Add top tab margins (#1479)

adapted from #810 to allow styles to decide upon the top margin of the tab list

data/core/node.lua

@@ -334,10 +334,17 @@ function Node:get_child_overlapping_point(x, y)
   return child:get_child_overlapping_point(x, y)
 end
 
+-- returns: total height, text padding, top margin
+local function get_tab_y_sizes()
+  local height = style.font:get_height()
+  local padding = style.padding.y
+  local margin = style.margin.tab.top
+  return height + (padding * 2) + margin, padding, margin
+end
 
 function Node:get_scroll_button_rect(index)
   local w, pad = get_scroll_button_width()
-  local h = style.font:get_height() + style.padding.y * 2
+  local h = get_tab_y_sizes()
   local x = self.position.x + (index == 1 and self.size.x - w * 2 or self.size.x - w)
   return x, self.position.y, w, h, pad
 end
@@ -348,8 +355,8 @@ function Node:get_tab_rect(idx)
   local x0 = self.position.x
   local x1 = x0 + common.clamp(self.tab_width * (idx - 1) - self.tab_shift, 0, maxw)
   local x2 = x0 + common.clamp(self.tab_width * idx - self.tab_shift, 0, maxw)
-  local h = style.font:get_height() + style.padding.y * 2
-  return x1, self.position.y, x2 - x1, h
+  local h, pad_y, margin_y = get_tab_y_sizes()
+  return x1, self.position.y, x2 - x1, h, margin_y
 end
 
 
@@ -540,6 +547,7 @@ function Node:draw_tab_borders(view, is_active, is_hovered, x, y, w, h, standalo
   if is_active then
     color = style.text
     renderer.draw_rect(x, y, w, h, style.background)
+    renderer.draw_rect(x, y, w, ds, style.divider)
     renderer.draw_rect(x + w, y, ds, h, style.divider)
     renderer.draw_rect(x - ds, y, ds, h, style.divider)
   end
@@ -547,7 +555,8 @@ function Node:draw_tab_borders(view, is_active, is_hovered, x, y, w, h, standalo
 end
 
 function Node:draw_tab(view, is_active, is_hovered, is_close_hovered, x, y, w, h, standalone)
-  x, y, w, h = self:draw_tab_borders(view, is_active, is_hovered, x, y, w, h, standalone)
+  local _, padding_y, margin_y = get_tab_y_sizes()
+  x, y, w, h = self:draw_tab_borders(view, is_active, is_hovered, x, y + margin_y, w, h - margin_y, standalone)
   -- Close button
   local cx, cw, cpad = close_button_location(x, w)
   local show_close_button = ((is_active or is_hovered) and not standalone and config.tab_close_button)
@@ -768,7 +777,7 @@ function Node:get_drag_overlay_tab_position(x, y, dragged_node, dragged_index)
       tab_index = self:get_visible_tabs_number() + (self.tab_offset - 1 or 0)
     end
   end
-  local tab_x, tab_y, tab_w, tab_h = self:get_tab_rect(tab_index)
+  local tab_x, tab_y, tab_w, tab_h, margin_y = self:get_tab_rect(tab_index)
   if x > tab_x + tab_w / 2 and tab_index <= #self.views then
     -- use next tab
     tab_x = tab_x + tab_w
@@ -779,7 +788,7 @@ function Node:get_drag_overlay_tab_position(x, y, dragged_node, dragged_index)
     tab_index = tab_index - 1
     tab_x = tab_x - tab_w
   end
-  return tab_index, tab_x, tab_y, tab_w, tab_h
+  return tab_index, tab_x, tab_y + margin_y, tab_w, tab_h - margin_y
 end
 
 return Node

data/core/style.lua

@@ -1,13 +1,23 @@
 local common = require "core.common"
 local style = {}
 
-style.padding = { x = common.round(14 * SCALE), y = common.round(7 * SCALE) }
 style.divider_size = common.round(1 * SCALE)
 style.scrollbar_size = common.round(4 * SCALE)
 style.expanded_scrollbar_size = common.round(12 * SCALE)
 style.caret_width = common.round(2 * SCALE)
 style.tab_width = common.round(170 * SCALE)
 
+style.padding = {
+  x = common.round(14 * SCALE),
+  y = common.round(7 * SCALE),
+}
+
+style.margin = {
+  tab = {
+    top = common.round(-style.divider_size * SCALE)
+  }
+}
+
 -- The function renderer.font.load can accept an option table as a second optional argument.
 -- It shoud be like the following:
 --