SkLS accepts nullptr for pointer args, handles alpha accurately, has new GM

gm/lightingshader2.cpp

Index: gm/lightingshader2.cpp
diff --git a/gm/lightingshader2.cpp b/gm/lightingshader2.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..58c5a638900a84307680d54b76cbe34867e4765a
--- /dev/null
+++ b/gm/lightingshader2.cpp
@@ -0,0 +1,153 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gm.h"
+
+#include "SkBitmapProcShader.h"
+#include "SkLightingShader.h"
+#include "SkNormalSource.h"
+#include "SkPoint3.h"
+#include "SkShader.h"
+
+// Create a truncated pyramid normal map
+static SkBitmap make_frustum_normalmap(int texSize) {
+    SkBitmap frustum;
+    frustum.allocN32Pixels(texSize, texSize);
+
+    sk_tool_utils::create_frustum_normal_map(&frustum, SkIRect::MakeWH(texSize, texSize));
+    return frustum;
+}
+
+namespace skiagm {
+
+// This GM exercises lighting shaders. Specifically, nullptr arguments, scaling when using
+// normal maps, and paint transparency.
+class LightingShader2GM : public GM {
+public:
+    LightingShader2GM() {
+        this->setBGColor(sk_tool_utils::color_to_565(0xFFCCCCCC));
+    }
+
+protected:
+    SkString onShortName() override {
+        return SkString("lightingshader2");
+    }
+
+    SkISize onISize() override {
+        return SkISize::Make(kGMSize, kGMSize);
+    }
+
+    void onOnceBeforeDraw() override {
+        SkLights::Builder builder;
+        const SkVector3 kLightFromUpperRight = SkVector3::Make(0.788f, 0.394f, 0.473f);
+
+        builder.add(SkLights::Light(SkColor3f::Make(1.0f, 1.0f, 1.0f),
+                                    kLightFromUpperRight));
+        builder.add(SkLights::Light(SkColor3f::Make(0.2f, 0.2f, 0.2f)));
+        fLights = builder.finish();
+
+        fDiffuse = sk_tool_utils::create_checkerboard_bitmap(
+                                                        kTexSize, kTexSize,
+                                                        sk_tool_utils::color_to_565(0x0),
+                                                        sk_tool_utils::color_to_565(0xFF804020),
+                                                        8);
+
+        fNormalMap = make_frustum_normalmap(kTexSize);
+    }
+
+    // Scales shape around origin, rotates shape around origin, then translates shape to GM center
+    void positionCTM(SkCanvas *canvas, SkScalar scale, SkScalar rotate) const {
+        canvas->translate(kGMSize / 2.0f, kGMSize / 2.0f);
+        canvas->scale(scale, scale);
+        canvas->rotate(rotate);
+        canvas->translate(-kTexSize/2.0f, -kTexSize/2.0f);
+    }
+
+    void drawRect(SkCanvas* canvas, const SkRect& r, SkScalar scale,
+                  SkScalar rotate, bool useNormalSource, bool useDiffuseShader,
+                  bool useTransparentPaint) {
+        this->positionCTM(canvas, scale, rotate);
+
+        SkRect bitmapBounds = SkRect::MakeIWH(fDiffuse.width(), fDiffuse.height());
+
+        SkMatrix matrix;
+        matrix.setRectToRect(bitmapBounds, r, SkMatrix::kFill_ScaleToFit);
+
+        const SkMatrix& ctm = canvas->getTotalMatrix();
+
+        SkPaint paint;
+        sk_sp<SkNormalSource> normalSource = nullptr;
+        sk_sp<SkShader> diffuseShader = nullptr;
+
+        if (useNormalSource) {
+            sk_sp <SkShader> normalMap = SkMakeBitmapShader(fNormalMap, SkShader::kClamp_TileMode,
+                                                            SkShader::kClamp_TileMode, &matrix,
+                                                            nullptr);
+            normalSource = SkNormalSource::MakeFromNormalMap(
+                    std::move(normalMap),
+                    ctm);
+        }
+        if (useDiffuseShader) {
+            diffuseShader = SkMakeBitmapShader(fDiffuse, SkShader::kClamp_TileMode,
+                                               SkShader::kClamp_TileMode, &matrix, nullptr);
+        } else {
+            paint.setColor(0xFF00FF00);
+        }
+        if (useTransparentPaint) {

[egdaniel, 2016/07/14 17:10:35]

Let's also add a case for when we have a diffuse shader with is transparent.

[dvonbeck, 2016/07/19 21:31:12]

Done.

+            paint.setAlpha(0x55);
+        }
+        paint.setShader(SkLightingShader::Make(std::move(diffuseShader), std::move(normalSource),
+                                               fLights));
+
+        canvas->drawRect(r, paint);
+    }
+
+    void onDraw(SkCanvas* canvas) override {
+        SkRect r = SkRect::MakeWH(SkIntToScalar(kTexSize), SkIntToScalar(kTexSize));

[egdaniel, 2016/07/14 17:10:35]

So I think what would give us the best coverage would be first to draw the cross
product of useDiffuseShader, DiffuseAlpha, paintAlpha. Then we can add a few
special cases like rotated (I assume this is just to check the normals), various
scales, and lack of normal shader.

[dvonbeck, 2016/07/19 21:31:12]

Done.

+
+        canvas->save();
+        canvas->translate(0.0f, -SkScalarSqrt(2.0f) * kTexSize);
+        this->drawRect(canvas, r, 1.0f, 45.f, true, true, true);
+        canvas->restore();
+
+        canvas->save();
+        canvas->translate(-SK_ScalarSqrt2 * kTexSize, -SK_ScalarSqrt2 * kTexSize);
+        this->drawRect(canvas, r, 1.2f, 0.f, true, true, false);
+        canvas->restore();
+
+        canvas->save();
+        canvas->translate(SK_ScalarSqrt2 * kTexSize, -SK_ScalarSqrt2 * kTexSize);
+        this->drawRect(canvas, r, 0.5f, 0.f, true , true, false);
+        canvas->restore();
+
+        canvas->save();
+        canvas->translate(-SK_ScalarSqrt2 * kTexSize, 0.0f);
+        this->drawRect(canvas, r, 1.0f, 0.f, true, false, true);
+        canvas->restore();
+
+        canvas->save();
+        canvas->translate(SK_ScalarSqrt2 * kTexSize, 0.0f);
+        this->drawRect(canvas, r, 1.0f, 0.f, false, true, false);
+        canvas->restore();
+    }
+
+private:
+    static const int kTexSize = 128;
+    static const int kGMSize  = 512;
+
+    SkBitmap        fDiffuse;
+    SkBitmap        fNormalMap;
+
+    sk_sp<SkLights> fLights;
+
+    typedef GM INHERITED;
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
+DEF_GM(return new LightingShader2GM;)
+}