Page scale parameter is not taken into account for page size preview

[DanLo-peratingSystem]

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Describe the bug
The page size do not correspond to reality if the Page scale parameter is not set to 100%.
This mean that one could think the diagram fits on the page, send it to print, and realize out of the printer that the diagram were cut into multiple pages.

To Reproduce
Steps to reproduce the behavior:

1. Create new diagram
2. Set Paper size on the diagram parameters to A4 (should be default ?) (you can disable grid view also to better see the pages borders)
3. Go to View > Page Scale, set page scale to 150% (should be default)
4. Create any shape(s) that seems to fit in the full page (almost full width of the page)
   => it will look like the shape fits the page, and a print would put it on a single page.
5. If we set View > Unit to mm, we can notice that our shapes are bigger then 210mm, which is the supposed page size. That's contradictory with the view that makes it look like the shape fits in 1 page.
6. Set the Page Scale to 100%, that's the only value where the page size is actually correct => we notice that actually the shape would require multiple pages to fit..!

Expected behavior
When modifying the Page Scale, we should still have proper alignment between the shapes sizes and the page size preview. Current situation gives a wrong page size relatively to the shapes sizes.

Screenshots
Screenshot 1 :

• page scale set to 150, paper size to A4 (210x297mm), it seems like my 2 diagrams would fit on 2 pages.

Screenshot 2 :

• page scale set to 100, paper size to A4 (210x297mm), actually my 2 diagrams does not fit on 2 pages..!

draw.io version (In the Help->About menu of the draw.io editor):

• draw.io version 29.6.6 (installed app)

Desktop (please complete the following information):

• OS: Windows
• Browser Edge
• Browser Version 146.0.3856.97 (Official build) (64-bit)

I tested the problem in incognito/private mode with all browser extensions switched off, write "yes" below:

• The issue was seen from installed app, not checked from web browser.

Additional context
Add any other context about the problem here.

I'm not 100% sure what is the purpose of the Page Scale parameter. But it anyway feels like something is not aligned properly as page size preview should always properly indicate where the pages will "cut" if the file is printed or exported to PDF.

[draw-io-triage-bot]

👋 Thank you for opening this issue!

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Summary: When the Page Scale (View > Page Scale) is set to a value other than 100%, the page boundary indicators in the editor do not correctly reflect the actual paper size relative to shape dimensions. This causes shapes to appear as if they fit on a single page when they actually span multiple pages upon printing or PDF export.

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📝 Additional Information Needed

To help us investigate this more effectively, could you please provide:

• Can you confirm whether the issue also manifests when exporting to PDF (i.e., the exported PDF pages don't match what's shown on screen), or is it purely a visual/preview discrepancy in the editor?
• Have you tried using File > Print (or Export as PDF) with 'Fit to Page' options to see if the actual print output respects the page boundaries correctly regardless of the Page Scale setting?

📋 Bug Report Template

**Environment:**
- draw.io version: [e.g., web app / desktop 24.x.x / Confluence plugin]
- Browser (if web): [e.g., Chrome 120, Firefox 121]
- OS: [e.g., Windows 11, macOS 14, Ubuntu 22.04]

**Steps to Reproduce:**
1. Go to ...
2. Click on ...
3. See error

**Expected Behavior:**
What you expected to happen.

**Actual Behavior:**
What actually happened.

**Screenshots/Files:**
If applicable, add screenshots or attach the .drawio file.

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_{🤖 This is an automated response to help with initial triage. A human maintainer will review this issue. If you've provided all the requested information, no further action is needed - we'll get back to you soon!}

[DanLo-peratingSystem]

Tested with PDF, interesting behavior :

• if we do explicit export to PDF, through the File > Export as... > PDF menu, then it works as expected, the diagram fits as per the editor preview in a single page
• if we use the File > Print... menu (and select "print as PDF" kind of options), then we have the problematic behavior with the diagram bigger than page size, from the Page Scale setting.

Of course if we check "fit to page" on the print settings then the diagram fits to the page size, which is not expected neither. The diagram lost its original size and layout relative to the overall page. So that's an uncontrolled and not a good workaround neither. (when one's takes care of organizing it's shapes specifically to fit precisely in the page, it's not to be dependent on the print auto-fit options, which will then be highly dependent on margin configs, and many other parameters)