Use int when possible to calculate atlas indices in shaders.

On certain iOS devices half has a mantissa of only 10 bits, which is not
enough to perform the floating point trickery to get the lower bits
out of the "texture coordinates". Instead we use int if available, and
float if not available.

Also re-enables multitexturing for iOS and adds a sample which
stresses the issue.

Bug: skia:7285
Change-Id: I365532c7cbbcca7c7753af209bef46e05be49e11
Reviewed-on: https://skia-review.googlesource.com/71181
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>

1 files changed, 107 insertions, 0 deletions

diff --git a/samplecode/SampleFlutterAnimate.cpp b/samplecode/SampleFlutterAnimate.cpp
new file mode 100644
index 0000000000..63b453b240
--- /dev/null
+++ b/samplecode/SampleFlutterAnimate.cpp
@@ -0,0 +1,107 @@
+/*
+ * Copyright 2015 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 "SkAnimTimer.h"
+#include "SkView.h"
+#include "SkCanvas.h"
+#include "SkUtils.h"
+#include "SkColorPriv.h"
+#include "SkColorFilter.h"
+#include "SkImage.h"
+#include "SkRandom.h"
+#include "SkSystemEventTypes.h"
+#include "SkTime.h"
+#include "SkTypeface.h"
+#include "Timer.h"
+
+#if SK_SUPPORT_GPU
+#include "GrContext.h"
+#endif
+
+class FlutterAnimateView : public SampleView {
+public:
+    FlutterAnimateView() : fCurrTime(0), fResetTime(0) {}
+
+protected:
+    void onOnceBeforeDraw() override {
+        initChars();
+    }
+
+    // overrides from SkEventSink
+    bool onQuery(SkEvent* evt) override {
+        if (SampleCode::TitleQ(*evt)) {
+            SampleCode::TitleR(evt, "FlutterAnimate");
+            return true;
+        }
+
+        return this->INHERITED::onQuery(evt);
+    }
+
+    void onDrawContent(SkCanvas* canvas) override {
+        SkPaint paint;
+        paint.setTypeface(SkTypeface::MakeFromFile("/skimages/samplefont.ttf"));
+        paint.setAntiAlias(true);
+        paint.setFilterQuality(kMedium_SkFilterQuality);
+        paint.setTextSize(50);
+
+        canvas->clear(SK_ColorWHITE);
+        for (int i = 0; i < kNumChars; ++i) {
+            canvas->save();
+            double rot = fChars[i].fStartRotation + (fChars[i].fEndRotation - fChars[i].fStartRotation)*fCurrTime/kDuration;
+            canvas->translate(fChars[i].fPosition.fX + 35,fChars[i].fPosition.fY - 50);
+            canvas->rotate(rot*180.0/SK_MScalarPI);
+            canvas->translate(-35,+50);
+            canvas->drawString(fChars[i].fChar, 0, 0,
+                               paint);
+            canvas->restore();
+        }
+    }
+
+    bool onAnimate(const SkAnimTimer& timer) override {
+        fCurrTime = timer.secs() - fResetTime;
+        if (fCurrTime > kDuration) {
+            this->initChars();
+            fResetTime = timer.secs();
+            fCurrTime = 0;
+        }
+
+        return true;
+    }
+
+private:
+    void initChars() {
+        for (int i = 0; i < kNumChars; ++i) {
+            char c = fRand.nextULessThan(26) + 65;
+            fChars[i].fChar.set(&c, 1);
+            fChars[i].fPosition = SkPoint::Make(fRand.nextF()*748 + 10, fRand.nextF()*1004 + 10);
+            fChars[i].fStartRotation = fRand.nextF();
+            fChars[i].fEndRotation = fRand.nextF() * 20 - 10;
+        }
+    }
+
+    static constexpr double kDuration = 5.0;
+    double fCurrTime;
+    double fResetTime;
+    SkRandom fRand;
+
+    struct AnimatedChar {
+        SkString fChar;
+        SkPoint  fPosition;
+        SkScalar fStartRotation;
+        SkScalar fEndRotation;
+    };
+    static constexpr int kNumChars = 40;
+    AnimatedChar fChars[kNumChars];
+
+    typedef SampleView INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+static SkView* MyFactory() { return new FlutterAnimateView; }
+static SkViewRegister reg(MyFactory);