Add support for non-scrolling fifo buffers

rc/grep.kak

@@ -12,7 +12,7 @@ def -shell-params -file-completion \
      fi
 
      echo "eval -try-client '$kak_opt_toolsclient' %{
-               edit! -fifo ${output} *grep*
+               edit! -fifo ${output} -scroll *grep*
                set buffer filetype grep
                hook buffer BufClose .* %{ nop %sh{ rm -r $(dirname ${output}) } }
            }"

rc/make.kak

@@ -7,7 +7,7 @@ def -shell-params make %{ %sh{
      ( eval ${kak_opt_makecmd} "$@" > ${output} 2>&1 ) > /dev/null 2>&1 < /dev/null &
 
      echo "eval -try-client '$kak_opt_toolsclient' %{
-               edit! -fifo ${output} *make*
+               edit! -fifo ${output} -scroll *make*
                set buffer filetype make
                hook buffer BufClose .* %{ nop %sh{ rm -r $(dirname ${output}) } }
            }"

src/buffer_utils.cc

@@ -22,16 +22,29 @@ CharCount get_column(const Buffer& buffer,
     return col;
 }
 
-Buffer* create_fifo_buffer(String name, int fd)
+Buffer* create_fifo_buffer(String name, int fd, bool scroll)
 {
     Buffer* buffer = new Buffer(std::move(name), Buffer::Flags::Fifo | Buffer::Flags::NoUndo);
 
-    auto watcher = new FDWatcher(fd, [buffer](FDWatcher& watcher) {
+    auto watcher = new FDWatcher(fd, [buffer, scroll](FDWatcher& watcher) {
         constexpr size_t buffer_size = 1024 * 16;
         char data[buffer_size];
         ssize_t count = read(watcher.fd(), data, buffer_size);
-        buffer->insert(buffer->end()-1, count > 0 ? String(data, data+count)
+        auto pos = buffer->end()-1;
-                                                  : "*** kak: fifo closed ***\n");
+
+        bool prevent_scrolling = pos == buffer->begin() and not scroll;
+        if (prevent_scrolling)
+            ++pos;
+
+        buffer->insert(pos, count > 0 ? String(data, data+count)
+                                      : "*** kak: fifo closed ***\n");
+
+        if (prevent_scrolling)
+        {
+            buffer->erase(buffer->begin(), buffer->begin()+1);
+            buffer->insert(buffer->end(), "\n");
+        }
+
         if (count <= 0)
         {
             kak_assert(buffer->flags() & Buffer::Flags::Fifo);

src/buffer_utils.hh

@@ -41,7 +41,7 @@ inline void avoid_eol(const Buffer& buffer, Selection& sel)
 CharCount get_column(const Buffer& buffer,
                      CharCount tabstop, BufferCoord coord);
 
-Buffer* create_fifo_buffer(String name, int fd);
+Buffer* create_fifo_buffer(String name, int fd, bool scroll = false);
 
 }
 

src/commands.cc

@@ -46,7 +46,7 @@ Buffer* open_or_create(const String& filename, Context& context)
     return buffer;
 }
 
-Buffer* open_fifo(const String& name , const String& filename)
+Buffer* open_fifo(const String& name , const String& filename, bool scroll)
 {
     int fd = open(parse_filename(filename).c_str(), O_RDONLY);
     fcntl(fd, F_SETFD, FD_CLOEXEC);
@@ -55,7 +55,7 @@ Buffer* open_fifo(const String& name , const String& filename)
 
     BufferManager::instance().delete_buffer_if_exists(name);
 
-    return create_fifo_buffer(std::move(name), fd);
+    return create_fifo_buffer(std::move(name), fd, scroll);
 }
 
 const PerArgumentCommandCompleter filename_completer({
@@ -111,7 +111,7 @@ void edit(const ParametersParser& parser, Context& context)
             buffer = new Buffer(name, Buffer::Flags::None);
         }
         else if (parser.has_option("fifo"))
-            buffer = open_fifo(name, parser.option_value("fifo"));
+            buffer = open_fifo(name, parser.option_value("fifo"), parser.has_option("scroll"));
         else
             buffer = open_or_create(name, context);
     }
@@ -139,7 +139,8 @@ void edit(const ParametersParser& parser, Context& context)
 
 ParameterDesc edit_params{
     SwitchMap{ { "scratch", { false, "create a scratch buffer, not linked to a file" } },
-               { "fifo", { true, "create a buffer reading its content from a named fifo" } } },
+               { "fifo", { true, "create a buffer reading its content from a named fifo" } },
+               { "scroll", { false, "place the initial cursor so that the fifo will scroll to show new data" } } },
     ParameterDesc::Flags::None, 1, 3
 };