Revs fdb0e9c and 2b2fffea complete work on the essentials of the demo.py
plugin. The highlights:
1. scripts.leo now contains a copy of the test script I used during
development:
@button test-demo @key=Ctrl-9
Today's major innovation is that the script uses the Ctrl-9 key binding to
*start
and continue *the demo. This is the *only* key binding appropriated by the
demo! Not having to switch keys eliminates a big annoyance.
This script is really a template for all demos. As I write this, I see that
Leo should have a demo;; abbreviation that creates this template
automatically. Coming next.
The @button node creates a custom MyDemo class that overrides the
do-nothing Demo.setup_script method so that it calls demo.delete_widgets.
This shows the power of subclassing the Demo class.
2. After several false starts, the *graphics classes* (Callout, Label, and
Title) in demo.py now can use all helpers in the Demo class *without* using
mixin class. This involved moving set_position and its helpers out of the
Label class and back into the Demo class.
The inheritance of graphics classes is now *clean*. That is, the Callout
and Title classes derive *only* from the base Label class. This is *extremely
important*. Using a mixin class prevented easy subclassing.
Now, all graphics classes can be QtWidget's, of whatever kind. For example,
Callout instances *are* QLabels because Callout is a subclass of Label,
which is a QLabel. pyzo shows that having many base classes can work, but
demo.py's present scheme is the simplest thing that could possibly work.
*Summary*
The overall framework for demo.py is now stable.
A new demo;; abbreviation will create a template for top-level demo scripts.
Your own demo scripts can easily define new graphics classes, using the
Label, Callout and Title classes as a model.
I plan to add Image, Arrow, RedArrow and BlueArrow graphics classes soon.
These will provide further examples of how to create your own graphics
classes.
Do *not* use image-related methods of the Demo class. They will go away
when the Image class is in place.
All questions and comments welcome.
Edward
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