refactor: cursor events consolidated into one interface (#483)

`mbtn_left` and `wheel` events are now only fired on a `cursor.on_{event}` object, which resets at the beginning of each frame, so elements need to bind these listeners in their render functions. These properties are overwritable which allows elements to take over cursor event handling from their parents if necessary.

scripts/uosc_shared/elements/TopBar.lua

@@ -16,7 +16,7 @@ function TopBarButton:init(id, props)
 	self.command = props.command
 end
 
-function TopBarButton:on_mbtn_left_down()
+function TopBarButton:handle_cursor_down()
 	mp.command(type(self.command) == 'function' and self.command() or self.command)
 end
 
@@ -28,6 +28,7 @@ function TopBarButton:render()
 	-- Background on hover
 	if self.proximity_raw == 0 then
 		ass:rect(self.ax, self.ay, self.bx, self.by, {color = self.background, opacity = visibility})
+		cursor.on_primary_down = function() self:handle_cursor_down() end
 	end
 
 	local width, height = self.bx - self.ax, self.by - self.ay
@@ -151,10 +152,6 @@ function TopBar:on_prop_maximized()
 	self:update_dimensions()
 end
 
-function TopBar:on_mbtn_left_down()
-	if cursor.x < self.title_bx then self:toggle_title() end
-end
-
 function TopBar:on_display() self:update_dimensions() end
 
 function TopBar:render()
@@ -193,6 +190,12 @@ function TopBar:render()
 				}
 				local bx = math.min(max_bx, title_ax + text_width(main_title, opts) + padding * 2)
 				local by = self.by - bg_margin
+				local rect = {ax = title_ax, ay = self.ay, bx = bx, by = self.by}
+
+				if get_point_to_rectangle_proximity(cursor, rect) == 0 then
+					cursor.on_primary_down = function() self:toggle_title() end
+				end
+
 				ass:rect(title_ax, title_ay, bx, by, {
 					color = bg, opacity = visibility * options.top_bar_title_opacity, radius = 2,
 				})