From 197081f10dcc7ae9c6baf26eff912fd0c8987088 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Thu, 4 Aug 2022 23:04:16 +0200
Subject: [PATCH] keyboardhandler

---
 codeAst/src/prog8/code/ast/AstExpressions.kt |  6 +++---
 compiler/res/prog8lib/cx16/syslib.p8         |  2 +-
 examples/cx16/keyboardhandler.p8             | 13 ++++++++++---
 3 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/codeAst/src/prog8/code/ast/AstExpressions.kt b/codeAst/src/prog8/code/ast/AstExpressions.kt
index 8308c2d17..0a10473bb 100644
--- a/codeAst/src/prog8/code/ast/AstExpressions.kt
+++ b/codeAst/src/prog8/code/ast/AstExpressions.kt
@@ -15,9 +15,9 @@ sealed class PtExpression(val type: DataType, position: Position) : PtNode(posit
         if(type==DataType.UNDEFINED) {
             @Suppress("LeakingThis")
             when(this) {
-                is PtBuiltinFunctionCall -> {}
-                is PtFunctionCall -> {}
-                is PtIdentifier -> {}
+                is PtBuiltinFunctionCall -> { /* void function call */ }
+                is PtFunctionCall -> { /* void function call */ }
+                is PtIdentifier -> { /* non-variable identifier */ }
                 else -> throw IllegalArgumentException("type should be known @$position")
             }
         }
diff --git a/compiler/res/prog8lib/cx16/syslib.p8 b/compiler/res/prog8lib/cx16/syslib.p8
index 8fc2d27e0..3a24b27b6 100644
--- a/compiler/res/prog8lib/cx16/syslib.p8
+++ b/compiler/res/prog8lib/cx16/syslib.p8
@@ -98,7 +98,7 @@ cx16 {
     &uword  ISTOP           = $0328
     &uword  IGETIN          = $032a
     &uword  ICLALL          = $032c
-    &uword  KEYHDL          = $032e     ; keyboard scan code handler
+    &uword  KEYHDL          = $032e     ; keyboard scan code handler see examples/cx16/keyboardhandler.p8
     &uword  ILOAD           = $0330
     &uword  ISAVE           = $0332
     &uword  NMI_VEC         = $FFFA     ; 65c02 nmi vector, determined by the kernal if banked in
diff --git a/examples/cx16/keyboardhandler.p8 b/examples/cx16/keyboardhandler.p8
index 8f1450f1e..ae224bd90 100644
--- a/examples/cx16/keyboardhandler.p8
+++ b/examples/cx16/keyboardhandler.p8
@@ -6,7 +6,7 @@ main {
 
     sub start() {
 
-        txt.print("ps2 scancode handler test - press keys! esc to quit!\n")
+        txt.print("ps2 custom key handler test - press keys! esc to quit!\n")
 
         sys.set_irqd()
         uword old_keyhdl = cx16.KEYHDL
@@ -22,7 +22,7 @@ main {
         sys.clear_irqd()
     }
 
-    sub keyboard_scancode_handler(ubyte prefix, ubyte scancode, bool updown) {
+    sub keyboard_scancode_handler(ubyte prefix, ubyte scancode, bool updown) -> bool {
         txt.print_ubhex(prefix, true)
         txt.chrout(':')
         txt.print_ubhex(scancode, true)
@@ -36,7 +36,7 @@ main {
             ; escape was pressed! exit back to basic
             main.start.escape_pressed = true
         }
-        return
+        return true     ; true = consume key event, false = continue processing it
 
 asm_shim:
         %asm {{
@@ -49,8 +49,15 @@ asm_shim:
 +           stx  prefix
             sta  scancode
             jsr  keyboard_scancode_handler
+            beq  +
             plx
             pla
+            lda #0     ;By setting A=0 we will consume this key event
+            tax
+            plp
+            rts
++           plx
+            pla     ; leave A untouched, continue processing
             plp
             rts
         }}