mouse-mode: add support for custom scrolling (#22)

Implements a new scrolling system for mouse-mode and properly calculates
the hovered item when scrolling the list.

This hover should work with custom font sizes, but currently the
calculations are not adding up for the header, so that is hardcoded.

See the next commit for keybinds.

Author: CogentRedTester

Diff for: file-browser.lua

@@ -186,11 +186,12 @@ local style = {
 }
 
 local state = {
-    list = {},
-    selected = 1,
-    hidden = true,
-    flag_update = false,
-    keybinds = nil,
+    list = {},                      -- list of items
+    selected = 1,                   -- currently selected item
+    scroll_offset = 0,
+    hidden = true,                  -- whether the browser is hidden
+    flag_update = false,            -- should we redraw the browser when next opened
+    keybinds = nil,                 -- array of dynamic deybinds
 
     parser = nil,
     directory = nil,
@@ -710,18 +711,13 @@ local function update_ass()
     local start = 1
     local finish = start+o.num_entries-1
 
-    --handling cursor positioning
-    local mid = math.ceil(o.num_entries/2)+1
-    if state.selected+mid > finish then
-        local offset = state.selected - finish + mid
-
-        --if we've overshot the end of the list then undo some of the offset
-        if finish + offset > #state.list then
-            offset = offset - ((finish+offset) - #state.list)
+    --handling the offset caused by scrolling
+    if state.scroll_offset > 0 then
+        if finish + state.scroll_offset > #state.list then
+            state.scroll_offset = #state.list - finish
         end
-
-        start = start + offset
-        finish = finish + offset
+        start = start + state.scroll_offset
+        finish = finish + state.scroll_offset
     end
 
     --making sure that we don't overstep the boundaries
@@ -832,6 +828,12 @@ local function scroll(n, wrap)
     end
 
     if state.multiselect_start then drag_select(original_pos, state.selected) end
+
+    --moves the scroll window down so that the selected item is in the middle of the screen
+    state.scroll_offset = state.selected - (math.ceil(o.num_entries/2)-1)
+    if state.scroll_offset < 0 or (state.scroll_offset + o.num_entries) > #state.list then
+        state.scroll_offset = 0
+    end
     update_ass()
 end
 
@@ -863,13 +865,30 @@ end
 
 --update the selected item based on the mouse position
 local function update_mouse_pos(_, mouse_pos)
+    if not mouse_pos then mouse_pos = mp.get_property_native("mouse-pos") end
     if not mouse_pos.hover then return end
     local scale = mp.get_property_number("osd-height", 0) / 720
+
+    --this will currently not work with different sized headers
+    --for some reason the scaling calculation works differently for the header
     local header_offset = 65
-    state.selected = math.ceil((mouse_pos.y-header_offset) / (25* scale))
+    if state.scroll_offset > 0 then
+        header_offset = header_offset + o.font_size_wrappers*scale
+    end
+
+    state.selected = math.ceil((mouse_pos.y-header_offset) / (o.font_size_body* scale)) + state.scroll_offset
     update_ass()
 end
 
+-- scrolls the view window when using mouse mode
+local function wheel(direction)
+    state.scroll_offset = state.scroll_offset + direction
+    if state.scroll_offset < 0 or (state.scroll_offset + o.num_entries) > #state.list then
+        state.scroll_offset = 0
+    end
+    update_mouse_pos()
+end
+
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