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From: "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com>
To: git@vger.kernel.org
Cc: Johannes Schindelin <johannes.schindelin@gmx.de>,
	Johannes Schindelin <johannes.schindelin@gmx.de>
Subject: [PATCH v4 08/10] built-in add -p: handle Escape sequences in interactive.singlekey mode
Date: Tue, 14 Jan 2020 18:43:51 +0000	[thread overview]
Message-ID: <cdc609f8fa349b9ffada68dfd6fd183365222ba7.1579027433.git.gitgitgadget@gmail.com> (raw)
In-Reply-To: <pull.175.v4.git.1579027433.gitgitgadget@gmail.com>

From: Johannes Schindelin <johannes.schindelin@gmx.de>

This recapitulates part of b5cc003253c8 (add -i: ignore terminal escape
sequences, 2011-05-17):

    add -i: ignore terminal escape sequences

    On the author's terminal, the up-arrow input sequence is ^[[A, and
    thus fat-fingering an up-arrow into 'git checkout -p' is quite
    dangerous: git-add--interactive.perl will ignore the ^[ and [
    characters and happily treat A as "discard everything".

    As a band-aid fix, use Term::Cap to get all terminal capabilities.
    Then use the heuristic that any capability value that starts with ^[
    (i.e., \e in perl) must be a key input sequence.  Finally, given an
    input that starts with ^[, read more characters until we have read a
    full escape sequence, then return that to the caller.  We use a
    timeout of 0.5 seconds on the subsequent reads to avoid getting stuck
    if the user actually input a lone ^[.

    Since none of the currently recognized keys start with ^[, the net
    result is that the sequence as a whole will be ignored and the help
    displayed.

Note that we leave part for later which uses "Term::Cap to get all
terminal capabilities", for several reasons:

1. it is actually not really necessary, as the timeout of 0.5 seconds
   should be plenty sufficient to catch Escape sequences,

2. it is cleaner to keep the change to special-case Escape sequences
   separate from the change that reads all terminal capabilities to
   speed things up, and

3. in practice, relying on the terminal capabilities is a bit overrated,
   as the information could be incomplete, or plain wrong. For example,
   in this developer's tmux sessions, the terminal capabilities claim
   that the "cursor up" sequence is ^[M, but the actual sequence
   produced by the "cursor up" key is ^[[A.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 compat/terminal.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 55 insertions(+), 1 deletion(-)

diff --git a/compat/terminal.c b/compat/terminal.c
index 1b2564042a..b7f58d1781 100644
--- a/compat/terminal.c
+++ b/compat/terminal.c
@@ -161,6 +161,37 @@ static int enable_non_canonical(void)
 	return disable_bits(ENABLE_ECHO_INPUT | ENABLE_LINE_INPUT | ENABLE_PROCESSED_INPUT);
 }
 
+/*
+ * Override `getchar()`, as the default implementation does not use
+ * `ReadFile()`.
+ *
+ * This poses a problem when we want to see whether the standard
+ * input has more characters, as the default of Git for Windows is to start the
+ * Bash in a MinTTY, which uses a named pipe to emulate a pty, in which case
+ * our `poll()` emulation calls `PeekNamedPipe()`, which seems to require
+ * `ReadFile()` to be called first to work properly (it only reports 0
+ * available bytes, otherwise).
+ *
+ * So let's just override `getchar()` with a version backed by `ReadFile()` and
+ * go our merry ways from here.
+ */
+static int mingw_getchar(void)
+{
+	DWORD read = 0;
+	unsigned char ch;
+
+	if (!ReadFile(GetStdHandle(STD_INPUT_HANDLE), &ch, 1, &read, NULL))
+		return EOF;
+
+	if (!read) {
+		error("Unexpected 0 read");
+		return EOF;
+	}
+
+	return ch;
+}
+#define getchar mingw_getchar
+
 #endif
 
 #ifndef FORCE_TEXT
@@ -228,8 +259,31 @@ int read_key_without_echo(struct strbuf *buf)
 		restore_term();
 		return EOF;
 	}
-
 	strbuf_addch(buf, ch);
+
+	if (ch == '\033' /* ESC */) {
+		/*
+		 * We are most likely looking at an Escape sequence. Let's try
+		 * to read more bytes, waiting at most half a second, assuming
+		 * that the sequence is complete if we did not receive any byte
+		 * within that time.
+		 *
+		 * Start by replacing the Escape byte with ^[ */
+		strbuf_splice(buf, buf->len - 1, 1, "^[", 2);
+
+		for (;;) {
+			struct pollfd pfd = { .fd = 0, .events = POLLIN };
+
+			if (poll(&pfd, 1, 500) < 1)
+				break;
+
+			ch = getchar();
+			if (ch == EOF)
+				return 0;
+			strbuf_addch(buf, ch);
+		}
+	}
+
 	restore_term();
 	return 0;
 }
-- 
gitgitgadget


