Smallest possible desktop application that uses Skia to render stuff.

experimental/SkiaExamples/HelloSkiaExample.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 "BaseExample.h"
+
+#include "SkApplication.h"
+#include "SkDraw.h"
+#include "SkGradientShader.h"
+#include "SkGraphics.h"
+#include "SkUnitMappers.h"
+
+class HelloSkia : public BaseExample {
+    public:
+        HelloSkia(void* hWnd, int argc, char** argv)
+            : INHERITED(hWnd, argc, argv)
+        {
+            fBGColor = SK_ColorWHITE;
+            fRotationAngle = SkIntToScalar(0);
+
+            setupBackend(kGPU_DeviceType);

[caryclark, 2013/06/17 15:08:39]

add comment that caller can also use kRaster_DeviceType instead

+        }

[caryclark, 2013/06/17 15:08:39]

add a blank line

+    protected:
+        virtual void draw(SkCanvas* canvas) SK_OVERRIDE {
+            // Clear background
+            canvas->drawColor(fBGColor);
+
+            SkPaint paint;
+            paint.setColor(SK_ColorRED);  // SkColor is ARGB

[caryclark, 2013/06/17 15:08:39]

not sure the comment clarifies

+
+            // Draw a rectangle with blue paint
+            SkRect rect = {SkIntToScalar(10), SkIntToScalar(10), SkIntToScalar(128), SkIntToScalar(128)};

[caryclark, 2013/06/17 15:08:39]

too wide (rewrap to fit in 100 cols)

+            canvas->drawRect(rect, paint);
+
+            // Set up a linear gradient and draw a circle
+            {
+                SkPoint linearPoints[] = {
+                    {SkIntToScalar(0), SkIntToScalar(0)}, {SkIntToScalar(300), SkIntToScalar(300)}};
+                SkColor linearColors[] = {SK_ColorGREEN, SK_ColorBLACK};
+
+                SkUnitMapper* linearMapper = new SkDiscreteMapper(100);
+                SkAutoUnref lm_deleter(linearMapper);
+
+                SkShader* shader = SkGradientShader::CreateLinear(
+                        linearPoints, linearColors, NULL, 2, SkShader::kMirror_TileMode, linearMapper);

[caryclark, 2013/06/17 15:08:39]

too wide (rewrap to fit in 100 cols)

+                SkAutoUnref shader_deleter(shader);
+
+                paint.setShader(shader);
+                paint.setFlags(SkPaint::kAntiAlias_Flag);
+
+                canvas->drawCircle(SkIntToScalar(200), SkIntToScalar(200), SkIntToScalar(64), paint);

[caryclark, 2013/06/17 15:08:39]

too wide (rewrap to fit in 100 cols)

+
+                // Detach shader
+                paint.setShader(NULL);
+            }
+
+
+            // Draw a message with a nice black paint.
+            paint.setFlags(
+                    SkPaint::kAntiAlias_Flag |
+                    SkPaint::kSubpixelText_Flag |  // ... avoid waggly text when rotating.
+                    SkPaint::kUnderlineText_Flag);
+            paint.setColor(SK_ColorBLACK);
+            paint.setTextSize(SkIntToScalar(20));
+
+            canvas->save();
+
+            static const char message[] = "Hello Skia!!!";
+
+            // Translate and rotate
+            canvas->translate(SkIntToScalar(300), SkIntToScalar(300));
+            fRotationAngle += SkDoubleToScalar(0.2);
+            if (fRotationAngle > SkDoubleToScalar(360.0)) {
+                fRotationAngle -= SkDoubleToScalar(360.0);
+            }
+            canvas->rotate(fRotationAngle);
+
+            // Draw the text:
+            canvas->drawText(message, strlen(message), SkIntToScalar(0), SkIntToScalar(0), paint);

[caryclark, 2013/06/17 15:08:39]

sizeof(message) - 1 would also work

[sglez, 2013/06/17 18:04:35]

Is that a suggestion or just a note? strlen seems to be the convention.

+
+            canvas->restore();
+
+            // Invalidate the window to force a redraw. Poor man's animation mechanism.
+            this->inval(NULL);
+            canvas->flush();

[caryclark, 2013/06/17 15:08:39]

Do you need this? It shouldn't normally be required

+
+            INHERITED::draw(canvas);
+        }
+
+    private:
+        SkScalar fRotationAngle;
+        SkColor fBGColor;
+        typedef BaseExample INHERITED;
+};
+
+SkOSWindow* create_sk_window(void* hwnd, int argc, char** argv) {

[caryclark, 2013/06/17 15:08:39]

It would be great if I could switch between multiple examples trivially. Right
now, I comment out all but the one I want to run. 

Maybe this could be a macro in BaseExample.h to make this easier?

Skia's unit tests and others have a test class that is registered with a static
initializer so that all the tests can live simultaneously, and then the desired
test is selected by an argument to command line. I'm not suggesting we do this
now, but something like that would allow this to be scalable.

[sglez, 2013/06/17 18:04:35]

Perhaps do this on a new CL after this one is submitted?

+    return new HelloSkia(hwnd, argc, argv);
+}
+