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Custom views

Instruction on how to use custom views.

views.py file

Firstly a views.py file must be created - it can be based or copied from example.py file. It must contain a list VIEWS containing View class objects only. examplary_usages.py file shows examplary usages of examplary_views classes.

View class

Every custom view must be a child of a View class. Also a method _epd_change must be defined with first_call argument - this methods interacts with EPD. This parameter might be useful to determine if a current view was displayed during current interval. If the image should be rotated by desired angle (coming either from config or argument), a self._rotate_image should be called before running eg. epd.display method.

Arguments passed to a constructor

In addition each view instance must be initiated with a name and interval. Optional third parameter is an angle.

Parameter Purpose Value type
name View name string
interval Interval by which a method show will be called in a loop. To disable this feature set it to 0 integer
view_angle [Optional] Angle by which a final view will be rotated. By default it uses view_angle from config. Rotating is triggered via _rotate_image() method of View integer

View fallback

In addition a fallback can be displayed if a _epd_change method will fail with an exception. To achieve this:

  • _epd_change method bust be decorated with @view_fallback decorator (imported from helpers.py) and
  • _fallback method which displays fallback view must be defined.

Conditional showing

By default if a view has interval it triggers EPD change within each loop - even when the data itself didn't changed and this operation is redundant. As an example - a basic clock view (HH:MM) which should check for current time in each second (interval = 1) but update only once per minute. To achieve this a method _conditional must be overrided and return boolean value based on desired condition.

Examplary usage of custom Views

Basing on example.py and using a few defined views from examplary_views a VIEWS list might look like:

VIEWS = [
    DummyView(name='Dummy view 1', interval=0),
    DummyView(name='Dummy view 2', interval=6, view_angle=180),
    BrokenDummyView(name='Dummy view 3', interval=0),
    ConditionalDummyView(name='Dummy view 4', interval=4),
    ClockView(name='Clock', interval=1)
]

and:

  • views 1 and 3 have no interval (0)
  • views 2 and 4 have interval (in seconds) by which a _epd_change method will be called unless a switching view action gets called.
  • view 2 is rotated by 180 degrees
  • view 3 will show a fallback image since its _epd_change method raises an exception (but is decorated with a @view_fallback)
  • view 4 will trigger EPD change conditionally (since _conditional method is overrided)
  • view 5 will display Clock View, which has a fallback and triggers EPD change conditionally within time interval

Custom requirements

If a View uses any additional Python packages they should be added to a controller/custom_views/custom_requirements.txt file. If this file doesn't exist it must be created first.

Examplary Views

There's a set of predefined View-based classes ready to use - go to Examplary Views.