new kind of scroller impl

scroller3.p8

@@ -0,0 +1,99 @@
+pico-8 cartridge // http://www.pico-8.com
+version 27
+__lua__
+-- scroller3
+-- by MBoffin extended by apa64
+-- https://www.lexaloffle.com/bbs/?pid=78801#p
+-- right to left marquee scroller
+-- version: 2.0
+
+-- consts
+left, right, up, down, fire1, fire2 = 0, 1, 2, 3, 4, 5
+black, dark_blue, dark_purple, dark_green, brown, dark_gray, light_gray, white, red, orange, yellow, green, blue, indigo, pink, peach = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+palsorted = { 0, 5, 6, 7, 15, 14, 8, 2, 4, 9, 10, 11, 3, 12, 13, 1 }
+
+function _init()
+    -- palsorted index
+    pal_background = 2
+    pal_text = 13
+    speed = 10
+    print_time = 0
+end
+
+function _update()
+    update_colour()
+    update_speed()
+    if (btnp() != 0) then
+        sfx(0)
+    end
+end
+
+function _draw()
+    cls(palsorted[pal_background])
+    print("scroller3", 45, 2, light_gray)
+    print("⬅️➡️ text color", 34, 8, light_gray)
+    print("⬆️⬇️ bkg color", 36, 14, light_gray)
+    print("❎🅾️ scroll speed", 30, 20, light_gray)
+
+    -- draw the actual scrollers
+    txtscroll("lorem ipsum dolor sit amet, consectetur... ", 4, 60, 120, speed, palsorted[pal_text])
+    txtscroll("12345", 50, 70, 40, speed*2, red)
+    txtscroll("secret messages from backwards records", 20, 80, 88, -speed*0.8, black)
+end
+
+-->8
+-- ######################## scroller
+
+-- draws scroller text, by MBoffin
+-- note: negative speed goes backwards!
+-- params: text, x, y, field width, speed px/sec, color for print
+function txtscroll(text, x, y, w, speed, color)
+    -- all drawing inside clip region. font height 5 px
+    clip(x, y, w, 5)
+    -- printable text len in px, font width 4 px. add width to get blank start.
+    -- TODO: adjust for 8 px glyphs
+    local len = #text * 4 + w
+    -- origin x inside text 0..len, t() returns seconds since run
+    local ox = (t() / (1/speed)) % len
+    -- print x goes actually from end of field to start?! and clip limits printing. wow.
+    print(text, x + w - ox, y, color)
+    -- reset clip to fullscreen
+    clip()
+
+    -- print("spd:"..speed..", t:"..flr(t())..", ox:"..ox, 0, 117, pink)
+    -- print("w:"..w..", len:"..len, 0, 123, pink)
+end
+
+-->8
+-- ###################### update
+
+-- cycle colors with direction keys
+function update_colour()
+    -- add +1 because % gives 0..15 but palsorted index needs to be 1..16
+    if (btnp(right)) pal_text = (pal_text % #palsorted) + 1
+    -- subtract -2 because we add the +1 anyway
+    if (btnp(left)) pal_text = ((pal_text - 2) % #palsorted) + 1
+    if (btnp(up)) pal_background = (pal_background % #palsorted) + 1
+    if (btnp(down)) pal_background = ((pal_background - 2) % #palsorted) + 1
+end
+
+-- cycle speed with fire keys
+function update_speed()
+    if (btnp(fire1)) speed = ((speed - 1) % 101)
+    if (btnp(fire2)) speed = ((speed + 1) % 101)
+end
+
+-->8
+-- ######################## draw
+
+
+__gfx__
+00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+00700700000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+00077000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+00077000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+00700700000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+__sfx__
+000100000506007000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+000200000c00011000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000