shared: Bring joypad into a proper style

Put functions inside of the scope, avoid useless fallthroughs and be
more realistic on what is needed from elsewhere.

Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>

9 files changed, 66 insertions, 78 deletions

diff --git a/basics/flicker.s b/basics/flicker.s
index 2522cb2..5677968 100644
--- a/basics/flicker.s
+++ b/basics/flicker.s
@@ -38,7 +38,7 @@
 @main_game_loop:
     ;; NOTE: the logic is pretty simple: read the pad, move the player
     ;; accordingly, and apply the flickering effect.
-    jsr joypad_read
+    READ_JOYPAD1
     jsr Diskun::update
 
     ;; NOTE: comment this `jsr` out if you want to see what happens if no
diff --git a/fx/blink.s b/fx/blink.s
index c9a38b1..ce63b2c 100644
--- a/fx/blink.s
+++ b/fx/blink.s
@@ -277,7 +277,7 @@
     sta $2001
 
 @main_game_loop:
-    jsr joypad_read
+    READ_JOYPAD1
     jsr Diskun::update
 
     lda #%10000000
diff --git a/scroll/include/driver.s b/scroll/include/driver.s
index abb3f5e..acf5a11 100644
--- a/scroll/include/driver.s
+++ b/scroll/include/driver.s
@@ -50,7 +50,7 @@
         ;; If `select` is pressed, then go for a new level. Otherwise check
         ;; whether there is a pending column to be loaded.
         lda #Joypad::BUTTON_SELECT
-        and Joypad::m_buttons1
+        and Joypad::zp_buttons1
         beq @check_column
 
         ;; Set the counter.
diff --git a/scroll/include/player.s b/scroll/include/player.s
index 239cec6..a4f750c 100644
--- a/scroll/include/player.s
+++ b/scroll/include/player.s
@@ -76,7 +76,7 @@
     .proc update
         ;; Is the player requesting to go up?
         lda #Joypad::BUTTON_UP
-        and Joypad::m_buttons1
+        and Joypad::zp_buttons1
         beq @check_down
 
         ;; If we are already at the top disregard this button press and check
@@ -108,7 +108,7 @@
     @check_down:
         ;; Is the player requesting to go down?
         lda #Joypad::BUTTON_DOWN
-        and Joypad::m_buttons1
+        and Joypad::zp_buttons1
         beq @check_left
 
         ;; We have to move down unless we are already at the very bottom.
@@ -135,7 +135,7 @@
     @check_left:
         ;; Is the player requesting to go left?
         lda #Joypad::BUTTON_LEFT
-        and Joypad::m_buttons1
+        and Joypad::zp_buttons1
         beq @check_right
 
         ;; We have to move left unless we are already at the leftmost edge.
@@ -160,7 +160,7 @@
     @check_right:
         ;; Last check! Is the player requesting to go right?
         lda #Joypad::BUTTON_RIGHT
-        and Joypad::m_buttons1
+        and Joypad::zp_buttons1
         bne @check_level_end
         rts
 
diff --git a/scroll/level.s b/scroll/level.s
index de386db..28de7f0 100644
--- a/scroll/level.s
+++ b/scroll/level.s
@@ -57,7 +57,7 @@
     sta PPU::CONTROL
 
 @main_game_loop:
-    jsr joypad_read
+    READ_JOYPAD1
     jsr Player::update
     jsr Driver::update
 
diff --git a/scroll/sprite0.s b/scroll/sprite0.s
index 4bd940d..a1944e6 100644
--- a/scroll/sprite0.s
+++ b/scroll/sprite0.s
@@ -142,7 +142,7 @@ BACKGROUND_ROW_OFFSET = 1
     sta PPU::CONTROL
 
 @main_game_loop:
-    jsr joypad_read
+    READ_JOYPAD1
     jsr Player::update
     jsr Driver::update
 
diff --git a/scroll/toggle.s b/scroll/toggle.s
index b9214b4..32fc39f 100644
--- a/scroll/toggle.s
+++ b/scroll/toggle.s
@@ -70,11 +70,11 @@
     bne @end
 
     ;; Read the joypad.
-    jsr joypad_read
+    READ_JOYPAD1
 
     ;; Is the player pressing left? If so then the direction is to the left.
     lda #Joypad::BUTTON_LEFT
-    and Joypad::m_buttons1
+    and Joypad::zp_buttons1
     beq @check_right
     inc Vars::zp_scrolling
     lda #0
@@ -84,7 +84,7 @@
 @check_right:
     ;; Is the player pressing right? If so then the direction is to the right.
     lda #Joypad::BUTTON_RIGHT
-    and Joypad::m_buttons1
+    and Joypad::zp_buttons1
     beq @check_select
     inc Vars::zp_scrolling
     lda #1
@@ -95,7 +95,7 @@
     ;; Is the player pressing Select? Then the direction depends on the current
     ;; nametable.
     lda #Joypad::BUTTON_SELECT
-    and Joypad::m_buttons1
+    and Joypad::zp_buttons1
     beq @end
     inc Vars::zp_scrolling
     ldx #0
diff --git a/shared/diskun.s b/shared/diskun.s
index 8349748..ffe8028 100644
--- a/shared/diskun.s
+++ b/shared/diskun.s
@@ -41,7 +41,7 @@
 
