workaround for FB_set_pixels bug

compiler/res/prog8lib/cx16/syslib.p8

@@ -277,6 +277,40 @@ romsub $fecc = monitor()  clobbers(A,X,Y)
         }}
     }
 
+    sub FB_set_pixels_from_buf(uword buffer, uword count) {
+        %asm {{
+            ; -- This is replacement code for the normal FB_set_pixels subroutine in ROM
+            ;    However that routine contains a bug in the current v38 ROM that makes it crash when count > 255.
+            ;    So the code below replaces that. Once the ROM is patched this routine is no longer necessary.
+            ;    See https://github.com/commanderx16/x16-rom/issues/179
+            phx
+            lda  buffer
+            ldy  buffer+1
+            sta  P8ZP_SCRATCH_W1
+            sty  P8ZP_SCRATCH_W1+1
+            jsr  _pixels
+            plx
+            rts
+
+_pixels     lda  count+1
+            beq  +
+            ldx  #0
+-           jsr  _loop
+            inc  P8ZP_SCRATCH_W1+1
+            dec  count+1
+            bne  -
+
++           ldx  count
+_loop       ldy  #0
+-           lda  (P8ZP_SCRATCH_W1),y
+            sta  cx16.VERA_DATA0
+            iny
+            dex
+            bne  -
+            rts
+        }}
+    }
+
 
 ; ---- system stuff -----
 

examples/cx16/imgviewer/civiewer.p8

@@ -184,20 +184,9 @@ main {
             cx16.r1 = y
             cx16.FB_cursor_position()
 
-            ; FB_set_pixels crashes with a size > 255 hence the loop for strips of 128
-            ; TODO remove this workaround once the bug is fixed, see https://github.com/commanderx16/x16-rom/issues/179
-            cx16.r1 = 128
-            ubyte rest = lsb(width) & 127
-            repeat width >> 7 {
-                cx16.r0 = bitmapptr
-                cx16.FB_set_pixels()
-                bitmapptr += 128
-            }
-            if rest {
-                cx16.r0 = bitmapptr
-                cx16.FB_set_pixels()
-                bitmapptr += rest
-            }
+            ; FB_set_pixels in rom v38 crashes with a size > 255 so we use our own replacement for now
+            cx16.FB_set_pixels_from_buf(bitmapptr, width)
+            bitmapptr += width
         }
     }