Generate max. one event for a SGR sequence with colons as seperators

Sequences with colons are used when only the first parameter
determines the kind of SGR event caused by the sequence and the rest
of the parameters are additional arguments. This means that the
arguments can contain numbers which are meaningful by themselves, like
0 (reset).

This means that if such a sequence is not supported by saneterm we
previously erroneously interpreted arguments in such a way that we
generated wrong events. This happened for example in vte's sgr-test.sh
which relied on kitty's non standard underline escape sequences which
we don't support at this time:
https://sw.kovidgoyal.net/kitty/protocol-extensions.html#colored-and-styled-underlines

1 files changed, 31 insertions, 15 deletions

diff --git a/saneterm/pty.py b/saneterm/pty.py
index 72e7fbd..fd423c6 100644
--- a/saneterm/pty.py
+++ b/saneterm/pty.py
@@ -335,24 +335,37 @@ def parse_sgr_sequence(params, special_evs):
     We also support ':' as a separator which is
     only necessary for extended color sequences
     as specified in ITU-T Rec. T.416 | ISO/IEC 8613-6
-    (see also parse_extended_color()). Actually
-    those sequences _must_ use colons and semicolons
-    would be invalid. In reality, however, the
-    incorrect usage of semicolons seems to be much
-    more common. Thus we are extremely lenient and
-    allow both ':' and ';' as well as a mix of both
-    as separators.
+    (see also parse_extended_color()). This separator
+    is used for sequences which only contain one
+    parameter identifying the kind of sequence and
+    additional arguments. This is contrary to normal
+    SGR sequences where multiple parameters are
+    treatet as if they were in separate sequences.
+
+    The sequences specified in ITU-T Rec. T.416
+    must use colons as separators. In reality however
+    CLIs often use semicolons instead, so we support
+    both. This can cause issues in edge cases, but
+    is probably better than some applications not
+    working properly.
     """
-    args = re.split(r'[:;]', params)
-
-    arg_it = iter(args)
-    for arg in arg_it:
-        if len(arg) == 0:
+    # If a colon is used as seperator we know that
+    # the params following the first one are just
+    # parameters and may not be intepreted as
+    # normal SGR parameters. We respect this
+    # by breaking after the first loop iteration.
+    single_param_with_args = ':' in params
+
+    params_split = re.split(r'[:;]', params)
+
+    params_it = iter(params_split)
+    for p in params_it:
+        if len(p) == 0:
             # empty implies 0
             sgr_type = 0
         else:
             try:
-                sgr_type = int(arg)
+                sgr_type = int(p)
             except ValueError:
                 raise AssertionError("Invalid Integer")
 
@@ -415,7 +428,7 @@ def parse_sgr_sequence(params, special_evs):
             try:
                 change_payload = (
                     TextStyleChange.FOREGROUND_COLOR,
-                    parse_extended_color(arg_it)
+                    parse_extended_color(params_it)
                 )
             except AssertionError:
                 # TODO: maybe fail here?
@@ -434,7 +447,7 @@ def parse_sgr_sequence(params, special_evs):
             try:
                 change_payload = (
                     TextStyleChange.BACKGROUND_COLOR,
-                    parse_extended_color(arg_it)
+                    parse_extended_color(params_it)
                 )
             except AssertionError:
                 # TODO: maybe fail here?
@@ -461,6 +474,9 @@ def parse_sgr_sequence(params, special_evs):
         if change_payload != None:
             special_evs.append((EventType.TEXT_STYLE, change_payload))
 
+        if single_param_with_args:
+            break
+
 def parse_csi_sequence(it, special_evs):
     """
     Parses control sequences which begin with a