Temporary state

arith16.a

@@ -144,7 +144,7 @@ USE_MUL_TABLE = 1
 ; the immediate value given in .value.
 ; 
 ; Z  flag is set in case these values are equal. Carry is set
-; if .value is greater or equal than the value store at .memAddr
+; if .value is greater or equal than the value stored at .memAddr
 ; --------------------------------------------------
 !macro cmp16BitImmediate .value, .memAddr {
     lda #>.value

arith32.a

@@ -22,6 +22,19 @@
 ; --------------------------------------------------
 
 
+; --------------------------------------------------
+; This subroutine expects its operand in the zero page pointer ADDR_OPER_LEFT and clears
+; it, i.e. sets its value tp +0
+; --------------------------------------------------
+clear32Bit
+    ldy #4
+    lda #0
+.loopClear
+    sta (ADDR_OPER_LEFT), y
+    dey
+    bpl .loopClear
+    rts
+
 ; --------------------------------------------------
 ; This subroutine expects it operands in the zero page pointers ADDR_OPER_LEFT and ADDR_OPER_RIGHT
 ; and adds them. This routine ignores the sign byte.

main.a

@@ -8,6 +8,7 @@
 
 RES_X = 320
 RES_Y = 240
+MAX_ZOOM_LEVEL = 17
 
 ENTRY_POINT
 jmp progStart
@@ -37,7 +38,7 @@ NUM_ITER
 !byte 0
 
 ; **************************************************
-; The following 4 values have to be contiguously laid out
+; The following 5 values have to be contiguously laid out
 ; in memory. The load and save routines expect this.
 
 ; x offset to move in complex plane for next point
@@ -55,6 +56,9 @@ INIT_REAL
 ; imaginary part of upper left point of picture
 INIT_IMAG
 !byte 0, 0, 0, $25, 1
+
+ZOOM_LEVEL
+!byte 0
 ; **************************************************
 
 ; Number of points (resolution) in x direction
@@ -306,6 +310,12 @@ mandelLoop
 ; --------------------------------------------------
 progStart
     jsr initArithmetic
+
+    ;jsr bitMapOn
+    jsr drawZoomRect
+    jsr waitForKey
+    jsr drawZoomRect
+
     jsr bitMapOn
     jsr mandelLoop
     lda .INTERRUPTED

mandelhelp.a

@@ -9,7 +9,8 @@ resetParametersHires
     +callFunc move32Bit, DEFAULT_STEP_X, STEP_X
     +callFunc move32Bit, DEFAULT_STEP_Y, STEP_Y 
     +callFunc move32Bit, DEFAULT_INIT_REAL, INIT_REAL
-    +callFunc move32Bit, DEFAULT_INIT_IMAG, INIT_IMAG       
+    +callFunc move32Bit, DEFAULT_INIT_IMAG, INIT_IMAG
+    stz ZOOM_LEVEL       
     rts
 
 ; --------------------------------------------------
@@ -19,8 +20,13 @@ resetParametersHires
 ; increaseZoomLevel has no return value. 
 ; --------------------------------------------------
 increaseZoomLevel
+    lda ZOOM_LEVEL
+    cmp #MAX_ZOOM_LEVEL
+    bcs .zoomDone
+    inc ZOOM_LEVEL
     +callFuncMono halve32Bit, STEP_X
     +callFuncMono halve32Bit, STEP_Y
+.zoomDone
     rts
 
 .TEMP_X

vera.a

@@ -4,7 +4,6 @@ VERA_DATA_0 = $9F23
 CINT = $FF81
 screen_mode = $FF5F
 
-
 ; --------------------------------------------------
 ; This routine set the next point in a colour defined by 
 ; NUM_ITER.
@@ -52,4 +51,77 @@ bitMapOn
 ; --------------------------------------------------
 bitMapOff
     jsr CINT
+    rts
+
+ZOOM_DIFF
+!byte 0
+
+REV_X
+!byte 0, 0
+REV_Y
+!byte 0
+
+TEMP_32_X
+!byte 0, 0, 0, 0, 0
+
+TEMP_32_Y
+!byte 0, 0, 0, 0, 0
+
+reversePixel
+    ; calculate Video RAM address
+    +callFuncMono clear32Bit, TEMP_32_X
+    +callFuncMono clear32Bit, TEMP_32_Y
+    lda REV_Y
+    sta TEMP_32_Y + 1
+    +move16Bit REV_X, TEMP_32_X + 1
+    +callFunc mul32BitUnsignedInt, TEMP_32_Y, TEMP_32_X
+    +printFixedPoint TEMP_32_X
+
+    ; select data port 0
+    lda #%11111110
+    and VERA_CTRL
+    sta VERA_CTRL        
+
+    ; copy video RAM addresses
+    lda TEMP_32_X
+    sta VERA
+    lda TEMP_32_X + 1
+    sta VERA + 1
+    lda TEMP_32_X + 2
+    sta VERA + 2                       ; also set increment to 0 and no decrement
+    ; modify video RAM
+    lda VERA_DATA_0
+    eor #$FF
+    sta VERA_DATA_0
+
+    rts
+
+ZOOM_X_SIZE
+!byte $40, $01
+ZOOM_Y_SIZE
+!byte 240
+
+ZOOM_X_POS
+!byte 0,0
+ZOOM_Y_POS
+!byte 0
+; --------------------------------------------------
+; This routine draws a rectangle on the bitmap screen which symbolizes the
+; zoom level.
+;
+; drawZoomRect has no return value
+; --------------------------------------------------
+drawZoomRect
+    +move16Bit ZOOM_X_POS, REV_X
+    lda ZOOM_Y_POS
+    sta REV_Y
+.loopZoomX
+    jsr reversePixel
+    +inc16Bit REV_X
+    +cmp16BitImmediate RES_X, REV_X
+;    php
+;    +printByteLN REV_X
+;    plp
+    bne .loopZoomX
+
     rts