use common impl for drawTextOnPath

src/core/SkDevice.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 "SkDevice.h"
 #include "SkDeviceProperties.h"
 #include "SkDraw.h"
 #include "SkMetaData.h"
 #include "SkPatchUtils.h"
+#include "SkPathMeasure.h"
+#include "SkRasterClip.h"
 #include "SkShader.h"
 #include "SkTextBlob.h"
+#include "SkTextToPathIter.h"
 
 SkBaseDevice::SkBaseDevice()
     : fLeakyProperties(SkNEW_ARGS(SkDeviceProperties, (SkDeviceProperties::kLegacyLCD_InitType)))
 #ifdef SK_DEBUG
     , fAttachedToCanvas(false)
 #endif
 {
     fOrigin.setZero();
     fMetaData = NULL;
 }
@@ skipping 179 matching lines @@
     return NULL;
 }
 
 bool SkBaseDevice::EXPERIMENTAL_drawPicture(SkCanvas*, const SkPicture*, const SkMatrix*,
                                             const SkPaint*) {
     // The base class doesn't perform any accelerated picture rendering
     return false;
 }
 
 //////////////////////////////////////////////////////////////////////////////////////////
 

[robertphillips, 2015/02/17 18:50:47]

morph_points ?

+static void morphpoints(SkPoint dst[], const SkPoint src[], int count,
+                        SkPathMeasure& meas, const SkMatrix& matrix) {
+    SkMatrix::MapXYProc proc = matrix.getMapXYProc();
+    
+    for (int i = 0; i < count; i++) {
+        SkPoint pos;
+        SkVector tangent;
+        
+        proc(matrix, src[i].fX, src[i].fY, &pos);
+        SkScalar sx = pos.fX;
+        SkScalar sy = pos.fY;
+        
+        if (!meas.getPosTan(sx, &pos, &tangent)) {
+            // set to 0 if the measure failed, so that we just set dst == pos
+            tangent.set(0, 0);
+        }
+        
+        /*  This is the old way (that explains our approach but is way too slow
+         SkMatrix    matrix;
+         SkPoint     pt;
+         
+         pt.set(sx, sy);
+         matrix.setSinCos(tangent.fY, tangent.fX);
+         matrix.preTranslate(-sx, 0);
+         matrix.postTranslate(pos.fX, pos.fY);
+         matrix.mapPoints(&dst[i], &pt, 1);
+         */
+        dst[i].set(pos.fX - SkScalarMul(tangent.fY, sy),
+                   pos.fY + SkScalarMul(tangent.fX, sy));
+    }
+}
+
+/*  TODO
+ 
+ Need differentially more subdivisions when the follow-path is curvy. Not sure how to
+ determine that, but we need it. I guess a cheap answer is let the caller tell us,
+ but that seems like a cop-out. Another answer is to get Rob Johnson to figure it out.
+ */

[robertphillips, 2015/02/17 18:50:47]

morph_path ?

+static void morphpath(SkPath* dst, const SkPath& src, SkPathMeasure& meas,
+                      const SkMatrix& matrix) {
+    SkPath::Iter    iter(src, false);
+    SkPoint         srcP[4], dstP[3];
+    SkPath::Verb    verb;
+    
+    while ((verb = iter.next(srcP)) != SkPath::kDone_Verb) {
+        switch (verb) {
+            case SkPath::kMove_Verb:
+                morphpoints(dstP, srcP, 1, meas, matrix);
+                dst->moveTo(dstP[0]);
+                break;
+            case SkPath::kLine_Verb:
+                // turn lines into quads to look bendy
+                srcP[0].fX = SkScalarAve(srcP[0].fX, srcP[1].fX);
+                srcP[0].fY = SkScalarAve(srcP[0].fY, srcP[1].fY);
+                morphpoints(dstP, srcP, 2, meas, matrix);
+                dst->quadTo(dstP[0], dstP[1]);
+                break;
+            case SkPath::kQuad_Verb:
+                morphpoints(dstP, &srcP[1], 2, meas, matrix);
+                dst->quadTo(dstP[0], dstP[1]);
+                break;

[robertphillips, 2015/02/17 18:50:47]

kConic_Verb ?

+            case SkPath::kCubic_Verb:
+                morphpoints(dstP, &srcP[1], 3, meas, matrix);
+                dst->cubicTo(dstP[0], dstP[1], dstP[2]);
+                break;
+            case SkPath::kClose_Verb:
+                dst->close();
+                break;
+            default:
+                SkDEBUGFAIL("unknown verb");
+                break;
+        }
+    }
+}
+
+void SkBaseDevice::drawTextOnPath(const SkDraw& draw, const void* text, size_t byteLength,
+                                  const SkPath& follow, const SkMatrix* matrix,
+                                  const SkPaint& paint) {
+    SkASSERT(byteLength == 0 || text != NULL);
+    
+    // nothing to draw
+    if (text == NULL || byteLength == 0 || draw.fRC->isEmpty()) {
+        return;
+    }
+    
+    SkTextToPathIter    iter((const char*)text, byteLength, paint, true);
+    SkPathMeasure       meas(follow, false);
+    SkScalar            hOffset = 0;
+    
+    // need to measure first
+    if (paint.getTextAlign() != SkPaint::kLeft_Align) {
+        SkScalar pathLen = meas.getLength();
+        if (paint.getTextAlign() == SkPaint::kCenter_Align) {
+            pathLen = SkScalarHalf(pathLen);
+        }
+        hOffset += pathLen;
+    }
+    
+    const SkPath*   iterPath;
+    SkScalar        xpos;
+    SkMatrix        scaledMatrix;
+    SkScalar        scale = iter.getPathScale();
+    
+    scaledMatrix.setScale(scale, scale);
+    
+    while (iter.next(&iterPath, &xpos)) {
+        if (iterPath) {
+            SkPath      tmp;
+            SkMatrix    m(scaledMatrix);
+            
+            tmp.setIsVolatile(true);
+            m.postTranslate(xpos + hOffset, 0);
+            if (matrix) {
+                m.postConcat(*matrix);
+            }
+            morphpath(&tmp, *iterPath, meas, m);
+            this->drawPath(draw, tmp, iter.getPaint(), NULL, true);
+        }
+    }
+}
+
+//////////////////////////////////////////////////////////////////////////////////////////
+
 uint32_t SkBaseDevice::filterTextFlags(const SkPaint& paint) const {
     uint32_t flags = paint.getFlags();
 
     if (!paint.isLCDRenderText() || !paint.isAntiAlias()) {
         return flags;
     }
 
     if (kUnknown_SkPixelGeometry == fLeakyProperties->pixelGeometry()
         || this->onShouldDisableLCD(paint)) {
 
         flags &= ~SkPaint::kLCDRenderText_Flag;
         flags |= SkPaint::kGenA8FromLCD_Flag;
     }
 
     return flags;
 }