Updated SkLumaXfermode GM (take two).

gm/lumamode.cpp

 /*
  * 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 "gm.h"
 #include "SkCanvas.h"
+#include "SkGradientShader.h"
 #include "SkLumaXfermode.h"
 
-static void show_scene(SkCanvas* canvas, SkXfermode* mode, const char* label) {
+static SkScalar kSize   = 80;
+static SkScalar kInset  = 10;
+static SkColor  kColor1 = SkColorSetARGB(0xff, 0xff, 0xff, 0);
+static SkColor  kColor2 = SkColorSetARGB(0xff, 0x80, 0xff, 0);
+
+static void draw_label(SkCanvas* canvas, const char* label,
+                       const SkPoint& offset) {
     SkPaint paint;
-    paint.setAntiAlias(true);
-    SkRect r, c, bounds = { 10, 10, 110, 110 };
+    size_t len = strlen(label);
+
+    SkScalar width = paint.measureText(label, len);
+    canvas->drawText(label, len, offset.x() - width / 2, offset.y(),
+                     paint);
+}
+
+static void draw_scene(SkCanvas* canvas, SkXfermode* mode, bool aa,
+                       SkShader* s1, SkShader* s2) {
+    SkPaint paint;
+    paint.setAntiAlias(aa);
+    SkRect r, c, bounds = SkRect::MakeWH(kSize, kSize);
 
     c = bounds;
     c.fRight = bounds.centerX();
-    r = bounds;
-    r.fBottom = bounds.centerY();
-    canvas->drawRect(r, paint);
-
-    SkScalar tw = paint.measureText(label, strlen(label));
-    canvas->drawText(label, strlen(label), bounds.centerX() - tw / 2,
-                     bounds.bottom() + 15, paint);
+    canvas->drawRect(bounds, paint);
 
     canvas->saveLayer(&bounds, NULL);
 
     r = bounds;
-    r.inset(20, 0);
-    paint.setColor(0x80FFFF00);
+    r.inset(kInset, 0);
+    paint.setShader(s1);
+    paint.setColor(s1 ? SK_ColorBLACK : SkColorSetA(kColor1, 0x80));
     canvas->drawOval(r, paint);
-    canvas->save();
-    canvas->clipRect(c);
-    paint.setColor(0xFFFFFF00);
-    canvas->drawOval(r, paint);
-    canvas->restore();
+    if (!s1) {
+        canvas->save();
+        canvas->clipRect(c);
+        paint.setColor(s1 ? SK_ColorBLACK : kColor1);
+        canvas->drawOval(r, paint);
+        canvas->restore();
+    }
 
     SkPaint xferPaint;
     xferPaint.setXfermode(mode);
     canvas->saveLayer(&bounds, &xferPaint);
 
     r = bounds;
-    r.inset(0, 20);
-    paint.setColor(0x8080FF00);
+    r.inset(0, kInset);
+    paint.setShader(s2);
+    paint.setColor(s2 ? SK_ColorBLACK : SkColorSetA(kColor2, 0x80));
     canvas->drawOval(r, paint);
-    canvas->save();
-    canvas->clipRect(c);
-    paint.setColor(0xFF80FF00);
-    canvas->drawOval(r, paint);
-    canvas->restore();
+    if (!s2) {
+        canvas->save();
+        canvas->clipRect(c);
+        paint.setColor(s2 ? SK_ColorBLACK : kColor2);
+        canvas->drawOval(r, paint);
+        canvas->restore();
+    }
 
     canvas->restore();
     canvas->restore();
 }
 
 class LumaXfermodeGM : public skiagm::GM {
 public:
-    LumaXfermodeGM() {}
+    LumaXfermodeGM() {
+        fSrcInXfer.reset(SkLumaMaskXfermode::Create(SkXfermode::kSrcIn_Mode));
+        fDstInXfer.reset(SkLumaMaskXfermode::Create(SkXfermode::kDstIn_Mode));
+
+        SkColor  g1Colors[] = { kColor1, SkColorSetA(kColor1, 0x20) };
+        SkColor  g2Colors[] = { kColor2, SkColorSetA(kColor2, 0x20) };
+        SkPoint  g1Points[] = { { 0, 0 }, { 0,     100 } };
+        SkPoint  g2Points[] = { { 0, 0 }, { kSize, 0   } };
+        SkScalar pos[] = { 0.2f, 1.0f };
+
+        fGr1.reset(SkGradientShader::CreateLinear(g1Points,
+                                                  g1Colors,
+                                                  pos,
+                                                  SK_ARRAY_COUNT(g1Colors),
+                                                  SkShader::kClamp_TileMode));
+        fGr2.reset(SkGradientShader::CreateLinear(g2Points,
+                                                  g2Colors,
+                                                  pos,
+                                                  SK_ARRAY_COUNT(g2Colors),
+                                                  SkShader::kClamp_TileMode));
+    }
 
 protected:
     virtual SkString onShortName() SK_OVERRIDE {
         return SkString("lumamode");
     }
 
     virtual SkISize onISize() SK_OVERRIDE {
-        return SkISize::Make(450, 140);
+        return SkISize::Make(600, 420);
     }
 
     virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
-        show_scene(canvas, NULL, "SrcOver");
-        canvas->translate(150, 0);
-        SkAutoTUnref<SkXfermode> src_in(SkLumaMaskXfermode::Create(SkXfermode::kSrcIn_Mode));
-        show_scene(canvas, src_in.get(), "SrcInLuma");
-        canvas->translate(150, 0);
-        SkAutoTUnref<SkXfermode> dst_in(SkLumaMaskXfermode::Create(SkXfermode::kDstIn_Mode));
-        show_scene(canvas, dst_in.get(), "DstInLuma");
+        SkXfermode* modes[] = { NULL, fSrcInXfer, fDstInXfer };
+        struct {
+            SkShader*   fShader1;
+            SkShader*   fShader2;
+        } shaders[] = {
+            { NULL, NULL },
+            { NULL, fGr2 },
+            { fGr1, NULL },
+            { fGr1, fGr2 },
+        };
+
+        SkScalar gridStep = kSize + 2 * kInset;
+        draw_label(canvas, "SrcOver", SkPoint::Make(gridStep, 20));
+        draw_label(canvas, "SrcInLuma", SkPoint::Make(gridStep * 3, 20));
+        draw_label(canvas, "DstInLuma", SkPoint::Make(gridStep * 5, 20));
+        for (size_t i = 0; i < SK_ARRAY_COUNT(shaders); ++i) {
+            canvas->save();
+            canvas->translate(kInset, gridStep * i + 30);
+            for (size_t m = 0; m < SK_ARRAY_COUNT(modes); ++m) {
+                draw_scene(canvas, modes[m], true, shaders[i].fShader1,
+                           shaders[i].fShader2);
+                canvas->translate(gridStep, 0);
+                draw_scene(canvas, modes[m], false, shaders[i].fShader1,
+                           shaders[i].fShader2);
+                canvas->translate(gridStep, 0);
+            }
+            canvas->restore();
+        }
     }
 
 private:
+    SkAutoTUnref<SkShader>   fGr1, fGr2;
+    SkAutoTUnref<SkXfermode> fSrcInXfer, fDstInXfer;
+
     typedef skiagm::GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 DEF_GM( return SkNEW(LumaXfermodeGM); )