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%%%-------------------------------------------------------------------
%% @doc Parser for XDG .desktop files.
%%
%% Reads the `[Desktop Entry]' group of a desktop entry file and
%% extracts the fields needed to build a menu item: `Name', `Exec'
%% and (optionally) `Icon'. Other groups (e.g. `[Desktop Action ...]')
%% and localized keys (e.g. `Name[fr]') are ignored.
%% @end
%%%-------------------------------------------------------------------
-module(er_xdg_pipe_menu_desktop_entry).
-include("er_xdg_pipe_menu.hrl").
-export([parse_file/1, parse/1]).
-define(GROUP, <<"Desktop Entry">>).
-define(WANTED_KEYS, [
<<"Name">>, <<"Exec">>, <<"Icon">>, <<"NoDisplay">>, <<"Hidden">>, <<"Type">>
]).
-define(FIELD_CODES, "fFuUdDnNickvm").
-spec parse_file(file:filename_all()) -> {ok, #desktop_entry{}} | {error, term()}.
parse_file(Path) ->
case file:read_file(Path) of
{ok, Bin} -> parse(Bin);
{error, Reason} -> {error, Reason}
end.
-spec parse(binary()) -> {ok, #desktop_entry{}} | {error, missing_name | missing_exec}.
parse(Bin) ->
to_entry(scan(Bin)).
%% Fold every line into a map of the fields we care about, tracking
%% which `[Group]' we're currently inside.
scan(Bin) ->
Lines = binary:split(Bin, [<<"\r\n">>, <<"\n">>], [global]),
{_Group, Fields} = lists:foldl(fun scan_line/2, {undefined, #{}}, Lines),
Fields.
scan_line(Line, {Group, Fields}) ->
case classify(string:trim(Line)) of
skip ->
{Group, Fields};
{section, Name} ->
{Name, Fields};
{kv, Key, Value} ->
case Group =:= ?GROUP andalso lists:member(Key, ?WANTED_KEYS) of
true -> {Group, maps:put(Key, unescape(Value), Fields)};
false -> {Group, Fields}
end
end.
classify(<<>>) ->
skip;
classify(<<"#", _/binary>>) ->
skip;
classify(<<"[", Rest/binary>>) ->
Size = byte_size(Rest) - 1,
case Rest of
<<Name:Size/binary, "]">> -> {section, string:trim(Name)};
_ -> skip
end;
classify(Line) ->
case binary:split(Line, <<"=">>) of
[Key, Value] -> {kv, string:trim(Key), string:trim(Value)};
[_] -> skip
end.
%% Desktop entry escape sequences: \\ \s \n \t \r
unescape(Bin) ->
unescape(Bin, <<>>).
unescape(<<>>, Acc) ->
Acc;
unescape(<<$\\, $\\, Rest/binary>>, Acc) ->
unescape(Rest, <<Acc/binary, $\\>>);
unescape(<<$\\, $s, Rest/binary>>, Acc) ->
unescape(Rest, <<Acc/binary, $\s>>);
unescape(<<$\\, $n, Rest/binary>>, Acc) ->
unescape(Rest, <<Acc/binary, $\n>>);
unescape(<<$\\, $t, Rest/binary>>, Acc) ->
unescape(Rest, <<Acc/binary, $\t>>);
unescape(<<$\\, $r, Rest/binary>>, Acc) ->
unescape(Rest, <<Acc/binary, $\r>>);
unescape(<<C, Rest/binary>>, Acc) ->
unescape(Rest, <<Acc/binary, C>>).
to_entry(Fields) ->
case maps:find(<<"Name">>, Fields) of
error ->
{error, missing_name};
{ok, Name} ->
case maps:find(<<"Exec">>, Fields) of
error ->
{error, missing_exec};
{ok, Exec} ->
{ok, #desktop_entry{
name = Name,
exec = strip_field_codes(Exec),
icon = maps:get(<<"Icon">>, Fields, undefined),
hidden = is_hidden(Fields)
}}
end
end.
%% Niche variations (e.g. a Type-less override dropped into
%% ~/.local/share/applications) are left to be special-cased there
%% rather than accounted for here.
is_hidden(Fields) ->
maps:get(<<"NoDisplay">>, Fields, <<"false">>) =:= <<"true">> orelse
maps:get(<<"Hidden">>, Fields, <<"false">>) =:= <<"true">> orelse
case maps:find(<<"Type">>, Fields) of
{ok, Type} -> Type =/= <<"Application">>;
error -> false
end.
%% Field codes (%f, %u, %i, ...) are expanded by launchers that pass
%% files/URIs on the command line; a pipemenu has none to pass, so
%% each code is dropped along with the whitespace around it. `%%' is
%% then unescaped to a literal `%'.
strip_field_codes(Exec) ->
Tokens = binary:split(Exec, <<" ">>, [global]),
Kept = [T || T <- Tokens, T =/= <<>>, not is_field_code(T)],
Joined = iolist_to_binary(lists:join(<<" ">>, Kept)),
binary:replace(Joined, <<"%%">>, <<"%">>, [global]).
is_field_code(<<"%", C>>) ->
lists:member(C, ?FIELD_CODES);
is_field_code(_) ->
false.
|
