Abstraction methods of PdfViewerController.goTo

[xaqtr]

Hi,

first of all thanks for this library @espresso3389, it's really saving us for a work related project right now due to its flexiblity and features.

As I was trying to integrate this plugin into my App, I was kind of lost on how to programmatically scale into the PDF with the PdfViewerController (I wanted to implement a double tap zoom in /out functionality).

I digged into the plugin code and realized that you have the control about everything by using the PdfViewerController.goTo method. and passing a suited Matrix4 value. So my question is whether it would be possible to have methods that abstract the usage of this Matrix4. I think this would benefit many developers as in my opinion it requires some additional knowledge hurdle.

So my proposal would be some additional methods for PdfViewerController, e.g.:

// In this case, scale would be the destination scale 
// (so calling this method more than once with the same parameter will not change the scaling / position)
Future<void> scaleTo({ required double scale, Duration duration })

// Pan to a relative point of the specified page
// x and y would be relative values of the page, where the destination origin will be
// e.g.: pageNumber = 1, x = 0.5, y = 0.5 will put the origin into the center of the first page
Future<void> panTo({ required int pageNumber, required double x, required double y, Duration duration })

I dont' have the best understand about the usage of Matrix4 yet, so I'm not sure whether it's even possible to have such methods, but I would like to hear some opinions on that.
In the meantime I will try to implement the above mentioned methods.

[espresso3389]

I see your point. They seems very convenient when implementing typical PDF viewer.
OK, I'll implement them.

[espresso3389]

daa6d7d implements panTo method:

/// Pan to the specified page point.
///
/// [x],[y] should be in [0 1] range and they indicate relative position in the page:
/// - 0 for top/left
/// - 1 for bottom/right
/// - 0.5 for center (the default)
///
/// [anchor] specifies which view corner, edge, or center the point specified by ([x],[y]) is anchored to.
///
/// [zoomRatio] specifies the zoom ratio. The default is to use the zoom ratio that fit the page into the view.
/// If you want to keep the current zoom ratio, use [PdfViewerController.zoomRatio] for the value.
///
/// If the page does not exist in the layout, it returns null.
/// If the controller is not ready([isReady]), the method throws an exception.
Future<void> panTo({
  required int pageNumber,
  double? padding,
  double x = 0.5,
  double y = 0.5,
  PdfViewerAnchor anchor = PdfViewerAnchor.center,
  double? zoomRatio,
  Duration duration = const Duration(milliseconds: 500),
)

[espresso3389]

• scale is renamed to zoomRatio in correspondence to the existing zoomRatio property.
• anchor is where the point of (x,y) is anchored to. Based on your original use case, it's default is set to center. But you can of course change it to one of topLeft, top, topRight, left, center, right, bottomLeft, bottom, bottomRight.

[espresso3389]

9b57f1e:

• panTo is renamed to goToPointInPage
• setZoomRatio is introduced

final controller = PdfViewerController();
TapDownDetails? doubleTapDetails;

...

GestureDetector(
  // Supporting double-tap gesture on the viewer.
  onDoubleTapDown: (details) => doubleTapDetails = details,
  onDoubleTap: () => controller.ready?.setZoomRatio(
    zoomRatio: controller.zoomRatio * 1.5,
    center: doubleTapDetails!.localPosition,
  ),
  child: PdfViewer.openAsset(
    'assets/hello.pdf',
    viewerController: controller,
    ...

[espresso3389]

1.0.22 that contains the changes is released!

[espresso3389]

Because of the consistency/compatibility to the existing codes/interfaces, the naming is changed from your first suggestion, I think the designs of the new methods covers what you want to do.

Anyway, please test them and feel free to suggest/comment anything here!

[xaqtr]

Thanks a lot! I actually will start integrating both new methods in the upcoming week for a production app and will let you know, if I see something odd.