From f6825b244a17980ef453b58a3afbf7e5a6cb0ac3 Mon Sep 17 00:00:00 2001
From: "ol.sc" <ol.sc@b7a2c559-68d2-44c3-8de9-860c34a00d81>
Date: Tue, 28 Feb 2012 21:24:17 +0000
Subject: [PATCH] Added screen initialization on Apple GEOS.

git-svn-id: svn://svn.cc65.org/cc65/trunk@5568 b7a2c559-68d2-44c3-8de9-860c34a00d81
---
 libsrc/geos-common/system/crt0.s | 42 +++++++++++++++++++++++---------
 1 file changed, 31 insertions(+), 11 deletions(-)

diff --git a/libsrc/geos-common/system/crt0.s b/libsrc/geos-common/system/crt0.s
index df4e9d8f9..8dba46f6d 100644
--- a/libsrc/geos-common/system/crt0.s
+++ b/libsrc/geos-common/system/crt0.s
@@ -5,43 +5,63 @@
 ; 26.10.99, 10.3.2000, 15.8.2001, 23.12.2002
 
 	    .export _exit
-            .export __STARTUP__ : absolute = 1		; Mark as startup
+	    .export __STARTUP__ : absolute = 1		; Mark as startup
 	    .import __VLIR0_START__, __VLIR0_SIZE__	; Linker generated
-	    .import __STACKSIZE__			; Linker generated
+	    .import __STACKSIZE__, __BACKBUFSIZE__	; Linker generated
 	    .import initlib, donelib
 	    .import callmain
 	    .import zerobss
 	    .importzp sp
 
 	    .include "jumptab.inc"
+	    .include "geossym.inc"
+	    .include "const.inc"
 
 ; ------------------------------------------------------------------------
 ; Place the startup code in a special segment.
 
 .segment	"STARTUP"
 
-; Clear the BSS data
+; GEOS 64/128 initializes the screen before starting an application while
+; Apple GEOS does not. In order to provide identical startup conditions
+; we initialize the screen here on Apple GEOS. For the same reason we set
+; the pattern and dispBufferOn even on GEOS 64/128 although we don't use
+; them here.
+
+	lda #2			; Checkerboard pattern
+	jsr SetPattern
+	lda #<(ST_WR_FORE | .MIN (ST_WR_BACK, __BACKBUFSIZE__))
+	sta dispBufferOn
+.ifdef __GEOS_APPLE__
+	jsr i_Rectangle
+	.byte 0
+	.byte SC_PIX_HEIGHT-1
+	.word 0
+	.word SC_PIX_WIDTH-1
+.endif
+
+; Clear the BSS data.
 
 	jsr zerobss
 
-; Setup stack
+; Setup stack.
 
 	lda #<(__VLIR0_START__ + __VLIR0_SIZE__ + __STACKSIZE__)
+	ldx #>(__VLIR0_START__ + __VLIR0_SIZE__ + __STACKSIZE__)
 	sta sp
-	lda #>(__VLIR0_START__ + __VLIR0_SIZE__ + __STACKSIZE__)
-       	sta sp+1   		; Set argument stack ptr
+	stx sp+1
 
-; Call module constructors
+; Call module constructors.
 
 	jsr initlib
 
-; Push arguments and call main()
+; Push arguments and call main().
 
 	cli
-       	jsr callmain
+	jsr callmain
 
 ; Call module destructors.
 
-_exit:	jsr donelib	 	; Run module destructors
+_exit:	jsr donelib
 
-	jmp EnterDeskTop	; return control to the system
+	jmp EnterDeskTop	; Return control to the system