Adapt help to terminal size

If the error stream is a terminal, and we can retrieve the terminal
size, wrap the lines at terminal boundaries.

app/meson.build

@@ -29,6 +29,7 @@ src = [
     'src/util/process.c',
     'src/util/strbuf.c',
     'src/util/str_util.c',
+    'src/util/term.c',
     'src/util/thread.c',
     'src/util/tick.c',
 ]
@@ -187,7 +188,9 @@ if get_option('buildtype') == 'debug'
             'tests/test_cli.c',
             'src/cli.c',
             'src/options.c',
+            'src/util/strbuf.c',
             'src/util/str_util.c',
+            'src/util/term.c',
         ]],
         ['test_clock', [
             'tests/test_clock.c',
@@ -196,6 +199,7 @@ if get_option('buildtype') == 'debug'
         ['test_control_msg_serialize', [
             'tests/test_control_msg_serialize.c',
             'src/control_msg.c',
+            'src/util/strbuf.c',
             'src/util/str_util.c',
         ]],
         ['test_device_msg_deserialize', [
@@ -211,6 +215,7 @@ if get_option('buildtype') == 'debug'
         ]],
         ['test_strutil', [
             'tests/test_strutil.c',
+            'src/util/strbuf.c',
             'src/util/str_util.c',
         ]],
     ]

app/src/util/str_util.c

@@ -1,9 +1,11 @@
 #include "str_util.h"
 
+#include <assert.h>
 #include <errno.h>
 #include <limits.h>
 #include <stdlib.h>
 #include <string.h>
+#include "util/strbuf.h"
 
 #ifdef _WIN32
 # include <windows.h>
@@ -209,3 +211,81 @@ utf8_from_wide_char(const wchar_t *ws) {
 }
 
 #endif
+
+char *wrap_lines(const char *input, unsigned columns, unsigned indent) {
+    assert(indent < columns);
+
+    struct sc_strbuf buf;
+
+    // The output string should not be a lot longer than the input string (just
+    // a few '\n' added), so this initial capacity should almost always avoid
+    // internal realloc() in string buffer
+    size_t cap = strlen(input) * 3 / 2;
+
+    if (!sc_strbuf_init(&buf, cap)) {
+        return false;
+    }
+
+#define APPEND(S,N) if (!sc_strbuf_append(&buf, S, N)) goto error
+#define APPEND_CHAR(C) if (!sc_strbuf_append_char(&buf, C)) goto error
+#define APPEND_N(C,N) if (!sc_strbuf_append_n(&buf, C, N)) goto error
+#define APPEND_INDENT() if (indent) APPEND_N(' ', indent)
+
+    APPEND_INDENT();
+
+    // The last separator encountered, it must be inserted only conditionnaly,
+    // depending on the next token
+    char pending = 0;
+
+    // col tracks the current column in the current line
+    size_t col = indent;
+    while (*input) {
+        size_t sep_idx = strcspn(input, "\n ");
+        size_t new_col = col + sep_idx;
+        if (pending == ' ') {
+            // The pending space counts
+            ++new_col;
+        }
+        bool wrap = new_col > columns;
+
+        char sep = input[sep_idx];
+        if (sep == ' ')
+            sep = ' ';
+
+        if (wrap) {
+            APPEND_CHAR('\n');
+            APPEND_INDENT();
+            col = indent;
+        } else if (pending) {
+            APPEND_CHAR(pending);
+            ++col;
+            if (pending == '\n')
+            {
+                APPEND_INDENT();
+                col = indent;
+            }
+        }
+
+        if (sep_idx) {
+            APPEND(input, sep_idx);
+            col += sep_idx;
+        }
+
+        pending = sep;
+
+        input += sep_idx;
+        if (*input != '\0') {
+            // Skip the separator
+            ++input;
+        }
+    }
+
+    if (pending)
+        APPEND_CHAR(pending);
+
+    return buf.s;
+
+error:
+    free(buf.s);
+    return NULL;
+}

