command: extend osd-overlay command with bounds reporting

This is more or less a minimal hack to make _some_ text measurement
functionality available to scripts. Since libass does not support such a
thing, this simply uses the bounding box of the rendered text.

This is far from ideal. Problems include:
- using a bitmap bounding box
- additional memory waste and/or flushing caches
- dependency on window size
- odd small deviations with different window sizes (run osd-test.lua and
  resize the window after each timer update; the bounding boxes aren't
  adjusted in an overly useful way)
- inability to query the size _after_ actual rendering

But I guess it's a start. Since I'm aware that it's crap, add a threat
to the manpage that this may be changed/removed again. For now, I'm
interested whether anyone will have use for it in its current form, as
it's an often requested feature.

1 files changed, 35 insertions, 0 deletions

diff --git a/TOOLS/lua/osd-test.lua b/TOOLS/lua/osd-test.lua
new file mode 100644
index 0000000000..1b1781956d
--- /dev/null
+++ b/TOOLS/lua/osd-test.lua
@@ -0,0 +1,35 @@
+local assdraw = require 'mp.assdraw'
+local utils = require 'mp.utils'
+
+things = {}
+for i = 1, 2 do
+    things[i] = {
+        osd1 = mp.create_osd_overlay("ass-events"),
+        osd2 = mp.create_osd_overlay("ass-events")
+    }
+end
+things[1].text = "{\\an5}hello\\Nworld"
+things[2].text = "{\\pos(400, 200)}something something"
+
+mp.add_periodic_timer(2, function()
+    for i, thing in ipairs(things) do
+        thing.osd1.data = thing.text
+        thing.osd1.compute_bounds = true
+        --thing.osd1.hidden = true
+        local res = thing.osd1:update()
+        print("res " .. i .. ": " .. utils.to_string(res))
+
+        thing.osd2.hidden = true
+        if res ~= nil and res.x0 ~= nil then
+            local draw = assdraw.ass_new()
+            draw:append("{\\alpha&H80}")
+            draw:draw_start()
+            draw:pos(0, 0)
+            draw:rect_cw(res.x0, res.y0, res.x1, res.y1)
+            draw:draw_stop()
+            thing.osd2.hidden = false
+            thing.osd2.data = draw.text
+        end
+        thing.osd2:update()
+    end
+end)