webkit: Color Inversion for power saving and eye strain relief

This patch allows to set an 'inversion flag' on the Web View to
render the content (but not images) inverting the color. The typical
usage is when rendering some black text on white page: using color
inversion you get a more readable text and you save power at the
same time.

This patch is based on ec1ce8d8eac4a768b5888fe956a3defc7d457f6f.

Change-Id: I0693426589bd5f8c83457a5b8899fe5b85285120

Author: Enrico Ros

WebKit/android/jni/PictureSet.cpp

@@ -37,12 +37,12 @@
 #include "SkRect.h"
 #include "SkRegion.h"
 #include "SkStream.h"
+#include "SyncProxyCanvas.h"
 #include "TimeCounter.h"
 
 #ifdef CACHED_IMAGE_DECODE
 #include <wtf/PassOwnPtr.h>
 #include "SkPixelRef.h"
-#include "SyncProxyCanvas.h"
 #endif
 
 #define MAX_DRAW_TIME 100
@@ -247,8 +247,9 @@ class BitmapProxyCanvas: public SyncProxyCanvas, public Noncopyable
 public:
     static WTF::PassOwnPtr<BitmapProxyCanvas> create(SkCanvas* canvas,
         WTF::Vector<const SkBitmap*>* pBitmaps,
-        WTF::Vector<SkRect>* pBitmapRects) {
-        return new BitmapProxyCanvas(canvas, pBitmaps, pBitmapRects);
+        WTF::Vector<SkRect>* pBitmapRects,
+        bool invert) {
+        return new BitmapProxyCanvas(canvas, pBitmaps, pBitmapRects, invert);
     }
 
     virtual void drawBitmap(const SkBitmap& bitmap, SkScalar x, SkScalar y,
@@ -265,6 +266,16 @@ class BitmapProxyCanvas: public SyncProxyCanvas, public Noncopyable
                 appendBitmap(bitmap, fastBounds);
         } else {
             target->drawBitmap(bitmap, x, y, paint);
+            if (invertBitmaps) {
+                target->save();
+                SkRect inversionRect;
+                inversionRect.set(x, y,
+                                  x + SkIntToScalar(bitmap.width()),
+                                  y + SkIntToScalar(bitmap.height()));
+                target->clipRect(inversionRect);
+                target->drawARGB(255, 255, 255, 255, SkXfermode::kDifference_Mode);
+                target->restore();
+            }
         }
     }
 
@@ -278,6 +289,12 @@ class BitmapProxyCanvas: public SyncProxyCanvas, public Noncopyable
                 appendBitmap(bitmap, dst);
         } else {
             target->drawBitmapRect(bitmap, src, dst, paint);
+            if (invertBitmaps) {
+                target->save();
+                target->clipRect(dst);
+                target->drawARGB(255, 255, 255, 255, SkXfermode::kDifference_Mode);
+                target->restore();
+            }
         }
     }
 
@@ -290,13 +307,16 @@ class BitmapProxyCanvas: public SyncProxyCanvas, public Noncopyable
 
     WTF::Vector<const SkBitmap*> *pBitmapsForDecoding;
     WTF::Vector<SkRect>          *pBitmapRectsForDecoding;
+    bool                          invertBitmaps;
 
     BitmapProxyCanvas(SkCanvas* canvas,
         WTF::Vector<const SkBitmap*> *pBitmaps,
-        WTF::Vector<SkRect>          *pBitmapRects)
+        WTF::Vector<SkRect>          *pBitmapRects,
+        bool                          invert)
         : SyncProxyCanvas(canvas)
         , pBitmapsForDecoding(pBitmaps)
         , pBitmapRectsForDecoding(pBitmapRects)
+        , invertBitmaps(invert)
     {
     }
 
@@ -342,9 +362,38 @@ class BitmapProxyCanvas: public SyncProxyCanvas, public Noncopyable
     }
 };
 
+#else
+class ImageInverter: public SyncProxyCanvas
+{
+public:
+
+    ImageInverter(SkCanvas* canvas): SyncProxyCanvas(canvas) {}
+
+    void drawBitmap(const SkBitmap& bitmap, SkScalar x, SkScalar y,
+                    const SkPaint* paint) {
+        target->drawBitmap(bitmap, x, y, paint);
+        target->save();
+        SkRect inversionRect;
+        inversionRect.set(x, y,
+                          x + SkIntToScalar(bitmap.width()),
+                          y + SkIntToScalar(bitmap.height()));
+        target->clipRect(inversionRect);
+        target->drawARGB(255, 255, 255, 255, SkXfermode::kDifference_Mode);
+        target->restore();
+    }
+
+    void drawBitmapRect(const SkBitmap& bitmap, const SkIRect* src,
+                        const SkRect& dst, const SkPaint* paint) {
+        target->drawBitmapRect(bitmap, src, dst, paint);
+        target->save();
+        target->clipRect(dst);
+        target->drawARGB(255, 255, 255, 255, SkXfermode::kDifference_Mode);
+        target->restore();
+    }
+};
 #endif
 
