Fix CSSLayout to Support RTL

Summary:
The current CSSLayout can't support RTL because wrong calculation for absolute position.
This change is mainly to fix the issue: facebook/yoga#197
Three main problems I fixed:
1. Calculate the position in the same way as margin, boarder, and padding. So that to fix the absolute problem.
2. Fix one wrong calculation for leading value when we only know the trailing value. It was hard code for the LTR situation. Now I changed it to depends on the main Axis.
3. Expose getter and setter function for RN to read layout direction and start/end position value.

Reviewed By: fkgozali

Differential Revision: D3616949

fbshipit-source-id: ae7a47cc0a5d02b42b95f87232be51ab144056d9

Author: MengjueW

React/CSSLayout/CSSLayout-internal.h

@@ -65,7 +65,7 @@ typedef struct CSSStyle {
   CSSOverflow overflow;
   float flex;
   float margin[6];
-  float position[4];
+  float position[6];
   /**
    * You should skip all the rules that contain negative values for the
    * following attributes. For example:

React/CSSLayout/CSSLayout.c

@@ -70,6 +70,8 @@ void CSSNodeInit(CSSNodeRef node) {
   node->style.position[CSSPositionTop] = CSSUndefined;
   node->style.position[CSSPositionRight] = CSSUndefined;
   node->style.position[CSSPositionBottom] = CSSUndefined;
+  node->style.position[CSSPositionStart] = CSSUndefined;
+  node->style.position[CSSPositionEnd] = CSSUndefined;
 
   node->style.margin[CSSPositionStart] = CSSUndefined;
   node->style.margin[CSSPositionEnd] = CSSUndefined;
@@ -173,6 +175,8 @@ CSS_NODE_STYLE_PROPERTY_IMPL(float, PositionLeft, positionLeft, position[CSSPosi
 CSS_NODE_STYLE_PROPERTY_IMPL(float, PositionTop, positionTop, position[CSSPositionTop]);
 CSS_NODE_STYLE_PROPERTY_IMPL(float, PositionRight, positionRight, position[CSSPositionRight]);
 CSS_NODE_STYLE_PROPERTY_IMPL(float, PositionBottom, positionBottom, position[CSSPositionBottom]);
+CSS_NODE_STYLE_PROPERTY_IMPL(float, PositionStart, positionStart, position[CSSPositionStart]);
+CSS_NODE_STYLE_PROPERTY_IMPL(float, PositionEnd, positionEnd, position[CSSPositionEnd]);
 
 CSS_NODE_STYLE_PROPERTY_IMPL(float, MarginLeft, marginLeft, margin[CSSPositionLeft]);
 CSS_NODE_STYLE_PROPERTY_IMPL(float, MarginTop, marginTop, margin[CSSPositionTop]);
@@ -208,6 +212,7 @@ CSS_NODE_LAYOUT_PROPERTY_IMPL(float, Right, position[CSSPositionRight]);
 CSS_NODE_LAYOUT_PROPERTY_IMPL(float, Bottom, position[CSSPositionBottom]);
 CSS_NODE_LAYOUT_PROPERTY_IMPL(float, Width, dimensions[CSSDimensionWidth]);
 CSS_NODE_LAYOUT_PROPERTY_IMPL(float, Height, dimensions[CSSDimensionHeight]);
+CSS_NODE_LAYOUT_PROPERTY_IMPL(CSSDirection, Direction, direction);
 
 int gCurrentGenerationCount = 0;
 
@@ -623,18 +628,36 @@ static bool isLayoutDimDefined(CSSNode* node, CSSFlexDirection axis) {
   return !isUndefined(value) && value >= 0.0;
 }
 
