Merge pull request boriel-basic#645 from boriel/refact/libraries

Refact/libraries

src/arch/zx48k/library/clearbox.bas

@@ -0,0 +1,110 @@
+' ----------------------------------------------------------------
+' This file is released under the MIT License
+'
+' Copyleft (k) 2008-2023
+' by Paul Fisher (a.k.a. BritLion) <http://www.boriel.com>
+' ----------------------------------------------------------------
+
+#ifndef __LIBRARY_CLEARBOX__
+
+REM Avoid recursive / multiple inclusion
+
+#define __LIBRARY_CLEARBOX__
+
+#pragma push(case_insensitive)
+#pragma case_insensitive = True
+
+
+' ----------------------------------------------------------------
+' SUB clearBox
+'
+' Blanks the pixels for a box, measured in Character Squares
+' from print positions X,Y to X + Width, Y + height
+'
+' Parameters:
+'   x - x coordinate (cell column)
+'   y - y coordinate (cell row)
+'   width - width (number of columns)
+'   height - height (number of rows)
+'
+' ----------------------------------------------------------------
+SUB clearBox(x as uByte, y as uByte, width as uByte, height as uByte)
+' THE ERROR CHECKING IS NONEXISTENT.
+' Please make sure you send sensible data -
+' 0 < x < 32, 0 < y < 23, x + width < 32 and y + height < 23
+' Britlion 2012.
+
+ASM
+    PROC
+    LOCAL clearbox_outer_loop, clearbox_mid_loop
+    LOCAL clearbox_inner_loop, clearbox_row_skip
+
+    ld b,(IX+5)     ;' get x value
+    ld c,(IX+7)     ;' get y value
+
+    ld a, c         ;' Set HL to screen offset byte for this character.
+    and 24
+    ld h, a
+    ld a, c
+    and 7
+    rra
+    rra
+    rra
+    rra
+    add a, b
+    ld l, a
+
+    ld b, (IX+11)   ;' get height
+    ld c,(IX+9)     ;' get width
+
+clearbox_outer_loop:
+    xor a
+    push bc       ;' save height.
+    push hl       ;' save screen address.
+
+    ld de, (.core.SCREEN_ADDR)
+    add hl, de    ; 'Adds offset to the screen address pointer
+    ld d, 8       ;' 8 rows to a character.
+clearbox_mid_loop:
+    push hl       ;' save screen address
+    ld b,c        ;' get width.
+
+clearbox_inner_loop:
+    ld (hl), a    ;' write out a zero to the screen.
+
+    inc hl        ;' go right.
+    djnz clearbox_inner_loop    ;' repeat.
+
+    pop hl        ;' recover screen address
+    inc h         ;' down a row (+256)
+
+    dec d
+    jp nz, clearbox_mid_loop  ;' repeat for this row.
+
+    pop hl        ;' get back address at start of line
+    pop bc        ;' get back char count.
+
+    ld a, 32      ;' Go down to next character row.
+    add a, l
+    ld l, a
+    jr nc, clearbox_row_skip
+
+    ld a, 8
+    add a, h
+    ld h, a
+
+clearbox_row_skip:
+    djnz clearbox_outer_loop
+
+    ENDP
+END ASM
+END SUB
+
+
+
+#require "sysvars.asm"
+
+#pragma pop(case_insensitive)
+
+#endif
+