Decoupling video rendering (Part 1).

src/cpu.cpp

@@ -235,10 +235,12 @@ void power()
     INT<RESET>();
 }
 
-/* Start the execution */
-void run()
+/* Run the CPU for roughly a frame */
+void run_frame()
 {
-    while (true)
+    unsigned remaining = 29781;
+
+    while (remaining--)
     {
         exec();
 

src/cpu.hpp

@@ -24,7 +24,7 @@ class Flags
 void set_nmi(bool v = true);
 void set_irq(bool v = true);
 void power();
-void run();
+void run_frame();
 
 
 }

src/gui.cpp

@@ -15,8 +15,6 @@ SDL_Renderer* renderer;
 SDL_Texture* texture;
 u8 const* keys;
 
-u32 pixels[width * height];  // Video buffer.
-
 /* Initialize SDL */
 void init()
 {
@@ -37,8 +35,8 @@ void init()
     signal(SIGINT, SIG_DFL);
 }
 
-/* Get the keys state from SDL */
-u8 get_keys_state(int n)
+/* Get the joypad state from SDL */
+u8 get_joypad_state(int n)
 {
     u8 j = 0;
     SDL_PumpEvents();
@@ -57,14 +55,8 @@ u8 get_keys_state(int n)
     return j;
 }
 
-/* Draw a pixel at the given coordinates */
-void draw_pixel(unsigned x, unsigned y, u32 rgb)
-{
-    pixels[y*width + x] = rgb;
-}
-
-/* Put the pixels on screen */
-void flush_screen()
+/* Send the rendered frame to the GUI */
+void new_frame(u32* pixels)
 {
     SDL_UpdateTexture(texture, NULL, pixels, width * sizeof(u32));
     SDL_RenderClear(renderer);

src/gui.hpp

@@ -5,9 +5,9 @@ namespace GUI {
 
 
 void init();
-u8 get_keys_state(int n);
+u8 get_joypad_state(int n);
 void draw_pixel(unsigned x, unsigned y, u32 rgb);
-void flush_screen();
+void new_frame(u32* pixels);
 
 
 }

src/joypad.cpp

@@ -11,7 +11,7 @@ u8 read_state(int n)
 {
     // When strobe is high, it keeps reading A:
     if (strobe)
-        return 0x40 | (GUI::get_keys_state(n) & 1);
+        return 0x40 | (GUI::get_joypad_state(n) & 1);
 
     // Get the status of a button and shift the register:
     u8 j = 0x40 | (joypad_bits[n] & 1);
@@ -24,7 +24,7 @@ void write_strobe(bool v)
     // Read the joypad data on strobe's transition 1 -> 0.
     if (strobe and !v)
         for (int i = 0; i < 2; i++)
-            joypad_bits[i] = GUI::get_keys_state(i);
+            joypad_bits[i] = GUI::get_joypad_state(i);
 
     strobe = v;
 }

src/main.cpp

@@ -10,7 +10,8 @@ int main(int argc, char *argv[])
     Cartridge::load(argv[1]);
     CPU::power();
 
-    CPU::run();
+    while(true)
+        CPU::run_frame();
 
     return 0;
 }

src/ppu.cpp

@@ -12,6 +12,7 @@ u8 ciRam[0x800];           // VRAM for nametables.
 u8 cgRam[0x20];            // VRAM for palettes.
 u8 oamMem[0x100];          // VRAM for sprite properties.
 Sprite oam[8], secOam[8];  // Sprite buffers.
+u32 pixels[256 * 240];     // Video buffer.
 
 Addr vAddr, tAddr;  // Loopy V, T.
 u8 fX;              // Fine X.
@@ -254,7 +255,7 @@ void pixel()
         // Evaluate priority:
         if (objPalette && (palette == 0 || objPriority == 0)) palette = objPalette;
 
-        GUI::draw_pixel(x, scanline, nesRgb[rd(0x3F00 + (rendering() ? palette : 0))]);
+        pixels[scanline*256 + x] = nesRgb[rd(0x3F00 + (rendering() ? palette : 0))];
     }
     // Perform background shifts:
     bgShiftL <<= 1; bgShiftH <<= 1;
@@ -268,7 +269,7 @@ template<Scanline s> void scanline_cycle()
     static u16 addr;
 
     if (s == NMI and dot == 1) { status.vBlank = true; if (ctrl.nmi) CPU::set_nmi(); }
-    else if (s == POST and dot == 0) GUI::flush_screen();
+    else if (s == POST and dot == 0) GUI::new_frame(pixels);
     else if (s == VISIBLE or s == PRE)
     {
         // Sprites: