Make the clipboard size limit configurable

Fixes #3937

docs/changelog.rst

@@ -10,6 +10,10 @@ To update |kitty|, :doc:`follow the instructions <binary>`.
 - macOS: Fix themes kitten failing to download themes because of missing SSL
   certificates (:iss:`3936`)
 
+- A new option :opt:`clipboard_max_size` to control the maximum size
+  of data that kitty will transmit to the system clipboard on behalf of
+  programs running inside it (:iss:`3937`)
+
 - A new :doc:`themes kitten </kittens/themes>` to easily change kitty themes.
 0.23.0 [2021-08-16]
 ----------------------

kitty/options/definition.py

@@ -2533,10 +2533,17 @@ control exactly which actions are allowed. The set of possible actions is:
 write-clipboard read-clipboard write-primary read-primary. The default is to
 allow writing to the clipboard and primary selection. Note that enabling the
 read functionality is a security risk as it means that any program, even one
-running on a remote server via SSH can read your clipboard.
+running on a remote server via SSH can read your clipboard. See also :opt:`
+clipboard_max_size`.
 '''
     )
 
+opt('clipboard_max_size', 64, option_type='positive_float', long_text='''
+The maximum size (in MB) of data from programs running in kitty that will be
+stored for writing to the system clipboard. See also :opt:`clipboard_control`.
+A value of zero means no size limit is applied.
+''')
+
 opt('allow_hyperlinks', 'yes',
     option_type='allow_hyperlinks', ctype='bool',
     long_text='''

kitty/options/parse.py

@@ -102,6 +102,9 @@ class Parser:
     def clipboard_control(self, val: str, ans: typing.Dict[str, typing.Any]) -> None:
         ans['clipboard_control'] = clipboard_control(val)
 
+    def clipboard_max_size(self, val: str, ans: typing.Dict[str, typing.Any]) -> None:
+        ans['clipboard_max_size'] = positive_float(val)
+
     def close_on_child_death(self, val: str, ans: typing.Dict[str, typing.Any]) -> None:
         ans['close_on_child_death'] = to_bool(val)
 

kitty/options/types.py

@@ -65,6 +65,7 @@ option_names = (  # {{{
  'clear_all_shortcuts',
  'click_interval',
  'clipboard_control',
+ 'clipboard_max_size',
  'close_on_child_death',
  'color0',
  'color1',
@@ -458,6 +459,7 @@ class Options:
     clear_all_shortcuts: bool = False
     click_interval: float = -1.0
     clipboard_control: typing.Tuple[str, ...] = ('write-clipboard', 'write-primary')
+    clipboard_max_size: float = 64.0
     close_on_child_death: bool = False
     command_on_bell: typing.List[str] = ['none']
     confirm_os_window_close: int = 0

kitty/window.py

@@ -791,7 +791,8 @@ class Window:
                 self.clipboard_pending = ClipboardPending(where, text)
             else:
                 self.clipboard_pending = self.clipboard_pending._replace(data=self.clipboard_pending[1] + text)
-                if len(self.clipboard_pending.data) > 8 * 1024 * 1024:
+                limit = get_options().clipboard_max_size
+                if limit and len(self.clipboard_pending.data) > limit * 1024 * 1024:
                     log_error('Discarding part of too large OSC 52 paste request')
                     self.clipboard_pending = self.clipboard_pending._replace(data='', truncated=True)
             return