Automatically detect whether the terminal background is a light color #28739
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What is the user has changed the way the default colours are shown in the terminal to already fix this issue? Then we will still swap to these non-standard colors. If the defaults in some terminals make colors unreadable, maybe it is the defaults that need to be changed? |
stdlib/REPL/src/Terminals.jl
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| # (We could/should use more mechanisms here) | ||
| # Blindly guess an OS-dependent default | ||
| if Sys.isapple() | ||
| return true |
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This is a bad assumption. iTerm2 defaults to black. However, iTerm2 does have color query escape codes.
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To my knowledge, iTerm2 sets the COLORFGBG environment variable that we check above, thus this default isn't reached.
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I don't think we should ever default this to true solely based on OS.
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I removed the default based on OS; all OS now use the same default
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@KristofferC If the user sets colors, then Julia won't use its default colors. This change only modifies the defaults that Julia uses if there is no customization. I don't think it is possible to choose colors that work with every background. Light colors are unreadable on light backgrounds, and dark colors are unreadable on dark backgrounds. Plus, Julia wants to use several different colors to improve the output. |
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This seems like a good direction to make the default experience better. But does this light/dark background detection really work? It seems kind of implausible to me that it would actually work. |
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Appveyor reports an all-green status, but the Github status here on this page doesn't update. |
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Introduce a distinction between light and dark text colors. Use different default colors in both cases. The text color scheme can be set via a command line option (--color=[light | dark]), or Julia can try to detect the terminal's background color. In this case, it roughly follows vim's approach: 1. Look for COLORFGBG environment variable 2. Use an ANSI escape sequence to query the terminal for the background color 3. Make an educated guess from the terminal name Tested with iTerm2, Terminal, xterm on MacOS, Linux.
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The patch now uses roughly the same mechanism as vim. Querying the terminal via ANSI escape sequences work for iTerm2 and xterm (and probably their derivatives). There are also command line options to override things ( |
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Bump, who should review? |
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I now find that many Julia packages set colours directly (e.g. by using A work-around would be to conditionally change the definition of In summary, I'm disappointed that my pull request didn't actually solve the problem it was supposed to solve. I don't know whether it's actually useful in practice. If so, then it's only a first step towards making Julia output readable on a light background. |
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| # Use OSC 11 escape sequence |
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this implementation seems overcomplicated. I think if you leave this out, we can merge the rest, then work on this more
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Leave out which part – looking at the COLORFGBG variable?
| if term.term_type == "linux" || # Linux console | ||
| term.term_type == "screen.linux" || # Linux console with screen | ||
| startswith(term.term_type, "cygwin") || # Cygwin shell | ||
| startswith(term.term_type, "putty") # Putty progrem |
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I know this list comes from VIM, but it seems likely ancient. I think most terminals I use report as "xterm" now
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This is a list of terminals which default to using a dark background. The terminals which default to a light background (xterm and friends) are not in this list.
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I think we've somewhat essentially decided not to go with this PR. I think the |
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Probably better as an environment variable since you presumably don't want to have to set it on each invocation. |
This detects (or tries to) whether the terminal background is a light color. The REPL then chooses a different default color scheme that is easier to read, avoiding e.g. yellow.
This only affects the default colors; any user-chosen colors remain the same.
Closes #28690.