From 201d9bf15cf06ad34434535593c03e234be0a322 Mon Sep 17 00:00:00 2001
From: Brooke Vibber <bvibber@pobox.com>
Date: Sun, 25 Feb 2024 15:15:23 -0800
Subject: [PATCH] clear screen after zoom/scroll

---
 mandel.s | 59 ++++++++++++++++++++++++++++++++++----------------------
 1 file changed, 36 insertions(+), 23 deletions(-)

diff --git a/mandel.s b/mandel.s
index ae8b897..6dedb17 100644
--- a/mandel.s
+++ b/mandel.s
@@ -890,6 +890,37 @@ done:
 
 .endproc
 
+.proc clear_screen
+    ; zero the range from framebuffer_top to display_list
+    lda #.lobyte(framebuffer_top)
+    sta temp
+    lda #.hibyte(framebuffer_top)
+    sta temp + 1
+
+zero_page_loop:
+    lda #0
+    ldy #0
+zero_byte_loop:
+    sta (temp),y
+    iny
+    bne zero_byte_loop
+
+    inc temp + 1
+    lda temp + 1
+    cmp #.hibyte(display_list)
+    bne zero_page_loop
+
+    rts
+.endproc
+
+.proc status_bar
+    ; Status bar
+    draw_text 0, str_self_len, str_self
+    draw_text 40 - str_run_len, str_run_len, str_run
+
+    rts
+.endproc
+
 .proc start
 
     ; ox = 0; oy = 0; zoom = 0
@@ -916,24 +947,7 @@ done:
     lda #0
     sta DMACTL
 
-    ; zero the range from framebuffer_top to framebuffer_end
-    lda #.lobyte(framebuffer_top)
-    sta temp
-    lda #.hibyte(framebuffer_top)
-    sta temp + 1
-
-zero_page_loop:
-    lda #0
-    ldy #0
-zero_byte_loop:
-    sta (temp),y
-    iny
-    bne zero_byte_loop
-
-    inc temp + 1
-    lda temp + 1
-    cmp #.hibyte(framebuffer_end)
-    bne zero_page_loop
+    jsr clear_screen
 
     ; Copy the display list into properly aligned memory
     ; Can't cross 1024-byte boundaries :D
@@ -953,10 +967,6 @@ copy_byte_loop:
     sta DLISTH ; actual register
     sta SDLSTH ; shadow register the OS will copy in
 
-    ; Status bar
-    draw_text 0, str_self_len, str_self
-    draw_text 40 - str_run_len, str_run_len, str_run
-
     ; Re-enable display DMA
     lda #$22
     sta DMACTL
@@ -968,6 +978,9 @@ copy_byte_loop:
     jsr SETVBV
 
 main_loop:
+    jsr clear_screen
+    jsr status_bar
+
     lda #0
     sta fill_level
 
@@ -1031,7 +1044,7 @@ not_skipped_mask:
     jsr keycheck
     beq no_key
     ; @fixme clear the pixel stats
-    jmp fill_loop
+    jmp main_loop
 
 no_key:
     ; check if we should update the counters