  parent reply	other threads:[~2020-01-14 18:44 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-21 22:41 [PATCH 0/9] built-in add -p: add support for the same config settings as the Perl version Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 1/9] built-in add -p: support interactive.diffFilter Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 2/9] built-in add -p: handle diff.algorithm Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 3/9] terminal: make the code of disable_echo() reusable Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 4/9] terminal: accommodate Git for Windows' default terminal Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 5/9] terminal: add a new function to read a single keystroke Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 6/9] built-in add -p: respect the `interactive.singlekey` config setting Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 7/9] built-in add -p: handle Escape sequences in interactive.singlekey mode Johannes Schindelin via GitGitGadget
2019-12-21 22:41 ` [PATCH 8/9] built-in add -p: handle Escape sequences more efficiently Johannes Schindelin via GitGitGadget
2019-12-21 22:42 ` [PATCH 9/9] ci: include the built-in `git add -i` in the `linux-gcc` job Johannes Schindelin via GitGitGadget
2019-12-21 22:53   ` SZEDER Gábor
2019-12-25 11:56     ` Johannes Schindelin
2019-12-22  0:11   ` Junio C Hamano
2019-12-25 11:57     ` Johannes Schindelin
2019-12-24 18:23 ` [PATCH 0/9] built-in add -p: add support for the same config settings as the Perl version Junio C Hamano
2019-12-24 18:39   ` Junio C Hamano
2019-12-25  8:46     ` Simon Ruderich
2019-12-25 12:09     ` Johannes Schindelin
2019-12-25 12:02   ` Johannes Schindelin
2019-12-25 11:56 ` [PATCH v2 " Johannes Schindelin via GitGitGadget
2019-12-25 11:56   ` [PATCH v2 1/9] built-in add -p: support interactive.diffFilter Johannes Schindelin via GitGitGadget
2020-01-07 22:57     ` SZEDER Gábor
2020-01-13  6:47       ` Johannes Schindelin
2019-12-25 11:56   ` [PATCH v2 2/9] built-in add -p: handle diff.algorithm Johannes Schindelin via GitGitGadget
2019-12-25 11:56   ` [PATCH v2 3/9] terminal: make the code of disable_echo() reusable Johannes Schindelin via GitGitGadget
2019-12-25 11:56   ` [PATCH v2 4/9] terminal: accommodate Git for Windows' default terminal Johannes Schindelin via GitGitGadget
2019-12-25 11:56   ` [PATCH v2 5/9] terminal: add a new function to read a single keystroke Johannes Schindelin via GitGitGadget
2019-12-25 11:56   ` [PATCH v2 6/9] built-in add -p: respect the `interactive.singlekey` config setting Johannes Schindelin via GitGitGadget
2019-12-25 11:56   ` [PATCH v2 7/9] built-in add -p: handle Escape sequences in interactive.singlekey mode Johannes Schindelin via GitGitGadget
2019-12-25 11:56   ` [PATCH v2 8/9] built-in add -p: handle Escape sequences more efficiently Johannes Schindelin via GitGitGadget
2019-12-25 11:57   ` [PATCH v2 9/9] ci: include the built-in `git add -i` in the `linux-gcc` job Johannes Schindelin via GitGitGadget
2019-12-26 20:48     ` Derrick Stolee
2020-01-01 22:10       ` Johannes Schindelin
2019-12-26 20:45   ` [PATCH v2 0/9] built-in add -p: add support for the same config settings as the Perl version Junio C Hamano
2020-01-13  8:29   ` [PATCH v3 00/10] " Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 01/10] built-in add -i/-p: treat SIGPIPE as EOF Johannes Schindelin via GitGitGadget
2020-01-13 17:04       ` SZEDER Gábor
2020-01-13 18:33         ` Jeff King
2020-01-15 18:32           ` Junio C Hamano
2020-01-15 19:03             ` Jeff King
2020-01-14 12:47         ` Johannes Schindelin
2020-01-17 14:32         ` SZEDER Gábor
2020-01-17 18:58           ` Jeff King
2020-01-13  8:29     ` [PATCH v3 02/10] built-in add -p: support interactive.diffFilter Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 03/10] built-in add -p: handle diff.algorithm Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 04/10] terminal: make the code of disable_echo() reusable Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 05/10] terminal: accommodate Git for Windows' default terminal Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 06/10] terminal: add a new function to read a single keystroke Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 07/10] built-in add -p: respect the `interactive.singlekey` config setting Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 08/10] built-in add -p: handle Escape sequences in interactive.singlekey mode Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 09/10] built-in add -p: handle Escape sequences more efficiently Johannes Schindelin via GitGitGadget
2020-01-13  8:29     ` [PATCH v3 10/10] ci: include the built-in `git add -i` in the `linux-gcc` job Johannes Schindelin via GitGitGadget
2020-01-14 18:43     ` [PATCH v4 00/10] built-in add -p: add support for the same config settings as the Perl version Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 01/10] t3701: adjust difffilter test Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 02/10] built-in add -p: support interactive.diffFilter Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 03/10] built-in add -p: handle diff.algorithm Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 04/10] terminal: make the code of disable_echo() reusable Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 05/10] terminal: accommodate Git for Windows' default terminal Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 06/10] terminal: add a new function to read a single keystroke Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 07/10] built-in add -p: respect the `interactive.singlekey` config setting Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` Johannes Schindelin via GitGitGadget [this message]
2020-01-14 18:43       ` [PATCH v4 09/10] built-in add -p: handle Escape sequences more efficiently Johannes Schindelin via GitGitGadget
2020-01-14 18:43       ` [PATCH v4 10/10] ci: include the built-in `git add -i` in the `linux-gcc` job Johannes Schindelin via GitGitGadget

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