create simple skia app for android using jni

experimental/HelloSkia/jni/helloskia.cpp

+#include <math.h>
+#include <string.h>
+#include <jni.h>
+#include <android/bitmap.h>
+
+#include "SkCanvas.h"
+#include "SkData.h"
+#include "SkGraphics.h"
+#include "SkSurface.h"
+#include "SkImage.h"
+#include "SkStream.h"
+#include "SkString.h"
+#include "SkTime.h"
+
+extern "C"
+JNIEXPORT void JNICALL Java_com_example_HelloSkiaActivity_drawIntoBitmap(JNIEnv* env,

[djsollen, 2013/06/03 18:24:45]

add a brief comment explaining what this method does.

[Zach Reizner, 2013/06/03 22:54:25]

Done.

+        jobject thiz, jobject dstBitmap)
+{

[djsollen, 2013/06/03 18:24:45]

move to previous line 

[Zach Reizner, 2013/06/03 22:54:25]

Done.

+
+    // Grab the dst bitmap info and pixels
+    AndroidBitmapInfo dstInfo;
+    void* dstPixels;
+    AndroidBitmap_getInfo(env, dstBitmap, &dstInfo);
+    AndroidBitmap_lockPixels(env, dstBitmap, &dstPixels);
+
+    SkAutoGraphics ag;

[Zach Reizner, 2013/06/03 22:54:25]

This was removed because repeated constructions/destructions cause SkAssert to
trip after a certain number of times

+    SkString path("skhello.png");

[djsollen, 2013/06/03 18:24:45]

remove this unless you plan on drawing it.

[Zach Reizner, 2013/06/03 22:54:25]

Done.

+    SkString text("Skia is the Best!");

[djsollen, 2013/06/03 18:24:45]

define text where you use it not at the beginning of the function.

[Zach Reizner, 2013/06/03 22:54:25]

Done.

+
+    // Setup
+    SkPaint paint;

[djsollen, 2013/06/03 18:24:45]

same as above (define it closer to where it is used).

[Zach Reizner, 2013/06/03 22:54:25]

Done.

+    paint.setAntiAlias(true);
+    paint.setTextSize(SkIntToScalar(30));
+    paint.setTextAlign(SkPaint::kLeft_Align);
+
+    SkImage::Info info = {
+        dstInfo.width, dstInfo.height, SkImage::kPMColor_ColorType, SkImage::kPremul_AlphaType
+    };
+
+    // Create a surface and get its canvas
+    SkAutoTUnref<SkSurface> surface(SkSurface::NewRaster(info));
+    SkCanvas* canvas = surface->getCanvas();
+
+    // Draw something "interesting"

[djsollen, 2013/06/03 18:24:45]

let's draw some more interesting stuff. You can probably get some ideas from
looking at our sample slides.  Also put a comment next to each interesting group
of drawing ops describing what is drawn.

[Zach Reizner, 2013/06/03 22:54:25]

Done.

+    SkScalar fontHeight = paint.getFontSpacing();
+    canvas->drawColor(SK_ColorWHITE);
+    canvas->drawText(text.c_str(), text.size(),
+                      10, fontHeight,
+                      paint);
+
+    // Grab the pixels from the canvas
+    SkBitmap canvasBitmap;

[djsollen, 2013/06/03 18:24:45]

you shouldn't need this at all.

[Zach Reizner, 2013/06/03 22:54:25]

Done.

+    canvasBitmap.setConfig(SkBitmap::kARGB_8888_Config, dstInfo.width, dstInfo.height);
+    canvas->readPixels(&canvasBitmap, 0, 0); // Read from the top corner
+
+    // Copy the pixels from Skia into the Java Bitmap
+    for (uint32_t row = 0; row < dstInfo.height; row++)

[djsollen, 2013/06/03 18:24:45]

this isn't very efficient. We should just have our canvas write directly into. 
We should just create the SkSurface using NewRasterDirect(...).

[Zach Reizner, 2013/06/03 22:54:25]

Done.

+    {
+        void* dstRow = (char*)dstPixels + dstInfo.stride * row;
+        void* srcRow = canvasBitmap.getAddr(0, row);
+        memcpy(dstRow, srcRow, dstInfo.stride);
+    }
+
+    // Unlock the dst
+    AndroidBitmap_unlockPixels(env, dstBitmap);
+}