-static bool isPosDefined(CSSNode* node, CSSPosition position) {
-  return !isUndefined(node->style.position[position]);
+static bool isLeadingPosDefined(CSSNode* node, CSSFlexDirection axis) {
+  return (isRowDirection(axis) && !isUndefined(node->style.position[CSSPositionStart]))
+    || !isUndefined(node->style.position[leading[axis]]);
+}
+
+static bool isTrailingPosDefined(CSSNode* node, CSSFlexDirection axis) {
+  return (isRowDirection(axis) && !isUndefined(node->style.position[CSSPositionEnd]))
+    || !isUndefined(node->style.position[trailing[axis]]);
 }
 
 static bool isMeasureDefined(CSSNode* node) {
   return node->measure;
 }
 
-static float getPosition(CSSNode* node, CSSPosition position) {
-  float result = node->style.position[position];
-  if (!isUndefined(result)) {
-    return result;
+static float getLeadingPosition(CSSNode* node, CSSFlexDirection axis) {
+  if (isRowDirection(axis) && !isUndefined(node->style.position[CSSPositionStart])) {
+    return node->style.position[CSSPositionStart];
+  }
+  if (!isUndefined(node->style.position[leading[axis]])) {
+    return node->style.position[leading[axis]];
+  }
+  return 0;
+}
+
+static float getTrailingPosition(CSSNode* node, CSSFlexDirection axis) {
+  if (isRowDirection(axis) && !isUndefined(node->style.position[CSSPositionEnd])) {
+    return node->style.position[CSSPositionEnd];
+  }
+  if (!isUndefined(node->style.position[trailing[axis]])) {
+    return node->style.position[trailing[axis]];
   }
   return 0;
 }
@@ -670,20 +693,18 @@ static float boundAxis(CSSNode* node, CSSFlexDirection axis, float value) {
 }
 
 static void setTrailingPosition(CSSNode* node, CSSNode* child, CSSFlexDirection axis) {
-  float size = child->style.positionType == CSSPositionTypeAbsolute ?
-    0 :
-    child->layout.measuredDimensions[dim[axis]];
+  float size = child->layout.measuredDimensions[dim[axis]];
   child->layout.position[trailing[axis]] = node->layout.measuredDimensions[dim[axis]] - size - child->layout.position[pos[axis]];
 }
 
 // If both left and right are defined, then use left. Otherwise return
 // +left or -right depending on which is defined.
 static float getRelativePosition(CSSNode* node, CSSFlexDirection axis) {
-  float lead = node->style.position[leading[axis]];
+  float lead = getLeadingPosition(node, axis);
   if (!isUndefined(lead)) {
     return lead;
   }
-  return -getPosition(node, trailing[axis]);
+  return -getTrailingPosition(node, axis);
 }
 
 static void setPosition(CSSNode* node, CSSDirection direction) {
@@ -1294,12 +1315,12 @@ static void layoutNodeImpl(CSSNode* node, float availableWidth, float availableH
       child = CSSNodeListGet(node->children, i);
 
       if (child->style.positionType == CSSPositionTypeAbsolute &&
-          isPosDefined(child, leading[mainAxis])) {
+          isLeadingPosDefined(child, mainAxis)) {
         if (performLayout) {
           // In case the child is position absolute and has left/top being
           // defined, we override the position to whatever the user said
           // (and margin/border).
-          child->layout.position[pos[mainAxis]] = getPosition(child, leading[mainAxis]) +
+          child->layout.position[pos[mainAxis]] = getLeadingPosition(child, mainAxis) +
             getLeadingBorder(node, mainAxis) +
             getLeadingMargin(child, mainAxis);
         }
@@ -1361,8 +1382,8 @@ static void layoutNodeImpl(CSSNode* node, float availableWidth, float availableH
         if (child->style.positionType == CSSPositionTypeAbsolute) {
           // If the child is absolutely positioned and has a top/left/bottom/right
           // set, override all the previously computed positions to set it correctly.
-          if (isPosDefined(child, leading[crossAxis])) {
-            child->layout.position[pos[crossAxis]] = getPosition(child, leading[crossAxis]) +
+          if (isLeadingPosDefined(child, crossAxis)) {
+            child->layout.position[pos[crossAxis]] = getLeadingPosition(child, crossAxis) +
               getLeadingBorder(node, crossAxis) +
               getLeadingMargin(child, crossAxis);
           } else {
@@ -1518,38 +1539,7 @@ static void layoutNodeImpl(CSSNode* node, float availableWidth, float availableH
       paddingAndBorderAxisCross);
   }
 
