Reuse style element for theme injection into custom components #7914
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vdonato
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Jan 9, 2024
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Thanks for the contribution @Tom-Julux!
While this change doesn't change any functionality as seen by the user, I think we'll still want to add a test that verifies that the style tag only gets appended once for completeness.
This can likely be done most easily by modifying this test to send a second streamlit:render event at the current end of the test, then verifying that no additional style tag was appended.
Once that test is added, this change should be good to go.
zyxue
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Apr 16, 2024
…mlit#7914) * Reuse style element for theme injection into custom components * Test for reuse of style element for theme injection into custom components * Run precommit --------- Co-authored-by: Vincent Donato <vincent@streamlit.io>
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Describe your changes
In the current implementation, whenever a custom component receives a render event, the theme (which may have changed) is injected as a new style element, and this element is appended to the head of the iframe document.
This pull request introduces a modification to this behaviour. Instead of creating a new style element for each render event, a single style element is now created and reused for subsequent style updates.
The updated approach offers several advantages, primarily preventing the linear growth of the iframe document size with the increasing number of render events. This optimization enhances the efficiency and performance of the custom components, in particular for long lived custom components that receive a large number of or frequent render events.
Testing Plan
Since the injected css is constant in terms of its attributes and selectors, the current behaviour of appending new style elements is equal to the overwriting introduced in this PR. Thus no testing is required
Contribution License Agreement
By submitting this pull request I agree that all contributions to this project are made under the Apache 2.0 license.