implement margin when scrolling

3 files changed, 16 insertions, 12 deletions

diff --git a/config.lua b/config.lua
index 9dc9bff..bd0819c 100644
--- a/config.lua
+++ b/config.lua
@@ -7,6 +7,8 @@ local config = {}
 -- font size is in units of osd height, which is scaled to 720
 config.font_size = 20
 
+config.scroll_margin = 4
+
 config.bg_alpha = '44'
 config.colours = {
 	title = '999999',
diff --git a/main.lua b/main.lua
index 12c7f4d..4014d16 100644
--- a/main.lua
+++ b/main.lua
@@ -101,11 +101,11 @@ local function set_cursor(pos, opts)
 end
 
 local function cursor_up()
-	set_cursor(state:menu().cursor - 1)
+	set_cursor(state:menu().cursor - 1, {margin = config.scroll_margin})
 end
 
 local function cursor_down()
-	set_cursor(state:menu().cursor + 1)
+	set_cursor(state:menu().cursor + 1, {margin = config.scroll_margin})
 end
 
 local function cursor_start()
@@ -163,11 +163,11 @@ local function move_option(pos, opts)
 end
 
 local function move_option_up()
-	move_option(state:menu().cursor - 1)
+	move_option(state:menu().cursor - 1, {margin = config.scroll_margin})
 end
 
 local function move_option_down()
-	move_option(state:menu().cursor + 1)
+	move_option(state:menu().cursor + 1, {margin = config.scroll_margin})
 end
 
 local function move_option_start()
diff --git a/state.lua b/state.lua
index 8bf4ddd..41c317c 100644
--- a/state.lua
+++ b/state.lua
@@ -85,8 +85,9 @@ end
 function menu_mt:set_cursor(pos, lines, opts)
 	local pos = math.max(1, math.min(pos, #self.options))
 	local top = self.view_top
+	local margin = 0
 
-	if not lines then
+	if not lines or lines < 2 then
 		top = pos
 		goto update
 	end
@@ -95,15 +96,16 @@ function menu_mt:set_cursor(pos, lines, opts)
 		top = pos - math.floor((lines - 1) / 2)
 	elseif opts and opts.keep_offset then
 		top = top + pos - self.cursor
+	elseif opts and opts.margin then
+		margin = math.max(0, math.min(
+			opts.margin,
+			math.floor((lines - 1) / 2),
+			self.cursor - self.view_top,
+			self.view_top + lines - 1 - self.cursor))
 	end
 
-	-- move view to keep selected option visible
-	if pos < top then
-		top = pos
-	elseif pos > top + lines - 1 then
-		top = pos - lines + 1
-	end
-
+	-- keep selected option visible and view in bounds
+	top = math.max(pos - lines + 1 + margin, math.min(top, pos - margin))
 	top = math.max(1, math.min(top, #self.options - lines + 1))
 
 	::update::