20402 - implement line-height and leading properly

Status: VERIFIED INVALID

(Core :: Layout, defect, P3)

Description

[Erik van der Poel]

The nsIFontMetrics::GetLeading() method is inappropriate. In the CSS world,
leading is determined by line-height and font-size (i.e. leading is
line-height - font-size).

Currently, the MathML engine is the only caller. It is probably calling this
method for the wrong reason. Cc'ing Roger.

Comment 1

[troy]

This is not a layout bug. nsIFontMetrics is gfx and not layout...

Comment 2

[rbs]

I was using GetLeading() as a work around to the lack of other metrics.
But now that we have a better GetBoundingMetrics() method, many things are
going to change in the MathML world. GetLeading() is going to be removed in
the near future. Were you planning to remove GetLeading() anytime soon?

Comment 3

[Erik van der Poel]

Actually, there is something called "line-height: normal" in CSS. We may want to
use the font's recommended leading for this. So let's leave GetLeading in there
for now. (I may want to move it to nsIRenderingContext for other reasons later,
though.) Re-assigning to myself.

Comment 4

[Erik van der Poel]

Moving all of my M15s to M16. Please add comments if you disagree.

Comment 5

[Hixie (not reading bugmail)]

We must probably fix bug 27874, "line-height should use em-square height, not 
bounding box height", before getting rid of nsIFontMetrics::GetLeading().
Marking dependency.

Comment 6

[Hixie (not reading bugmail)]

(Oops, I stomped over my own dependency within a minute of making it! Ok, 
reinstating the bug 27874 dependency...)

Comment 7

[Erik van der Poel]

I've decided not to get rid of the GetLeading method. Line height will be
addressed by 27874, so I'm closing this bug as INVALID.

Comment 8

[Hixie (not reading bugmail)]

Ok. VERIFIED.

Comment 9

[Pulsebot]

Pushed by ffxbld-merge:
https://hg.mozilla.org/releases/mozilla-beta/rev/7539a2144372
[fenix] Issue https://github.com/mozilla-mobile/fenix/issues/20402: Disable LastMediaAccessMiddleware temporarily
https://hg.mozilla.org/releases/mozilla-beta/rev/6e1abbcdd5b9
[fenix] For https://github.com/mozilla-mobile/fenix/issues/20402 - Re-enable "in progress media tab"