implement cursor position reporting (u7)

This is used by a number of programs (including vim) to determine utf8
terminal capabilities.

The feed functions now return none or a bytes object. If a bytes object
is returned, it is sent back to the requesting program.

1 files changed, 15 insertions, 7 deletions

diff --git a/tcvt.py b/tcvt.py
index c30f4e0..de62116 100755
--- a/tcvt.py
+++ b/tcvt.py
@@ -520,6 +520,10 @@ class Terminal:
         self.screen.move(n - 1, x)
         self.request_refresh()
 
+    def do_u7(self):
+        y, x = self.screen.getyx()
+        return b"\x1b[%d;%dR" % (y + 1, x + 1)
+
     def feed_reset(self):
         if self.graphics_font:
             self.mode = (self.feed_graphics,)
@@ -527,7 +531,7 @@ class Terminal:
             self.mode = (self.feed_simple,)
 
     def feed(self, char):
-        self.mode[0](char, *self.mode[1:])
+        return self.mode[0](char, *self.mode[1:])
 
     feed_simple_table = {
         ord('\a'): do_bel,
@@ -661,6 +665,8 @@ class Terminal:
             self.request_refresh()
         elif char == ord(b'K') and prev == b'1':
             self.do_el1()
+        elif char == ord(b'n') and prev == b'6':
+            return self.do_u7()
         else:
             raise ValueError("feed esc [ %r %r" % (prev, char))
 
@@ -845,13 +851,15 @@ def main():
                         if not data:
                             break
                         for char in bytearray(data):
-                            if "TCVT_DEVEL" in os.environ:
-                                t.feed(char)
+                            try:
+                                response = t.feed(char)
+                            except ValueError:
+                                if "TCVT_DEVEL" in os.environ:
+                                    raise
+                                t.feed_reset()
                             else:
-                                try:
-                                    t.feed(char)
-                                except ValueError:
-                                    t.feed_reset()
+                                if response:
+                                    os.write(masterfd, response)
                         t.refresh(0.1)
                     else:
                         t.refresh()