-  // STEP 10: SETTING TRAILING POSITIONS FOR CHILDREN
-  if (performLayout) {
-    bool needsMainTrailingPos = false;
-    bool needsCrossTrailingPos = false;
-
-    if (mainAxis == CSSFlexDirectionRowReverse ||
-        mainAxis == CSSFlexDirectionColumnReverse) {
-      needsMainTrailingPos = true;
-    }
-
-    if (crossAxis == CSSFlexDirectionRowReverse ||
-        crossAxis == CSSFlexDirectionColumnReverse) {
-      needsCrossTrailingPos = true;
-    }
-
-    // Set trailing position if necessary.
-    if (needsMainTrailingPos || needsCrossTrailingPos) {
-      for (i = 0; i < childCount; ++i) {
-        child = CSSNodeListGet(node->children, i);
-
-        if (needsMainTrailingPos) {
-          setTrailingPosition(node, child, mainAxis);
-        }
-
-        if (needsCrossTrailingPos) {
-          setTrailingPosition(node, child, crossAxis);
-        }
-      }
-    }
-  }
-
-  // STEP 11: SIZING AND POSITIONING ABSOLUTE CHILDREN
+  // STEP 10: SIZING AND POSITIONING ABSOLUTE CHILDREN
   currentAbsoluteChild = firstAbsoluteChild;
   while (currentAbsoluteChild != NULL) {
     // Now that we know the bounds of the container, perform layout again on the
@@ -1563,10 +1553,10 @@ static void layoutNodeImpl(CSSNode* node, float availableWidth, float availableH
         childWidth = currentAbsoluteChild->style.dimensions[CSSDimensionWidth] + getMarginAxis(currentAbsoluteChild, CSSFlexDirectionRow);
       } else {
         // If the child doesn't have a specified width, compute the width based on the left/right offsets if they're defined.
-        if (isPosDefined(currentAbsoluteChild, CSSPositionLeft) && isPosDefined(currentAbsoluteChild, CSSPositionRight)) {
+        if (isLeadingPosDefined(currentAbsoluteChild, CSSFlexDirectionRow) && isTrailingPosDefined(currentAbsoluteChild, CSSFlexDirectionRow)) {
           childWidth = node->layout.measuredDimensions[CSSDimensionWidth] -
             (getLeadingBorder(node, CSSFlexDirectionRow) + getTrailingBorder(node, CSSFlexDirectionRow)) -
-            (currentAbsoluteChild->style.position[CSSPositionLeft] + currentAbsoluteChild->style.position[CSSPositionRight]);
+            (getLeadingPosition(currentAbsoluteChild, CSSFlexDirectionRow) + getTrailingPosition(currentAbsoluteChild, CSSFlexDirectionRow));
           childWidth = boundAxis(currentAbsoluteChild, CSSFlexDirectionRow, childWidth);
         }
       }
@@ -1575,10 +1565,10 @@ static void layoutNodeImpl(CSSNode* node, float availableWidth, float availableH
         childHeight = currentAbsoluteChild->style.dimensions[CSSDimensionHeight] + getMarginAxis(currentAbsoluteChild, CSSFlexDirectionColumn);
       } else {
         // If the child doesn't have a specified height, compute the height based on the top/bottom offsets if they're defined.
-        if (isPosDefined(currentAbsoluteChild, CSSPositionTop) && isPosDefined(currentAbsoluteChild, CSSPositionBottom)) {
+        if (isLeadingPosDefined(currentAbsoluteChild, CSSFlexDirectionColumn) && isTrailingPosDefined(currentAbsoluteChild, CSSFlexDirectionColumn)) {
           childHeight = node->layout.measuredDimensions[CSSDimensionHeight] -
             (getLeadingBorder(node, CSSFlexDirectionColumn) + getTrailingBorder(node, CSSFlexDirectionColumn)) -
-            (currentAbsoluteChild->style.position[CSSPositionTop] + currentAbsoluteChild->style.position[CSSPositionBottom]);
+            (getLeadingPosition(currentAbsoluteChild, CSSFlexDirectionColumn) + getTrailingPosition(currentAbsoluteChild, CSSFlexDirectionColumn));
           childHeight = boundAxis(currentAbsoluteChild, CSSFlexDirectionColumn, childHeight);
         }
       }
@@ -1613,25 +1603,56 @@ static void layoutNodeImpl(CSSNode* node, float availableWidth, float availableH
 
       layoutNodeInternal(currentAbsoluteChild, childWidth, childHeight, direction, CSSMeasureModeExactly, CSSMeasureModeExactly, true, "abs-layout");
 
