cx16: fix signature return values of cx16.screen_mode(), add get_screen_mode() and set_screen_mode() convenience routines

compiler/res/prog8lib/cx16/syslib.p8

@@ -328,7 +328,7 @@ cx16 {
 romsub $ff4a = close_all(ubyte device @A)  clobbers(A,X,Y)
 romsub $ff59 = lkupla(ubyte la @A)  clobbers(A,X,Y)
 romsub $ff5c = lkupsa(ubyte sa @Y)  clobbers(A,X,Y)
-romsub $ff5f = screen_mode(ubyte mode @A, bool getCurrent @Pc)  clobbers(A, X, Y) -> bool @Pc
+romsub $ff5f = screen_mode(ubyte mode @A, bool getCurrent @Pc)  clobbers(X, Y) -> ubyte @A, bool @Pc        ; note: X,Y size result is not supported, use SCREEN or get_screen_mode routine for that
 romsub $ff62 = screen_set_charset(ubyte charset @A, uword charsetptr @XY)  clobbers(A,X,Y)      ; incompatible with C128  dlchr()
 ; not yet supported: romsub $ff65 = pfkey()  clobbers(A,X,Y)
 romsub $ff6e = jsrfar()  ; following word = address to call, byte after that=rom/ram bank it is in
@@ -415,6 +415,23 @@ romsub $C09F = audio_init() clobbers(A,X,Y) -> bool @Pc                ; (re)ini
 ; TODO: add more of the audio routines?
 
 
+asmsub set_screen_mode(ubyte mode @A) clobbers(A,X,Y) -> bool @Pc {
+    ; -- convenience wrapper for screen_mode() to just set a new mode (and return success)
+    %asm {{
+        clc
+        jmp  screen_mode
+    }}
+}
+
+asmsub get_screen_mode() -> byte @A, byte @X, byte @Y {
+    ; -- convenience wrapper for screen_mode() to just get the current mode in A, and size in tiles in X+Y
+    ;    this does need a piece of inlined asm to call it ans store the result values if you call this from prog8 code
+    %asm {{
+        sec
+        jmp  screen_mode
+    }}
+}
+
 asmsub kbdbuf_clear() {
     ; -- convenience helper routine to clear the keyboard buffer
     %asm {{

docs/source/todo.rst

@@ -1,7 +1,9 @@
 TODO
 ====
 
-- IR: instructions that do type conversion (such as EXT, SZ etc, CONCAT, SGN) should put the result in a DIFFERENT register.
+- fix VM print_w
+- fix VM abs(byte) it always returns 0
+- IR: instructions that do type conversion (SZ etc, CONCAT, SGN) should put the result in a DIFFERENT register.
 
 ...
 

examples/test.p8

@@ -1,7 +1,47 @@
-%import palette
+%import textio
 %zeropage basicsafe
+%option no_sysinit
 
 main {
     sub start() {
+        ubyte @shared current = cx16.screen_mode(0, true)
+        ubyte @shared width
+        ubyte @shared height
+        txt.print_ub(current)
+        txt.nl()
+        cx16.set_screen_mode(128)
+        %asm {{
+            phx
+            jsr  cx16.get_screen_mode
+            sta  p8_current
+            stx  p8_width
+            sty  p8_height
+            plx
+        }}
+        txt.print_ub(current)
+        txt.spc()
+        txt.print_ub(width)
+        txt.spc()
+        txt.print_ub(height)
+        txt.nl()
+        txt.nl()
+
+        byte intensity = -25
+        txt.print_b(intensity)
+        txt.nl()
+        txt.print_b(abs(intensity))
+        intensity = abs(intensity)
+        txt.nl()
+        txt.print_b(intensity)
+        txt.nl()
+        word intensityw = 2555
+        txt.print_uw0(12345)
+        txt.nl()
+        txt.print_w(intensityw)
+        txt.nl()
+        txt.print_w(abs(intensityw))
+        intensityw = abs(intensityw)
+        txt.nl()
+        txt.print_w(intensityw)
     }
 }