43 lines
1.9 KiB
Python
43 lines
1.9 KiB
Python
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"""Schema 7: an anchor is a peg.
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`[:xform :anchor]` is gone from the transform. `T(a)·M·T(-a)` is a transform
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conjugated by a translation — "do M in a frame shifted by a" — and a parent
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already is a shifted frame, so an anchor was a peg written inline: one that could
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not be selected, keyed, shared between nodes, or placed above a measured channel.
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A pivot nobody chose is now derived from what the node draws, per drag, and stored
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nowhere; a pivot to keep is a peg, an ordinary `:group` parent.
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Nothing is converted, as in schema 6. Every project is marked 7, and one that
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still carries an anchor is refused when it is opened, by name and with what to do
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about it — `node/problems` in the frontend.
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Not converted rather than not worth converting. Dropping an anchor is in fact
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pixel-exact wherever rotation and scale are the identity, since the anchor
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cancels out of the composition there — and that is everywhere a freeze, a drop or
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a new drawing wrote one. It is NOT exact on anything a hand has since turned or
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scaled, where the composed translation is `a + p - M·a`, and it cannot be made
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exact at all where `pos` is dense, because tier 2 is content-addressed and not
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rewritable here. A conversion would therefore be silent and right for most nodes
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and silent and wrong for exactly the ones somebody had hand-placed, which is the
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worse failure: a refusal names the document and says what to do.
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"""
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from django.db import migrations, models
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def forwards(apps, schema_editor):
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apps.get_model("clips", "Project").objects.update(schema_version=7)
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class Migration(migrations.Migration):
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dependencies = [("clips", "0015_tracing_images")]
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operations = [
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migrations.AlterField(
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model_name="project",
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name="schema_version",
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field=models.PositiveIntegerField(default=7),
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),
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migrations.RunPython(forwards, migrations.RunPython.noop),
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]
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