Add proper support for fixed position elements

this is two-part change, see  http://android-git.corp.google.com/g/#change,37092 for the java counterpart.
This CL implements fixed position elements (css position: fixed) using layers, supporting pixels and percent lengths.

It addresses http://b/1914365

3 files changed, 61 insertions, 23 deletions

diff --git a/WebCore/platform/graphics/android/GraphicsLayerAndroid.cpp b/WebCore/platform/graphics/android/GraphicsLayerAndroid.cpp
index f518ffb..6901f52 100644
--- a/WebCore/platform/graphics/android/GraphicsLayerAndroid.cpp
+++ b/WebCore/platform/graphics/android/GraphicsLayerAndroid.cpp
@@ -111,9 +111,10 @@ GraphicsLayerAndroid::GraphicsLayerAndroid(GraphicsLayerClient* client) :
       m_contentLayer->setIsRootLayer(renderLayer->isRootLayer());
       RenderView* view = static_cast<RenderView*>(renderLayer->renderer());
       if (view->isPositioned() && view->style()->position() == FixedPosition) {
-          FloatPoint position(view->style()->left().value(),
-                              view->style()->right().value());
-          m_contentLayer->setFixedPosition(position);
+          m_contentLayer->setFixedPosition(view->style()->left(),
+                                           view->style()->top(),
+                                           view->style()->right(),
+                                           view->style()->bottom());
       }
     }
     gDebugGraphicsLayerAndroidInstances++;
diff --git a/WebCore/platform/graphics/android/LayerAndroid.cpp b/WebCore/platform/graphics/android/LayerAndroid.cpp
index 347021a..3b5d5b5 100644
--- a/WebCore/platform/graphics/android/LayerAndroid.cpp
+++ b/WebCore/platform/graphics/android/LayerAndroid.cpp
@@ -62,9 +62,12 @@ LayerAndroid::LayerAndroid(bool isRootLayer) :
     m_size(0, 0),
     m_position(0, 0),
     m_translation(0, 0),
-    m_fixedPosition(0, 0),
     m_anchorPoint(0, 0, 0),
     m_scale(1, 1, 1),
+    m_fixedLeft(Auto),
+    m_fixedTop(Auto),
+    m_fixedRight(Auto),
+    m_fixedBottom(Auto),
     m_recordingPicture(0)
 {
     gDebugLayerAndroidInstances++;
@@ -84,9 +87,12 @@ LayerAndroid::LayerAndroid(LayerAndroid* layer) :
     m_size(layer->m_size),
     m_position(layer->m_position),
     m_translation(layer->m_translation),
-    m_fixedPosition(layer->m_fixedPosition),
     m_anchorPoint(layer->m_anchorPoint),
-    m_scale(layer->m_scale)
+    m_scale(layer->m_scale),
+    m_fixedLeft(layer->m_fixedLeft),
+    m_fixedRight(layer->m_fixedRight),
+    m_fixedTop(layer->m_fixedTop),
+    m_fixedBottom(layer->m_fixedBottom)
 {
     if (layer->m_recordingPicture) {
         layer->m_recordingPicture->ref();
@@ -167,9 +173,13 @@ void LayerAndroid::removeAnimation(const String& name)
     m_animations.remove(name);
 }
 
-void LayerAndroid::setFixedPosition(FloatPoint position)
+void LayerAndroid::setFixedPosition(Length left, Length top,
+                                    Length right, Length bottom)
 {
-    m_fixedPosition = position;
+    m_fixedLeft = left;
+    m_fixedTop = top;
+    m_fixedRight = right;
+    m_fixedBottom = bottom;
     m_isFixed = true;
 }
 
@@ -205,10 +215,12 @@ void LayerAndroid::setBackgroundColor(const Color& color)
 
 static int gDebugChildLevel;
 
-void LayerAndroid::paintOn(float scrollX, float scrollY, float scale, SkCanvas* canvas)
+void LayerAndroid::paintOn(int scrollX, int scrollY,
+                           int width, int height,
+                           float scale, SkCanvas* canvas)
 {
     gDebugChildLevel = 0;
-    paintChildren(scrollX, scrollY, scale, canvas, 1);
+    paintChildren(scrollX, scrollY, width, height, scale, canvas, 1);
 }
 
 void LayerAndroid::setClip(SkCanvas* canvas)
@@ -221,7 +233,8 @@ void LayerAndroid::setClip(SkCanvas* canvas)
     canvas->clipRect(clip);
 }
 
-void LayerAndroid::paintChildren(float scrollX, float scrollY,
+void LayerAndroid::paintChildren(int scrollX, int scrollY,
+                                 int width, int height,
                                  float scale, SkCanvas* canvas,
                                  float opacity)
 {
@@ -230,7 +243,7 @@ void LayerAndroid::paintChildren(float scrollX, float scrollY,
     if (m_haveClip)
         setClip(canvas);
 
