Abe Crabtree complains that flushing the log file as often as we do in 0.56

results in unacceptable performance for him on Win2000. Add a checkbox to
revert to the old behaviour.

[originally from svn r4988]
[this svn revision also touched putty-wishlist]

config.c

@@ -885,6 +885,9 @@ void setup_config_box(struct controlbox *b, struct sesslist *sesslist,
 		      "Always overwrite it", I(LGXF_OVR),
 		      "Always append to the end of it", I(LGXF_APN),
 		      "Ask the user every time", I(LGXF_ASK), NULL);
+    ctrl_checkbox(s, "Flush log file frequently", 'u',
+		 HELPCTX(logging_flush),
+		 dlg_stdcheckbox_handler, I(offsetof(Config,logflush)));
 
     if ((midsession && protocol == PROT_SSH) ||
 	(!midsession && backends[3].name != NULL)) {

doc/config.but

@@ -206,6 +206,22 @@ Finally (the default option), you might not want to have any
 automatic behaviour, but to ask the user every time the problem
 comes up.
 
+\S{config-logflush} \q{Flush log file frequently}
+
+\cfg{winhelp-topic}{logging.flush}
+
+This option allows you to control how frequently logged data is
+flushed to disc. By default, PuTTY will flush data as soon as it is
+displayed, so that if you view the log file while a session is still
+open, it will be up to date; and if the client system crashes, there's
+a greater chance that the data will be preserved.
+
+However, this can incur a performance penalty. If PuTTY is running
+slowly with logging enabled, you could try unchecking this option. Be
+warned that the log file may not always be up to date as a result
+(although it will of course be flushed when it is closed, for instance
+at the end of a session).
+
 \S{config-logssh} Options specific to SSH packet logging
 
 These options only apply if SSH packet data is being logged.

putty.h

@@ -452,6 +452,7 @@ struct config_tag {
     Filename logfilename;
     int logtype;
     int logxfovr;
+    int logflush;
     int logomitpass;
     int logomitdata;
     int hide_mouseptr;

settings.c

@@ -167,6 +167,7 @@ void save_open_settings(void *sesskey, int do_host, Config *cfg)
     write_setting_filename(sesskey, "LogFileName", cfg->logfilename);
     write_setting_i(sesskey, "LogType", cfg->logtype);
     write_setting_i(sesskey, "LogFileClash", cfg->logxfovr);
+    write_setting_i(sesskey, "LogFlush", cfg->logflush);
     write_setting_i(sesskey, "SSHLogOmitPasswords", cfg->logomitpass);
     write_setting_i(sesskey, "SSHLogOmitData", cfg->logomitdata);
     p = "raw";
@@ -395,6 +396,7 @@ void load_open_settings(void *sesskey, int do_host, Config *cfg)
     gppfile(sesskey, "LogFileName", &cfg->logfilename);
     gppi(sesskey, "LogType", 0, &cfg->logtype);
     gppi(sesskey, "LogFileClash", LGXF_ASK, &cfg->logxfovr);
+    gppi(sesskey, "LogFlush", 1, &cfg->logflush);
     gppi(sesskey, "SSHLogOmitPasswords", 1, &cfg->logomitpass);
     gppi(sesskey, "SSHLogOmitData", 0, &cfg->logomitdata);
 

terminal.c

@@ -4337,7 +4337,8 @@ static void term_out(Terminal *term)
     }
 
     term_print_flush(term);
-    logflush(term->logctx);
+    if (term->cfg.logflush)
+	logflush(term->logctx);
 }
 
 /*

windows/winhelp.h

@@ -13,6 +13,7 @@
 #define WINHELP_CTX_logging_main "logging.main"
 #define WINHELP_CTX_logging_filename "logging.filename"
 #define WINHELP_CTX_logging_exists "logging.exists"
+#define WINHELP_CTX_logging_flush "logging.flush"
 #define WINHELP_CTX_logging_ssh_omit_password "logging.ssh.omitpassword"
 #define WINHELP_CTX_logging_ssh_omit_data "logging.ssh.omitdata"
 #define WINHELP_CTX_keyboard_backspace "keyboard.backspace"