remember previous x-offset when we re-enter the runs array. speeds up paths

with lots of x-transitions in a single scanline



git-svn-id: http://skia.googlecode.com/svn/trunk@1456 2bbb7eff-a529-9590-31e7-b0007b416f81

src/core/SkAlphaRuns.cpp

@@ -16,10 +16,14 @@
 */
 
 #include "SkAntiRun.h"
+#include "SkUtils.h"
 
 void SkAlphaRuns::reset(int width) {
     SkASSERT(width > 0);
 
+#ifdef SK_DEBUG
+    sk_memset16((uint16_t*)fRuns, (uint16_t)(-42), width);
+#endif
     fRuns[0] = SkToS16(width);
     fRuns[width] = 0;
     fAlpha[0] = 0;
@@ -75,13 +79,17 @@ void SkAlphaRuns::Break(int16_t runs[], uint8_t alpha[], int x, int count) {
     }
 }
 
-void SkAlphaRuns::add(int x, U8CPU startAlpha, int middleCount, U8CPU stopAlpha,
-                      U8CPU maxValue) {
+int SkAlphaRuns::add(int x, U8CPU startAlpha, int middleCount, U8CPU stopAlpha,
+                     U8CPU maxValue, int offsetX) {
     SkASSERT(middleCount >= 0);
     SkASSERT(x >= 0 && x + (startAlpha != 0) + middleCount + (stopAlpha != 0) <= fWidth);
 
-    int16_t*    runs = fRuns;
-    uint8_t*     alpha = fAlpha;
+    SkASSERT(fRuns[offsetX] >= 0);
+
+    int16_t*    runs = fRuns + offsetX;
+    uint8_t*    alpha = fAlpha + offsetX;
+    uint8_t*    lastAlpha = alpha;
+    x -= offsetX;
 
     if (startAlpha) {
         SkAlphaRuns::Break(runs, alpha, x, 1);
@@ -97,6 +105,7 @@ void SkAlphaRuns::add(int x, U8CPU startAlpha, int middleCount, U8CPU stopAlpha,
         runs += x + 1;
         alpha += x + 1;
         x = 0;
+        lastAlpha += x; // we don't want the +1
         SkDEBUGCODE(this->validate();)
     }
 
@@ -114,13 +123,18 @@ void SkAlphaRuns::add(int x, U8CPU startAlpha, int middleCount, U8CPU stopAlpha,
             middleCount -= n;
         } while (middleCount > 0);
         SkDEBUGCODE(this->validate();)
+        lastAlpha = alpha;
     }
 
     if (stopAlpha) {
         SkAlphaRuns::Break(runs, alpha, x, 1);
-        alpha[x] = SkToU8(alpha[x] + stopAlpha);
+        alpha += x;
+        alpha[0] = SkToU8(alpha[0] + stopAlpha);
         SkDEBUGCODE(this->validate();)
+        lastAlpha = alpha;
     }
+
+    return lastAlpha - fAlpha;  // new offsetX
 }
 
 #ifdef SK_DEBUG

src/core/SkAntiRun.h

@@ -31,7 +31,15 @@ public:
     }
 
     void    reset(int width);
-    void    add(int x, U8CPU startAlpha, int middleCount, U8CPU stopAlpha, U8CPU maxValue);
+    
+    /**
+     *  Returns the offsetX value that should be passed on the next call,
+     *  assuming we're on the same scanline. If the caller is switching
+     *  scanlines, then offsetX should be 0 when this is called.
+     */
+    int add(int x, U8CPU startAlpha, int middleCount, U8CPU stopAlpha,
+            U8CPU maxValue, int offsetX);
+
     SkDEBUGCODE(void assertValid(int y, int maxStep) const;)
     SkDEBUGCODE(void dump() const;)
 

src/core/SkScan_AntiPath.cpp

@@ -53,7 +53,7 @@ protected:
     int         fWidth, fLeft, fSuperLeft;
 
     SkDEBUGCODE(int fCurrX;)
-    SkDEBUGCODE(int fCurrY;)
+    int fCurrY;
 };
 
 BaseSuperBlitter::BaseSuperBlitter(SkBlitter* realBlitter, const SkIRect& ir,
@@ -89,6 +89,7 @@ public:
 
 private:
     SkAlphaRuns fRuns;
+    int         fOffsetX;
 };
 
 SuperBlitter::SuperBlitter(SkBlitter* realBlitter, const SkIRect& ir,
@@ -100,6 +101,8 @@ SuperBlitter::SuperBlitter(SkBlitter* realBlitter, const SkIRect& ir,
     fRuns.fRuns = (int16_t*)sk_malloc_throw((width + 1 + (width + 2)/2) * sizeof(int16_t));
     fRuns.fAlpha = (uint8_t*)(fRuns.fRuns + width + 1);
     fRuns.reset(width);
+
+    fOffsetX = 0;
 }
 
 void SuperBlitter::flush() {
@@ -108,6 +111,7 @@ void SuperBlitter::flush() {
         //  SkDEBUGCODE(fRuns.dump();)
             fRealBlitter->blitAntiH(fLeft, fCurrIY, fRuns.fAlpha, fRuns.fRuns);
             fRuns.reset(fWidth);
+            fOffsetX = 0;
         }
         fCurrIY = -1;
         SkDEBUGCODE(fCurrX = -1;)
@@ -134,11 +138,14 @@ void SuperBlitter::blitH(int x, int y, int width) {
     }
 
 #ifdef SK_DEBUG
-    SkASSERT(y >= fCurrY);
     SkASSERT(y != fCurrY || x >= fCurrX);
-    fCurrY = y;
 #endif
-
+    SkASSERT(y >= fCurrY);
+    if (fCurrY != y) {
+        fOffsetX = 0;
+        fCurrY = y;
+    }
+    
     if (iy != fCurrIY) {  // new scanline
         this->flush();
         fCurrIY = iy;
@@ -167,8 +174,10 @@ void SuperBlitter::blitH(int x, int y, int width) {
             fb = (1 << SHIFT) - fb;
         }
     }
-    fRuns.add(x >> SHIFT, coverage_to_alpha(fb), n, coverage_to_alpha(fe),
-              (1 << (8 - SHIFT)) - (((y & MASK) + 1) >> SHIFT));
+
+    fOffsetX = fRuns.add(x >> SHIFT, coverage_to_alpha(fb), n, coverage_to_alpha(fe),
+                         (1 << (8 - SHIFT)) - (((y & MASK) + 1) >> SHIFT),
+                         fOffsetX);
 
 #ifdef SK_DEBUG
     fRuns.assertValid(y & MASK, (1 << (8 - SHIFT)));