How to understand the parameters of gtk_snapshot_scale?

[q962 (提及)]

Without relevant experience, I can’t understand it.

I played around with some parameters, trying to understand what the parameters mean.

For the meaning of factor_x, I can see the law from the results.
But I can’t understand factor_y.

gtk_snapshot_scale( snapshot, 0.8, 0.8 )

[q962 (提及)]

Well, the meaning of the parameters is as I thought.
Just why the offset happens, I don’t understand

gtk_snapshot_scale( child_snapshot, 1.5, 1.8 );

[q962 (提及)]

I get it! Both x and y are scaled, so the image is offset