Highlights: invert dialog colors in night mode#14923
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Frenzie
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Feb 4, 2026
| if Screen.night_mode then | ||
| local r, g, b = Blitbuffer.HIGHLIGHT_COLORS[color_name]:match("#(..)(..)(..)") | ||
| return Blitbuffer.colorFromString(string.format("#%02x%02x%02x", | ||
| 255 - tonumber(r, 16), 255 - tonumber(g, 16), 255 - tonumber(b, 16))) |
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I think bit.bxor(tonumber(r, 16), 0xFF) should do the same thing fwiw. (It doesn't matter here with just a few colors, but presumably it would when processing a picture pixel by pixel.)
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As far as AI advises, bit.bxor(x, 0xFF) is not faster than 255 - x.
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Better to use AI to write a test in less than a minute than to ask it things it can't know. ;-)
local bit = require("bit")
local bxor = bit.bxor -- local cache
local function test(n)
local clock = os.clock
-- prebuild test data as hex strings, numbers
local hex = {}
local nums = {}
for x = 0, 255 do
hex[x] = ("%02X"):format(x)
nums[x] = x
end
-- warm-up
for i = 1, 10000 do
local x = nums[i % 256]
local _ = bxor(x, 0xFF)
local _ = 255 - x
end
print("=== Original: bxor(tonumber(x, 16), 0xFF) ===")
local start = clock()
for i = 1, n do
local h = hex[i % 256]
local x = tonumber(h, 16)
local y = bxor(x, 0xFF)
end
print(("time: %.6f s"):format(clock() - start))
print("=== Cached bxor(x, 0xFF) ===")
start = clock()
for i = 1, n do
local x = nums[i % 256]
local y = bxor(x, 0xFF)
end
print(("time: %.6f s"):format(clock() - start))
print("=== 255 - x (arithmetic) ===")
start = clock()
for i = 1, n do
local x = nums[i % 256]
local y = 255 - x
end
print(("time: %.6f s"):format(clock() - start))
print()
end
-- run with e.g. luajit test.lua 100000000
local n = tonumber(arg[1]) or 1e8
test(n)=== Original: bxor(tonumber(x, 16), 0xFF) ===
time: 2.501012 s
=== Cached bxor(x, 0xFF) ===
time: 0.042331 s
=== 255 - x (arithmetic) ===
time: 0.044898 s
=== Original: bxor(tonumber(x, 16), 0xFF) ===
time: 2.486529 s
=== Cached bxor(x, 0xFF) ===
time: 0.042634 s
=== 255 - x (arithmetic) ===
time: 0.040219 s
tl;dr There's no difference, at least on this AMD Ryzen 7 7800X3D. So I'm still wrong. :-) (I'll have to double check if it's the same on some actual ereaders though.)
0xstillb
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May 9, 2026
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