Use E3 to completely clear console on Unix when possible #88487

natehitze · 2023-07-06T19:17:28Z

Some terminals define an extra sequence to clear the terminal scroll buffer. Using it after the clear sequence makes Clear() work like the 'clear' command.

Fix #84351

The linked issue has a detailed analysis and explanation which was the guide for this PR.

Some terminals define an extra sequence to clear the terminal scroll buffer. Using it after the clear sequence makes Clear() work like the 'clear' command. Fix dotnet#84351

ghost · 2023-07-06T19:17:38Z

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Issue Details

Some terminals define an extra sequence to clear the terminal scroll buffer. Using it after the clear sequence makes Clear() work like the 'clear' command.

Fix #84351

The linked issue has a detailed analysis and explanation which was the guide for this PR.

Author:	natehitze
Assignees:	-
Labels:	`area-System.Console`
Milestone:	-

natehitze · 2023-07-06T19:18:43Z

@dotnet-policy-bot agree

adamsitnik

@natehitze big thanks for your contribution! PTAL at my comments, we need to solve the macOS CI failure.

adamsitnik · 2023-07-07T09:27:31Z

src/libraries/System.Console/tests/TermInfo.Unix.cs

-    [InlineData("mach-color", "\u001B\u005B\u00335m", "\u001B\u005B\u00345m", 5)]
-    [InlineData("mach-color", "\u001B\u005B\u003312m", "\u001B\u005B\u003412m", 12)]
-    public void TermInfoVerification(string termToTest, string expectedForeground, string expectedBackground, int colorValue)
+    [InlineData("xterm-256color", "\u001B\u005B\u00330m", "\u001B\u005B\u00340m", 0, true)]


the test failures indicate that E3 is missing on xterm-256color, but only macOS. I wonder why: does macOS simply not provide it or it has a different name?

Please let me know if you need a copy of macOS terminfo file.

/private/tmp/helix/working/AFB20920/w/BFE50A43/e /private/tmp/helix/working/AFB20920/w/BFE50A43/e Discovering: System.Console.Tests (method display = ClassAndMethod, method display options = None) Discovered: System.Console.Tests (found 113 of 148 test cases) Starting: System.Console.Tests (parallel test collections = on, max threads = 4) Color.RedirectedOutput_EnvVarSet_EmitsAnsiCodes [SKIP] Condition(s) not met: "TermIsSetAndRemoteExecutorIsSupported" 0 0 TermInfoTests.TermInfoVerification(termToTest: "xterm-256color", expectedForeground: "\x1b[30m", expectedBackground: "\x1b[40m", colorValue: 0, expectedScrollbackClearSupport: True) [FAIL] Assert.Equal() Failure Expected: True Actual: False Stack Trace: /_/src/libraries/System.Console/tests/TermInfo.Unix.cs(102,0): at TermInfoTests.TermInfoVerification(String termToTest, String expectedForeground, String expectedBackground, Int32 colorValue, Boolean expectedScrollbackClearSupport) at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor) /_/src/libraries/System.Private.CoreLib/src/System/Reflection/MethodInvoker.cs(59,0): at System.Reflection.MethodInvoker.Invoke(Object obj, IntPtr* args, BindingFlags invokeAttr) TermInfoTests.TermInfoVerification(termToTest: "xterm-256color", expectedForeground: "\x1b[31m", expectedBackground: "\x1b[41m", colorValue: 1, expectedScrollbackClearSupport: True) [FAIL] Assert.Equal() Failure Expected: True Actual: False Stack Trace: /_/src/libraries/System.Console/tests/TermInfo.Unix.cs(102,0): at TermInfoTests.TermInfoVerification(String termToTest, String expectedForeground, String expectedBackground, Int32 colorValue, Boolean expectedScrollbackClearSupport) at InvokeStub_TermInfoTests.TermInfoVerification(Object, Object, IntPtr*) at System.Reflection.MethodInvoker.Invoke(Object obj, IntPtr* args, BindingFlags invokeAttr) TermInfoTests.TermInfoVerification(termToTest: "xterm-256color", expectedForeground: "\x1b[90m", expectedBackground: "\x1b[100m", colorValue: 8, expectedScrollbackClearSupport: True) [FAIL] Assert.Equal() Failure Expected: True Actual: False Stack Trace: /_/src/libraries/System.Console/tests/TermInfo.Unix.cs(102,0): at TermInfoTests.TermInfoVerification(String termToTest, String expectedForeground, String expectedBackground, Int32 colorValue, Boolean expectedScrollbackClearSupport) at InvokeStub_TermInfoTests.TermInfoVerification(Object, Object, IntPtr*) at System.Reflection.MethodInvoker.Invoke(Object obj, IntPtr* args, BindingFlags invokeAttr) Finished: System.Console.Tests

According to https://github.com/watchexec/clearscreen/blob/main/TERMINALS.md#platforms macOS doesn't include E3 in terminfo. That seems to be true on the mac I have access to -- and the clear command with xterm-256color does not clear the scrollback buffer but does clear it on my machine (PopOS 22.04) with xterm-256color.

