Quick search

Scatter

_images/scatter.gif

Scatter is used to build interactive widgets that can be translated, rotated and scaled with two or more fingers on a multitouch system.

Scatter has its own matrix transformation: the modelview matrix is changed before the children are drawn and the previous matrix is restored when the drawing is finished. That makes it possible to perform rotation, scaling and translation over the entire children tree without changing any widget properties. That specific behavior makes the scatter unique, but there are some advantages / constraints that you should consider:

  1. The children are positioned relative to the scatter similarly to a RelativeLayout. So when dragging the scatter, the position of the children don’t change, only the position of the scatter does.
  2. The scatter size has no impact on the size of it’s children.
  3. If you want to resize the scatter, use scale, not size (read #2). Scale transforms both the scatter and its children, but does not change size.
  4. The scatter is not a layout. You must manage the size of the children yourself.

For touch events, the scatter converts from the parent matrix to the scatter matrix automatically in on_touch_down/move/up events. If you are doing things manually, you will need to use to_parent() and to_local().

Usage

By default, the Scatter does not have a graphical representation: it is a container only. The idea is to combine the Scatter with another widget, for example an Image:

scatter = Scatter()
image = Image(source='sun.jpg')
scatter.add_widget(image)

Control Interactions

By default, all interactions are enabled. You can selectively disable them using the do_rotation, do_translation and do_scale properties.

Disable rotation:

scatter = Scatter(do_rotation=False)

Allow only translation:

scatter = Scatter(do_rotation=False, do_scale=False)

Allow only translation on x axis:

scatter = Scatter(do_rotation=False, do_scale=False,
                  do_translation_y=False)

Automatic Bring to Front

If the Scatter.auto_bring_to_front property is True, the scatter widget will be removed and re-added to the parent when it is touched (brought to front, above all other widgets in the parent). This is useful when you are manipulating several scatter widgets and don’t want the active one to be partially hidden.

Scale Limitation

We are using a 32-bit matrix in double representation. That means we have a limit for scaling. You cannot do infinite scaling down/up with our implementation. Generally, you don’t hit the minimum scale (because you don’t see it on the screen), but the maximum scale is 9.99506983235e+19 (2^66).

You can also limit the minimum and maximum scale allowed:

scatter = Scatter(scale_min=.5, scale_max=3.)

Behavior

Changed in version 1.1.0: If no control interactions are enabled, then the touch handler will never return True.

class kivy.uix.scatter.Scatter(**kwargs)[source]

Bases: kivy.uix.widget.Widget

Scatter class. See module documentation for more information.

Events:
on_transform_with_touch:

Fired when the scatter has been transformed by user touch or multitouch, such as panning or zooming.

on_bring_to_front:

Fired when the scatter is brought to the front.

Changed in version 1.9.0: Event on_bring_to_front added.

Changed in version 1.8.0: Event on_transform_with_touch added.

apply_transform(trans, post_multiply=False, anchor=(0, 0))[source]

Transforms the scatter by applying the “trans” transformation matrix (on top of its current transformation state). The resultant matrix can be found in the transform property.

Parameters:
trans: Matrix.

Transformation matix to be applied to the scatter widget.

anchor: tuple, defaults to (0, 0).

The point to use as the origin of the transformation (uses local widget space).

post_multiply: bool, defaults to False.

If True, the transform matrix is post multiplied (as if applied before the current transform).

Usage example:

from kivy.graphics.transformation import Matrix
mat = Matrix().scale(3, 3, 3)
scatter_instance.apply_transform(mat)
auto_bring_to_front

If True, the widget will be automatically pushed on the top of parent widget list for drawing.

auto_bring_to_front is a BooleanProperty and defaults to True.

bbox

Bounding box of the widget in parent space:

((x, y), (w, h))
# x, y = lower left corner

bbox is an AliasProperty.

do_collide_after_children

If True, the collision detection for limiting the touch inside the scatter will be done after dispaching the touch to the children. You can put children outside the bounding box of the scatter and still be able to touch them.

New in version 1.3.0.

do_rotation

Allow rotation.

do_rotation is a BooleanProperty and defaults to True.

do_scale

Allow scaling.

do_scale is a BooleanProperty and defaults to True.

do_translation

Allow translation on the X or Y axis.

do_translation is an AliasProperty of (do_translation_x + do_translation_y)

do_translation_x

Allow translation on the X axis.

do_translation_x is a BooleanProperty and defaults to True.

do_translation_y

Allow translation on Y axis.

do_translation_y is a BooleanProperty and defaults to True.

on_bring_to_front(touch)[source]

Called when a touch event causes the scatter to be brought to the front of the parent (only if auto_bring_to_front is True)

Parameters:
touch:

The touch object which brought the scatter to front.

New in version 1.9.0.

on_transform_with_touch(touch)[source]

Called when a touch event has transformed the scatter widget. By default this does nothing, but can be overriden by derived classes that need to react to transformations caused by user input.

Parameters:
touch:

The touch object which triggered the transformation.

New in version 1.8.0.

rotation

Rotation value of the scatter.

rotation is an AliasProperty and defaults to 0.0.

scale

Scale value of the scatter.

scale is an AliasProperty and defaults to 1.0.

scale_max

Maximum scaling factor allowed.

scale_max is a NumericProperty and defaults to 1e20.

scale_min

Minimum scaling factor allowed.

scale_min is a NumericProperty and defaults to 0.01.

transform

Transformation matrix.

transform is an ObjectProperty and defaults to the identity matrix.

Note

This matrix reflects the current state of the transformation matrix but setting it directly will erase previously applied transformations. To apply a transformation considering context, please use the apply_transform method.

transform_inv

Inverse of the transformation matrix.

transform_inv is an ObjectProperty and defaults to the identity matrix.

translation_touches

Determine whether translation was triggered by a single or multiple touches. This only has effect when do_translation = True.

translation_touches is a NumericProperty and defaults to 1.

New in version 1.7.0.

class kivy.uix.scatter.ScatterPlane(**kwargs)[source]

Bases: kivy.uix.scatter.Scatter

This is essentially an unbounded Scatter widget. It’s a convenience class to make it easier to handle infinite planes.