378930 - tree widgets have extra space when CSS pixels scaled (high dpi mode)

Status: RESOLVED WONTFIX

(Core :: XUL, defect)

Description

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

In high dpi mode, when a CSS pixel is more than one physical pixel, tree widgets containing text in system fonts have the rows double the height they should be.

Steps to reproduce:
 1. start firefox on a fresh profile
 2. go to about:config and set layout.css.dpi to 192
 3. look at about:config

Actual results: Each row in the tree has the text in a system font (at the system font's size, which is correct), but there's a lot of extra whitespace around the text as though the font had been doubled in size.

Expected results: the tree widget should appear without extra space

Comment 1

[Eli Friedman]

Quote from chrome://global/skin/tree.css:

treechildren::-moz-tree-row {
  border: 1px solid transparent;
  min-height: 18px;
  height: 1.3em;
}

That seems likely to cause issues...

Comment 2

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

Hrm, maybe it's not so bad, then.  I suppose that's there for images that go in trees?

Comment 3

[Jan Varga [:janv]]

Tree rows used to have fixed height of 18px and they didn't scale with size of fonts. I fixed it by adding min-height and height: 1.3em

Comment 4

[Eli Friedman]

(In reply to comment #3)
> Tree rows used to have fixed height of 18px and they didn't scale with size of
> fonts. I fixed it by adding min-height and height: 1.3em

What exactly do you mean by "used to"?  Is there some patch somewhere I'm missing?  Or some non-default theme?  All 5 instances of tree.css in the tree contain min-height: 18px.

Comment 5

[Jan Varga [:janv]]

I fixed it very long ago (several years). There must be a patch somewhere in bugzilla. The bug was assigned to me.
I think the tree widget code, method GetRowHeight() should be adjusted to count with scaled CSS pixels.

Comment 6

[Eli Friedman]

My patch to bug 386640 appears to solve this.

Comment 7

[Jan Varga [:janv]]

I don't think anyone is going to work on this given the plan to remove the XUL "tree" widget (bug 1446335).