app/src/util/str_util.h

@@ -62,4 +62,8 @@ char *
 utf8_from_wide_char(const wchar_t *s);
 #endif
 
+// Wrap input lines at words boundaries (spaces) so that they fit in 'columns'
+// columns, left-indented by 'indent' spaces
+char *wrap_lines(const char *input, unsigned columns, unsigned indent);
+
 #endif

app/src/util/term.c

@@ -0,0 +1,51 @@
+#include "term.h"
+
+#include <assert.h>
+
+#ifdef _WIN32
+# include <windows.h>
+#else
+# include <unistd.h>
+# include <sys/ioctl.h>
+#endif
+
+bool
+sc_term_get_size(unsigned *rows, unsigned *cols) {
+#ifdef _WIN32
+    CONSOLE_SCREEN_BUFFER_INFO csbi;
+
+    bool ok =
+        GetConsoleScreenBufferInfo(GetStdHandle(STD_OUTPUT_HANDLE), &csbi);
+    if (!ok) {
+        return false;
+    }
+
+    if (rows) {
+        assert(csbi.srWindow.Bottom >= csbi.srWindow.Top);
+        *rows = csbi.srWindow.Bottom - csbi.srWindow.Top + 1;
+    }
+
+    if (cols) {
+        assert(csbi.srWindow.Right >= csbi.srWindow.Left);
+        *cols = csbi.srWindow.Right - csbi.srWindow.Left + 1;
+    }
+
+    return true;
+#else
+    struct winsize ws;
+    int r = ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws);
+    if (r == -1) {
+        return false;
+    }
+
+    if (rows) {
+        *rows = ws.ws_row;
+    }
+
+    if (cols) {
+        *cols = ws.ws_col;
+    }
+
+    return true;
+#endif
+}

app/src/util/term.h

@@ -0,0 +1,11 @@
+#ifndef SC_TERM_H
+#define SC_TERM_H
+
+#include "common.h"
+
+#include <stdbool.h>
+
+bool
+sc_term_get_size(unsigned *rows, unsigned *cols);
+
+#endif

app/tests/test_strutil.c

@@ -299,6 +299,44 @@ static void test_strlist_contains(void) {
     assert(strlist_contains("xyz", '\0', "xyz"));
 }
 
+static void test_wrap_lines(void) {
+    const char *s = "This is a text to test line wrapping. The lines must be "
+                    "wrapped at a space or a line break.\n"
+                    "\n"
+                    "This rectangle must remains a rectangle because it is "
+                    "drawn in lines having lengths lower than the specified "
+                    "number of columns:\n"
+                    "  +----+\n"
+                    "  |    |\n"
+                    "  +----+\n";
+
+    //                     |----      1    1    2  2|
+    //                     |0    5    0    5    0  3| <-- 24 columns
+    const char *expected = "    This is a text to\n"
+                           "    test line wrapping.\n"
+                           "    The lines must be\n"
+                           "    wrapped at a space\n"
+                           "    or a line break.\n"
+                           "    \n"
+                           "    This rectangle must\n"
+                           "    remains a rectangle\n"
+                           "    because it is drawn\n"
+                           "    in lines having\n"
+                           "    lengths lower than\n"
+                           "    the specified number\n"
+                           "    of columns:\n"
+                           "      +----+\n"
+                           "      |    |\n"
+                           "      +----+\n";
+
+    char *formatted = wrap_lines(s, 24, 4);
+    assert(formatted);
+
+    assert(!strcmp(formatted, expected));
+
+    free(formatted);
+}
+
 int main(int argc, char *argv[]) {
     (void) argc;
     (void) argv;
@@ -317,5 +355,6 @@ int main(int argc, char *argv[]) {
     test_parse_integers();
     test_parse_integer_with_suffix();
     test_strlist_contains();
+    test_wrap_lines();
     return 0;
 }