shell: use msg_outtrans_len_attr for :!cmd

fixes #7830 and #7788

src/nvim/eval.c

@@ -19372,14 +19372,10 @@ void ex_echo(exarg_T *eap)
             }
             msg_putchar_attr((uint8_t)(*p), echo_attr);
           } else {
-            if (has_mbyte) {
             int i = (*mb_ptr2len)((const char_u *)p);
 
             (void)msg_outtrans_len_attr((char_u *)p, i, echo_attr);
             p += i - 1;
-            } else {
-              (void)msg_outtrans_len_attr((char_u *)p, 1, echo_attr);
-            }
           }
         }
       }

src/nvim/ex_cmds.c

@@ -1175,7 +1175,7 @@ static void do_filter(
   // to read the error messages. Otherwise errors are ignored, so you can see
   // the error messages from the command that appear on stdout; use 'u' to fix
   // the text.
-  // Pass on the kShellDoOut flag when the output is being redirected.
+  // Pass on the kShellOptDoOut flag when the output is being redirected.
   if (call_shell(
         cmd_buf,
         kShellOptFilter | shell_flags,

src/nvim/os/shell.c

@@ -123,6 +123,9 @@ int os_call_shell(char_u *cmd, ShellOpts opts, char_u *extra_args)
     if (opts & kShellOptRead) {
       output_ptr = &output;
       forward_output = false;
+    } else if (opts & kShellOptDoOut) {
+      // Caller has already redirected output
+      forward_output = false;
     }
   }
 
@@ -257,11 +260,25 @@ static int do_os_system(char **argv,
   // busy state.
   ui_busy_start();
   ui_flush();
+  if (forward_output) {
+    msg_sb_eol();
+    msg_start();
+    msg_no_more = true;
+    lines_left = -1;
+  }
   int exitcode = process_wait(proc, -1, NULL);
   if (!got_int && out_data_decide_throttle(0)) {
     // Last chunk of output was skipped; display it now.
     out_data_ring(NULL, SIZE_MAX);
   }
+  if (forward_output) {
+    // caller should decide if wait_return is invoked
+    no_wait_return++;
+    msg_end();
+    no_wait_return--;
+    msg_no_more = false;
+  }
+
   ui_busy_stop();
 
   // prepare the out parameters if requested
@@ -436,47 +453,17 @@ static void out_data_ring(char *output, size_t size)
 static void out_data_append_to_screen(char *output, size_t remaining,
                                       bool new_line)
 {
-  static colnr_T last_col = 0;  // Column of last row to append to.
+  char *p = output, *end = output + remaining;
+  while (p < end) {
+    if (*p == '\n' || *p == '\r' || *p == TAB) {
+      msg_putchar_attr((uint8_t)(*p), 0);
+      p++;
+    } else {
+      int i = *p ? mb_ptr2len_len((char_u *)p, (int)(end-p)) : 1;
 
-  size_t off = 0;
+      (void)msg_outtrans_len_attr((char_u *)p, i, 0);
-  int last_row = (int)Rows - 1;
+      p += i;
-
-  while (output != NULL && off < remaining) {
-    // Found end of line?
-    if (output[off] == NL) {
-      // Can we start a new line or do we need to continue the last one?
-      if (last_col == 0) {
-        screen_del_lines(0, 0, 1, (int)Rows, NULL);
     }
-      screen_puts_len((char_u *)output, (int)off, last_row, last_col, 0);
-      last_col = 0;
-
-      size_t skip = off + 1;
-      output += skip;
-      remaining -= skip;
-      off = 0;
-      continue;
-    }
-
-    // TODO(bfredl): using msg_puts would be better until
-    // terminal emulation is implemented.
-    if (output[off] < 0x20) {
-      output[off] = ' ';
-    }
-
-    off++;
-  }
-
-  if (output != NULL && remaining) {
-    if (last_col == 0) {
-      screen_del_lines(0, 0, 1, (int)Rows, NULL);
-    }
-    screen_puts_len((char_u *)output, (int)remaining, last_row, last_col, 0);
-    last_col += (colnr_T)remaining;
-  }
-
-  if (new_line) {
-    last_col = 0;
   }
 
   ui_flush();

src/nvim/quickfix.c

@@ -3148,10 +3148,9 @@ void ex_make(exarg_T *eap)
   }
   msg_start();
   MSG_PUTS(":!");
-  msg_outtrans((char_u *) cmd);  // show what we are doing
+  msg_outtrans((char_u *)cmd);  // show what we are doing
 
-  // let the shell know if we are redirecting output or not
+  do_shell((char_u *)cmd, 0);
-  do_shell((char_u *) cmd, *p_sp != NUL ? kShellOptDoOut : 0);
 
 
   res = qf_init(wp, fname, (eap->cmdidx != CMD_make