I'll take a look at the Console.ReadKey tests you mentioned below and get the tests fixed up for CI. Thanks for reviewing!

adamsitnik · 2023-07-07T09:39:16Z

src/libraries/System.Console/tests/TermInfo.Unix.cs

+    [InlineData("wsvt25", "\u001B\u005B\u003311m", "\u001B\u005B\u003411m", 11, false)]
+    [InlineData("mach-color", "\u001B\u005B\u00330m", "\u001B\u005B\u00340m", 0, false)]
+    [InlineData("mach-color", "\u001B\u005B\u00335m", "\u001B\u005B\u00345m", 5, false)]
+    [InlineData("mach-color", "\u001B\u005B\u003312m", "\u001B\u005B\u003412m", 12, false)]


it's a pity that it's not supported by more terminals. FWIW we have Console.ReadKey tests that have copies of terminfo files for multiple terminals:

runtime/src/libraries/System.Console/tests/KeyParserTests.cs

Line 446 in 104752a

protected override string EncodedTerminalDb => "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"; // /lib/terminfo/x/xterm-256color

runtime/src/libraries/System.Console/tests/KeyParserTests.cs

Lines 16 to 26 in 104752a

new XTermData(),

new GNOMETerminalData(),

new LinuxConsole(),

new PuTTYData_xterm(),

new PuTTYData_linux(),

new PuTTYData_putty(),

new WindowsTerminalData(),

new TmuxData(),

new Tmux256ColorData(),

new RxvtUnicode(),

new AlacrittyData(),

if you want to check anything related to this terminals you can just hack these tests, the TermInfo.Database is created here:

runtime/src/libraries/System.Console/tests/KeyParserTests.cs

Lines 431 to 432 in 104752a

internal TerminalFormatStrings TerminalDb => _terminalDb ??=

new TerminalFormatStrings(new TermInfo.Database(Term, Convert.FromBase64String(EncodedTerminalDb)));

You can even debug that on Windows, as these tests are platform-independent.

adamsitnik · 2023-07-07T10:21:40Z

src/libraries/System.Console/src/System/ConsolePal.Unix.cs

@@ -223,6 +223,10 @@ public static void Clear()
            if (!Console.IsOutputRedirected)
            {
                WriteStdoutAnsiString(TerminalFormatStringsInstance.Clear);
+                if (!string.IsNullOrEmpty(TerminalFormatStringsInstance.ClearScrollbackBuffer))


according to https://unix.stackexchange.com/a/375784 we should do E3 before clear:

If the terminfo/termcap entry has an E3 capability it, it first writes out that.
It then uses the clear capability to clear the visible screen.

The snippet of clear shared in the issue had E3 being issued after clear, but I'm not sure it matters either way. I'll switch the order.

I assume we manually validated the behavior on at least some system with the E3 and then clear?

@stephentoub I had tested before, but unfortunately just assumed the switched order was okay per the linked answer. I just ran my manual test again and having E3 issued before clear does not clear the scrollback buffer.

That means this order needs reversed back to the original: Clear, then E3. Would you mind making that change on your PR? Or do you want me to submit a new PR with the optimization mentioned below + this fix?

Would you mind making that change on your PR?

No problem; I switched the order back.

adamsitnik

LGTM, again big thanks for your contribution @natehitze !

stephentoub · 2023-07-17T13:20:13Z

src/libraries/System.Console/src/System/ConsolePal.Unix.cs

+                if (!string.IsNullOrEmpty(TerminalFormatStringsInstance.ClearScrollbackBuffer))
+                {
+                    WriteStdoutAnsiString(TerminalFormatStringsInstance.ClearScrollbackBuffer);
+                }
                WriteStdoutAnsiString(TerminalFormatStringsInstance.Clear);


This is the only place Clear is used, right? Rather than doing two separate writes, could we just update TerminalFormatStringsInstance.Clear to be constructed as the concatenation with ClearScrollbackBuffer if it exists, and then this call site doesn't change from what it was before... it just writes out Clear, which will issue both commands if they're supported.

Use E3 to clear console on Unix when possible

5939770

Some terminals define an extra sequence to clear the terminal scroll buffer. Using it after the clear sequence makes Clear() work like the 'clear' command. Fix dotnet#84351

dotnet-issue-labeler bot added the area-System.Console label Jul 6, 2023

ghost added the community-contribution Indicates that the PR has been added by a community member label Jul 6, 2023

build-analysis bot mentioned this pull request Jul 6, 2023

LibraryImportGenerator.Unit.Tests crashed in CI #87951

Closed

Use IsNullOrEmpty instead of null check

832b6c4

adamsitnik reviewed Jul 7, 2023

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adamsitnik self-assigned this Jul 7, 2023

Send E3 before clear and fix tests

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adamsitnik added this to the 8.0.0 milestone Jul 7, 2023

adamsitnik merged commit 4a788bb into dotnet:main Jul 7, 2023
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stephentoub reviewed Jul 17, 2023

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stephentoub mentioned this pull request Jul 17, 2023

Avoid extra console write for clearing on Unix #89026

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Use E3 to completely clear console on Unix when possible #88487

Use E3 to completely clear console on Unix when possible #88487

natehitze commented Jul 6, 2023

ghost commented Jul 6, 2023

natehitze commented Jul 6, 2023 •

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stephentoub Jul 17, 2023

	new XTermData(),
	new GNOMETerminalData(),
	new LinuxConsole(),
	new PuTTYData_xterm(),
	new PuTTYData_linux(),
	new PuTTYData_putty(),
	new WindowsTerminalData(),
	new TmuxData(),
	new Tmux256ColorData(),
	new RxvtUnicode(),
	new AlacrittyData(),

	internal TerminalFormatStrings TerminalDb => _terminalDb ??=
	new TerminalFormatStrings(new TermInfo.Database(Term, Convert.FromBase64String(EncodedTerminalDb)));

Use E3 to completely clear console on Unix when possible #88487

Use E3 to completely clear console on Unix when possible #88487

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natehitze commented Jul 6, 2023 •

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