added c64 starfield example

compiler/test/TestCompilerOnExamples.kt

@@ -70,6 +70,7 @@ class TestCompilerOnExamplesC64: FunSpec({
             "cube3d-sprites",
             "plasma",
             "sprites",
+            "starfield",
             "turtle-gfx",
             "wizzine",
         ),

docs/source/todo.rst

@@ -3,6 +3,18 @@ TODO
 
 For next release
 ^^^^^^^^^^^^^^^^
+- fix operator precedence: if rasterCount ^ $80 >= 230    EOR should precede >=
+- @(ptr) |= 3 -> asm peephole optimize remove the second ldy  if the instruction before doesn't modify y
+	ldy  #0
+	lda  (starfieldPtr2),y
+	ora  #3
+	ldy  #0
+	sta  (starfieldPtr2),y
+- vm: intermediate code: don't flatten everything. Instead, as a new intermediary step,
+  convert the new Ast into *structured* intermediary code.
+  Basically keep the blocks and subroutines structure, including full subroutine signature information,
+
+
 ...
 
 

examples/starfield.p8

@@ -0,0 +1,163 @@
+; Galencia starfield ported to Prog8. Original: https://github.com/JasonAldred/C64-Starfield
+; This is for the C64 only.
+
+%option no_sysinit
+
+main {
+    const uword starScreenChar  = $0400         ; Screen address
+    const uword StarScreenCols  = $d800         ; Character attribute address
+
+    const uword charBase  = $3000         ; Address of our character set
+    const uword star1Init = charBase+$1d0 ; Init address for each star
+    const uword star2Init = charBase+$298
+    const uword star3Init = charBase+$240
+    const uword star4Init = charBase+$2e0
+
+    const uword star1Limit  = charBase+$298 ; Limit for each star
+    const uword star2Limit  = charBase+$360 ; Once limit is reached, they are reset
+    const uword star3Limit  = charBase+$298
+    const uword star4Limit  = charBase+$360
+    const uword star1Reset  = charBase+$1d0 ; Reset address for each star
+    const uword star2Reset  = charBase+$298
+    const uword star3Reset  = charBase+$1d0
+    const uword star4Reset  = charBase+$298
+    const uword staticStar1 = charBase+$250 ; 2 Locations for blinking static stars
+    const uword staticStar2 = charBase+$1e0
+
+    const ubyte starColourLimit = 20            ; use values 1 to 20
+                                ; Galencia uses these values
+                                ; 1     = mono
+                                ; 2     = duo
+                                ; 20    = full colour
+
+    ; 4 x pointers for moving stars
+    uword @zp starfieldPtr1
+    uword @zp starfieldPtr2
+    uword @zp starfieldPtr3
+    uword @zp starfieldPtr4
+
+    ubyte rasterCount    ; Counter that increments each frame
+
+    sub start () {
+        sys.set_irqd()
+        sys.memset(charBase, 8*256, 0)     ; clear charset data
+        c64.EXTCOL = 0
+        c64.BGCOL0 = 0
+        c64.VMCSB = (charBase/1024) | %00010000     ; Characters at $3000
+        initStarfield()
+        createStarScreen()
+
+        repeat {
+            sys.waitvsync()
+            rasterCount ++
+            doStarfield()
+        }
+    }
+
+    sub doStarfield() {
+        ; This routine does 3 things:
+        ; 1) Erases stars
+        ; 2) Moves stars
+        ; 3) Draws stars in new position
+
+        @(starfieldPtr1) = 0
+        @(starfieldPtr2) = 0
+        @(starfieldPtr3) = 0
+        @(starfieldPtr4) = 0
+
+        if rasterCount & 1 {
+            starfieldPtr1++
+            if starfieldPtr1==star1Limit
+                starfieldPtr1=star1Reset
+        }
+        starfieldPtr2++
+        if starfieldPtr2==star2Limit
+            starfieldPtr2=star2Reset
+        if rasterCount & 3 == 0 {
+            starfieldPtr3++
+            if starfieldPtr3==star3Limit
+                starfieldPtr3=star3Reset
+        }
+        starfieldPtr4 += 2
+        if starfieldPtr4==star4Limit
+            starfieldPtr4=star4Reset
+
+        ; 2 static stars that flicker
+        if rasterCount >= 230
+            @(staticStar1) = 0
+        else
+            @(staticStar1) = 192
+        if (rasterCount ^ $80) >= 230
+            @(staticStar2) = 0
+        else
+            @(staticStar2) = 192
+
+        ; Plot new stars
+        @(starfieldPtr1) |= 3
+        @(starfieldPtr2) |= 3
+        @(starfieldPtr3) |= 12
+        @(starfieldPtr4) |= 48
+    }
+
+    sub initStarfield() {
+        starfieldPtr1 = star1Init
+        starfieldPtr2 = star2Init
+        starfieldPtr3 = star3Init
+        starfieldPtr4 = star4Init
+    }
+
+    sub createStarScreen() {
+        ; Creates the starfield charmap and colour charmap
+        ; This routine paints vertical stripes of colour into the colourmap
+        ; so the stars are different colours
+        ; It also plots the correct characters to the screen, wrapping them around
+        ; at the correct char count to give to the starfield effect.
+
+        uword @zp ptr
+        ubyte x
+        for x in 0 to 39 {
+            ubyte limit
+            ubyte char = starfieldRow[x]
+            if char >= 58+25
+                limit = 58+50
+            else
+                limit = 58+25
+            ubyte start = limit - 25
+            ptr = starScreenChar
+            repeat 25 {
+                ptr[x] = char
+                ptr += 40
+                char ++
+                if char == limit
+                    char = start
+            }
+        }
+
+        ; Fill colour map with vertical stripes of colour for starfield
+        ptr = StarScreenCols
+        ubyte ci = 0
+        repeat 25 {
+            for x in 0 to 39 {
+                ptr[x] = starfieldCols[ci]
+                ci ++
+                if ci==starColourLimit
+                    ci=0
+            }
+            ptr += 40
+        }
+    }
+
+    ; Dark starfield so it doesnt distract from bullets and text
+    ubyte[20] starfieldCols = [
+        14,10,12,15,14,13,12,11,10,14,
+        14,10,14,15,14,13,12,11,10,12
+        ]
+
+    ; Star positions, 40 X positions, range 58-107
+    ubyte[40] starfieldRow = [
+        058,092,073,064,091,062,093,081,066,094,
+        086,059,079,087,080,071,076,067,082,095,
+        100,078,099,060,075,063,084,065,083,096,
+        068,088,074,061,090,098,085,101,097,077
+        ]
+}

gradle.properties

@@ -4,4 +4,4 @@ org.gradle.parallel=true
 org.gradle.daemon=true
 kotlin.code.style=official
 javaVersion=11
-kotlinVersion=1.7.0
+kotlinVersion=1.7.10