-    paintMe(scrollX, scrollY, scale, canvas, opacity);
+    paintMe(scrollX, scrollY, width, height, scale, canvas, opacity);
     canvas->translate(m_position.x() + m_translation.x(),
                       m_position.y() + m_translation.y());
 
@@ -238,7 +251,8 @@ void LayerAndroid::paintChildren(float scrollX, float scrollY,
         LayerAndroid* layer = m_children[i].get();
         if (layer) {
             gDebugChildLevel++;
-            layer->paintChildren(scrollX, scrollY, scale, canvas, opacity * m_opacity);
+            layer->paintChildren(scrollX, scrollY, width, height, scale,
+                                 canvas, opacity * m_opacity);
             gDebugChildLevel--;
         }
     }
@@ -246,8 +260,10 @@ void LayerAndroid::paintChildren(float scrollX, float scrollY,
     canvas->restore();
 }
 
-void LayerAndroid::paintMe(float scrollX,
-                           float scrollY,
+void LayerAndroid::paintMe(int scrollX,
+                           int scrollY,
+                           int viewWidth,
+                           int viewHeight,
                            float scale,
                            SkCanvas* canvas,
                            float opacity)
@@ -275,10 +291,24 @@ void LayerAndroid::paintMe(float scrollX,
 
     paintMode.setXfermodeMode(SkXfermode::kSrc_Mode);
 
-    float x, y;
+    float x = 0;
+    float y = 0;
     if (m_isFixed) {
-        x = m_fixedPosition.x() + (scrollX / scale);
-        y = m_fixedPosition.y() + (scrollY / scale);
+        float w = viewWidth / scale;
+        float h = viewHeight / scale;
+        float dx = scrollX / scale;
+        float dy = scrollY / scale;
+
+        if (m_fixedLeft.type())
+            x = dx + m_fixedLeft.calcFloatValue(w);
+        else if (m_fixedRight.type())
+            x = dx + w - m_fixedRight.calcFloatValue(w) - m_size.width();
+
+        if (m_fixedTop.type())
+            y = dy + m_fixedTop.calcFloatValue(h);
+        else if (m_fixedBottom.type())
+            y = dy + h - m_fixedBottom.calcFloatValue(h) - m_size.height();
+
     } else {
         x = m_translation.x() + m_position.x();
         y = m_translation.y() + m_position.y();
diff --git a/WebCore/platform/graphics/android/LayerAndroid.h b/WebCore/platform/graphics/android/LayerAndroid.h
index 284185d..467c7dd 100644
--- a/WebCore/platform/graphics/android/LayerAndroid.h
+++ b/WebCore/platform/graphics/android/LayerAndroid.h
@@ -25,6 +25,7 @@
 #include "FloatSize.h"
 #include "GraphicsContext.h"
 #include "GraphicsLayer.h"
+#include "Length.h"
 #include "RefPtr.h"
 #include "StringHash.h"
 #include "Vector.h"
@@ -64,7 +65,7 @@ public:
     void setBackgroundColor(const Color& color);
     void setIsRootLayer(bool isRootLayer) { m_isRootLayer = isRootLayer; }
 
-    void paintOn(float scrollX, float scrollY, float scale, SkCanvas*);
+    void paintOn(int scrollX, int scrollY, int width, int height, float scale, SkCanvas*);
     GraphicsContext* paintContext();
     void removeAllChildren() { m_children.clear(); }
     void addChildren(LayerAndroid* layer) { m_children.append(layer); }
@@ -77,7 +78,7 @@ public:
     FloatPoint translation() { return m_translation; }
     FloatSize size() { return m_size; }
 
-    void setFixedPosition(FloatPoint position);
+    void setFixedPosition(Length left, Length top, Length right, Length bottom);
     void addAnimation(PassRefPtr<AndroidAnimation> anim);
     void removeAnimation(const String& name);
     Vector<RefPtr<AndroidAnimationValue> >* evaluateAnimations() const;
@@ -87,11 +88,13 @@ public:
 
 private:
 
-    void paintChildren(float scrollX, float scrollY,
+    void paintChildren(int scrollX, int scrollY,
+                       int width, int height,
                        float scale, SkCanvas* canvas,
                        float opacity);
 
-    void paintMe(float scrollX, float scrollY,
+    void paintMe(int scrollX, int scrollY,
+                 int width, int height,
                  float scale, SkCanvas* canvas,
                  float opacity);
 
@@ -110,10 +113,14 @@ private:
     FloatSize m_size;
     FloatPoint m_position;
     FloatPoint m_translation;
-    FloatPoint m_fixedPosition;
     FloatPoint3D m_anchorPoint;
     FloatPoint3D m_scale;
 
+    Length m_fixedLeft;
+    Length m_fixedTop;
+    Length m_fixedRight;
+    Length m_fixedBottom;
+
     SkPicture* m_recordingPicture;
     Color m_backgroundColor;