redesigned display peripheral

DisplaySDL.cpp

@@ -1,8 +1,10 @@
 #include "DisplaySDL.hpp"
+#include "Peripherals.hpp"
 
 #include <stdexcept>
 
-DisplaySDL::DisplaySDL(int w, int h, uint32_t fgColor, uint32_t bgColor) {
+DisplaySDL::DisplaySDL(int w, int h, uint32_t fgColor, uint32_t bgColor):
+  mpFramebuffer{std::make_unique<Framebuffer>()} {
   // Create SDL Window
   mpWindow = SDL_CreateWindow(
     "ChocoChip-8",
@@ -35,43 +37,48 @@ DisplaySDL::~DisplaySDL() {
   SDL_DestroyWindow(mpWindow);
 }
 
-void DisplaySDL::updateWindow() const {
+void DisplaySDL::clear() {
+  for(auto &scanline : *mpFramebuffer) {
+    scanline.reset();
+  }
+  SDL_FillRect(SDL_GetWindowSurface(mpWindow), nullptr, mBgColor);
+}
+
+int DisplaySDL::blit(const chocochip8::Scanline &spriteScanline, int y) {
+  using chocochip8::Scanline;
+  Scanline &targetScanline = mpFramebuffer->at(y);
+  Scanline bitsToSet = spriteScanline & ~targetScanline;
+  Scanline bitsToReset = spriteScanline & targetScanline;
+  targetScanline ^= spriteScanline;
+
   SDL_Surface *pSurface = SDL_GetWindowSurface(mpWindow);
-  SDL_LockSurface(pSurface);
+  SDL_Rect rect;
+  // Map framebuffer pixel to SDL surface rectangle
+  auto mapChipxelToPixel = [&rect, pSurface](int x, int y) {
+      // Note that the MSB of an scanline's bitset is the leftmost pixel.
+      x = (chocochip8::gcWidth - 1) - x;
+      int x1 = (      x * pSurface->w) / chocochip8::gcWidth;
+      int x2 = ((x + 1) * pSurface->w) / chocochip8::gcWidth;
+      int y1 = (      y * pSurface->h) / chocochip8::gcHeight;
+      int y2 = ((y + 1) * pSurface->h) / chocochip8::gcHeight;
+      rect.x = x1;
+      rect.y = y1;
+      rect.w = x2 - x1;
+      rect.h = y2 - y1;
+  };
 
-  int fx, fy; // ChocoChip8 Framebuffer coordinates
-  int sx, sy; // SDL Surface coordinates
-  int lx, ly; // Last-used ChocoChip8 Framebuffer coordinates
-  Uint32 lc;  // Last-used SDL color
-  
-  // Fill the entire SDL surface, one pixel at a time
-  lx = -1;
-  ly = -1;
-  for(sy = 0; sy < pSurface->h; sy++) {
-    for(sx = 0; sx < pSurface->w; sx++) {
-      // Map SDL surface coordinates to Chocochip8 Framebuffer coordinates
-      fx = sx * (double(chocochip8::gcWidth) / pSurface->w);
-      fy = sy * (double(chocochip8::gcHeight) / pSurface->h);
-
-      // Reuse color if this screen pixel maps to the same ChocoChip8 pixel as the last
-      if(fx != lx || fy != ly) {
-        lx = fx;
-        ly = ly;
-        // Read Chocochip8 Framebuffer and choose appropriate color,
-        // note that the MSB of an scanline's bitset is the leftmost pixel.
-        lc = (mpFramebuffer->at(fy)[(chocochip8::gcWidth - 1) - fx] ? mFgColor : mBgColor);
-      }
-
-      // Convert (x, y) indexes into SDL Surface pixel array index
-      Uint32 *pPixel = static_cast<Uint32*>(static_cast<void*>(
-          static_cast<char*>(pSurface->pixels)
-          + sy * pSurface->pitch
-          + sx * pSurface->format->BytesPerPixel
-      ));
-      *pPixel = lc;
-    }
+  for(int x = bitsToReset._Find_first(); x < bitsToReset.size(); x = bitsToReset._Find_next(x)) {
+    mapChipxelToPixel(x, y);
+    SDL_FillRect(pSurface, &rect, mBgColor);
+  }
+  for(int x = bitsToSet._Find_first(); x < bitsToSet.size(); x = bitsToSet._Find_next(x)) {
+    mapChipxelToPixel(x, y);
+    SDL_FillRect(pSurface, &rect, mFgColor);
   }
 
-  SDL_UnlockSurface(pSurface);
+  return bitsToReset.any();
+}
+
+void DisplaySDL::updateWindow() const {
   SDL_UpdateWindowSurface(mpWindow);
 }