added cx16.mouse_present() routine to check for presence of mouse

compiler/res/prog8lib/cx16/syslib.p8

@@ -603,6 +603,14 @@ asmsub mouse_pos() -> ubyte @A, uword @R0, uword @R1, byte @X {
     }}
 }
 
+sub mouse_present() -> bool {
+    ; -- check if a mouse is connected to the machine
+    cx16.r0L, void = cx16.i2c_read_byte($42, $22)         ; $22 = I2C_GET_MOUSE_DEVICE_ID
+    if_cs
+        return false
+    return cx16.r0L != $fc       ; $fc = BAT_FAIL
+}
+
 ; shims for the kernal routines called via the extapi call:
 
 asmsub mouse_set_pos(uword xpos @R0, uword ypos @R1) clobbers(X) {

docs/source/todo.rst

@@ -7,6 +7,9 @@ in overwriting registers that already got their value, which requires a lot of s
 Maybe this routine can be made more intelligent.  See usesOtherRegistersWhileEvaluating() and argumentsViaRegisters().
 
 
+Regenerate skeletons in doc.
+
+
 Future Things and Ideas
 ^^^^^^^^^^^^^^^^^^^^^^^
 Compiler:

examples/test.p8

@@ -5,23 +5,6 @@
 
 main {
     sub start() {
-        uword active_world = memory("world", 80*50, 0)
+        txt.print_bool(cx16.mouse_present())
-        uword @shared cell_off = 500
-        uword @shared cell_off_1 = cell_off+1
-        const uword STRIDE = 40
-        sys.memset(active_world, 80*50, 1)
-
-        txt.print_ub(active_world[500] + active_world[501])  ; 2
-        txt.nl()
-        txt.print_ub(active_world[cell_off] + active_world[cell_off_1])  ; 2
-        txt.nl()
-        txt.print_ub(count())       ; 8
-        txt.nl()
-
-        sub count() -> ubyte {
-            return active_world[cell_off-STRIDE-1] + active_world[cell_off-STRIDE] + active_world[cell_off-STRIDE+1] +
-                   active_world[cell_off-1] + active_world[cell_off+1] +
-                   active_world[cell_off+STRIDE-1] + active_world[cell_off+STRIDE] + active_world[cell_off+STRIDE+1]
-        }
     }
 }