feat: add functions for darkening/lightening highlight groups

I'm not documenting these yet as I they are probably riddled with bugs,
but they seem to work in the simple test cases that I have tried out so
far. Specifically, I'm doing this in my dotfiles to make floating
windows look better:

    local dark = vim.o.background == 'dark'
    local factor = dark and 0.15 or -0.15
    local normal = pinnacle.adjust_lightness('Normal', factor)
    vim.cmd('highlight! clear NormalFloat')
    vim.cmd('highlight! NormalFloat ' .. pinnacle.highlight(normal))
    normal['fg'] = dark and '#ffffff' or '#000000'
    vim.cmd('highlight! clear FloatBorder')
    vim.cmd('highlight! FloatBorder ' .. pinnacle.highlight(normal))

diff --git a/lua/wincent/pinnacle.lua b/lua/wincent/pinnacle.lua
index 33a07a575c5366225a5508d024aa9bf3bb2a416d..810442782844609815cc51cec7d31b022ddc8056 100644 (file)
--- a/lua/wincent/pinnacle.lua
+++ b/lua/wincent/pinnacle.lua
@@ -140,4 +140,151 @@ pinnacle.underline = function(group)
   return pinnacle.decorate('underline', group)
 end
 
+local clamp = function (value, lower, upper)
+  return math.max(lower, math.min(upper, value))
+end
+
+local round = function(value)
+  -- There is no math.round, so adjust and use math.floor. As noted here, this
+  -- is subject to small but acceptable precision errors:
+  -- https://stackoverflow.com/a/18313481/2103996
+  return math.floor(value + 0.5)
+end
+
+-- Receives red/green/blue values in the range of 0 to 255.
+-- Returns hue (0 to 360), saturation (0 to 100), and lightness (0 to 100).
+local rgb_to_hsl = function(r, g, b)
+  -- Based on:
+  -- https://css-tricks.com/converting-color-spaces-in-javascript/#aa-rgb-to-hsl
+  local h = nil
+  local s = nil
+  local l = nil
+  local r_f = r / 255
+  local g_f = g / 255
+  local b_f = b / 255
+  local min = math.min(r_f, g_f, b_f)
+  local max = math.max(r_f, g_f, b_f)
+  local delta = max - min
+  if delta == 0 then
+    h = 0
+  elseif max == r_f then
+    h = ((g_f - b_f) / delta) % 6
+  elseif max == g_f then
+    h = (b_f - r_f) / delta + 2
+  else -- max == b_f
+    h = (r_f - g_f) / delta + 4
+  end
+  h = round(h * 60)
+  if h < 0 then
+    h = h + 360
+  end
+  l = (min + max) / 2
+  if delta == 0 then
+    s = 0
+  else
+    s = delta / (1 - math.abs(2 * l - 1))
+  end
+  s = s * 100
+  l = l * 100
+  return h, s, l
+end
+
+-- Receives a hue (0 to 360), saturation (0 to 100), and lightness (0 to 100).
+-- Returns red/green/blue values in the range of 0 to 255.
+local hsl_to_rgb = function(h, s, l)
+  -- Based on:
+  -- https://css-tricks.com/converting-color-spaces-in-javascript/#aa-hsl-to-rgb
+  local s_f = s / 100
+  local l_f = l / 100
+  local c = (1 - math.abs(2 * l_f - 1)) * s_f -- chroma (color intensity)
+  local x = c * (1 - math.abs((h / 60) % 2 - 1)) -- second largest component
+  local m = l_f - c / 2 -- lightness
+  local r = 0
+  local g = 0
+  local b = 0
+  if 0 <= h and h < 60 then
+    r = c
+    g = x
+    b = 0
+  elseif 60 <= h and h < 120 then
+    r = x
+    g = c
+    b = 0
+  elseif 120 <= h and h < 180 then
+    r = 0
+    g = c
+    b = x
+  elseif 180 <= h and h < 240 then
+    r = 0
+    g = x
+    b = c
+  elseif 240 <= h and h < 300 then
+    r = x
+    g = 0
+    b = c
+  elseif 300 <= h and h < 360 then
+    r = c
+    g = 0
+    b = x
+  end
+  r = round((r + m) * 255)
+  g = round((g + m) * 255)
+  b = round((b + m) * 255)
+  return r, g, b
+end
+
+local to_hex = function(value)
+  return string.format('%.2x', value)
+end
+
+-- Returns a dictionary representation of the specified `group`, with all color
+-- values darkened by `percentage` (a number between 0 and 1).
+--
+-- Percentages are absolute and not relative to the lightness of the colors in
+-- the group. For example, given an HSL color space with possible lightness
+-- values ranging from 0 to 100, passing in a percentage of 0.1 here will
+-- decrease the lightness of each color by 10.
+pinnacle.darken = function(group, percentage)
+  return pinnacle.adjust_lightness(group, percentage * -1)
+end
+
+-- Returns a dictionary representation of the specified `group`, with all color
+-- values brightened by `percentage` (a number between 0 and 1).
+--
+-- Percentages are absolute and not relative to the lightness of the colors in
+-- the group. For example, given an HSL color space with possible lightness
+-- values ranging from 0 to 100, passing in a percentage of 0.1 here will
+-- increase the lightness of each color by 10.
+pinnacle.brighten = function(group, percentage)
+  return pinnacle.adjust_lightness(group, percentage * 1)
+end
+
+-- Returns a dictionary representation of the specified `group`, with all color
+-- values darkened or brightened by `percentage` (a number between -1 and 1).
+-- Negative percentages make the colors darker, positive numbers make the colors
+-- brighter, and a value of zero results in no change.
+--
+-- Percentages are absolute and not relative to the lightness of the colors in
+-- the group. For example, given an HSL color space with possible lightness
+-- values ranging from 0 to 100, passing in a percentage of plus or minus 0.1
+-- here will increase or decrease the lightness of each color by 10.
+pinnacle.adjust_lightness = function(group, percentage)
+  local dict = pinnacle.dump(group)
+  for key, value in pairs(dict) do
+    -- 'Grey70' → 11776947, '#839496' → 8623254, 'reverse' → -1
+    local rgb = vim.api.nvim_get_color_by_name(value)
+    if rgb ~= -1 then
+      local r = bit.rshift(rgb, 16)
+      local g = bit.band(bit.rshift(rgb, 8), 0xff)
+      local b = bit.band(rgb, 0xff)
+      local h, s, l = rgb_to_hsl(r, g, b)
+      l = l + (percentage * 100)
+      l = clamp(l, 0, 100)
+      r, g, b = hsl_to_rgb(h, s, l)
+      dict[key] = '#' .. to_hex(r) .. to_hex(g) .. to_hex(b)
+    end
+  end
+  return dict
+end
+
 return pinnacle