console.lua: improve the hovered item calculation with background-box

Follow up to c438732 which improved the calculation with the default
outline-and-shadow. We can make the calculation accurate for
background-box too without making semitransparent rectangle backgrounds
overlap by disabling the shadow of selectable items, and drawing a
single rectangle below the items.

We could also calculate the height of each item to make them perfectly
adjacent by rendering each one with compute_bounds, but that takes 15ms
per render even on a new CPU, so 20 lines would take 300ms, which is too
slow.

The rectangle is as wide as the longest item. Even using compute_bounds
once on the longest item on each render() slows it to the point of
making updating the highlight while moving the mouse slower than with
outline-and-shadow, especially on old hardware. So cache the width of
the longest item when opening the console and update it when
osd-dimensions change. The calculation is only done with background-box
to not slow down outline-and-shadow unnecessarily, though it would be
fine since it's only calculated on open, and therefore we also observe
osd-border-style for the unlikely event that it changes during
selection.

Also increase the items' height to opts.font_size * 1.1 because it looks
better with some margin between the items. It is possible to do it now
because selectable items are drawn in separate ASS events in all border
styles.

player/lua/console.lua

@@ -107,6 +107,8 @@ local matches = {}
 local selected_match = 1
 local first_match_to_print = 1
 local default_item
+local item_positions = {}
+local longest_width = 0
 
 local complete
 local cycle_through_completions
@@ -280,6 +282,10 @@ local function get_scaled_osd_dimensions()
     return dims.w / scale, dims.h /scale
 end
 
+local function get_line_height()
+    return selectable_items and opts.font_size * 1.1 or opts.font_size
+end
+
 local function calculate_max_log_lines()
     if not mp.get_property_native('vo-configured')
        or not mp.get_property_native('video-osd') then
@@ -292,12 +298,33 @@ local function calculate_max_log_lines()
     return math.floor((select(2, get_scaled_osd_dimensions())
                        * (1 - global_margins.t - global_margins.b)
                        - get_margin_y())
-                      / opts.font_size
+                      / get_line_height()
                       -- Subtract 1 for the input line and 0.5 for the empty
                       -- line between the log and the input line.
                       - 1.5)
 end
 
+local function calculate_longest_width()
+    if not selectable_items or mp.get_property('osd-border-style') ~= 'background-box' then
+        return
+    end
+
+    local longest_item = selectable_items[1]
+    for _, item in pairs(selectable_items) do
+        if #item > #longest_item then
+            longest_item = item
+        end
+    end
+
+    local width_overlay = mp.create_osd_overlay('ass-events')
+    width_overlay.compute_bounds = true
+    width_overlay.hidden = true
+    width_overlay.res_x, width_overlay.res_y = get_scaled_osd_dimensions()
+    width_overlay.data = '{\\b1}' .. longest_item
+    local result = width_overlay:update()
+    longest_width = result.x1 - result.x0
+end
+
 local function should_highlight_completion(i)
     return i == selected_completion_index or
            (i == 1 and selected_completion_index == 0 and input_caller == nil)
@@ -627,21 +654,36 @@ local function render()
 
     local log_ass = ''
     local log_buffer = log_buffers[id]
-    local box = mp.get_property('osd-border-style') == 'background-box'
+    local line_height = get_line_height()
+    item_positions = {}
+
+    -- Disable background-box for selectable items to not draw separate
+    -- rectangles with different widths, and draw a single rectangle instead.
+    if selectable_items and mp.get_property('osd-border-style') == 'background-box' then
+        style = style .. '{\\4aff}'
+
+        ass:new_event()
+        ass:an(1)
+        ass:pos(x, y)
+        ass:append('{\\1aff}')
+        ass:draw_start()
+        ass:rect_cw(0, 0, longest_width, (1.5 + #matches) * line_height)
+        ass:draw_stop()
+    end
 
     for i = #log_buffer - math.min(max_lines, #log_buffer) + 1, #log_buffer do
         local log_item = style .. log_buffer[i].style .. ass_escape(log_buffer[i].text)
 
-        -- Put every selectable item in its own event to prevent libass from
-        -- drawing them taller than opts.font_size with taller fonts, which
-        -- makes the hovered item calculation inaccurate and clips the counter.
-        -- But not with background-box, because it makes it look bad by
-        -- overlapping the semitransparent backgrounds of every line.
-        if selectable_items and not box then
+        if selectable_items then
+            local item_y = y - (1.5 + #log_buffer - i) * line_height
             ass:new_event()
             ass:an(1)
-            ass:pos(x, y - (1.5 + #log_buffer - i) * opts.font_size)
+            ass:pos(x, item_y)
             ass:append(log_item)
+
+            if #matches <= max_lines or i > 1 then -- skip the counter
+                item_positions[#item_positions + 1] = { item_y - line_height, item_y }
+            end
         else
             log_ass = log_ass .. log_item .. '\\N'
         end
@@ -920,27 +962,12 @@ local function handle_enter()
 end
 
 local function determine_hovered_item()
-    local height = select(2, get_scaled_osd_dimensions())
     local y = mp.get_property_native('mouse-pos').y / scale_factor()
-    local log_bottom_pos = height * (1 - global_margins.b)
-                           - get_margin_y()
-                           - 1.5 * opts.font_size
 
-    if y > log_bottom_pos then
-        return
-    end
-
-    local max_lines = calculate_max_log_lines()
-    -- Subtract 1 line for the position counter.
-    if #matches > max_lines then
-        max_lines = max_lines - 1
-    end
-    local last = math.min(first_match_to_print - 1 + max_lines, #matches)
-
-    local hovered_item = last - math.floor((log_bottom_pos - y) / opts.font_size)
-
-    if hovered_item >= first_match_to_print then
-        return hovered_item
+    for i, positions in ipairs(item_positions) do
+        if y >= positions[1] and y <= positions[2] then
+            return first_match_to_print - 1 + i
+        end
     end
 end
 
@@ -1079,6 +1106,7 @@ local function search_history()
         selectable_items[i] = history[#history + 1 - i]
     end
 
+    calculate_longest_width()
     handle_edit()
     bind_mouse()
 end
@@ -1886,6 +1914,7 @@ mp.register_script_message('get-input', function (script_name, args)
             selectable_items[i] = item:gsub("[\r\n].*", "⋯"):sub(1, 300)
         end
         default_item = args.default_item
+        calculate_longest_width()
         handle_edit()
         bind_mouse()
     end
@@ -1953,11 +1982,12 @@ mp.register_script_message('complete', function(list, start_pos)
     render()
 end)
 
--- Redraw the REPL when the OSD size changes. This is needed because the
--- PlayRes of the OSD will need to be adjusted.
-mp.observe_property('osd-width', 'native', render)
-mp.observe_property('osd-height', 'native', render)
-mp.observe_property('display-hidpi-scale', 'native', render)
+for _, property in pairs({'osd-width', 'osd-height', 'display-hidpi-scale', 'osd-border-style'}) do
+    mp.observe_property(property, 'native', function ()
+        calculate_longest_width()
+        render()
+    end)
+end
 mp.observe_property('focused', 'native', render)
 
 mp.observe_property("user-data/osc/margins", "native", function(_, val)