Factor code to rotate a canvas about a point.

SkMatrix::scale and ::rotate take a point around which to scale or rotate.
Canvas lacks these helpers, so the code to rotate a canvas around a
point has been duplicated many times. Factor all of these
implementations into SkCanvas::rotate.

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2142033002

Review-Url: https://codereview.chromium.org/2142033002

6 files changed, 8 insertions, 56 deletions

diff --git a/gm/dftext.cpp b/gm/dftext.cpp
index 42d650ed2f..8ab2df71ba 100644
--- a/gm/dftext.cpp
+++ b/gm/dftext.cpp
@@ -33,14 +33,6 @@ protected:
         return SkISize::Make(1024, 768);
     }
 
-    static void rotate_about(SkCanvas* canvas,
-        SkScalar degrees,
-        SkScalar px, SkScalar py) {
-        canvas->translate(px, py);
-        canvas->rotate(degrees);
-        canvas->translate(-px, -py);
-    }
-
     virtual void onDraw(SkCanvas* inputCanvas) override {
         SkScalar textSizes[] = { 9.0f, 9.0f*2.0f, 9.0f*5.0f, 9.0f*2.0f*5.0f };
         SkScalar scales[] = { 2.0f*5.0f, 5.0f, 2.0f, 1.0f };
@@ -95,7 +87,7 @@ protected:
 
             SkAutoCanvasRestore acr(canvas, true);
             canvas->translate(SkIntToScalar(10 + i * 200), -80);
-            rotate_about(canvas, SkIntToScalar(i * 5), rotX, rotY);
+            canvas->rotate(SkIntToScalar(i * 5), rotX, rotY);
             for (int ps = 6; ps <= 32; ps += 3) {
                 paint.setTextSize(SkIntToScalar(ps));
                 canvas->drawText(text, textLen, rotX, rotY, paint);
diff --git a/gm/fontscaler.cpp b/gm/fontscaler.cpp
index 69cf346c4d..cc9815c9d9 100644
--- a/gm/fontscaler.cpp
+++ b/gm/fontscaler.cpp
@@ -15,9 +15,6 @@ public:
         this->setBGColor(0xFFFFFFFF);
     }
 
-    virtual ~FontScalerGM() {
-    }
-
 protected:
 
     SkString onShortName() override {
@@ -30,14 +27,6 @@ protected:
         return SkISize::Make(1450, 750);
     }
 
-    static void rotate_about(SkCanvas* canvas,
-                             SkScalar degrees,
-                             SkScalar px, SkScalar py) {
-        canvas->translate(px, py);
-        canvas->rotate(degrees);
-        canvas->translate(-px, -py);
-    }
-
     void onDraw(SkCanvas* canvas) override {
         SkPaint paint;
 
@@ -59,7 +48,7 @@ protected:
                 SkAutoCanvasRestore acr(canvas, true);
                 canvas->translate(SkIntToScalar(50 + i * 230),
                                   SkIntToScalar(20));
-                rotate_about(canvas, SkIntToScalar(i * 5), x, y * 10);
+                canvas->rotate(SkIntToScalar(i * 5), x, y * 10);
 
                 {
                     SkPaint p;
diff --git a/gm/fontscalerdistortable.cpp b/gm/fontscalerdistortable.cpp
index b4f2ca370c..be6a7ebc58 100644
--- a/gm/fontscalerdistortable.cpp
+++ b/gm/fontscalerdistortable.cpp
@@ -19,8 +19,6 @@ public:
         this->setBGColor(0xFFFFFFFF);
     }
 
-    virtual ~FontScalerDistortableGM() { }
-
 protected:
 
     SkString onShortName() override {
@@ -31,12 +29,6 @@ protected:
         return SkISize::Make(550, 700);
     }
 
-    static void rotate_about(SkCanvas* canvas, SkScalar degrees, SkScalar px, SkScalar py) {
-        canvas->translate(px, py);
-        canvas->rotate(degrees);
-        canvas->translate(-px, -py);
-    }
-
     void onDraw(SkCanvas* canvas) override {
         SkPaint paint;
         paint.setAntiAlias(true);
@@ -63,7 +55,7 @@ protected:
 
