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GeezerVison is showing github.com — Creating a smaller buffer for `PolygonSelector` when selection changes significantly? · Issue #955 · fastplotlib/fastplotlib

Creating a smaller buffer for PolygonSelector when selection changes significantly? #955

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#958
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Creating a smaller buffer for PolygonSelector when selection changes significantly?#955
#958
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@kushalkolar
kushalkolar
opened on Dec 1, 2025
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I was taking a look at how the new mesh positions and indices buffers are set in the polygon selector, a new buffer is allocated if a larger one is required for the new selection. But if the selection is smaller, than a new buffer is not allocated. @almarklein just curious about the reason so I can understand it better. I'm working on the PolygonGraphic.

fastplotlib/fastplotlib/graphics/features/_selection_features.py

Lines 419 to 435 in 7b4c687

# Need larger buffer?
if len(value) > geometry.positions.nitems:
arr = np.zeros((geometry.positions.nitems * 2, 3), np.float32)
geometry.positions = gfx.Buffer(arr)
if len(indices) > geometry.indices.nitems:
arr = np.zeros((geometry.indices.nitems * 2, 3), np.int32)
geometry.indices = gfx.Buffer(arr)
geometry.positions.data[: len(value)] = value
geometry.positions.data[len(value) :] = value[-1] if len(value) else (0, 0, 0)
geometry.positions.draw_range = 0, len(value)
geometry.positions.update_full()
geometry.indices.data[: len(indices)] = indices
geometry.indices.data[len(indices) :] = 0
geometry.indices.draw_range = 0, len(indices)
geometry.indices.update_full()

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  1. almarklein commented on Dec 1, 2025

    @almarklein
    almarklein
    on Dec 1, 2025
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    Mmm, that code could indeed be improved. It also fails if the new value is more than twice as large as previous.
    I can make a pr to improve this, so we can use that in the polygongraphic too.

  2. kushalkolar
    closed this as completedin #958on Dec 4, 2025
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