console: respect the top margin shared script property

Console already respected the bottom margin to not overlap with the
bottom bar from the OSC, but it would still overlap with the window
decorations from the OSC.

Now everything is clipped above the top margin and no superfluous lines
are drawn.

player/lua/console.lua

@@ -64,7 +64,8 @@ local history = {}
 local history_pos = 1
 local log_buffer = {}
 local key_bindings = {}
-local global_margin_y = 0
+local global_margin_top = 0
+local global_margin_bottom = 0
 
 local update_timer = nil
 update_timer = mp.add_periodic_timer(0.05, function()
@@ -84,9 +85,11 @@ utils.shared_script_property_observe("osc-margins", function(_, val)
         for v in string.gmatch(val, "[^,]+") do
             vals[#vals + 1] = tonumber(v)
         end
-        global_margin_y = vals[4] -- bottom
+        global_margin_top = vals[3] -- top
+        global_margin_bottom = vals[4] -- bottom
     else
-        global_margin_y = 0
+        global_margin_top = 0
+        global_margin_bottom = 0
     end
     update()
 end)
@@ -143,12 +146,16 @@ function update()
         return
     end
 
+    local coordinate_top = math.floor(global_margin_top * screeny + 0.5)
+    local clipping_coordinates = '0,' .. coordinate_top .. ',' ..
+                                 screenx .. ',' .. screeny
     local ass = assdraw.ass_new()
     local style = '{\\r' ..
                   '\\1a&H00&\\3a&H00&\\4a&H99&' ..
                   '\\1c&Heeeeee&\\3c&H111111&\\4c&H000000&' ..
                   '\\fn' .. opts.font .. '\\fs' .. opts.font_size ..
-                  '\\bord1\\xshad0\\yshad1\\fsp0\\q1}'
+                  '\\bord1\\xshad0\\yshad1\\fsp0\\q1' ..
+                  '\\clip(' .. clipping_coordinates .. ')}'
     -- Create the cursor glyph as an ASS drawing. ASS will draw the cursor
     -- inline with the surrounding text, but it sets the advance to the width
     -- of the drawing. So the cursor doesn't affect layout too much, make it as
@@ -168,7 +175,10 @@ function update()
     -- messages.
     local log_ass = ''
     local log_messages = #log_buffer
-    local log_max_lines = math.ceil(screeny / opts.font_size)
+    local screeny_factor = (1 - global_margin_top - global_margin_bottom)
+    -- subtract 1.5 to account for the input line
+    local log_max_lines = screeny * screeny_factor / opts.font_size - 1.5
+    log_max_lines = math.ceil(log_max_lines)
     if log_max_lines < log_messages then
         log_messages = log_max_lines
     end
@@ -178,7 +188,7 @@ function update()
 
     ass:new_event()
     ass:an(1)
-    ass:pos(2, screeny - 2 - global_margin_y * screeny)
+    ass:pos(2, screeny - 2 - global_margin_bottom * screeny)
     ass:append(log_ass .. '\\N')
     ass:append(style .. '> ' .. before_cur)
     ass:append(cglyph)
@@ -188,7 +198,7 @@ function update()
     -- cursor appear in front of the text.
     ass:new_event()
     ass:an(1)
-    ass:pos(2, screeny - 2 - global_margin_y * screeny)
+    ass:pos(2, screeny - 2 - global_margin_bottom * screeny)
     ass:append(style .. '{\\alpha&HFF&}> ' .. before_cur)
     ass:append(cglyph)
     ass:append(style .. '{\\alpha&HFF&}' .. after_cur)