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--[[
obs-hotkey-window-capture v0.1

Allows using a hotkey to change capture window for Window Capture
sources.
   
Partly derived from https://obsproject.com/forum/resources/bounce.947/ 

MIT Licensed
]]--

local obs = obslua
local bit = require('bit')
local ffi = require('ffi')

--- name of source to modify
local source_name = ''
--- scene item to be adjusted
local scene_item = nil

--- the hotkey assigned to window_capture_foreground in OBS's hotkey config
local hotkey_id = obs.OBS_INVALID_HOTKEY_ID

ffi.cdef[[
void* GetAncestor(void *hwnd, unsigned int flags);
void* GetForegroundWindow();
int GetWindowTextLengthA(void* hwnd);
int GetWindowTextA(void* hwnd, char* str, int count);
int GetClassNameA(void* hwnd, char* str, int count);
]]

local function get_active_window_title()
   local hwnd = ffi.C.GetAncestor(ffi.C.GetForegroundWindow(), 3)
   local sz = ffi.C.GetWindowTextLengthA(hwnd)
   local ws = ffi.new('char[?]', sz)
   ffi.C.GetWindowTextA(hwnd, ws, sz+1)
   
   return ffi.string(ws)
end

local function get_active_window_class()
   local hwnd = ffi.C.GetAncestor(ffi.C.GetForegroundWindow(), 3)
   local ws = ffi.new('char[?]', 64)
   ffi.C.GetClassNameA(hwnd, ws, 64)
   
   return ffi.string(ws)
end

--- get a list of source names, sorted alphabetically
local function get_source_names()
   local sources = obs.obs_enum_sources()
   local source_names = {}
   if sources then
      for _, source in ipairs(sources) do
         -- exclude Desktop Audio and Mic/Aux by their capabilities
         local capability_flags = obs.obs_source_get_output_flags(source)
         if bit.band(capability_flags, obs.OBS_SOURCE_DO_NOT_SELF_MONITOR) == 0 and
            capability_flags ~= bit.bor(obs.OBS_SOURCE_AUDIO, obs.OBS_SOURCE_DO_NOT_DUPLICATE) then
            table.insert(source_names, obs.obs_source_get_name(source))
         end
      end
   end
   obs.source_list_release(sources)
   table.sort(source_names, function(a, b)
      return string.lower(a) < string.lower(b)
   end)
   return source_names
end

function find_scene_item()
   if not source_name or source_name == '' then
      obs.script_log(obs.LOG_INFO, 'no source name')
      return false
   end
   
   local source = obs.obs_frontend_get_current_scene()
   if not source then
      obs.script_log(obs.LOG_INFO, 'no current scene')
      return false
   end

   local scene = obs.obs_scene_from_source(source)
   obs.obs_source_release(source)

   scene_item = obs.obs_scene_find_source(scene, source_name)

   scene_item = obs.obs_sceneitem_get_source(scene_item)

   if scene_item then
      return true
   end

   obs.script_log(obs.LOG_INFO, source_name .. ' not found')

   return false
end

function script_description()
   return 'Allows using a hotkey to change capture window for Window Capture sources.'
end

function script_properties()
   local props = obs.obs_properties_create()
   local source = obs.obs_properties_add_list(
      props,
      'source',
      'Source:',
      obs.OBS_COMBO_TYPE_EDITABLE,
      obs.OBS_COMBO_FORMAT_STRING)
   for _, name in ipairs(get_source_names()) do
      obs.obs_property_list_add_string(source, name, name)
   end
   return props
end

function script_update(settings)
   source_name = obs.obs_data_get_string(settings, 'source')

   find_scene_item()
end

function script_load(settings)
   hotkey_id = obs.obs_hotkey_register_frontend('window_capture_foreground', 'Set Window Capture to foreground', window_capture_foreground)
   local hotkey_save_array = obs.obs_data_get_array(settings, 'window_capture_foreground')
   obs.obs_hotkey_load(hotkey_id, hotkey_save_array)
   obs.obs_data_array_release(hotkey_save_array)
   obs.obs_frontend_add_event_callback(on_event)
end

function on_event(event)
    if event == obs.OBS_FRONTEND_EVENT_SCENE_CHANGED then
       find_scene_item()
    end
end

function script_save(settings)
   local hotkey_save_array = obs.obs_hotkey_save(hotkey_id)
   obs.obs_data_set_array(settings, 'window_capture_foreground', hotkey_save_array)
   obs.obs_data_array_release(hotkey_save_array)
end

function window_capture_foreground(pressed)
   if not pressed then
      return
   end
   
   if not scene_item then
      obs.script_log(obs.LOG_INFO, 'no window capture source')
      return
   end

   local window_title = get_active_window_title()
   local window_class = get_active_window_class()

   local data = obs.obs_source_get_settings(scene_item)
   obs.obs_data_set_string(data, 'window', window_title .. ':' .. window_class .. ': ')
   obs.obs_source_update(scene_item, data)
   obs.obs_data_release(data)
end