optimized display update region

Interpreter.cpp

@@ -87,9 +87,7 @@ void Interpreter::tick() {
   case 0x0000: // 0NNN - call machine language routine
     switch(inst) {
     case 0x00E0: // clear display
-      for(auto &scanline : *mrDisplay.mpFramebuffer) {
-        scanline.reset();
-      }
+      mrDisplay.clear();
       break;
     case 0x00EE: // return from subroutine
       mvSpecialReg[SR_PC] = mCallStack.top();
@@ -292,7 +290,7 @@ void Interpreter::executeDraw(uint8_t x, uint8_t y, uint8_t n) {
 
     // we draw one scanline per sprite row in high-res mode, but twice in low-res mode
     for(int j = 0; j < (mIsHighResMode ? 1 : 2); j++) {
-      Scanline &targetScanline = mrDisplay.mpFramebuffer->at(y + i * (mIsHighResMode ? 1 : 2) + j);
+      Scanline &targetScanline = mrDisplay.getModifyableScanline(y + i * (mIsHighResMode ? 1 : 2) + j);
       if((targetScanline & spriteScanline) != 0) {
         collisionCount += 1;
       }