Add animated line chart sample

R=robertphillips@google.com
Review URL: https://codereview.appspot.com/7307117

git-svn-id: http://skia.googlecode.com/svn/trunk@7727 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 188 insertions, 0 deletions

diff --git a/samplecode/SampleChart.cpp b/samplecode/SampleChart.cpp
new file mode 100644
index 0000000000..68d750f881
--- /dev/null
+++ b/samplecode/SampleChart.cpp
@@ -0,0 +1,188 @@
+
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#include "SampleCode.h"
+#include "SkCanvas.h"
+#include "SkPaint.h"
+#include "SkRandom.h"
+#include "SkView.h"
+
+namespace {
+
+// Generates y values for the chart plots.
+void gen_data(SkScalar yAvg, SkScalar ySpread, int count, SkTDArray<SkScalar>* dataPts) {
+    dataPts->setCount(count);
+    static SkMWCRandom gRandom;
+    for (int i = 0; i < count; ++i) {
+        (*dataPts)[i] = gRandom.nextRangeScalar(yAvg - SkScalarHalf(ySpread),
+                                                yAvg + SkScalarHalf(ySpread));
+    }
+}
+
+// Generates a path to stroke along the top of each plot and a fill path for the area below each
+// plot. The fill path is bounded below by the bottomData plot points or a horizontal line at
+// yBase if bottomData == NULL.
+// The plots are animated by rotating the data points by leftShift.
+void gen_paths(const SkTDArray<SkScalar>& topData,
+               const SkTDArray<SkScalar>* bottomData,
+               SkScalar yBase,
+               SkScalar xLeft, SkScalar xDelta,
+               int leftShift,
+               SkPath* plot, SkPath* fill) {
+    plot->rewind();
+    fill->rewind();
+    plot->incReserve(topData.count());
+    if (NULL == bottomData) {
+        fill->incReserve(topData.count() + 2);
+    } else {
+        fill->incReserve(2 * topData.count());
+    }
+
+    leftShift %= topData.count();
+    SkScalar x = xLeft;
+
+    // Account for the leftShift using two loops
+    int shiftToEndCount = topData.count() - leftShift;
+    plot->moveTo(x, topData[leftShift]);
+    fill->moveTo(x, topData[leftShift]);
+
+    for (int i = 1; i < shiftToEndCount; ++i) {
+        plot->lineTo(x, topData[i + leftShift]);
+        fill->lineTo(x, topData[i + leftShift]);
+        x += xDelta;
+    }
+
+    for (int i = 0; i < leftShift; ++i) {
+        plot->lineTo(x, topData[i]);
+        fill->lineTo(x, topData[i]);
+        x += xDelta;
+    }
+
+    if (NULL != bottomData) {
+        SkASSERT(bottomData->count() == topData.count());
+        // iterate backwards over the previous graph's data to generate the bottom of the filled
+        // area (and account for leftShift).
+        for (int i = 0; i < leftShift; ++i) {
+            x -= xDelta;
+            fill->lineTo(x, (*bottomData)[leftShift - 1 - i]);
+        }
+        for (int i = 0; i < shiftToEndCount; ++i) {
+            x -= xDelta;
+            fill->lineTo(x, (*bottomData)[bottomData->count() - 1 - i]);
+        }
+    } else {
+        fill->lineTo(x - xDelta, yBase);
+        fill->lineTo(xLeft, yBase);
+    }
+}
+
+}
+
+// A set of scrolling line plots with the area between each plot filled. Stresses out GPU path
+// filling
+class ChartView : public SampleView {
+public:
+    ChartView() {
+        fShift = 0;
+        fSize.set(-1, -1);
+    }
+
+protected:
+    virtual bool onQuery(SkEvent* evt) SK_OVERRIDE {
+        if (SampleCode::TitleQ(*evt)) {
+            SampleCode::TitleR(evt, "Chart");
+            return true;
+        }
+        return this->INHERITED::onQuery(evt);
+    }
+
+    virtual void onDrawContent(SkCanvas* canvas) SK_OVERRIDE {
+        bool sizeChanged = false;
+        if (canvas->getDeviceSize() != fSize) {
+            fSize = canvas->getDeviceSize();
+            sizeChanged = true;
+        }
+
+        SkScalar ySpread = SkIntToScalar(fSize.fHeight / 20);
+
+        SkScalar height = SkIntToScalar(fSize.fHeight);
+
+        if (sizeChanged) {
+            int dataPointCount = SkMax32(fSize.fWidth / kPixelsPerTick + 1, 2);
+
+            for (int i = 0; i < kNumGraphs; ++i) {
+                SkScalar y = (kNumGraphs - i) * (height - ySpread) / (kNumGraphs + 1);
+                fData[i].reset();
+                gen_data(y, ySpread, dataPointCount, fData + i);
+            }
+        }
+
+        canvas->clear(0xFFE0F0E0);
+
+        static SkMWCRandom colorRand;
+        static SkColor gColors[kNumGraphs] = { 0x0 };
+        if (0 == gColors[0]) {
+            for (int i = 0; i < kNumGraphs; ++i) {
+                gColors[i] = colorRand.nextU() | 0xff000000;
+            }
+        }
+
+        SkPath plotPath;
+        SkPath fillPath;
+
+        static const SkScalar kStrokeWidth = SkIntToScalar(2);
+        SkPaint plotPaint;
+        SkPaint fillPaint;
+        plotPaint.setAntiAlias(true);
+        plotPaint.setStyle(SkPaint::kStroke_Style);
+        plotPaint.setStrokeWidth(kStrokeWidth);
+        plotPaint.setStrokeCap(SkPaint::kRound_Cap);
+        plotPaint.setStrokeJoin(SkPaint::kRound_Join);
+        fillPaint.setAntiAlias(true);
+        fillPaint.setStyle(SkPaint::kFill_Style);
+
+        SkTDArray<SkScalar>* prevData = NULL;
+        for (int i = 0; i < kNumGraphs; ++i) {
+            gen_paths(fData[i],
+                      prevData,
+                      height,
+                      0,
+                      SkIntToScalar(kPixelsPerTick),
+                      fShift,
+                      &plotPath,
+                      &fillPath);
+
+            // Make the fills partially transparent
+            fillPaint.setColor((gColors[i] & 0x00ffffff) | 0x80000000);
+            canvas->drawPath(fillPath, fillPaint);
+
+            plotPaint.setColor(gColors[i]);
+            canvas->drawPath(plotPath, plotPaint);
+
+            prevData = fData + i;
+        }
+
+        fShift += kShiftPerFrame;
+        this->inval(NULL);
+    }
+
+private:
+    enum {
+        kNumGraphs = 5,
+        kPixelsPerTick = 3,
+        kShiftPerFrame = 1,
+    };
+    int                 fShift;
+    SkISize             fSize;
+    SkTDArray<SkScalar> fData[kNumGraphs];
+    typedef SampleView INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+static SkView* MyFactory() { return new ChartView; }
+static SkViewRegister reg(MyFactory);