display now uses SDL_FillRect

DisplaySDL.cpp

@@ -35,6 +35,14 @@ DisplaySDL::~DisplaySDL() {
   SDL_DestroyWindow(mpWindow);
 }
 
+void DisplaySDL::clear() {
+  Display::clear();
+  SDL_FillRect(SDL_GetWindowSurface(mpWindow), nullptr, mBgColor);
+  SDL_UpdateWindowSurface(mpWindow);
+  miTopDirtyScanline = chocochip8::gcHeight - 1;
+  miBottomDirtyScanline = 0;
+}
+
 void DisplaySDL::updateWindow() const {
   if(miTopDirtyScanline > miBottomDirtyScanline) {
     // No changes since the last update
@@ -42,48 +50,32 @@ void DisplaySDL::updateWindow() const {
   }
 
   SDL_Surface *pSurface = SDL_GetWindowSurface(mpWindow);
-  SDL_LockSurface(pSurface);
-
-  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++) {
-    // Map SDL surface coordinates to Chocochip8 Framebuffer coordinates
-    fy = sy * (double(chocochip8::gcHeight) / pSurface->h);
-    if(fy < miTopDirtyScanline || miBottomDirtyScanline < fy) {
+  for(int y = 0; y < chocochip8::gcHeight; y++) {
+    if(y < miTopDirtyScanline || miBottomDirtyScanline < y) {
       // Skip scanlines that haven't changed since the last update
       continue;
     }
 
-    for(sx = 0; sx < pSurface->w; sx++) {
-      fx = sx * (double(chocochip8::gcWidth) / pSurface->w);
+    for(int x = 0; x < chocochip8::gcWidth; x++) {
+      // Map framebuffer pixel to SDL surface rectangle
+      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;
+      SDL_Rect rect;
+      rect.x = x1;
+      rect.y = y1;
+      rect.w = x2 - x1;
+      rect.h = y2 - y1;
 
-      // 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;
+      // Read Chocochip8 Framebuffer and choose appropriate color,
+      // note that the MSB of an scanline's bitset is the leftmost pixel.
+      Uint32 color = (mpFramebuffer->at(y)[(chocochip8::gcWidth - 1) - x] ? mFgColor : mBgColor);
+      SDL_FillRect(pSurface, &rect, color);
     }
   }
 
   miTopDirtyScanline = chocochip8::gcHeight - 1;
   miBottomDirtyScanline = 0;
-  SDL_UnlockSurface(pSurface);
   SDL_UpdateWindowSurface(mpWindow);
 }

DisplaySDL.hpp

@@ -9,6 +9,7 @@ class DisplaySDL : public chocochip8::Display {
 public:
   DisplaySDL(int w, int h, uint32_t fgCol = 0xffffff, uint32_t bgCol = 0x000000);
   ~DisplaySDL() override;
+  void clear() override;
   void updateWindow() const;
 
 private: