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SVG · 24 Visible Regions and Level of Detail

Series contents · Technology map

Stage: Export and Large-Scale Comparisons · Editable example · Storage ID: svg-step-24

Goals and learning outcomes

Prerequisites

Prerequisite concepts: DOM size, Measurement interval. Prepare the result files and observation records from Unit 23.

Key concepts and explanations

Visible region

Omitting invisible nodes can reduce the work set. A policy is needed to avoid losing semantic information about selected nodes too.

Level of detail

You can reduce labels or decoration according to zoom level. Reducing presentation differs from deleting the data itself.

Practice setup

First check the execution scope guidance on the example screen. The following describes preparation for extending the assignment in a separate project. Implement this yourself in an HTML and ES module project on a separate local HTTP development server. Record the browser version, viewport, and DPR.

The linked example is a starting point. It does not implement every task below. Complete work beyond its supported scope in a separate project.

Practice tasks

  1. Prepare day-24.js and index.html in an external practice project. Calculate visible nodes from the current viewBox and node bounds.
  2. Hide labels when zoomed out, but keep the HTML list and selection description.
  3. Save the output under the input condition 1, then run again with 0.2. Compare the hypothesis, "Reducing labels may ease overlap and reduce DOM work," against the display and logs, and record the actual result and the causes of any differences in day-24-notes.md.

Variables to observe

VariableBaselineChangeExpected change / hypothesis
Scale10.2Reducing labels may ease overlap and reduce DOM work

Predictions in this table are not measured results. Change one condition at a time and record why the actual result differs.

Completion criteria

Self-check

  1. What should happen if an off-screen node has keyboard focus?
  2. How do you determine bounds for shapes with filters or thick strokes?

Official references

Linked example and execution scope

Example source · Runtime environments and limits

An editable browser experiment. Measurements vary with the current device and browser.

Source code and records are not overwritten automatically. Resetting an existing example also preserves your notes.

Next learning

Previous: Large Datasets and Update Cost · Next: Canvas Comparison Renderer

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