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fix unicode glitch in DCS strings, patch by Tim Allen - st - simple terminal |
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git clone git://git.suckless.org/st |
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--- |
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commit 818ec746f4caae453d09368b101c3e841cf39870 |
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parent 9ba7ecf7b15ec2986c6142036706aa353b249ef9 |
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Author: Hiltjo Posthuma <[email protected]> |
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Date: Wed, 17 Jun 2020 21:35:39 +0200 |
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fix unicode glitch in DCS strings, patch by Tim Allen |
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Reported on the mailinglist: |
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" |
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I discovered recently that if an application running inside st tries to |
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send a DCS string, subsequent Unicode characters get messed up. For |
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example, consider the following test-case: |
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printf '\303\277\033P\033\\\303\277' |
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...where: |
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- \303\277 is the UTF-8 encoding of U+00FF LATIN SMALL LETTER Y WITH |
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DIAERESIS (ÿ). |
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- \033P is ESC P, the token that begins a DCS string. |
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- \033\\ is ESC \, a token that ends a DCS string. |
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- \303\277 is the same ÿ character again. |
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If I run the above command in a VTE-based terminal, or xterm, or |
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QTerminal, or pterm (PuTTY), I get the output: |
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ÿÿ |
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...which is to say, the empty DCS string is ignored. However, if I run |
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that command inside st (as of commit 9ba7ecf), I get: |
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ÿÿ |
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...where those last two characters are \303\277 interpreted as ISO8859-1 |
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characters, instead of UTF-8. |
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I spent some time tracing through the state machines in st.c, and so far |
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as I can tell, this is how it works currently: |
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- ESC P sets the "ESC_DCS" and "ESC_STR" flags, indicating that |
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incoming bytes should be collected into the strescseq buffer, rather |
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than being interpreted. |
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- ESC \ sets the "ESC_STR_END" flag (when ESC is received), and then |
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calls strhandle() (when \ is received) to interpret the collected |
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bytes. |
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- If the collected bytes begin with 'P' (i.e. if this was a DCS |
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string) strhandle() sets the "ESC_DCS" flag again, confusing the |
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state machine. |
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If my understanding is correct, fixing the problem should be as easy as |
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removing the line that sets ESC_DCS from strhandle(): |
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diff --git a/st.c b/st.c |
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index ef8abd5..b5b805a 100644 |
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--- a/st.c |
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+++ b/st.c |
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@@ -1897,7 +1897,6 @@ strhandle(void) |
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xsettitle(strescseq.args[0]); |
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return; |
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case 'P': /* DCS -- Device Control String */ |
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- term.mode |= ESC_DCS; |
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case '_': /* APC -- Application Program Command */ |
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case '^': /* PM -- Privacy Message */ |
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return; |
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I've tried the above patch and it fixes my problem, but I don't know if |
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it introduces any others. |
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" |
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Diffstat: |
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M st.c | 1 - |
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1 file changed, 0 insertions(+), 1 deletion(-) |
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--- |
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diff --git a/st.c b/st.c |
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@@ -1897,7 +1897,6 @@ strhandle(void) |
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xsettitle(strescseq.args[0]); |
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return; |
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case 'P': /* DCS -- Device Control String */ |
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- term.mode |= ESC_DCS; |
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case '_': /* APC -- Application Program Command */ |
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case '^': /* PM -- Privacy Message */ |
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return; |
