libbb/lineedit: try to make FEATURE_EDITING_ASK_TERMINAL less ugly

function                                             old     new   delta
read_line_input                                     4809    4829     +20
lineedit_read_key                                    207     223     +16
put_prompt                                           110     117      +7
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/0 up/down: 43/0)               Total: 43 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index 2e1bc5d2ef0a133d9f8a8a48a18b44faf58661e1..b4c3fd35c7e12a6c0d5fb91e5b53a638c71c4298 100644 (file)
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -140,6 +140,9 @@ struct lineedit_statics {
        smallint newdelflag;     /* whether delbuf should be reused yet */
        CHAR_T delbuf[DELBUFSIZ];  /* a place to store deleted characters */
 #endif
+#if ENABLE_FEATURE_EDITING_ASK_TERMINAL
+       smallint sent_ESC_br_n6;
+#endif
 
        /* Formerly these were big buffers on stack: */
 #if ENABLE_FEATURE_TAB_COMPLETION
@@ -371,7 +374,8 @@ static void put_prompt(void)
 {
        out1str(cmdedit_prompt);
        fflush(NULL);
-       if (ENABLE_FEATURE_EDITING_ASK_TERMINAL) {
+#if ENABLE_FEATURE_EDITING_ASK_TERMINAL
+       {
                /* Ask terminal where is the cursor now.
                 * lineedit_read_key handles response and corrects
                 * our idea of current cursor position.
@@ -405,10 +409,12 @@ static void put_prompt(void)
                pfd.fd = STDIN_FILENO;
                pfd.events = POLLIN;
                if (safe_poll(&pfd, 1, 0) == 0) {
+                       S.sent_ESC_br_n6 = 1;
                        out1str("\033" "[6n");
                        fflush(NULL); /* make terminal see it ASAP! */
                }
        }
+#endif
        cursor = 0;
        {
                unsigned w = cmdedit_termw; /* volatile var */
@@ -1666,20 +1672,24 @@ static int lineedit_read_key(char *read_key_buffer)
                /* Note: read_key sets errno to 0 on success: */
                ic = read_key(STDIN_FILENO, read_key_buffer);
 
-               if (ENABLE_FEATURE_EDITING_ASK_TERMINAL
-                && cursor == 0 /* otherwise it may be bogus */
-                && (int32_t)ic == KEYCODE_CURSOR_POS
+#if ENABLE_FEATURE_EDITING_ASK_TERMINAL
+               if ((int32_t)ic == KEYCODE_CURSOR_POS
+                && S.sent_ESC_br_n6
                ) {
-                       int col = ((ic >> 32) & 0x7fff) - 1;
-                       if (col > cmdedit_prmt_len) {
-                               cmdedit_x += (col - cmdedit_prmt_len);
-                               while (cmdedit_x >= cmdedit_termw) {
-                                       cmdedit_x -= cmdedit_termw;
-                                       cmdedit_y++;
+                       S.sent_ESC_br_n6 = 0;
+                       if (cursor == 0) { /* otherwise it may be bogus */
+                               int col = ((ic >> 32) & 0x7fff) - 1;
+                               if (col > cmdedit_prmt_len) {
+                                       cmdedit_x += (col - cmdedit_prmt_len);
+                                       while (cmdedit_x >= cmdedit_termw) {
+                                               cmdedit_x -= cmdedit_termw;
+                                               cmdedit_y++;
+                                       }
                                }
                        }
                        goto poll_again;
                }
+#endif
 
 #if ENABLE_FEATURE_ASSUME_UNICODE
                {
@@ -2192,6 +2202,21 @@ int FAST_FUNC read_line_input(const char *prompt, char *command, int maxsize, li
 #endif
        } /* while (1) */
 
+#if ENABLE_FEATURE_EDITING_ASK_TERMINAL
+       if (S.sent_ESC_br_n6) {
+               /* "sleep 1; busybox ash" + hold [Enter] to trigger.
+                * We sent "ESC [ 6 n", but got '\n' first, and
+                * KEYCODE_CURSOR_POS response is now buffered from terminal.
+                * It's bad already and not much can be done with it
+                * (it _will_ be visible for the next process to read stdin),
+                * but without this delay it even shows up on the screen
+                * as garbage because we restore echo settings with tcsetattr
+                * before it comes in. UGLY!
+                */
+               usleep(20*1000);
+       }
+#endif
+
 /* Stop bug catching using "command_must_not_be_used" trick */
 #undef command