Add support for rendering line pattern fills line-by-line (Request in QGIS)

[qgis-bot]

Request for documentation

From pull request QGIS/qgis#45654 Author: @nyalldawson QGIS version: 3.24

Add support for rendering line pattern fills line-by-line

PR Description:

When exporting to a vector format (e.g. PDF) or when a line subsymbol has dynamic (data defined properties), automatically switch to a line-by-line based approach for rendering the fill instead of the previous raster tiled pattern based approach.

While it's slower to render (not noticable for desktop users, but likely enough to affect server deployments), this has many benefits:

1. Smaller PDF/SVG output file sizes, since the fills aren't rasterized
2. PDF/SVG files which are easier to modify in external apps for post production, as each individual line in the pattern can be modified.
3. Better quality PDF/SVG outputs, since the fill isn't DPI dependant and looks awesome regardless of how close in you zoom
4. No visible artefacts at certain angles/distances/line symbol styles

And even more excitingly, it opens the door for a range of new symbol styles, eg.

• line patterns where the individual lines change color/width/dash/...
• line patterns with marker line symbols on center point/etc
• geometry generator effects per line, e.g. wavy line patterns, hand drawn line styles, etc

Sponsored by North Road, thanks to SLYR

Fixes #16100

Showcase time!

Commits tagged with [need-docs] or [FEATURE]

[DelazJ]

Document at least at https://docs.qgis.org/testing/en/docs/user_manual/style_library/symbol_selector.html#fill-symbols. Maybe a mention in https://docs.qgis.org/testing/en/docs/user_manual/print_composer/create_output.html could be necessary