                 SkAutoCanvasRestore acr(canvas, true);
                 canvas->translate(SkIntToScalar(30 + i * 100), SkIntToScalar(20));
-                rotate_about(canvas, SkIntToScalar(i * 5), x, y * 10);
+                canvas->rotate(SkIntToScalar(i * 5), x, y * 10);
 
                 {
                     SkPaint p;
diff --git a/gm/imagefilterstransformed.cpp b/gm/imagefilterstransformed.cpp
index 7ceff00135..0906eb3f3c 100644
--- a/gm/imagefilterstransformed.cpp
+++ b/gm/imagefilterstransformed.cpp
@@ -140,18 +140,14 @@ DEF_SIMPLE_GM(rotate_imagefilter, canvas, 500, 500) {
 
         canvas->translate(150, 0);
         canvas->save();
-            canvas->translate(100, 100);
-            canvas->rotate(30);
-            canvas->translate(-100, -100);
+            canvas->rotate(30, 100, 100);
             canvas->drawRect(r, paint);
         canvas->restore();
 
         paint.setAntiAlias(true);
         canvas->translate(150, 0);
         canvas->save();
-            canvas->translate(100, 100);
-            canvas->rotate(30);
-            canvas->translate(-100, -100);
+            canvas->rotate(30, 100, 100);
             canvas->drawRect(r, paint);
         canvas->restore();
 
diff --git a/gm/strokes.cpp b/gm/strokes.cpp
index 61f5a8af6a..afbe5ee4da 100644
--- a/gm/strokes.cpp
+++ b/gm/strokes.cpp
@@ -290,12 +290,6 @@ protected:
         return SkISize::Make(W, H*2);
     }
 
-    static void rotate(SkScalar angle, SkScalar px, SkScalar py, SkCanvas* canvas) {
-        SkMatrix matrix;
-        matrix.setRotate(angle, px, py);
-        canvas->concat(matrix);
-    }
-
     void onDraw(SkCanvas* canvas) override {
         canvas->drawColor(SK_ColorWHITE);
 
@@ -316,7 +310,7 @@ protected:
             for (int i = 0; i < N/2; i++) {
                 SkRect r;
                 rnd_rect(&r, &paint, rand);
-                rotate(SkIntToScalar(15), SW/2, SH/2, canvas);
+                canvas->rotate(SkIntToScalar(15), SW/2, SH/2);
                 canvas->drawPath(fPath, paint);
             }
         }
diff --git a/gm/typeface.cpp b/gm/typeface.cpp
index 34420dbee1..d579a156a6 100644
--- a/gm/typeface.cpp
+++ b/gm/typeface.cpp
@@ -154,20 +154,9 @@ private:
     typedef skiagm::GM INHERITED;
 };
 
-static void rotate_about(SkCanvas* canvas,
-                         SkScalar degrees,
-                         SkScalar px, SkScalar py) {
-    canvas->translate(px, py);
-    canvas->rotate(degrees);
-    canvas->translate(-px, -py);
-}
-
 class TypefaceRenderingGM : public skiagm::GM {
     sk_sp<SkTypeface> fFace;
 
-public:
-    TypefaceRenderingGM() { }
-
 protected:
     void onOnceBeforeDraw() override {
         fFace = MakeResourceAsTypeface("/fonts/hintgasp.ttf");
@@ -256,8 +245,8 @@ protected:
                         for (const bool& rotateABit : rotateABitTypes) {
                             SkAutoCanvasRestore acr(canvas, true);
                             if (rotateABit) {
-                                rotate_about(canvas, 2, x + subpixel.offset.x(),
-                                                        y + subpixel.offset.y());
+                                canvas->rotate(2, x + subpixel.offset.x(),
+                                                  y + subpixel.offset.y());
                             }
                             canvas->drawText("A", 1, x + subpixel.offset.x(),
                                                      y + subpixel.offset.y(), paint);