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help: fix terminal newline handling in raw-mode terminals #322

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42 changes: 40 additions & 2 deletions ds4_help.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>

typedef struct {
Expand Down Expand Up @@ -69,17 +70,23 @@ static void print_colored_option_name(FILE *fp, const help_colors *c, const char
}

static void opt(FILE *fp, const help_colors *c, const char *name, const char *desc) {
const int col = 30;
int n = (int)strlen(name);
if (c->cyan) {
fputs(" ", fp);
print_colored_option_name(fp, c, name);
if (n > col) {
fprintf(fp, "\n %s%s%s\n",
c->white ? c->white : "", desc, c->white ? c->off : "");
return;
}
for (int i = n; i < col; i++) fputc(' ', fp);
fprintf(fp, " %s|%s ", c->grey ? c->grey : "", c->grey ? c->off : "");
fprintf(fp, "%s%s%s\n", c->white ? c->white : "", desc,
c->white ? c->off : "");
return;
}

const int col = 30;
int n = (int)strlen(name);
if (n > col) {
fprintf(fp, " %s\n %s\n", name, desc);
} else {
Expand Down Expand Up @@ -525,6 +532,32 @@ static void print_default(FILE *fp, const help_colors *c, ds4_help_tool tool) {
}

void ds4_help_print(FILE *fp, ds4_help_tool tool, const char *topic) {
/* Help is plain text, but it can be requested after a raw-mode UI left the
* terminal with output processing disabled. In that state '\n' moves down
* without returning to column zero, producing stair-stepped output. */
int term_fd = fileno(fp);
bool restore_term = false;
struct termios saved_term;
if (term_fd >= 0 && isatty(term_fd) && tcgetattr(term_fd, &saved_term) == 0) {
fflush(fp);
struct termios normal = saved_term;
bool changed = false;
#ifdef OPOST
if (!(normal.c_oflag & OPOST)) {
normal.c_oflag |= OPOST;
changed = true;
}
#endif
#ifdef ONLCR
if (!(normal.c_oflag & ONLCR)) {
normal.c_oflag |= ONLCR;
changed = true;
}
#endif
if (changed && tcsetattr(term_fd, TCSANOW, &normal) == 0)
restore_term = true;
}

help_colors c = help_make_colors(fp);
if (topic && !tool_has_topic(tool, topic)) {
fprintf(fp, "%s: unknown help topic '%s'\n\n", tool_name(tool), topic);
Expand All @@ -541,4 +574,9 @@ void ds4_help_print(FILE *fp, ds4_help_tool tool, const char *topic) {
print_more_info(fp, &c, tool);
}
print_examples(fp, &c, tool, topic);
/* Let queued help bytes drain before restoring the caller's terminal mode. */
if (restore_term) {
fflush(fp);
tcsetattr(term_fd, TCSADRAIN, &saved_term);
}
}