os/shell: Throttle :! output, pulse "..." message.

Periodically skip :! spam. This is a "cheat" that works for all UIs and greatly
improves responsiveness when :! spams MB or GB of output:
    :!yes
    :!while true; do date; done
    :!git grep ''
    :grep -r '' *

After ~10KB of data is seen from a single :! invocation, output will be skipped
for ~1s and three dots "..." will pulse in the bottom-left. Thereafter the
behavior alternates at every:
    * 10KB received
    * ~1s throttled

This also avoids out-of-memory which could happen with large :! outputs.

Note: This commit does not change the behavior of execute(':!foo').
      execute(':!foo') returns the string ':!foo^M', it captures *only* Vim
      messages, *not* shell command output. Vim behaves the same way.
      Use system('foo') for capturing shell command output.

Closes #1234

Helped-by: oni-link <knil.ino@gmail.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/test/functional/terminal/helpers.lua b/test/functional/terminal/helpers.lua
index aacf109f2f..ae5e6d4b1f 100644
--- a/test/functional/terminal/helpers.lua
+++ b/test/functional/terminal/helpers.lua
@@ -51,6 +51,7 @@ local function screen_setup(extra_height, command)
     [7] = {foreground = 130},
     [8] = {foreground = 15, background = 1}, -- error message
     [9] = {foreground = 4},
+    [10] = {foreground = 2},  -- "Press ENTER" in embedded :terminal session.
   })
 
   screen:attach({rgb=false})