feat: add automatic theme generation (#104)

THEMES.md

@@ -2,6 +2,9 @@
 
 All available themes are only best effort ports by myself/ other users. If you find a theme to be weird/ wrong please open an issue/ pr.
 
+### auto
+if your favourite colorcheme is not yet supported you can use `auto` to make
+lualine try to match your colorscheme.
 ### 16color
 ![16normal_cropped](https://user-images.githubusercontent.com/41551030/108648240-02d2ae00-74bb-11eb-9ac1-495849621366.png)
 ![16insert_cropped](https://user-images.githubusercontent.com/41551030/108648219-f77f8280-74ba-11eb-84e4-978bf918c21f.png)

lua/lualine/themes/auto.lua

@@ -0,0 +1,163 @@
+local utils = require'lualine.utils.utils'
+
+---------------
+-- Constents --
+---------------
+-- fg and bg must have this much contrast range 0 < contrast_threshold < 0.5
+local contrast_threshold = 0.3
+-- how much brightness is changed in percentage for light and dark themes
+local brightness_modifier_parameter = 10
+
+-- retrives color value from highlight group name in syntax_list
+-- first present highlight is returned
+local function getHi( scope, syntaxlist )
+  for _ , highlight_name in pairs( syntaxlist  ) do
+    if vim.fn.hlexists(highlight_name) ~= 0 then
+      local color = utils.extract_highlight_colors(highlight_name)
+      if color.reverse then
+        if scope == 'guibg' then scope = 'guifg' else scope = 'guibg' end
+      end
+      if color[scope] then return color[scope] end
+    end
+  end
+  return '#000000'
+end
+
+-- truns #rrggbb -> { red, green, blue }
+local function rgb_str2num(rgb_color_str)
+  if rgb_color_str:find('#') == 1 then rgb_color_str = rgb_color_str:sub(2, #rgb_color_str) end
+  local red = tonumber(rgb_color_str:sub(1,2), 16)
+  local green = tonumber(rgb_color_str:sub(3,4), 16)
+  local blue = tonumber(rgb_color_str:sub(5,6), 16)
+  return { red = red, green = green, blue = blue, }
+end
+
+-- turns { red, green, blue } -> #rrggbb
+local function rgb_num2str(rgb_color_num)
+  local rgb_color_str = string.format('#%02x%02x%02x', rgb_color_num.red,
+    rgb_color_num.green, rgb_color_num.blue)
+  return rgb_color_str
+end
+
+-- returns brightness lavel of color in range 0 to 1
+-- arbitary value it's basicaly an weighted average
+local function get_color_brightness(rgb_color)
+  local color = rgb_str2num(rgb_color)
+  local brightness = (color.red * 2 + color.green * 3 + color.blue) / 6
+  return brightness / 256
+end
+
+-- returns average of colors in range 0 to 1
+-- used to ditermine contrast lavel
+local function get_color_avg(rgb_color)
+  local color = rgb_str2num(rgb_color)
+  return (color.red + color.green + color.blue) / 3 / 256
+end
+
+-- clamps the val between left and right
+local function clamp(val, left, right)
+  if val > right then return right end
+  if val < left then return left end
+  return val
+end
+
+-- changes braghtness of rgb_color by percentage
+local function brightness_modifier(rgb_color, parcentage)
+  local color = rgb_str2num(rgb_color)
+  color.red = clamp(color.red + (color.red * parcentage / 100), 0, 255)
+  color.green = clamp(color.green + (color.green * parcentage / 100), 0, 255)
+  color.blue = clamp(color.blue + (color.blue * parcentage / 100), 0, 255)
+  return rgb_num2str(color)
+end
+
+-- changes contrast of rgb_color by amount
+local function contrast_modifier(rgb_color, amount)
+  local color = rgb_str2num(rgb_color)
+  color.red = clamp(color.red + amount, 0, 255)
+  color.green = clamp(color.green + amount, 0, 255)
+  color.blue = clamp(color.blue + amount, 0, 255)
+  return rgb_num2str(color)
+end
+
+-- Changes brightness of foreground color to achive contrast
+-- without changing the color
+local function apply_contrast(highlight)
+  local hightlight_bg_avg = get_color_avg(highlight.bg)
+  local contrast_threshold_config = clamp(contrast_threshold, 0, 0.5)
+  local contranst_change_step = 5
+  if hightlight_bg_avg > .5 then
+    contranst_change_step = -contranst_change_step
+  end
+
+  -- donn't waste too much time here max 25 interation should be more than enough
+  local iteration_count = 1
+  while (math.abs(get_color_avg(highlight.fg) - hightlight_bg_avg) < contrast_threshold_config and iteration_count < 25) do
+    highlight.fg = contrast_modifier(highlight.fg, contranst_change_step)
+    iteration_count = iteration_count + 1
+  end
+end
+
+-- Get the colors to create theme
+local colors = {
+  normal  = getHi( 'guibg', {'PmenuSel', 'PmenuThumb', 'TabLineSel' } ),
+  insert  = getHi( 'guifg', {'String', 'MoreMsg' } ),
+  replace = getHi( 'guifg', {'Number', 'Type' } ),
+  visual  = getHi( 'guifg', {'Special', 'Boolean', 'Constant' } ),
+  command = getHi( 'guifg', {'Identifier' } ),
+  back1   = getHi( 'guibg', {'Normal', 'StatusLineNC' } ),
+  fore    = getHi( 'guifg', {'Normal', 'StatusLine' } ),
+  back2   = getHi( 'guibg', {'StatusLine' } ),
+}
+
+
+-- Change brightness of colors
+-- darken incase of light theme lighten incase of dark theme
+
+if get_color_brightness(utils.extract_highlight_colors('Normal', 'guibg')) > 0.5 then
+  brightness_modifier_parameter = -brightness_modifier_parameter
+end
+
+for name, color in pairs(colors) do
+  colors[name] = brightness_modifier(color, brightness_modifier_parameter)
+end
+
+-- basic theme defination
+local M = {
+  normal = {
+    a = { bg = colors.normal,  fg = colors.back1, gui='bold' },
+    b = { bg = colors.back1,   fg = colors.normal            },
+    c = { bg = colors.back2,   fg = colors.fore              },
+  },
+  insert = {
+    a = { bg = colors.insert,  fg = colors.back1, gui='bold' },
+    b = { bg = colors.back1,   fg = colors.insert            },
+    c = { bg = colors.back2,   fg = colors.fore              },
+  },
+  replace = {
+    a = { bg = colors.replace, fg= colors.back1, gui='bold' },
+    b = { bg = colors.back1,   fg= colors.replace           },
+    c = { bg = colors.back2,   fg= colors.fore              },
+  },
+  visual = {
+    a = { bg = colors.visual,  fg= colors.back1, gui='bold' },
+    b = { bg = colors.back1,   fg= colors.visual            },
+    c = { bg = colors.back2,   fg= colors.fore              },
+  },
+  command = {
+    a = { bg = colors.command, fg = colors.back1, gui='bold' },
+    b = { bg = colors.back1,   fg = colors.command           },
+    c = { bg = colors.back2,   fg = colors.fore              },
+  },
+}
+
+M.terminal = M.command
+M.inactive = M.normal
+
+-- Apply prpper contrast so text is readable
+for _, section in pairs(M) do
+  for _, highlight in pairs(section) do
+    apply_contrast(highlight)
+  end
+end
+
+return M