tests - WIP - Create 'move pixel with keypad' program

test-programs/move-pixel-with-keypad.asm

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+; Draw a pixel, and move it when a key is pressed
+; 2023-08-26
+
+;; WIP - up and right should be working,
+;; but currently they're being tested with a
+;; faked keyboard input at the end of @xy2id
+;; (and down and left are still TODO)
+
+#flagZ   1
+#flagN   2
+#keypad  $1B ; contains latest key pressed
+
+; Starting (x, y) coordinates
+#input_x 1
+#input_y 2
+
+; Some handy shortcuts
+#x $FA
+#y $FB
+#px_addr $FD          ; holds return value from @xy2id
+#return_addr_ptr $FE
+
+; Main variables:
+;   F8
+;   F9 - xy2id temp
+;   FA - x coord
+;   FB - y coord
+;   FC - xy2id temp
+;   FD - xy2id return value / xy2id temp
+;   FE - Return address for subroutine
+
+
+@setup
+ LDA #input_x
+ STO #x
+ LDA #input_y
+ STO #y
+ LDA @update
+ STO #return_addr_ptr
+ JMP @xy2id
+
+
+@update
+ ; draw pixel
+ LDA $FF
+ STO (#px_addr)
+
+ ; determine direction
+ #up    2
+ #right 6
+ #down  8
+ #left  4
+ ;; #key_copy   $FC
+
+ ; test up
+ lda (#keypad)
+ sub #up
+ ftg #flagZ
+ fhp #flagZ
+  jmp @up
+
+ ; test right
+ lda (#keypad)
+ sub #right
+ ftg #flagZ
+ fhp #flagZ
+  jmp @right
+
+ ; TODO: down, left
+ end
+
+ @up
+  lda (#y)
+  sub 1
+  ftg #flagN
+  fhp #flagN
+   jmp @stay_put
+  sto #y
+  ; redundant - it's already in there:
+    lda @update
+    sto #return_addr_ptr
+  jmp @xy2id
+
+ @right
+  lda (#x)
+  sub 4
+  ftg #flagZ
+  fhp #flagZ
+   jmp @stay_put
+  lda (#x)
+  add 1
+  sto #x
+  ; redundant - it's already in there:
+    lda @update
+    sto #return_addr_ptr
+  jmp @xy2id
+
+ @stay_put
+  ; draw pixel
+  LDA $FF
+  STO (#px_addr)
+  ; TODO
+  END
+
+
+;; Convert a pair of (x, y) coords
+;; to the address of a pixel on the display
+;;
+;; Call with:
+;; - x in #x
+;; - y in #y
+;; - return address in #return_addr_ptr
+;;
+;; Returns:
+;; - pixel address in #px_addr
+@xy2id
+ ; stash x, y...
+ #xy2id_y $FC
+ #xy2id_x $F9
+ LDA (#y)
+ STO #xy2id_y
+ LDA (#x)
+ STO #xy2id_x
+ STO #px_addr
+
+ ; check if this is row 0...
+ LDA (#xy2id_y)
+ FHP #flagZ
+  JMP @xy2id_loop
+ JMP (#return_addr_ptr) ; if row 0, we're done
+
+ @xy2id_loop
+  LDA (#px_addr)
+  ADD 5           ; add 5 to get to the next row
+  STO #px_addr
+  LDA (#xy2id_y)  ; decrement y (it's acting as a loop counter) ...
+  SUB 1
+  STO #xy2id_y
+  FHP #flagZ
+   JMP @xy2id_loop
+  ;; JUST TO TEST: LOAD #up INTO KEYPAD MEM:
+   lda #right
+   sto #keypad
+  JMP (#return_addr_ptr)