Re: PSA: To see LAYOUT_WARNING(), add this to your .bash_aliases file: export NSPR_LOG_MODULES="layout:2"

On Wednesday, July 29, 2015 at 3:35:27 PM UTC-7, Daniel Holbert wrote:
> Hi Gecko layout hackers,
> 
> erahm has added new macros:
> 
>   LAYOUT_WARNING("Something's broken");
>   LAYOUT_WARN_IF_FALSE(booleanCondition, "Condition better be true");
> 
> These warnings are opt-in -- so, they're silent by default. Gecko
> developers who have an interest in layout code can & should opt in to
> seeing these warnings (in debug builds) by setting the following
> environmental variable (e.g. in your ~/.bash_aliases file):
> 
>   export NSPR_LOG_MODULES="layout:2"
> 
> DETAILS:
> These are basically identical in semantics to NS_WARNING /
> NS_WARN_IF_FALSE -- they're to be used when something happens that's
> possibly worrisome (but might also be normal/expected, given
> pathological content).  Unlike the NS_ versions, these LAYOUT_ macros
> are opt-in, so that our test suites (which do contain a lot of
> pathological content) don't spam zillions of lines for these warnings
> failing.
> 
> The macros are defined here:
> http://mxr.mozilla.org/mozilla-central/source/layout/base/LayoutLogging.h
> 
> USAGE RECOMMENDATION:
> Generally, I think we should still prefer the NS_WARNING variants for
> new code, so that bug reports are more likely to have useful contents if
> someone pastes in their debug-build terminal output from around when the
> bug happened. We should only fall back to these LAYOUT_ variants after
> we've determined that a NS_WARNING is *both* useful to us &
> spammy-during-usage-that-we-care-about (test suites / normal browsing).
> 
> ~Daniel

Also note: I plan on adding support for setting log levels at runtime through some rudimentary mechanism (probably prefs). This means a user will be able to turn on a specific log at runtime (in this case "layout").

Hopefully when this lands it will make the case for NS_WARNING somewhat less compelling, but I agree that in the meantime it can certainly be useful.

-e