From dc194d44f78821c1e83f8d30d69d32d0fb1e7151 Mon Sep 17 00:00:00 2001
From: Martin Haye <m1@snyder-haye.com>
Date: Sun, 18 Jan 2015 08:59:56 -0800
Subject: [PATCH] Simplified section math.

---
 .../Apple/virtual/src/plasma/gameloop.pla     | 49 ++++++++++++++++++-
 Platform/Apple/virtual/src/tile/tile.s        | 22 +++++++++
 2 files changed, 70 insertions(+), 1 deletion(-)

diff --git a/Platform/Apple/virtual/src/plasma/gameloop.pla b/Platform/Apple/virtual/src/plasma/gameloop.pla
index e5314540..d590b506 100644
--- a/Platform/Apple/virtual/src/plasma/gameloop.pla
+++ b/Platform/Apple/virtual/src/plasma/gameloop.pla
@@ -81,6 +81,11 @@ const playerY   = $60
 const backBuf   = $6A
 const frontBuf  = $6B
 
+///////////////////////////////////////////////////////////////////////////////////////////////////
+// Tile engine variables
+const relX = $50
+const relY = $51
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 // Font engine variables
 const wndleft   = $70  // left edge of the window
@@ -333,6 +338,21 @@ asm renderFrame
         rts
 end
 
+///////////////////////////////////////////////////////////////////////////////////////////////////
+// Deal with crossing into a new map section
+// Params: none
+asm checkCrossing
+        txa
+        pha
+        bit setROM
+        jsr $6006
+        pla
+        tax
+        dex                 ; don't-care return value
+        bit setLcRW+lcBank2
+        rts
+end
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 // Is the player's current position a physical obstruction?
 // Params: none
@@ -847,6 +867,29 @@ def strafeLeft()
   adjustDir(4)
 end
 
+///////////////////////////////////////////////////////////////////////////////////////////////////
+def move2D(ox, oy)
+  *relX = ox + *relX
+  *relY = oy + *relY
+  checkCrossing()
+end
+
+def moveNorth()
+  move2D(0, -1)
+end
+
+def moveEast()
+  move2D(1, 0)
+end
+
+def moveSouth()
+  move2D(0, 1)
+end
+
+def moveWest()
+  move2D(-1, 0)
+end
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 // Switch to a new map (2D or 3D)
 def setMap(is3D, num)
@@ -998,7 +1041,11 @@ end
 def initCmds2D()
   resetCmds()
 
-  //initCmd('W', @moveForward)
+  initCmd('W', @moveNorth)
+  initCmd('D', @moveEast)
+  initCmd('S', @moveSouth)
+  initCmd('X', @moveSouth)
+  initCmd('A', @moveWest)
 end
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
diff --git a/Platform/Apple/virtual/src/tile/tile.s b/Platform/Apple/virtual/src/tile/tile.s
index 8edfa466..303ac6f2 100644
--- a/Platform/Apple/virtual/src/tile/tile.s
+++ b/Platform/Apple/virtual/src/tile/tile.s
@@ -80,6 +80,7 @@ TILE_SOURCE     = $6D   ; Location of tile data
 ; Vectors used to call in from the outside.
 	jmp INIT
 	jmp DRAW
+	jmp CROSS
 
 ; Debug support -- must come after jump vectors, since it's not just macros.
 !source "../include/debug.i"
@@ -221,6 +222,27 @@ LOAD_ALL_TILES
 	JSR LOAD_ALL_TILES
 }
 
+; >> CHECK CROSSINGS
+!zone
+CROSS
+	LDA REL_Y
+	CMP #VIEWPORT_VERT_PAD-1
+	BPL .10
+	JSR CROSS_NORTH
+.10	LDA REL_Y
+	CMP #VIEWPORT_VERT_PAD+SECTION_HEIGHT
+	BMI .20
+	JSR CROSS_SOUTH
+.20	LDA REL_X
+	CMP #VIEWPORT_HORZ_PAD-1
+	BPL .30
+	JSR CROSS_WEST
+.30	LDA REL_X
+	CMP #VIEWPORT_HORZ_PAD+SECTION_WIDTH
+	BMI .40
+	JSR CROSS_EAST
+.40	RTS
+
 ; >> CROSS NORTH BOUNDARY (Load next section to the north)
 !zone
 CROSS_NORTH