Fixed a bug with linear gradient PDF matrices and added test cases

src/pdf/SkPDFShader.cpp

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkPDFShader.h"
@@ skipping 19 matching lines @@
     return true;
 }
 
 static void unitToPointsMatrix(const SkPoint pts[2], SkMatrix* matrix) {
     SkVector    vec = pts[1] - pts[0];
     SkScalar    mag = vec.length();
     SkScalar    inv = mag ? SkScalarInvert(mag) : 0;
 
     vec.scale(inv);
     matrix->setSinCos(vec.fY, vec.fX);
-    matrix->preTranslate(pts[0].fX, pts[0].fY);
     matrix->preScale(mag, mag);
+    matrix->postTranslate(pts[0].fX, pts[0].fY);
 }
 
 /* Assumes t + startOffset is on the stack and does a linear interpolation on t
    between startOffset and endOffset from prevColor to curColor (for each color
    component), leaving the result in component order on the stack. It assumes
    there are always 3 components per color.
    @param range                  endOffset - startOffset
    @param curColor[components]   The current color components.
    @param prevColor[components]  The previous color components.
    @param result                 The result ps function.
@@ skipping 550 matching lines @@
             return;
     }
 
     // Move any scaling (assuming a unit gradient) or translation
     // (and rotation for linear gradient), of the final gradient from
     // info->fPoints to the matrix (updating bbox appropriately).  Now
     // the gradient can be drawn on on the unit segment.
     SkMatrix mapperMatrix;
     unitToPointsMatrix(transformPoints, &mapperMatrix);
     SkMatrix finalMatrix = fState.get()->fCanvasTransform;
+    finalMatrix.preConcat(fState.get()->fShaderTransform);
     finalMatrix.preConcat(mapperMatrix);
-    finalMatrix.preConcat(fState.get()->fShaderTransform);
+
     SkRect bbox;
     bbox.set(fState.get()->fBBox);
     if (!transformBBox(finalMatrix, &bbox)) {
         return;
     }
 
     SkAutoTUnref<SkPDFArray> domain(new SkPDFArray);
     domain->reserve(4);
     domain->appendScalar(bbox.fLeft);
     domain->appendScalar(bbox.fRight);
@@ skipping 330 matching lines @@
         fPixelGeneration = fImage.getGenerationID();
     } else {
         fColorData.set(sk_malloc_throw(
                     fInfo.fColorCount * (sizeof(SkColor) + sizeof(SkScalar))));
         fInfo.fColors = reinterpret_cast<SkColor*>(fColorData.get());
         fInfo.fColorOffsets =
             reinterpret_cast<SkScalar*>(fInfo.fColors + fInfo.fColorCount);
         shader.asAGradient(&fInfo);
     }
 }