warn if encoder is not available

encoder.lua

@@ -139,7 +139,7 @@ this.create_clip = function(clip_type, on_complete)
 
     h.notify("Please wait...", "info", 9999)
 
-    local output_file_path, args  = (function()
+    local output_file_path, args = (function()
         local clip_filename_noext = construct_output_filename_noext()
         if clip_type == 'video' then
             local output_path = this.mk_out_path_video(clip_filename_noext)
@@ -172,9 +172,22 @@ this.create_clip = function(clip_type, on_complete)
     this.timings:reset()
 end
 
+this.set_encoder_alive = function()
+    local args = { 'mpv', '--version' }
+    local process_result = function(_, ret, _)
+        if ret.status ~= 0 or string.match(ret.stdout, "mpv") == nil then
+            this.alive = false
+        else
+            this.alive = true
+        end
+    end
+    h.subprocess_async(args, process_result)
+end
+
 this.init = function(config, timings_mgr)
     this.config = config
     this.timings = timings_mgr
+    this.set_encoder_alive()
 end
 
 return this

osd_styler.lua

@@ -26,7 +26,7 @@ function OSD:new()
 end
 
 function OSD:append(s)
-    table.insert(self.messages, s)
+    table.insert(self.messages, tostring(s))
     return self
 end
 
@@ -42,6 +42,10 @@ function OSD:size(size)
     return self:append('{\\fs'):append(size):append('}')
 end
 
+function OSD:font(name)
+    return self:append('{\\fn'):append(name):append('}')
+end
+
 function OSD:align(number)
     return self:append('{\\an'):append(number):append('}')
 end
@@ -62,6 +66,10 @@ function OSD:text(text)
     return self:append(text)
 end
 
+function OSD:new_layer()
+    return self:append('\n')
+end
+
 function OSD:bold(s)
     return self:append('{\\b1}'):append(s):append('{\\b0}')
 end
@@ -78,4 +86,12 @@ function OSD:item(text)
     return self:color('fef6dd'):bold(text):color('ffffff')
 end
 
+function OSD:selected(text)
+    return self:color('48a868'):bold(text):color('ffffff')
+end
+
+function OSD:red(text)
+    return self:color('ff0000'):bold(text):color('ffffff')
+end
+
 return OSD

videoclip.lua

@@ -256,6 +256,9 @@ end
 
 function main_menu:update()
     local osd = OSD:new():size(config.font_size):align(4)
+    if encoder.alive == false then
+        osd:red("Error: "):append("mpv is not found in the PATH."):newline()
+    end
     osd:submenu('Clip creator'):newline()
     osd:tab():item('Start time: '):append(h.human_readable_time(self.timings['start'])):newline()
     osd:tab():item('End time: '):append(h.human_readable_time(self.timings['end'])):newline()