-- Does graphics PAGE 1 display at all in 256-colour mode, and under what
-- priority?  page0 <- 0 everywhere, page1 <- 0xC0 (white) everywhere.
-- If page 0 composites on top TRANSPARENTLY, the screen should be white.
M=manager.machine; SP=M.devices[":maincpu"].spaces["program"]; SUB=nil
local function load_mode()
  for _,p in ipairs{"../tools/bench/crtc_mode.lua","tools/bench/crtc_mode.lua"} do
    local f=loadfile(p); if f then return f() end end
  error("no crtc_mode.lua") end
local MODE = load_mode()
local CRTC, GV, GPAL = 0xE80000, 0xC00000, 0xE82000
local function T() local t=M.time; return t.seconds+t.attoseconds/1e18 end
local st,tp,n = "wait",nil,0

-- (label, VCReg1, VCReg2, page1 scrollX)
local TRIALS = {
  {"vc1=0000 scroll384", 0x0000, 0x001F, 384},
  {"vc1=0002 scroll384", 0x0002, 0x001F, 384},
  {"vc1=06E4 scroll384", 0x06E4, 0x001F, 384},
  {"vc1=0000 scroll0",   0x0000, 0x001F, 0},
  {"vc1=0002 scroll0",   0x0002, 0x001F, 0},
  {"vc1=0000 vc2=00FF",  0x0000, 0x00FF, 0},
}

SUB = emu.add_machine_frame_notifier(function()
  local t=T()
  if st=="wait" then
    if t<3.0 then return end
    MODE.apply(SP)
    SP:write_u16(GPAL+0*2,     0x0000)          -- index 0 = black
    SP:write_u16(GPAL+0xC0*2,  0xFFFF)          -- index C0 = white
    -- buffer mode: one pass sets page0=0x00 and page1=0xC0 for every word
    SP:write_u16(CRTC+20*2, MODE.r20 | 0x0800)
    for y=0,255 do
      local base=GV+y*1024
      for x=0,255 do SP:write_u16(base+x*2, 0xC000) end
    end
    SP:write_u16(CRTC+20*2, MODE.r20)
    st,tp="run",t
  elseif st=="run" and t>tp+0.30 then
    n = n + 1
    if n > #TRIALS then print("[P1] done"); M:exit(); st="done"; return end
    local tr = TRIALS[n]
    SP:write_u16(0xE82500, tr[2])
    SP:write_u16(0xE82600, tr[3])
    SP:write_u16(CRTC+16*2, tr[4]); SP:write_u16(CRTC+18*2, tr[4])
    print(string.format("[P1] trial %d: %s", n, tr[1]))
    tp = t
    st = "snap"
  elseif st=="snap" and t>tp+0.20 then
    M.video:snapshot(); st="run"; tp=t
  end
end)