
+          },
-          size: Size.infinite, // todo add different paper dimensions
+          onScaleEnd: (details) {
+            basezoom = zoom;
+          },
+          child: CustomPaint(
+            painter: MyPainter(strokes: _strokes, offset: offset, zoom: zoom),
+            // todo not working
+            size: Size.infinite, // todo add different paper dimensions
           ),
         ),
       ),

lib/canvas/my_painter.dart

@@ -1,7 +1,13 @@
+import 'dart:math';
+
 import 'package:flutter/material.dart';
+import 'package:notes/canvas/screen_document_mapping.dart';
 
 import 'document_types.dart';
 
+final Rect a4Page =
+    Rect.fromPoints(const Offset(.0, .0), const Offset(210, 210 * sqrt2));
+
 class MyPainter extends CustomPainter {
   List<Stroke> strokes;
   double zoom;
@@ -9,40 +15,43 @@ class MyPainter extends CustomPainter {
 
   MyPainter({required this.strokes, required this.zoom, required this.offset});
 
+  Offset _translatept(Offset pt, Size canvasSize) {
+    final scale = calcPageDependentScale(zoom, a4Page, canvasSize);
+    return translateDocumentToScreenPoint(pt, scale, offset);
+  }
+
+  Paint backgroundPaint = Paint()..color = Colors.white;
+
   @override
   void paint(Canvas canvas, Size size) {
     var paint = Paint()
       ..color = Colors.blue
       ..strokeCap = StrokeCap.square;
 
+    canvas.drawColor(const Color(0xff3f3f3f), BlendMode.src);
+    canvas.drawRect(
+        Rect.fromPoints(_translatept(const Offset(0, .0), size),
+            _translatept(a4Page.bottomRight, size)),
+        backgroundPaint);
 
-
+    for (final stroke in strokes) {
-      // ..strokeWidth = 3.0;
+      for (int i = 0; i < stroke.points.length - 1; i++) {
-    // canvas.scale(zoom);
+        Offset pt1 = stroke.points[i].point;
-    print("zoom: ${zoom}");
+        pt1 = _translatept(pt1, size);
-    canvas.drawColor(Color.fromRGBO(255, 255, 255, .1), BlendMode.src);
+        Offset pt2 = stroke.points[i + 1].point;
-
+        pt2 = _translatept(pt2, size);
-    final pagewidth = size.width * zoom;
-
-    final sidewidth = (size.width - pagewidth) / 2;
-    canvas.drawLine(Offset(sidewidth, .0), Offset(sidewidth, size.height), paint);
-    canvas.drawLine(Offset(sidewidth + pagewidth, .0), Offset(sidewidth + pagewidth, size.height), paint);
-
-    for(final stroke in strokes){
-      for(int i = 0; i < stroke.points.length -1; i++){
-        final pt1 = stroke.points[i].point;
-        final pt2 = stroke.points[i+1].point;
 
         // final strokewidth = _calcAngleDependentWidth(pt1, pt2, stroke.points[i].thickness);
-        canvas.drawLine(pt1, pt2, paint..strokeWidth = stroke.points[i].thickness);
+        canvas.drawLine(
+            pt1, pt2, paint..strokeWidth = stroke.points[i].thickness);
       }
     }
-
-
   }
 
   @override
   bool shouldRepaint(MyPainter oldDelegate) {
-    return oldDelegate.strokes != strokes;
+    return oldDelegate.strokes != strokes ||
+        oldDelegate.zoom != zoom ||
+        oldDelegate.offset != offset;
   }
 }

lib/canvas/screen_document_mapping.dart

@@ -0,0 +1,13 @@
+import 'package:flutter/material.dart';
+
+Offset translateScreenToDocumentPoint(Offset pt, double scale, Offset offset) {
+  return pt.translate(-offset.dx, -offset.dy).scale(1 / scale, 1 / scale);
+}
+
+Offset translateDocumentToScreenPoint(Offset pt, double scale, Offset offset) {
+  return pt.scale(scale, scale).translate(offset.dx, offset.dy);
+}
+
+double calcPageDependentScale(double scale, Rect page, Size canvasSize) {
+  return scale * (canvasSize.width / page.width);
+}

lib/main.dart

@@ -1,5 +1,5 @@
 import 'package:flutter/material.dart';
-import 'package:notes/CollapseDrawer.dart';
+import 'package:notes/collapse_drawer.dart';
 import 'package:notes/all_notes_page.dart';
 import 'package:notes/canvas/drawing_page.dart';