3 files changed, 36 insertions, 12 deletions
diff --git a/agbx/source/gfx/flip.c b/agbx/source/gfx/flip.c
new file mode 100644
index 0000000..92b8939
--- /dev/null
+++ b/agbx/source/gfx/flip.c
@@ -0,0 +1,17 @@
+/*
+	Copyright 2022 Gabriel Jensen.
+	This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
+	If a copy of the MPL was not distributed with this file, You can obtain one at https://mozilla.org/MPL/2.0/.
+*/
+
+#include <agbx/priv.h>
+
+#include <agbx/gfx.h>
+
+agbx_i20 agbx_flip(void) {
+	agbx_i10 dispcnt = agbx_get10(0x400'0000u);
+	dispcnt ^= 0b10000u;
+	agbx_set10(0x400'0000u,dispcnt);
+	if (dispcnt & 0x10000u) {return 0x600'A000u;}
+	return 0x600'0000u;
+}
diff --git a/agbx/source/gfx/plot.c b/agbx/source/gfx/plot.c
index 2146c54..cc41d38 100644
--- a/agbx/source/gfx/plot.c
+++ b/agbx/source/gfx/plot.c
@@ -13,7 +13,7 @@ agbx_i10 agbx_plot3(agbx_i8 const _x,agbx_i8 const _y,agbx_i10 const _col) {
 	if (_x >= 0xF0u || _y >= 0xA0u) {agbx_done(agbx_err_pos2big);}
 #endif
 	agbx_i10 const px = _y * 0xF0u + _x;
-	__agbx_setpx2(px,_col)
+	__agbx_setpx2(0x600'0000u,px,_col)
 	return px;
 }
 
@@ -21,8 +21,9 @@ agbx_i10 agbx_plot4(agbx_i8 const _x,agbx_i8 const _y,agbx_i8 const _col) {
 #if defined(__agbx_dbg)
 	if (_x >= 0xF0u || _y >= 0xA0u) {agbx_done(agbx_err_pos2big);}
 #endif
+	agbx_i20 const vaddr = 0x600'0000u + (agbx_get10(0x400'0000u) >> 0x4u & 0x1u) * 0xA000u;
 	agbx_i10 const px = _y * 0xF0u + _x;
-	__agbx_setpx1(px,_col)
+	agbx_setpx1(vaddr,px,_col);
 	return px;
 }
 
@@ -30,7 +31,8 @@ agbx_i10 agbx_plot5(agbx_i8 const _x,agbx_i8 const _y,agbx_i10 const _col) {
 #if defined(__agbx_dbg)
 	if (_x >= 0xA0u || _y >= 0x80u) {agbx_done(agbx_err_pos2big);}
 #endif
-	agbx_i10 const px = _y * 0xA0u + _x;
-	__agbx_setpx2(px,_col)
+	agbx_i20 const vaddr = 0x600'0000u + (agbx_get10(0x400'0000u) >> 0x4u & 0x1u) * 0xA000u;
+	agbx_i10 const px = _y * 0xF0u + _x;
+	__agbx_setpx2(vaddr,px,_col)
 	return px;
 }
diff --git a/agbx/source/gfx/setpx.c b/agbx/source/gfx/setpx.c
index 563fd3b..b2c5c2d 100644
--- a/agbx/source/gfx/setpx.c
+++ b/agbx/source/gfx/setpx.c
@@ -8,19 +8,24 @@
 
 #include <agbx/gfx.h>
 
-void agbx_setpx1(agbx_i10 const _px,agbx_i8 const  _col) {
+void agbx_setpx1(agbx_i20 const _vaddr,agbx_i10 const _px,agbx_i8 const _col) {
 #if defined(__agbx_dbg)
-	agbx_i10 const dispcnt = agbx_get10(0x4000000u);
+	agbx_i10 const dispcnt = agbx_get10(0x400'0000u);
 	agbx_i8 const  md      = dispcnt & 0x7u;
-	if (md == 0x3u || md == 0x5u) {agbx_done(agbx_err_badmd);}
-	if (_px >= 0x9600u)           {agbx_done(agbx_err_px2big);}
+	if (md != 0x4u)     {agbx_done(agbx_err_badmd);}
+	if (_px >= 0x9600u) {agbx_done(agbx_err_px2big);}
 #endif
-	__agbx_setpx1(_px,_col)
+	/* We can only write halfwords to VRAM, so we load the adjacent pixel value and combine it into a halfword. */
+	agbx_i20 const addr = _vaddr + _px - (_px & 0x1u) * 0x1u;
+	agbx_i10 col;
+	if (_px & 0x1u) {col = (agbx_i10)agbx_get8(addr) | (agbx_i10)_col << 0x8u;}
+	else            {col = (agbx_i10)agbx_get8(addr + 0x1u) << 0x8u | (agbx_i10)_col;}
+	__agbx_set10(addr,col)
 }
 
-void agbx_setpx2(agbx_i10 const _px,agbx_i10 const _col) {
+void agbx_setpx2(agbx_i20 const _vaddr,agbx_i10 const _px,agbx_i10 const _col) {
 #if defined(__agbx_dbg)
-	agbx_i10 const dispcnt = agbx_get10(0x4000000u);
+	agbx_i10 const dispcnt = agbx_get10(0x400'0000u);
 	agbx_i8 const  md      = dispcnt & 0x7u;
 	if (md == 0x4u) {agbx_done(agbx_err_badmd);}
 	if (md == 0x5u) {
@@ -31,5 +36,5 @@ void agbx_setpx2(agbx_i10 const _px,agbx_i10 const _col) {
 		if (_px >= 0x9600u) {agbx_done(agbx_err_px2big);}
 	}
 #endif
-	__agbx_setpx2(_px,_col)
+	__agbx_setpx2(_vaddr,_px,_col)
 }