added nicer vm example

compiler/res/prog8lib/virtual/syslib.p8

@@ -95,6 +95,15 @@ sys {
             syscall 10
         }}
     }
+
+    sub gfx_getpixel(uword xx, uword yy) -> ubyte {
+        %asm {{
+            loadm.w r0, {sys.gfx_getpixel.xx}
+            loadm.w r1, {sys.gfx_getpixel.yy}
+            syscall 30
+            return
+        }}
+    }
 }
 
 cx16 {

examples/test.p8

@@ -1,28 +1,9 @@
 %import textio
 %zeropage basicsafe
 
-; NOTE: meant to test to virtual machine output target (use -target virtual)
-
 main  {
 
     sub start() {
-
-        ; a "pixelshader":
-        sys.gfx_enable(0)       ; enable lo res screen
-        ubyte shifter
-
-        repeat {
-            uword xx
-            uword yy = 0
-            repeat 240 {
-                xx = 0
-                repeat 320 {
-                    sys.gfx_plot(xx, yy, xx*yy + shifter as ubyte)
-                    xx++
-                }
-                yy++
-            }
-            shifter+=4
-        }
+        txt.print("hello!\n")
      }
 }

examples/vm/bouncegfx.p8

@@ -0,0 +1,59 @@
+%import textio
+%zeropage basicsafe
+
+; NOTE: meant to test to virtual machine output target (use -target virtual)
+
+main  {
+
+    sub start() {
+        word[128] particleX
+        word[128] particleY
+        byte[128] particleDX
+        byte[128] particleDY
+
+        ubyte pi
+        for pi in 0 to 127 {
+            particleX[pi] = rndw() % 319 as word
+            particleY[pi] = rndw() % 240 as word
+            particleDX[pi] = (rnd() & 1)*2 as byte - 1
+            particleDY[pi] = (rnd() & 1)*2 as byte - 1
+        }
+
+        sys.gfx_enable(0)       ; enable lo res screen
+
+        repeat {
+            fade()
+            plot_particles()
+            sys.waitvsync()
+        }
+
+        sub fade() {
+            uword xx
+            uword yy
+            for yy in 0 to 239 {
+                for xx in 0 to 319 {
+                    ubyte pixel = sys.gfx_getpixel(xx, yy)
+                    if pixel>4
+                        pixel-=4
+                    sys.gfx_plot(xx, yy, pixel)
+                }
+            }
+        }
+
+        sub plot_particles() {
+            for pi in 0 to 127 {
+                particleX[pi] += particleDX[pi]
+                particleY[pi] += particleDY[pi]
+                if particleX[pi]<0 or particleX[pi]>319 {
+                    particleDX[pi] *= -1
+                    particleX[pi] += particleDX[pi] * 2
+                }
+                if particleY[pi]<0 or particleY[pi]>239 {
+                    particleDY[pi] *= -1
+                    particleY[pi] += particleDY[pi] * 2
+                }
+                sys.gfx_plot(particleX[pi] as uword, particleY[pi] as uword, 255)
+            }
+        }
+    }
+}

examples/vm/pixelshader.p8

@@ -0,0 +1,28 @@
+%import textio
+%zeropage basicsafe
+
+; NOTE: meant to test to virtual machine output target (use -target virtual)
+
+main  {
+
+    sub start() {
+
+        ; a "pixelshader":
+        sys.gfx_enable(0)       ; enable lo res screen
+        ubyte shifter
+
+        repeat {
+            uword xx
+            uword yy = 0
+            repeat 240 {
+                xx = 0
+                repeat 320 {
+                    sys.gfx_plot(xx, yy, xx*yy + shifter as ubyte)
+                    xx++
+                }
+                yy++
+            }
+            shifter+=4
+        }
+     }
+}

virtualmachine/src/prog8/vm/GraphicsWindow.kt

@@ -65,6 +65,14 @@ class GraphicsWindow(val pixelWidth: Int, val pixelHeight: Int, val pixelScaling
             throw IllegalArgumentException("plot y outside of screen: $y")
         image.setRGB(x, y, Color(color, color, color, 255).rgb)
     }
+
+    fun getpixel(x: Int, y: Int): Int {
+        if(x<0 || x>=pixelWidth)
+            throw IllegalArgumentException("plot x outside of screen: $x")
+        if(y<0 || y>=pixelHeight)
+            throw IllegalArgumentException("plot y outside of screen: $y")
+        return image.getRGB(x, y)
+    }
 }
 
 

virtualmachine/src/prog8/vm/SysCalls.kt

@@ -35,6 +35,7 @@ SYSCALLS:
 27 = reverse_words array
 28 = reverse_floats array
 29 = compare strings
+30 = gfx_getpixel      ; get byte pixel value at coordinates r0.w/r1.w
 */
 
 enum class Syscall {
@@ -67,7 +68,8 @@ enum class Syscall {
     REVERSE_BYTES,
     REVERSE_WORDS,
     REVERSE_FLOATS,
-    COMPARE_STRINGS
+    COMPARE_STRINGS,
+    GFX_GETPIXEL
 }
 
 object SysCalls {
@@ -114,6 +116,7 @@ object SysCalls {
             Syscall.GFX_ENABLE -> vm.gfx_enable()
             Syscall.GFX_CLEAR -> vm.gfx_clear()
             Syscall.GFX_PLOT -> vm.gfx_plot()
+            Syscall.GFX_GETPIXEL ->vm.gfx_getpixel()
             Syscall.WAIT -> {
                 val millis = vm.registers.getUW(0).toLong() * 1000/60
                 Thread.sleep(millis)

virtualmachine/src/prog8/vm/VirtualMachine.kt

@@ -1,6 +1,7 @@
 package prog8.vm
 
 import prog8.code.target.virtual.IVirtualMachineRunner
+import java.awt.Color
 import java.awt.Toolkit
 import java.util.*
 import kotlin.math.*
@@ -1799,6 +1800,15 @@ class VirtualMachine(val memory: Memory, program: List<Instruction>) {
         window?.plot(registers.getUW(0).toInt(), registers.getUW(1).toInt(), registers.getUB(2).toInt())
     }
 
+    fun gfx_getpixel() {
+        if(window==null)
+            registers.setUB(0, 0u)
+        else {
+            val color = Color(window!!.getpixel(registers.getUW(0).toInt(), registers.getUW(1).toInt()))
+            registers.setUB(0, color.green.toUByte())
+        }
+    }
+
     fun gfx_close() {
         window?.close()
     }