Discovered while testing MC-269437
The bug
If text_field or text_field_highlighted are given textures containing translucent pixels, they will render these pixels as entirely opaque in-game, which is inconsistent with other widgets such as buttons and sliders, which support translucent pixels just fine.
How to reproduce
Download and apply the attached resource pack
Look at any menu containing a text field
Expected results
The text field would have an opaque border and translucent center, just like the buttons.
Actual results
The text field is completely solid.
How to fix
Allow text fields to use translucent pixels.
Further notes
The attached screenshots were taken before I retextured buttons in this specific resource pack.
Can confirm.