karaoke-trim.lua

local tr = aegisub.gettext

script_name = tr"Trim karaoke lines"
script_description = tr"Remove first and last k-tags and adjust start and end times accordingly"

l_script_description = tr"Remove first k-tag and adjust start time accordingly"
l_script_name = tr"Trim karaoke lines - Left"

r_script_name = tr"Trim karaoke lines - Right"
r_script_description = tr"Remove last k-tag and adjust end time accordingly"

script_author = "Louis Royer"
script_version = "1.1"

--[[
-- Check if the line is a karaoke line
--]]
function is_trimmable(line)
    if line.comment then
        return line.effect == "karaoke"
    end
    return line.class == "dialogue"
end

--[[
--  Compute duration of a line using k-tags
--]]
function get_duration(line)
    local d = 0
    local kduration = "{[^}]-\\[kK][fo]?(%d+)[^}]-}"
    for match in line:gmatch(kduration) do
        d = d + tonumber(match)
    end
    return d * 10
end

--[[
--  Trim left
--]]
function l_trim_line(subs, sel)
    local txt_split_expr = "^[{[^}]-\\[kK][fo]?%d+[^}]-}%s*]*({[^}]-\\[kK][fo]?%d+[^}]-})(.*)"
    for _, i in ipairs(sel) do
        local line = subs[i]
        if is_trimmable(line) then
            local end_text_0, end_text_1 = line.text:match(txt_split_expr)
            if end_text_0 then
                local end_text = end_text_1 and (end_text_0 .. end_text_1) or end_text_0
                local total_dur = get_duration(line.text)
                local trim_dur = get_duration(end_text)
                line.start_time = line.start_time + (total_dur - trim_dur)
                line.text = end_text
                subs[i] = line
            end
        end
    end
end

--[[
--  Trim left, and set undo point
--]]
function l_trim_line_undo(subs, sel)
    l_trim_line(subs, sel)
    aegisub.set_undo_point(tr"Karaoke left-trim")
end

--[[
--  Trim right
--]]
function r_trim_line(subs, sel)
    local split_expr = "(.-)%s*{[^}]-\\[kK][fo]?%d+[^}]-}%s*$"
    for _, i in ipairs(sel) do
        local line = subs[i]
        if is_trimmable(line) then
            local start_text = line.text:match(split_expr)
            if start_text then
                line.end_time = line.start_time + get_duration(start_text)
                line.text = start_text
                subs[i] = line
            end
        end
    end
end

--[[
--  Trim right, and set undo point
--]]
function r_trim_line_undo(subs, sel)
    r_trim_line(subs, sel)
    aegisub.set_undo_point(tr"Karaoke right-trim")
end

--[[
--  Trim left, trim right, and set undo point
--]]
function trim_line(subs, sel)
    l_trim_line(subs, sel)
    r_trim_line(subs, sel)
    aegisub.set_undo_point(tr"Karaoke trim")
end

aegisub.register_macro(script_name, script_description, trim_line)
aegisub.register_macro(l_script_name, l_script_description, l_trim_line_undo)
aegisub.register_macro(r_script_name, r_script_description, r_trim_line_undo)