crop: Clamp cursor within video dimensions

...and display crop zone DAR

Previously, the script would allow for the drawing of the crop zone to
begin even if the crop cursor was placed outside video dimensions (e.g.
the area into which the video is rendered). This would show inaccurate
crop zone dimensions when drawing the text for the crop zone.

This PR limits placing of the crop cursor within video dimensions area,
and also adds a little quality-of-life feature that displays the
aspect ratio of the crop zone before validation.

Ref: occivink/mpv-scripts#67

Author: stanleyqubit

scripts/crop.lua

@@ -49,7 +49,7 @@ local rect_centered = false
 local rect_keepaspect = false
 local needs_drawing = false
 local crop_first_corner = nil -- in normalized video space
-local crop_cursor = {
+local cursor = {
     x = 0,
     y = 0
 }
@@ -82,6 +82,11 @@ function rect_from_two_points(p1, p2, centered, ratio)
     return { x = c1[1], y = c1[2] }, { x = c2[1], y = c2[2] }
 end
 
+function round(num, num_decimal_places)
+    local mult = 10^(num_decimal_places or 0)
+    return math.floor(num * mult + 0.5) / mult
+end
+
 function clamp(low, value, high)
     if value <= low then
         return low
@@ -92,10 +97,10 @@ function clamp(low, value, high)
     end
 end
 
-function clamp_point(top_left, point, bottom_right)
+function clamp_point(point, dim)
     return {
-        x = clamp(top_left.x, point.x, bottom_right.x),
-        y = clamp(top_left.y, point.y, bottom_right.y)
+        x = clamp(dim.ml, point.x, dim.w - dim.mr),
+        y = clamp(dim.mt, point.y, dim.h - dim.mb)
     }
 end
 
@@ -210,10 +215,7 @@ function draw_crop_zone()
             return
         end
 
-        local cursor = {
-            x = crop_cursor.x,
-            y = crop_cursor.y,
-        }
+        cursor = clamp_point(cursor, dim)
         local ass = assdraw.ass_new()
 
         if crop_first_corner and (opts.draw_shade or opts.draw_frame) then
@@ -247,9 +249,13 @@ function draw_crop_zone()
                 local cursor_norm = screen_to_video_norm(cursor, dim)
                 local text = string.format("%d, %d", cursor_norm.x * vop.w, cursor_norm.y * vop.h)
                 if crop_first_corner then
-                    text = string.format("%s (%dx%d)", text,
-                        math.abs((cursor_norm.x - crop_first_corner.x) * vop.w ),
-                        math.abs((cursor_norm.y - crop_first_corner.y) * vop.h )
+                    local crop_zone_w = math.abs((cursor_norm.x - crop_first_corner.x) * vop.w )
+                    local crop_zone_h = math.abs((cursor_norm.y - crop_first_corner.y) * vop.h )
+                    local crop_zone_aspect = round(crop_zone_w / crop_zone_h, 3)
+                    text = string.format("%s (%dx%d/%s)", text,
+                        crop_zone_w,
+                        crop_zone_h,
+                        crop_zone_aspect
                     )
                 end
                 draw_position_text(ass, text, cursor, { w = dim.w, h = dim.h }, 6)
@@ -308,14 +314,14 @@ function update_crop_zone_state()
         cancel_crop()
         return
     end
-    local corner = crop_cursor
+    cursor = clamp_point(cursor, dim)
     if crop_first_corner == nil then
-        crop_first_corner = screen_to_video_norm(crop_cursor, dim)
+        crop_first_corner = screen_to_video_norm(cursor, dim)
         redraw()
     else
         local c1, c2 = rect_from_two_points(
             video_norm_to_screen(crop_first_corner, dim),
-            crop_cursor,
+            cursor,
             rect_centered,
             rect_keepaspect and dim.w/dim.h)
         local c1norm = screen_to_video_norm(c1, dim)
@@ -361,7 +367,7 @@ function start_crop(mode)
     active_mode = mode_maybe
 
     if opts.mouse_support then
-        crop_cursor.x, crop_cursor.y = mp.get_mouse_pos()
+        cursor.x, cursor.y = mp.get_mouse_pos()
     end
     redraw()
     for key, func in pairs(bindings) do
@@ -405,7 +411,7 @@ end
 
 -- bindings
 if opts.mouse_support then
-    bindings["MOUSE_MOVE"] = function() crop_cursor.x, crop_cursor.y = mp.get_mouse_pos(); redraw() end
+    bindings["MOUSE_MOVE"] = function() cursor.x, cursor.y = mp.get_mouse_pos(); redraw() end
 end
 for _, key in ipairs(opts.accept) do
     bindings[key] = update_crop_zone_state
@@ -415,8 +421,8 @@ for _, key in ipairs(opts.cancel) do
 end
 function movement_func(move_x, move_y)
     return function()
-        crop_cursor.x = crop_cursor.x + move_x
-        crop_cursor.y = crop_cursor.y + move_y
+        cursor.x = cursor.x + move_x
+        cursor.y = cursor.y + move_y
         redraw()
     end
 end