From 05caed919c47863026bdad3c50e75978eb83ef89 Mon Sep 17 00:00:00 2001
From: Oleg Romashin <romaxa@gmail.com>
Date: Thu, 23 Sep 2010 16:06:27 -0700
Subject: [PATCH] Bug 598531 - pixman hitting slow path. disable scaling. r=roc
 a=blocking-fennec

---
 gfx/layers/ThebesLayerBuffer.cpp | 12 ++++++++++++
 gfx/thebes/gfxContext.cpp        | 16 +---------------
 gfx/thebes/gfxMatrix.cpp         | 20 ++++++++++++++++++++
 gfx/thebes/gfxMatrix.h           |  7 +++++++
 4 files changed, 40 insertions(+), 15 deletions(-)

diff --git a/gfx/layers/ThebesLayerBuffer.cpp b/gfx/layers/ThebesLayerBuffer.cpp
index bbbb199ba8a..8665ebca995 100644
--- a/gfx/layers/ThebesLayerBuffer.cpp
+++ b/gfx/layers/ThebesLayerBuffer.cpp
@@ -106,11 +106,23 @@ ThebesLayerBuffer::DrawBufferQuadrant(gfxContext* aTarget,
   pattern->SetFilter(filter);
 #endif
 
+  gfxContextMatrixAutoSaveRestore saveMatrix(aTarget);
+
   // Transform from user -> buffer space.
   gfxMatrix transform;
   transform.Scale(aXRes, aYRes);
   transform.Translate(-quadrantTranslation);
 
+  // in common cases the matrix after scaling by 1/aRes is close to 1.0,
+  // so we want to make it 1.0 in both cases
+  transform.Scale(1.0 / aXRes, 1.0 / aYRes);
+  transform.NudgeToIntegers();
+
+  gfxMatrix ctxMatrix = aTarget->CurrentMatrix();
+  ctxMatrix.Scale(1.0 / aXRes, 1.0 / aYRes);
+  ctxMatrix.NudgeToIntegers();
+  aTarget->SetMatrix(ctxMatrix);
+
   pattern->SetMatrix(transform);
   aTarget->SetPattern(pattern);
 
diff --git a/gfx/thebes/gfxContext.cpp b/gfx/thebes/gfxContext.cpp
index fd54d8fcc1c..eb4d6cddee7 100644
--- a/gfx/thebes/gfxContext.cpp
+++ b/gfx/thebes/gfxContext.cpp
@@ -318,26 +318,12 @@ gfxContext::CurrentMatrix() const
     return gfxMatrix(*reinterpret_cast<gfxMatrix*>(&mat));
 }
 
-static void NudgeToInteger(double *aVal)
-{
-    float f = float(*aVal);
-    float r = NS_roundf(f);
-    if (f == r) {
-        *aVal = r;
-    }
-}
-
 void
 gfxContext::NudgeCurrentMatrixToIntegers()
 {
     cairo_matrix_t mat;
     cairo_get_matrix(mCairo, &mat);
-    NudgeToInteger(&mat.xx);
-    NudgeToInteger(&mat.xy);
-    NudgeToInteger(&mat.yx);
-    NudgeToInteger(&mat.yy);
-    NudgeToInteger(&mat.x0);
-    NudgeToInteger(&mat.y0);
+    gfxMatrix(*reinterpret_cast<gfxMatrix*>(&mat)).NudgeToIntegers();
     cairo_set_matrix(mCairo, &mat);
 }
 
diff --git a/gfx/thebes/gfxMatrix.cpp b/gfx/thebes/gfxMatrix.cpp
index 1fc04c35658..e1e85146a50 100644
--- a/gfx/thebes/gfxMatrix.cpp
+++ b/gfx/thebes/gfxMatrix.cpp
@@ -193,3 +193,23 @@ gfx3DMatrix::Is2D(gfxMatrix* aMatrix) const
   }
   return PR_TRUE;
 }
+
+static void NudgeToInteger(double *aVal)
+{
+    float f = float(*aVal);
+    float r = NS_roundf(f);
+    if (f == r) {
+        *aVal = r;
+    }
+}
+
+void
+gfxMatrix::NudgeToIntegers(void)
+{
+    NudgeToInteger(&xx);
+    NudgeToInteger(&xy);
+    NudgeToInteger(&yx);
+    NudgeToInteger(&yy);
+    NudgeToInteger(&x0);
+    NudgeToInteger(&y0);
+}
diff --git a/gfx/thebes/gfxMatrix.h b/gfx/thebes/gfxMatrix.h
index 98b5271212f..839b4cfe5c3 100644
--- a/gfx/thebes/gfxMatrix.h
+++ b/gfx/thebes/gfxMatrix.h
@@ -258,6 +258,13 @@ public:
         return gfxSize(minor, major);
     }
 
+    /**
+     * Snap matrix components that are close to integers
+     * to integers. In particular, components that are integral when
+     * converted to single precision are set to those integers.
+     */
+    void NudgeToIntegers(void);
+
 private:
     static PRBool FuzzyEqual(gfxFloat aV1, gfxFloat aV2) {
         return fabs(aV2 - aV1) < 1e-6;