From e32535b01667efb46b3d74308bc5ead7b36e46b6 Mon Sep 17 00:00:00 2001
From: Matthew Laux <matthew.laux@gmail.com>
Date: Wed, 3 Aug 2022 01:22:22 -0500
Subject: [PATCH] support x and y flip, try to support 8x16 but i need to
 change the rendering to per-scanline

---
 src/cpu.c | 18 ++++++++++++++++++
 src/dmg.c | 29 +++++++++++++++++++++--------
 src/lcd.h |  5 +++++
 3 files changed, 44 insertions(+), 8 deletions(-)

diff --git a/src/cpu.c b/src/cpu.c
index d8b912d..6aec086 100644
--- a/src/cpu.c
+++ b/src/cpu.c
@@ -782,6 +782,24 @@ void cpu_step(struct cpu *cpu)
                 cpu->cycle_count += instructions[opc].cycles_branch - instructions[opc].cycles;
             }
             break;
+        case 0xd4: // CALL NC, u16
+            temp16 = read16(cpu, cpu->pc);
+            cpu->pc += 2;
+            if (!flag_isset(cpu, FLAG_CARRY)) {        
+                push(cpu, cpu->pc);
+                cpu->pc = temp16;
+                cpu->cycle_count += instructions[opc].cycles_branch - instructions[opc].cycles;
+            }
+            break;
+        case 0xdc: // CALL C, u16
+            temp16 = read16(cpu, cpu->pc);
+            cpu->pc += 2;
+            if (flag_isset(cpu, FLAG_CARRY)) {        
+                push(cpu, cpu->pc);
+                cpu->pc = temp16;
+                cpu->cycle_count += instructions[opc].cycles_branch - instructions[opc].cycles;
+            }
+            break;
         case 0xd0: // RET NC
             if (!flag_isset(cpu, FLAG_CARRY)) {
                 cpu->pc = pop(cpu);
diff --git a/src/dmg.c b/src/dmg.c
index 833d6cf..823746b 100644
--- a/src/dmg.c
+++ b/src/dmg.c
@@ -188,16 +188,18 @@ struct oam_entry {
     u8 attrs;
 };
 
-// TODO: only ten per scanline, priority
+// TODO: only ten per scanline, priority, attributes, move to lcd.c
 static void render_objs(struct dmg *dmg)
 {
     struct oam_entry *oam = (struct oam_entry *) dmg->lcd->oam;
     int k, lcd_x, lcd_y, off;
+    int tall = lcd_isset(dmg->lcd, REG_LCDC, LCDC_OBJ_SIZE);
+
     for (k = 0; k < 40; k++, oam++) {
         if (oam->pos_y == 0 || oam->pos_y >= 160) {
             continue;
         }
-        if (oam->pos_x == 0 || oam->pos_y >= 168) {
+        if (oam->pos_x == 0 || oam->pos_x >= 168) {
             continue;
         }
 
@@ -206,17 +208,28 @@ static void render_objs(struct dmg *dmg)
 
         off = 160 * lcd_y + lcd_x;
         int eff_addr = 0x8000 + 16 * oam->tile;
-        int b, i;
-        for (b = 0; b < 16; b += 2) {
-            int data1 = dmg_read(dmg, eff_addr + b);
-            int data2 = dmg_read(dmg, eff_addr + b + 1);
+        int b, i, limit = 16;
+        if (tall) {
+            limit = 32;
+        }
+        for (b = 0; b < limit; b += 2) {
+            int use_tile = b;
+            if (oam->attrs & OAM_ATTR_MIRROR_Y) {
+                use_tile = (limit - 2) - b;
+            }
+            int data1 = dmg_read(dmg, eff_addr + use_tile);
+            int data2 = dmg_read(dmg, eff_addr + use_tile + 1);
             for (i = 7; i >= 0; i--) {
                 if (off < 0 || off >= 160 * 144) {
                     // terrible clipping. need to not have an if per-pixel
                     continue;
                 }
-                dmg->lcd->pixels[off] = ((data1 & (1 << i)) ? 1 : 0) << 1;
-                dmg->lcd->pixels[off] |= (data2 & (1 << i)) ? 1 : 0;
+                int use_index = i;
+                if (oam->attrs & OAM_ATTR_MIRROR_X) {
+                    use_index = 7 - i;
+                }
+                dmg->lcd->pixels[off] = ((data1 & (1 << use_index)) ? 1 : 0) << 1;
+                dmg->lcd->pixels[off] |= (data2 & (1 << use_index)) ? 1 : 0;
                 off++;
             }
             off += 152;
diff --git a/src/lcd.h b/src/lcd.h
index 631b4e4..a3923bd 100644
--- a/src/lcd.h
+++ b/src/lcd.h
@@ -39,6 +39,11 @@
 #define LCDC_WINDOW_TILE_MAP (1 << 6)
 #define LCDC_ENABLE (1 << 7)
 
+#define OAM_ATTR_PALETTE (1 << 4)
+#define OAM_ATTR_MIRROR_X (1 << 5)
+#define OAM_ATTR_MIRROR_Y (1 << 6)
+#define OAM_ATTR_BEHIND_BG (1 << 7)
+
 struct lcd {
     u8 oam[0xa0];
     u8 regs[0x0c];