patman: Support limiting output to a single line

When outputing a progress line we don't want it to go past the end of the
current terminal line, or it will not be possible to erase it. Add an
option to Print() which allows limiting the output to the terminal width.

Since ANSI sequences do not take up space on the terminal, these are
removed.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/patman/terminal.py

@@ -11,6 +11,7 @@ from __future__ import print_function
 
 import os
 import re
+import shutil
 import sys
 
 # Selection of when we want our output to be colored
@@ -47,6 +48,9 @@ class PrintLine:
 def CalcAsciiLen(text):
     """Calculate the length of a string, ignoring any ANSI sequences
 
+    When displayed on a terminal, ANSI sequences don't take any space, so we
+    need to ignore them when calculating the length of a string.
+
     Args:
         text: Text to check
 
@@ -70,8 +74,57 @@ def CalcAsciiLen(text):
     result = ansi_escape.sub('', text)
     return len(result)
 
+def TrimAsciiLen(text, size):
+    """Trim a string containing ANSI sequences to the given ASCII length
 
-def Print(text='', newline=True, colour=None):
+    The string is trimmed with ANSI sequences being ignored for the length
+    calculation.
+
+    >>> col = Color(COLOR_ALWAYS)
+    >>> text = col.Color(Color.RED, 'abc')
+    >>> len(text)
+    14
+    >>> CalcAsciiLen(TrimAsciiLen(text, 4))
+    3
+    >>> CalcAsciiLen(TrimAsciiLen(text, 2))
+    2
+    >>> text += 'def'
+    >>> CalcAsciiLen(TrimAsciiLen(text, 4))
+    4
+    >>> text += col.Color(Color.RED, 'ghi')
+    >>> CalcAsciiLen(TrimAsciiLen(text, 7))
+    7
+    """
+    if CalcAsciiLen(text) < size:
+        return text
+    pos = 0
+    out = ''
+    left = size
+
+    # Work through each ANSI sequence in turn
+    for m in ansi_escape.finditer(text):
+        # Find the text before the sequence and add it to our string, making
+        # sure it doesn't overflow
+        before = text[pos:m.start()]
+        toadd = before[:left]
+        out += toadd
+
+        # Figure out how much non-ANSI space we have left
+        left -= len(toadd)
+
+        # Add the ANSI sequence and move to the position immediately after it
+        out += m.group()
+        pos = m.start() + len(m.group())
+
+    # Deal with text after the last ANSI sequence
+    after = text[pos:]
+    toadd = after[:left]
+    out += toadd
+
+    return out
+
+
+def Print(text='', newline=True, colour=None, limit_to_line=False):
     """Handle a line of output to the terminal.
 
     In test mode this is recorded in a list. Otherwise it is output to the
@@ -94,6 +147,9 @@ def Print(text='', newline=True, colour=None):
             print(text)
             last_print_len = None
         else:
+            if limit_to_line:
+                cols = shutil.get_terminal_size().columns
+                text = TrimAsciiLen(text, cols)
             print(text, end='', flush=True)
             last_print_len = CalcAsciiLen(text)