Add Zoom Controls, Alignment Options & Page-Separator Support

[danieljannai]

This PR introduces three ergonomic improvements to streamlit-pdf-viewer:

1. Interactive Zoom
   • zoom_level accepts float, "auto", "auto-height" or None (default = fit-to-width).
   • Top-right dropdown with presets, ± buttons and manual entry.

2. Viewer Alignment
   • viewer_align="left" | "center" | "right" (default = center).

3. Optional Page Separators
   • show_page_separator=True | False.

---

Additional updates

• README – feature list, parameter table and usage example updated.
• New e2e tests – 32 tests across Firefox & Chromium cover the new functionality; all pass locally.

No existing behaviour is changed; any failing CI checks stem from pre-existing legacy-mode tests.

[lfoppiano]

@danieljannai Thanks!! That's great someone implemented such a big feature. 🚀
I'm going to revise ASAP. @t29mato could you please also double check it?

[Copilot]

Pull Request Overview

This PR introduces three new ergonomic features to the PDF viewer component: interactive zoom controls, configurable viewer alignment, and optional page separators. Key changes include adding multiple zoom options (numeric values, "auto", and "auto-height"), aligning the viewer via a new parameter, and conditionally rendering horizontal separators between pages, with corresponding tests and documentation updates.

Reviewed Changes

Copilot reviewed 19 out of 20 changed files in this pull request and generated 1 comment.

File	Description
tests/*	New e2e tests covering zoom controls, auto zoom variants, page separator visibility, and viewer alignment
streamlit_pdf_viewer/frontend/src/PdfViewer.vue	Updated component template and script to include zoom controls, alignment logic, and page separator styling
streamlit_pdf_viewer/init.py	Updated parameter defaults and validations for zoom_level, viewer_align, and show_page_separator, with adjusted documentation
README.md	Documentation updated to reflect new features and options

Comments suppressed due to low confidence (1)

streamlit_pdf_viewer/init.py:39

• There is a spelling error in the printed message: 'disapper' should read 'disappear'.

        resolution_boost: int = 1,

[lfoppiano]

HI @danieljannai, you did a terrific job. 🚀

I have one question, what is the show_page_separator as compared with the option pages_vertical_spacing. I wonder if we could merge them into one option to make it simpler.

More generally, I'm also wondering whether we could get rid of all the legacy stuff which are just a pain to maintain.

[danieljannai]

Thanks @lfoppiano, just extended your terrific work 😄

The main idea behind show_page_separator was to have a visual cue of where one page ends and another ones starts, especially in multi-page documents with white background where it can be unclear. Not sure how to merge it with the pages_vertical_spacing parameter, to be honest. You could add a "separation config" but it feels like an overkill. What do you have in mind?

With regards to legacy stuff, I 100% agree. It might be a breaking change, but it's necessary. Especially since many tests don't pass at the moment.

[danieljannai]

@lfoppiano
I thought it would be really useful to allow full installation of the package (including the npm run build step) directly from GitHub. Are you okay with me adding it to this PR?

[lfoppiano]

Separating config looks a bit too complicated, indeed.

I would just like to make sure those two options don't clash:

• if show_page_separator = False, it's the same as pages_vertical_spacing = 0 (any other value will be ignored, and we should warn the user if they have them set)
• if show_page_separator = True, it's the same as pages_vertical_spacing = 1 or 2 (the default page separation)

Regarding the legacy rendering, we can release 0.1.0 and break compatibility. I think there is already a PR #96

[lfoppiano]

@lfoppiano I thought it would be really useful to allow full installation of the package (including the npm run build step) directly from GitHub. Are you okay with me adding it to this PR?

Sure! 🎉

[danieljannai]

Separating config looks a bit too complicated, indeed.

I would just like to make sure those two options don't clash:

• if show_page_separator = False, it's the same as pages_vertical_spacing = 0 (any other value will be ignored, and we should warn the user if they have them set)
• if show_page_separator = True, it's the same as pages_vertical_spacing = 1 or 2 (the default page separation)

Regarding the legacy rendering, we can release 0.1.0 and break compatibility. I think there is already a PR #96

They don't seem to clash. Take a look at the attached screenshots:

1. show_page_separator=True (default) and pages_vertical_spacing=2 (default). Note that there's a thin grey line, below it two white pixel rows and only then the light-blue stripe at the top of the second page:
   
2. show_page_separator=False and pages_vertical_spacing=2 (default). Note that the thin grey line is gone, but there are still two white pixel rows and only then the light-blue stripe at the top of the second page:
   
   It might be easier to note in this example where the first page is all red, second one is all blue. Note the white gap between them:
   
3. show_page_separator=True (default) and pages_vertical_spacing=0. Note that there's a thin grey line between the pages:
   
4. show_page_separator=False and pages_vertical_spacing=0. Note that the thin grey line between the pages is gone:
   

[danieljannai]

@lfoppiano Added the auto-build during setup :)

[lfoppiano]

I'm going to merge and release 0.0.26, then dump the legacy stuff and release 0.1.0 🎉
I'd keep some bug fixing on the branch 0.0 for a bit before decommissioning completely