-      if (isPosDefined(currentAbsoluteChild, trailing[CSSFlexDirectionRow]) &&
-          !isPosDefined(currentAbsoluteChild, leading[CSSFlexDirectionRow])) {
-        currentAbsoluteChild->layout.position[leading[CSSFlexDirectionRow]] =
-          node->layout.measuredDimensions[dim[CSSFlexDirectionRow]] -
-          currentAbsoluteChild->layout.measuredDimensions[dim[CSSFlexDirectionRow]] -
-          getPosition(currentAbsoluteChild, trailing[CSSFlexDirectionRow]);
+      if (isTrailingPosDefined(currentAbsoluteChild, mainAxis) &&
+          !isLeadingPosDefined(currentAbsoluteChild, mainAxis)) {
+        currentAbsoluteChild->layout.position[leading[mainAxis]] =
+          node->layout.measuredDimensions[dim[mainAxis]] -
+          currentAbsoluteChild->layout.measuredDimensions[dim[mainAxis]] -
+          getTrailingPosition(currentAbsoluteChild, mainAxis);
       }
 
-      if (isPosDefined(currentAbsoluteChild, trailing[CSSFlexDirectionColumn]) &&
-          !isPosDefined(currentAbsoluteChild, leading[CSSFlexDirectionColumn])) {
-        currentAbsoluteChild->layout.position[leading[CSSFlexDirectionColumn]] =
-          node->layout.measuredDimensions[dim[CSSFlexDirectionColumn]] -
-          currentAbsoluteChild->layout.measuredDimensions[dim[CSSFlexDirectionColumn]] -
-          getPosition(currentAbsoluteChild, trailing[CSSFlexDirectionColumn]);
+      if (isTrailingPosDefined(currentAbsoluteChild, crossAxis) &&
+          !isLeadingPosDefined(currentAbsoluteChild, crossAxis)) {
+        currentAbsoluteChild->layout.position[leading[crossAxis]] =
+          node->layout.measuredDimensions[dim[crossAxis]] -
+          currentAbsoluteChild->layout.measuredDimensions[dim[crossAxis]] -
+          getTrailingPosition(currentAbsoluteChild, crossAxis);
       }
     }
 
     currentAbsoluteChild = currentAbsoluteChild->nextChild;
   }
+
+  // STEP 11: SETTING TRAILING POSITIONS FOR CHILDREN
+  if (performLayout) {
+    bool needsMainTrailingPos = false;
+    bool needsCrossTrailingPos = false;
+
+    if (mainAxis == CSSFlexDirectionRowReverse ||
+        mainAxis == CSSFlexDirectionColumnReverse) {
+      needsMainTrailingPos = true;
+    }
+
+    if (crossAxis == CSSFlexDirectionRowReverse ||
+        crossAxis == CSSFlexDirectionColumnReverse) {
+      needsCrossTrailingPos = true;
+    }
+
+    // Set trailing position if necessary.
+    if (needsMainTrailingPos || needsCrossTrailingPos) {
+      for (i = 0; i < childCount; ++i) {
+        child = CSSNodeListGet(node->children, i);
+
+        if (needsMainTrailingPos) {
+          setTrailingPosition(node, child, mainAxis);
+        }
+
+        if (needsCrossTrailingPos) {
+          setTrailingPosition(node, child, crossAxis);
+        }
+      }
+    }
+  }
 }
 
 int gDepth = 0;

React/CSSLayout/CSSLayout.h

@@ -169,6 +169,8 @@ CSS_NODE_STYLE_PROPERTY(float, PositionLeft, positionLeft);
 CSS_NODE_STYLE_PROPERTY(float, PositionTop, positionTop);
 CSS_NODE_STYLE_PROPERTY(float, PositionRight, positionRight);
 CSS_NODE_STYLE_PROPERTY(float, PositionBottom, positionBottom);
+CSS_NODE_STYLE_PROPERTY(float, PositionStart, positionStart);
+CSS_NODE_STYLE_PROPERTY(float, PositionEnd, positionEnd);
 
