ImageShow.show on a PNG file returned True without displaying the image

[kailizcatman]

What did you do?

1. Download this PNG image from Wikipedia. https://en.wikipedia.org/wiki/PNG#/media/File:PNG_transparency_demonstration_1.png Save it as test.png.
2. Run the test script shown below.

from PIL import Image, ImageShow
img=Image.open("test.png")
print(ImageShow.show(img))

What did you expect to happen?

I expected a new window to be created in which the downloaded image was displayed.

What actually happened?

The command printed "True" on the command line and exited without displaying the image.

I think the cause of the issue is that in my environment, the first viewer tried by pillow was the XDGViewer. Unfortunately, xdg-open was not correctly configured. When I ran xdg-open test.png directly, the command exited with code 4 without displaying anything.

At the moment, XDGViewer.show_file does not check the return code of xdg-open, and always returns 1 after launching the xdg-open subprocess. This caused ImageShow.show to not bother trying the DisplayViewer option.

As far as I can tell, none of the viewers check the return code of the viewer subprocess. Is this a deliberate design decision?

What are your OS, Python and Pillow versions?

• OS: SLES15
• Python: 3.10.11
• Pillow: 11.3.0

[radarhere]

If we wanted to check the return code, we would need to wait until the command was finished. A command like eog might stay open until the viewing application is closed. We don't want to just hang the Python process until that time.

Similarly, it seems like waiting for xdg-open might take some time.