From bc3f7172858218ba16105c1cf7cf7f12e55f3273 Mon Sep 17 00:00:00 2001
From: Matthew Laux <matthew.laux@gmail.com>
Date: Thu, 14 Jul 2022 02:11:20 -0500
Subject: [PATCH] add vram tile viewer thing

---
 cli/imgui_example.cpp | 40 ++++++++++++++++++++++++++++++++++++++++
 src/cpu.c             |  8 ++++----
 src/dmg.c             |  2 +-
 3 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/cli/imgui_example.cpp b/cli/imgui_example.cpp
index d327068..0e3c721 100644
--- a/cli/imgui_example.cpp
+++ b/cli/imgui_example.cpp
@@ -50,6 +50,7 @@ GLuint make_output_texture() {
 }
 
 unsigned char output_image[256 * 256 * 4];
+unsigned char vram_tiles[256 * 96 * 4];
 
 void convert_output(struct lcd *lcd) {
     int x, y;
@@ -66,6 +67,33 @@ void convert_output(struct lcd *lcd) {
     }
 }
 
+void convert_vram(struct dmg *dmg) {
+    int tile_y, tile_x;
+    int off, in;
+    for (tile_y = 0; tile_y < 12; tile_y++) {
+        for (tile_x = 0; tile_x < 32; tile_x++) {
+            off = 256 * 8 * tile_y + 8 * tile_x;
+            in = 16 * (tile_y * 32 + tile_x);
+            int b, i;
+            for (b = 0; b < 16; b += 2) {
+                int data1 = dmg->video_ram[in + b];
+                int data2 = dmg->video_ram[in + b + 1];
+                for (i = 7; i >= 0; i--) {
+                    // monochrome for now
+                    int fill = (data1 & (1 << i)) ? 255 : 0;
+                    vram_tiles[4 * off + 0] = fill;
+                    vram_tiles[4 * off + 1] = fill;
+                    vram_tiles[4 * off + 2] = fill;
+                    vram_tiles[4 * off + 3] = 255;
+                    //dmg->lcd->buf[off] |= (data2 & (1 << i)) ? 1 : 0;
+                    off++;
+                }
+                off += 248;
+            }
+        }
+    }
+}
+
 char full_address_space[0x10000];
 void fill_memory_editor(struct dmg *dmg)
 {
@@ -165,6 +193,7 @@ int main(int argc, char *argv[])
 
     // setup output
     GLuint texture = make_output_texture();
+    GLuint vram_texture = make_output_texture();
 
     // Our state
     bool z_flag = false;
@@ -247,6 +276,17 @@ int main(int argc, char *argv[])
                 ImGui::End();
             }
 
+            {
+                ImGui::Begin("VRAM");
+
+                convert_vram(&dmg);
+                glBindTexture(GL_TEXTURE_2D, vram_texture);
+                glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 256, 96, 0, GL_RGBA, GL_UNSIGNED_BYTE, vram_tiles);
+                ImGui::Image((void*)(intptr_t) vram_texture, ImVec2(256, 96));
+
+                ImGui::End();
+            }
+
             fill_memory_editor(&dmg);
 
             editor.DrawWindow("Memory", full_address_space, 0x10000, 0x0000);
diff --git a/src/cpu.c b/src/cpu.c
index e13f813..e7d77df 100644
--- a/src/cpu.c
+++ b/src/cpu.c
@@ -136,12 +136,12 @@ static u8 rlc(struct cpu *cpu, u8 val)
 
 static u8 rotate_right(struct cpu *regs, u8 reg)
 {
-	// copy old rightmost bit to carry flag
+    int old_carry = flag_isset(regs, FLAG_CARRY) << 7;
+	// copy old rightmost bit to carry flag, clear ZNH
 	regs->f = (reg & 0x01) << 4;
 	// rotate
-	int result = reg >> 1;
-	// restore rightmost bit to left
-	result |= (regs->f & FLAG_CARRY) << 3;
+	int result = old_carry | reg >> 1;
+    if (!result) set_flag(regs, FLAG_ZERO);
     return result;
 }
 
diff --git a/src/dmg.c b/src/dmg.c
index 3a9f91b..6463bbe 100644
--- a/src/dmg.c
+++ b/src/dmg.c
@@ -92,7 +92,7 @@ void dmg_step(void *_dmg)
             int use_unsigned = lcdc & LCDC_BG_TILE_DATA;
             int tilebase = use_unsigned ? 0x8000 : 0x9000;
 
-            printf("bg_base %04x, tilebase %04x\n", bg_base, tilebase);
+            printf("tile map: %04x, tile data: %04x\n", bg_base, tilebase);
 
             int k = 0, off = 0;
             int tile_y = 0, tile_x = 0;