 CSS_NODE_STYLE_PROPERTY(float, MarginLeft, marginLeft);
 CSS_NODE_STYLE_PROPERTY(float, MarginTop, marginTop);
@@ -204,6 +206,7 @@ CSS_NODE_LAYOUT_PROPERTY(float, Right);
 CSS_NODE_LAYOUT_PROPERTY(float, Bottom);
 CSS_NODE_LAYOUT_PROPERTY(float, Width);
 CSS_NODE_LAYOUT_PROPERTY(float, Height);
+CSS_NODE_LAYOUT_PROPERTY(CSSDirection, Direction);
 
 CSS_EXTERN_C_END
 

ReactAndroid/src/main/java/com/facebook/csslayout/CSSNode.java

@@ -17,10 +17,12 @@
 
 import static com.facebook.csslayout.CSSLayout.DIMENSION_HEIGHT;
 import static com.facebook.csslayout.CSSLayout.DIMENSION_WIDTH;
-import static com.facebook.csslayout.CSSLayout.POSITION_BOTTOM;
 import static com.facebook.csslayout.CSSLayout.POSITION_LEFT;
-import static com.facebook.csslayout.CSSLayout.POSITION_RIGHT;
 import static com.facebook.csslayout.CSSLayout.POSITION_TOP;
+import static com.facebook.csslayout.Spacing.BOTTOM;
+import static com.facebook.csslayout.Spacing.LEFT;
+import static com.facebook.csslayout.Spacing.RIGHT;
+import static com.facebook.csslayout.Spacing.TOP;
 
 /**
  * A CSS Node. It has a style object you can manipulate at {@link #style}. After calling
@@ -373,16 +375,28 @@ public void setBorder(int spacingType, float border) {
     }
   }
 
+  /**
+   * Get this node's position, as defined by style.
+   */
+   public Spacing getPosition() {
+    return style.position;
+  }
+
+  public void setPosition(int spacingType, float position) {
+    if (style.position.set(spacingType, position)) {
+      dirty();
+    }
+  }
+
   /**
    * Get this node's position top, as defined by style.
    */
   public float getPositionTop() {
-    return style.position[POSITION_TOP];
+    return style.position.get(TOP);
   }
 
   public void setPositionTop(float positionTop) {
-    if (!valuesEqual(style.position[POSITION_TOP], positionTop)) {
-      style.position[POSITION_TOP] = positionTop;
+    if (style.position.set(TOP, positionTop)) {
       dirty();
     }
   }
@@ -391,12 +405,11 @@ public void setPositionTop(float positionTop) {
    * Get this node's position bottom, as defined by style.
    */
   public float getPositionBottom() {
-    return style.position[POSITION_BOTTOM];
+    return style.position.get(BOTTOM);
   }
 
   public void setPositionBottom(float positionBottom) {
-    if (!valuesEqual(style.position[POSITION_BOTTOM], positionBottom)) {
-      style.position[POSITION_BOTTOM] = positionBottom;
+    if (style.position.set(BOTTOM, positionBottom)) {
       dirty();
     }
   }
@@ -405,12 +418,11 @@ public void setPositionBottom(float positionBottom) {
    * Get this node's position left, as defined by style.
    */
   public float getPositionLeft() {
-    return style.position[POSITION_LEFT];
+    return style.position.get(LEFT);
   }
 
   public void setPositionLeft(float positionLeft) {
-    if (!valuesEqual(style.position[POSITION_LEFT], positionLeft)) {
-      style.position[POSITION_LEFT] = positionLeft;
+    if (style.position.set(LEFT, positionLeft)) {
       dirty();
     }
   }
@@ -419,12 +431,11 @@ public void setPositionLeft(float positionLeft) {
    * Get this node's position right, as defined by style.
    */
   public float getPositionRight() {
-    return style.position[POSITION_RIGHT];
+    return style.position.get(RIGHT);
   }
 
   public void setPositionRight(float positionRight) {
-    if (!valuesEqual(style.position[POSITION_RIGHT], positionRight)) {
-      style.position[POSITION_RIGHT] = positionRight;
+    if (style.position.set(RIGHT, positionRight)) {
       dirty();
     }
   }