# HG changeset patch
# User Mike Pavone <pavone@retrodev.com>
# Date 1355012178 28800
# Node ID 4d0c20ad815a7d2e2bc21e87163603215c3bef35
# Parent  30ae73f962671c7e64e9bb99560b033048bf3ed1
Fix vertical scroll value for plane B

diff -r 30ae73f96267 -r 4d0c20ad815a vdp.c
--- a/vdp.c	Sat Dec 08 16:09:43 2012 -0800
+++ b/vdp.c	Sat Dec 08 16:16:18 2012 -0800
@@ -129,7 +129,7 @@
 	//TODO: Implement me
 }
 
-void read_map_scroll(uint16_t column, uint32_t line, uint16_t address, uint16_t hscroll_val, vdp_context * context)
+void read_map_scroll(uint16_t column, uint16_t vsram_off, uint32_t line, uint16_t address, uint16_t hscroll_val, vdp_context * context)
 {
 	uint16_t vscroll;
 	switch(context->regs[REG_SCROLL] & 0x30)
@@ -148,7 +148,7 @@
 		vscroll = 0x3FF;
 		break;
 	}
-	vscroll &= (context->vsram[context->regs[REG_MODE_3] & 0x4 ? column : 0] + line);
+	vscroll &= (context->vsram[(context->regs[REG_MODE_3] & 0x4 ? column : 0) + vsram_off] + line);
 	context->v_offset = vscroll & 0x7;
 	printf("BG | line %d, vsram: %d, vscroll: %d, v_offset: %d\n", line, context->vsram[context->regs[REG_MODE_3] & 0x4 ? column : 0], vscroll, context->v_offset);
 	vscroll /= 8;
@@ -185,12 +185,12 @@
 
 void read_map_scroll_a(uint16_t column, uint32_t line, vdp_context * context)
 {
-	read_map_scroll(column, line, (context->regs[REG_SCROLL_A] & 0x38) << 10, context->hscroll_a, context);
+	read_map_scroll(column, 0, line, (context->regs[REG_SCROLL_A] & 0x38) << 10, context->hscroll_a, context);
 }
 
 void read_map_scroll_b(uint16_t column, uint32_t line, vdp_context * context)
 {
-	read_map_scroll(column, line, (context->regs[REG_SCROLL_B] & 0x7) << 13, context->hscroll_b, context);
+	read_map_scroll(column, 1, line, (context->regs[REG_SCROLL_B] & 0x7) << 13, context->hscroll_b, context);
 }
 
 void render_map(uint16_t col, uint8_t * tmp_buf, vdp_context * context)