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Merge pull request #1220 from collinjackson/scaling_focus

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Ensure that the item under the focal point stays in the same place despite zooming
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Collin Jackson 2015-10-01 07:27:54 -07:00
commit b05d42c3b9
1 changed files with 6 additions and 3 deletions
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9
examples/widgets/scale.dart
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@ -35,13 +35,16 @@ class ScaleAppState extends State<ScaleApp> {
void _handleScaleUpdate(double scale, Point focalPoint) {
setState(() {
_zoom = _previousZoom * scale;
_offset = _previousOffset + (focalPoint - _startingFocalPoint) / _zoom;
_zoom = (_previousZoom * scale);
// Ensure that item under the focal point stays in the same place despite zooming
Offset normalizedOffset = (_startingFocalPoint.toOffset() - _previousOffset) / _previousZoom;
_offset = focalPoint.toOffset() - normalizedOffset * _zoom;
});
}
void paint(PaintingCanvas canvas, Size size) {
Point center = size.center(Point.origin) + _offset * _zoom;
Point center = (size.center(Point.origin).toOffset() * _zoom + _offset).toPoint();
double radius = size.width / 2.0 * _zoom;
Gradient gradient = new RadialGradient(
center: center, radius: radius,