Less buggy PPU

README.md

@@ -37,6 +37,7 @@ only tested on Linux. Here is how to run the project:
 - Debug
    - Frame Delay: Done
    - Pattern Table Viewer: Done
+   - Nametable Viewer: Done
    - CPU Debugger: To Do
    - Memory Inspector: To Do
    - PPU Debugger: To Do

gui/gui.c

@@ -37,8 +37,6 @@ bool gui_init() {
         return false;
     }
 
-    main_window_init(&gui.main_window);
-
 #if DEBUG
     gui.tick = 0;
     pattern_window_init(&gui.pattern_window);
@@ -47,6 +45,8 @@ bool gui_init() {
     char_map_init(gui.main_window.sdl_context.renderer, gui.font);
 #endif
 
+    main_window_init(&gui.main_window);
+
     return true;
 }
 
@@ -86,8 +86,6 @@ int gui_input() {
 }
 
 void gui_render() {
-    main_window_render(&gui.main_window, ppu_get_state()->pixels);
-
 #if DEBUG
     pattern_window_render(&gui.pattern_window);
 
@@ -96,15 +94,17 @@ void gui_render() {
 
     gui.tick++;
 #endif
+
+    main_window_render(&gui.main_window, ppu_get_state()->pixels);
 }
 
 void gui_present() {
-    main_window_present(&gui.main_window);
-
 #if DEBUG
     pattern_window_present(&gui.pattern_window);
     nametable_window_present(&gui.nametable_window);
 #endif
+
+    main_window_present(&gui.main_window);
 }
 
 void gui_delay() {

main.c

@@ -24,6 +24,7 @@
 
 int main() {
     char *rom_path = "./test_roms/dk_jp.nes";
+//    char *rom_path = "./test_roms/nes-test-roms/other/BLOCKS.NES";
     log_set_level(LOG_INFO);
 
     if (!gui_init()) {

ppu/ppu.c

@@ -109,7 +109,19 @@ static inline void ppu_pixel_set_color(PPUPixel *pixel, byte pt_low, byte pt_hig
 void ppu_draw_tile() {
     PPUTileFetch fetch = ppu_state.tile_queue.displayed_fetch;
 
-    unsigned int pixel_index = ppu_state.scanline * PPU_VISIBLE_FRAME_END + ppu_state.cycle;
+    unsigned int y = ppu_state.scanline;
+    unsigned int x = ppu_state.cycle + 0;
+
+//    if (x > PPU_LINE_WIDTH) {
+//        x -= PPU_LINE_WIDTH;
+//        y++;
+//    }
+//
+//    if (y > PPU_PRE_RENDER_LINE) {
+//        y -= PPU_PRE_RENDER_LINE;
+//    }
+
+    unsigned int pixel_index = y * PPU_VISIBLE_FRAME_END + x;
     PPUPixel *pixel = &ppu_state.pixels[pixel_index];
     ppu_pixel_set_color(pixel, fetch.pattern_table_tile_low, fetch.pattern_table_tile_high);
 }
@@ -120,7 +132,7 @@ byte ppu_get_pattern(byte tile_index, byte high) {
     return ppu_read(pattern_addr);
 }
 
-void ppu_fetch_tile() {
+void ppu_fetch_tile(bool render) {
     byte fetch_cycle = (ppu_state.cycle - 1) % 8;
 
     if (fetch_cycle == 1) {
@@ -150,7 +162,10 @@ void ppu_fetch_tile() {
     } else if (fetch_cycle == 7) {
         ppu_state.fetch.pattern_table_tile_high = ppu_get_pattern(ppu_state.fetch.nametable, 1);
         ppu_state.tile_queue.displayed_fetch = ppu_state.fetch;
+
+        if (render) {
             ppu_draw_tile();
+        }
 
         if ((ppu_state.ppu_address & 0x1f) == 0x1f) {
             ppu_state.ppu_address &= ~0x1f;
@@ -169,8 +184,8 @@ void ppu_visible_frame(unsigned int cycle) {
 
     if (cycle == 0) {
         // Idle...
-    } else if (cycle <= 256) {
+    } else if (cycle >= 8 && cycle <= 256) {
-        ppu_fetch_tile();
+        ppu_fetch_tile(true);
 
         if (cycle == 256) {
             if ((ppu_state.ppu_address & 0x7000) != 0x7000) {
@@ -194,8 +209,8 @@ void ppu_visible_frame(unsigned int cycle) {
             ppu_state.ppu_address = (ppu_state.ppu_address & 0xfbe0) | (ppu_state.temp_ppu_addr & ~0xfbe0);
             ppu_state.x_scroll = 0;
         }
-    } else if (cycle <= 336) {
+    } else if (cycle <= 328) {
-        ppu_fetch_tile();
+        ppu_fetch_tile(false);
     }
 }