add verafx.transparency()

compiler/res/prog8lib/cx16/verafx.p8

@@ -98,4 +98,13 @@ verafx {
 ;            sta  $0403
         }}
     }
+
+    sub transparency(bool enable) {
+        cx16.VERA_CTRL = 2<<1       ; dcsel = 2
+        if enable
+            cx16.VERA_FX_CTRL |= %10000000
+        else
+            cx16.VERA_FX_CTRL &= %01111111
+        cx16.VERA_CTRL = 0
+    }
 }

docs/source/libraries.rst

@@ -514,5 +514,8 @@ the emulators already support it).
     There's also a ``clear`` routine here to very quickly clear a piece of vram to a given byte value (it writes 4 bytes at a time).
     The routine is around 3 times faster as a regular unrolled loop to clear vram.
 
+``transparency``
+    Enable or disable transparent writes (color 0 will be transparent if enabled).
+
 Read the `source code <https://github.com/irmen/prog8/tree/master/compiler/res/prog8lib/cx16/verafx.p8>`_
 to see what's in there.

docs/source/todo.rst

@@ -1,9 +1,7 @@
 TODO
 ====
 
-- add verafx transparent writes enable/disable routines
 - add %option verafxmuls in block to enable transparent verafx muls use for that block only + add warning message to docs to not use it it in prg AND irq code
-- '>>='  can be used as an operator in an expression?? should only be augmented assignment!
 
 - [on branch: shortcircuit] investigate McCarthy evaluation again? this may also reduce code size perhaps for things like if a>4 or a<2 ....
 - [on branch: ir-less-branch-opcodes] IR: reduce the number of branch instructions such as BEQ, BEQR, etc (gradually), replace with CMP(I) + status branch instruction

examples/test.p8

@@ -1,21 +1,20 @@
 %import textio
-%import emudbg
+%import gfx2
+%import verafx
 %zeropage basicsafe
-%option no_sysinit
 
 main {
     sub start() {
-
-        txt.print_ub(emudbg.is_emulator())
-        txt.nl()
-        emudbg.console_value1(123)
-        emudbg.console_value2(222)
-        for cx16.r0L in iso:"Hello debug console!\n"
-            emudbg.console_chrout(cx16.r0L)
-
-        emudbg.console_write(iso:"Hello another message!\n")
-
-        emudbg.EMU_DBG_HOTKEY_ENABLED=false
+        gfx2.screen_mode(4)
+        gfx2.disc(160, 120, 100, 2)
+        ; verafx.transparency(true)
+        gfx2.position(0, 70)
+        repeat 3000 {
+            gfx2.next_pixel(7)
+            repeat 10
+                gfx2.next_pixel(0)      ; transparent!
+        }
+        verafx.transparency(false)
     }
 }