FPDFAnnot_GetObject and FPDFPageObj_GetMatrix

[Ann-Sofie]

I'm trying to understand if this is a bug (or if I simply misunderstood something because pdfium is very new to me). In our software we have a user that uploaded a pdf and I'm getting some strange results. I have created this small example to illustrate what I think is a bug:

Input is a FPDF_PAGE page with 116 annotations. If I run this code

FPDF_ANNOTATION annotation31 = FPDFPage_GetAnnot(page, 31);
FPDFAnnot_GetObject(annotation31, 2); 

FPDF_ANNOTATION annotation48 = FPDFPage_GetAnnot(page, 48);
FPDF_PAGEOBJECT pageObject2 = FPDFAnnot_GetObject(annotation48, 2);
FPDF_PAGEOBJECT formObject2 = FPDFFormObj_GetObject(pageObject2, 2);

FS_MATRIX matrix = {};
FPDFPageObj_GetMatrix(formObject2, &matrix); 

 then I get a different matrix compared to if I simply remove 

FPDF_ANNOTATION annotation31 = FPDFPage_GetAnnot(page, 31);
FPDFAnnot_GetObject(annotation31, 2); 

from the above code. It seems to me that FPDFAnnot_GetObject(annotation31, 2) will change the output from FPDFPageObj_GetMatrix used for a completely different annotation.

[Lei Zhang]

Hi,

Is it the FPDFPage_GetAnnot(page, 31); call that's the issue, or the
FPDFAnnot_GetObject(annotation31, 2); call? This doesn't sound like an
issue that should be happening, as most getter functions are not
modifying data. If you suspect it's bug, please file a bug report on
https://crbug.com/pdfium/new and share a PDF to reproduce the issue if
possible.

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[Ann-Sofie]

Hi,

It's FPDFAnnot_GetObject(annotation31, 2); that makes changes to the matrix. I will create a bug report.

Thank you,

Ann-Sofie

[Lei Zhang]

Thanks for filing crbug.com/475719025.

On Wed, Jan 14, 2026 at 1:20 AM 'Ann-Sofie' via pdfium

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