almost there, tile ram is empty for some reason

cli/imgui_example.cpp

@@ -48,14 +48,14 @@ GLuint make_output_texture() {
     return image_texture;
 }
 
-unsigned char output_image[160 * 144 * 4];
+unsigned char output_image[256 * 256 * 4];
 
 void convert_output(struct lcd *lcd) {
     int x, y;
     int out_index = 0;
-    for (y = 0; y < 144; y++) {
-        for (x = 0; x < 160; x++) {
-            int val = lcd->pixels[y * 160 + x];
+    for (y = 0; y < 256; y++) {
+        for (x = 0; x < 256; x++) {
+            int val = lcd->buf[y * 256 + x];
             int fill = val ? 255 : 0;
             output_image[out_index++] = val;
             output_image[out_index++] = val;
@@ -77,10 +77,10 @@ void fill_memory_editor(struct dmg *dmg)
 // Main code
 int main(int argc, char *argv[])
 {
-    struct cpu cpu;
-    struct rom rom;
-    struct dmg dmg;
-    struct lcd lcd;
+    struct cpu cpu = { 0 };
+    struct rom rom = { 0 };
+    struct dmg dmg = { 0 };
+    struct lcd lcd = { 0 };
 
     int executed;
 
@@ -237,8 +237,8 @@ int main(int argc, char *argv[])
 
             convert_output(dmg.lcd);
             glBindTexture(GL_TEXTURE_2D, texture);
-            glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 160, 144, 0, GL_RGBA, GL_UNSIGNED_BYTE, output_image);
-            ImGui::Image((void*)(intptr_t) texture, ImVec2(160, 144));
+            glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 256, 256, 0, GL_RGBA, GL_UNSIGNED_BYTE, output_image);
+            ImGui::Image((void*)(intptr_t) texture, ImVec2(256, 256));
 
             ImGui::End();
         }
@@ -246,6 +246,7 @@ int main(int argc, char *argv[])
         fill_memory_editor(&dmg);
 
         editor.DrawWindow("Memory", full_address_space, 0x10000, 0x0000);
+        editor.DrawWindow("LCD", dmg.lcd->buf, 0x2000, 0);
 
         // Rendering
         ImGui::Render();

src/dmg.c

@@ -1,4 +1,5 @@
 #include <stdio.h>
+#include <string.h>
 
 #include "cpu.h"
 #include "rom.h"
@@ -82,6 +83,36 @@ void dmg_step(void *_dmg)
         if (next_scanline == 144) {
             // vblank has started, draw all the stuff from ram into the lcd
 
+            int lcdc = lcd_read(dmg->lcd, REG_LCDC);
+            int bg_base = (lcdc & LCDC_BG_TILE_MAP) ? 0x9c00 : 0x9800;
+            int window_base = (lcdc & LCDC_WINDOW_TILE_MAP) ? 0x9c00 : 0x9800;
+            int use_unsigned = lcdc & LCDC_BG_TILE_DATA;
+            int tilebase = use_unsigned ? 0x8000 : 0x9000;
+
+            printf("base is %04x\n", bg_base);
+
+            int k, off = 0;
+            for (k = 0; k < 1024; k++) {
+                int tile = dmg_read(dmg, bg_base + k);
+                int eff_addr;
+                if (use_unsigned) {
+                    eff_addr = tilebase + 16 * tile;
+                } else {
+                    eff_addr = tilebase + 16 * (signed char) 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);
+                    for (i = 0; i < 8; i++) {
+                        // monochrome for now
+                        dmg->lcd->buf[off] |= (data1 & (1 << i)) ? 1 : 0;
+                        dmg->lcd->buf[off] |= (data2 & (1 << i)) ? 1 : 0;
+                        off++;
+                    }
+                }
+            }
+
             // now copy 256x256 buf to 160x144 based on window registers
             lcd_copy(dmg->lcd);
             lcd_draw(dmg->lcd);

src/lcd.c

@@ -59,7 +59,7 @@ void lcd_put_pixel(struct lcd *lcd, u8 x, u8 y, u8 value)
 void lcd_copy(struct lcd *lcd)
 {
     // use all the registers to compute the pixel data
-
+    
 }
 
 int lcd_step(struct lcd *lcd)