-bool PictureSet::draw(SkCanvas* canvas)
+bool PictureSet::draw(SkCanvas* canvas, bool invertColor)
 {
     validate(__FUNCTION__);
     Pictures* first = mPictures.begin();
@@ -405,11 +454,14 @@ bool PictureSet::draw(SkCanvas* canvas)
         uint32_t startTime = getThreadMsec();
 #ifdef CACHED_IMAGE_DECODE
         {
-            WTF::OwnPtr<BitmapProxyCanvas> proxyCanvas = BitmapProxyCanvas::create(canvas, &mBitmapsForDecoding, &mBitmapRectsForDecoding);
+            WTF::OwnPtr<BitmapProxyCanvas> proxyCanvas = BitmapProxyCanvas::create(canvas, &mBitmapsForDecoding, &mBitmapRectsForDecoding, invertColor);
             proxyCanvas->drawPicture(*working->mPicture);
         }
 #else
-        canvas->drawPicture(*working->mPicture);
+        SkCanvas* painter = invertColor ? new ImageInverter(canvas) : canvas;
+        painter->drawPicture(*working->mPicture);
+        if (invertColor)
+            delete painter;
 #endif
         size_t elapsed = working->mElapsed = getThreadMsec() - startTime;
         working->mWroteElapsed = true;
@@ -441,6 +493,8 @@ bool PictureSet::draw(SkCanvas* canvas)
             working->mElapsed, working->mBase ? "true" : "false");
     }
  //   dump(__FUNCTION__);
+    if (invertColor)
+        canvas->drawARGB(255, 255, 255, 255, SkXfermode::kDifference_Mode);
     return maxElapsed >= MAX_DRAW_TIME;
 }
 

WebKit/android/jni/PictureSet.h

@@ -70,7 +70,7 @@ namespace android {
         // Update mWidth/mHeight, and adds any additional inval region
         void checkDimensions(int width, int height, SkRegion* inval);
         void clear();
-        bool draw(SkCanvas* );
+        bool draw(SkCanvas* , bool invertColor = false);
         static PictureSet* GetNativePictureSet(JNIEnv* env, jobject jpic);
         int height() const { return mHeight; }
         bool isEmpty() const; // returns true if empty or only trivial content

WebKit/android/jni/WebViewCore.cpp

@@ -302,6 +302,7 @@ WebViewCore::WebViewCore(JNIEnv* env, jobject javaWebViewCore, WebCore::Frame* m
     m_forwardingTouchEvents = false;
 #endif
     m_isPaused = false;
+    m_invertColor = false;
 
     LOG_ASSERT(m_mainFrame, "Uh oh, somehow a frameview was made without an initial frame!");
 
@@ -791,7 +792,7 @@ bool WebViewCore::drawContent(SkCanvas* canvas, SkColor color)
     canvas->clipRect(clip, SkRegion::kDifference_Op);
     canvas->drawColor(color);
     canvas->restoreToCount(sc);
-    bool tookTooLong = copyContent.draw(canvas);
+    bool tookTooLong = copyContent.draw(canvas, m_invertColor);
     m_contentMutex.lock();
     m_content.setDrawTimes(copyContent);
     m_contentMutex.unlock();
@@ -2448,6 +2449,17 @@ void WebViewCore::setBackgroundColor(SkColor c)
         view->setTransparent(true);
 }
 
+void WebViewCore::setColorInversion(bool invert)
+{
+    if (m_invertColor != invert) {
+        m_invertColor = invert;
+        if (invert)
+            DBG_SET_LOG("color invert active");
+        else
+            DBG_SET_LOG("no color invert");
+    }
+}
+
 jclass WebViewCore::getPluginClass(const WebCore::String& libName, const char* className)
 {
     JNIEnv* env = JSC::Bindings::getJNIEnv();
@@ -2969,6 +2981,14 @@ static void SetBackgroundColor(JNIEnv *env, jobject obj, jint color)
     viewImpl->setBackgroundColor((SkColor) color);
 }
 
+static void SetColorInversion(JNIEnv *env, jobject obj, jboolean invert)
+{
+    WebViewCore* viewImpl = GET_NATIVE_VIEW(env, obj);
+    LOG_ASSERT(viewImpl, "viewImpl not set in %s", __FUNCTION__);
+
+    viewImpl->setColorInversion(invert);
+}
+
 static void DumpDomTree(JNIEnv *env, jobject obj, jboolean useFile)
 {
     WebViewCore* viewImpl = GET_NATIVE_VIEW(env, obj);
@@ -3248,6 +3268,8 @@ static JNINativeMethod gJavaWebViewCoreMethods[] = {
         (void*) SplitContent },
     { "nativeSetBackgroundColor", "(I)V",
         (void*) SetBackgroundColor },
+    { "nativeSetColorInversion", "(Z)V",
+        (void*) SetColorInversion },
     { "nativeRegisterURLSchemeAsLocal", "(Ljava/lang/String;)V",
         (void*) RegisterURLSchemeAsLocal },
     { "nativeDumpDomTree", "(Z)V",

WebKit/android/jni/WebViewCore.h

@@ -362,6 +362,7 @@ namespace android {
         jobject getWebViewJavaObject();
 
         void setBackgroundColor(SkColor c);
+        void setColorInversion(bool invert);
         void updateFrameCache();
         void updateCacheOnNodeChange();
         void dumpDomTree(bool);
@@ -546,6 +547,7 @@ namespace android {
         bool m_check_domtree_version;
         PageGroup* m_groupForVisitedLinks;
         bool m_isPaused;
+        bool m_invertColor;
 
         SkTDArray<PluginWidgetAndroid*> m_plugins;
         WebCore::Timer<WebViewCore> m_pluginInvalTimer;