Print: Image does not fill the canvas (with screenshots)

[rekcodocker]

Describe the bug

I try to print an image on A4 paper.
It is cropped to A4 format.
It does not scale to fill the paper.

Removing the image, creating a new image area - nothing helps.
Creating a smaller image area will fill the imagearea with the picture. But when I drag sides of the image larger, to fill the A4 paper, the image stops scaling with it again.

Nothing I do lets the image fill the entire paper, not selecting other paper sizes, playing around with borders, nothing in the userinterface of the print module works to fill the paper.

It is clearly a bug.
I found this workaround:
When I rotate the image and print in portrait, it does fill the paper.

Steps to reproduce

I can provide the image and XMP if you like.
It is a simple JPeg and I cropped it and did a small retouch.

Expected behavior

Fill the entire canvas when printing.

Logfile | Screenshot | Screencast

It behaves different between portrait and landscape.
Note that I must rotate the image for that.

It behaves different between portrait and landscape.
Note that I must rotate the image for that.

Commit

No response

Where did you obtain darktable from?

downloaded from www.darktable.org

darktable version

4.8.1

What OS are you using?

Linux

What is the version of your OS?

Mint latest

Describe your system?

Laptop intel CPU using OpenCL

Are you using OpenCL GPU in darktable?

Yes

If yes, what is the GPU card and driver?

No response

Please provide additional context if applicable. You can attach files too, but might need to rename to .txt or .zip

No response

[ralfbrown]

Are you printing in borderless mode? If not, the actual printable area won't have a 1.41:1 aspect ratio and you'll need to change the crop accordingly.

[rekcodocker]

Are you printing in borderless mode? If not, the actual printable area won't have a 1.41:1 aspect ratio and you'll need to change the crop accordingly.

Good question. See screenshots. This is normal printing, not borderless.
However you see a big difference between landscape and portrait mode.
This is the biggest it gets in landscape mode. It is not even close to the borders.
In portrait mode you see it actually does fill the whole paper. It is the same paper. I did not switch papers between these two screenshots. I just rotated the image.

[ralfbrown]

I did a few experiments, and determined that on my system, dt isn't using the full long dimension of the selected image area for the image - the image extends to the top or left (portrait/landscape) but not to the opposite edge and is downscaled accordingly so that it doesn't reach either of the other two edges, being centered between them. If the image is more square than the image area, then it does touch the two long edges but isn't quite centered along them (closer to the top/left).

So it looks like a calculation error on determining the needed scaling factor and position.