     .proc update
         lda #Joypad::BUTTON_UP
-        and Joypad::m_buttons1
+        and Joypad::zp_buttons1
         beq @check_down
 
         dec Diskun::m_screen_y
@@ -49,21 +49,21 @@
         jmp @check_left
     @check_down:
         lda #Joypad::BUTTON_DOWN
-        and Joypad::m_buttons1
+        and Joypad::zp_buttons1
         beq @check_left
 
         inc Diskun::m_screen_y
         inc Diskun::m_screen_y
     @check_left:
         lda #Joypad::BUTTON_LEFT
-        and Joypad::m_buttons1
+        and Joypad::zp_buttons1
         beq @check_right
 
         dec Diskun::m_screen_x
         dec Diskun::m_screen_x
     @check_right:
         lda #Joypad::BUTTON_RIGHT
-        and Joypad::m_buttons1
+        and Joypad::zp_buttons1
         beq @end
 
         inc Diskun::m_screen_x
diff --git a/shared/joypad.s b/shared/joypad.s
index 7bfc575..05797fe 100644
--- a/shared/joypad.s
+++ b/shared/joypad.s
@@ -15,70 +15,58 @@
 
     ;; After running a `joypad_read_*` function these two variables will contain
     ;; the given result.
-    m_buttons1 = $22
-    m_buttons2 = $23
-.endscope
-
-;;;
-;; Read the first joypad. This method is fast but it might be vulnerable to the
-;; DPCM bug (see: https://www.nesdev.org/wiki/Controller_reading_code).
-joypad_unsafe_read:
-    ldx #$00
-    ;; NOTE: fallthrough
-
-;;;
-;; Read the joypad as indexed by the X register (0 for controller 1; 1 for
-;; controller 2). This method is fast but it might be vulnerable to the DPCM bug
-;; (see: https://www.nesdev.org/wiki/Controller_reading_code).
-joypad_unsafe_read_x:
-    ;; Start the latch process.
-    lda #$01
-    sta Joypad::JOYPAD1
-    sta Joypad::m_buttons1, x   ; Bit as a guard for the loop below.
-    lsr
-    sta Joypad::JOYPAD1
+    zp_buttons1 = $22
+    zp_buttons2 = $23
 
-    ;; Now the joypad is ready to accept reads.
-@joypad_unsafe_read_x_loop:
-    lda Joypad::JOYPAD1, x
-    and #%00000011              ; Ignore bits other than controller.
-    cmp #$01                    ; Set carry if and only if nonzero.
-    rol Joypad::m_buttons1, x   ; Carry -> bit 0; bit 7 -> Carry
-    bcc @joypad_unsafe_read_x_loop
-    rts
+    ;;;
+    ;; Safely read via a re-read algorithm the joypad as indexed by the X register
+    ;; (0 for controller 1; 1 for controller 2).
+    .proc read_x
+        jsr Joypad::unsafe_read_x
 
-;;;
-;; Safely read the first controller via a re-read algorithm.
-joypad_read:
-    ldx #$00
-
-    ;; NOTE: uncomment these two lines to also read safely the second
-    ;; controller.
-    ;;
-    ;; jsr joypad_read_x
-    ;; inx
+        ;; The main idea around a re-read algorithm is that you read the
+        ;; controller "unsafely" once, then you do it again and compare both
+        ;; reads. If they were the same then we are on the safe side. Otherwise
+        ;; we would need to loop until we get two identical reads. This sounds
+        ;; bad but in practice it's not so much (and hey, if it worked for Super
+        ;; Mario Bros. 3, it should work for us too :P). Otherwise there is the
+        ;; algorithm via OAM DMA, but it sure is tricky.
+    @reread:
+        lda Joypad::zp_buttons1, x
+        tay
+        jsr Joypad::unsafe_read_x
+        tya
+        cmp Joypad::zp_buttons1, x
+        bne @reread
 
-    ;; NOTE: fallthrough
+        rts
+    .endproc
 
-;;;
-;; Safely read via a re-read algorithm the joypad as indexed by the X register
-;; (0 for controller 1; 1 for controller 2).
-joypad_read_x:
-    jsr joypad_unsafe_read_x
+    ;;;
+    ;; Read the joypad as indexed by the X register (0 for controller 1; 1 for
+    ;; controller 2). This method is fast but it might be vulnerable to the DPCM
+    ;; bug (see: https://www.nesdev.org/wiki/Controller_reading_code).
+    .proc unsafe_read_x
+        ;; Start the latch process.
+        lda #$01
+        sta Joypad::JOYPAD1
+        sta Joypad::zp_buttons1, x   ; Bit as a guard for the loop below.
+        lsr
+        sta Joypad::JOYPAD1
 
-    ;; The main idea around a re-read algorithm is that you read the controller
-    ;; "unsafely" once, then you do it again and compare both reads. If they
-    ;; were the same then we are on the safe side. Otherwise we would need to
-    ;; loop until we get two identical reads. This sounds bad but in practice
-    ;; it's not so much (and hey, if it worked for Super Mario Bros. 3, it
-    ;; should work for us too :P). Otherwise there is the algorithm via OAM DMA,
-    ;; but it sure is tricky.
-@joypad_read_x_reread:
-    lda Joypad::m_buttons1, x
-    tay
-    jsr joypad_unsafe_read_x
-    tya
-    cmp Joypad::m_buttons1, x
-    bne @joypad_read_x_reread
+        ;; Now the joypad is ready to accept reads.
+    @loop:
+        lda Joypad::JOYPAD1, x
+        and #%00000011              ; Ignore bits other than controller.
+        cmp #$01                    ; Set carry if and only if nonzero.
+        rol Joypad::zp_buttons1, x   ; Carry -> bit 0; bit 7 -> Carry
+        bcc @loop
+        rts
+    .endproc
+.endscope
 
-    rts
+;; Shortcut for reading the joypad from the first player safely.
+.macro READ_JOYPAD1
+    ldx #$00
+    jsr Joypad::read_x
+.endmacro