Updates to LayoutRect API

Updates to the LayoutRect API as suggested by kkhorimoto@ in comments to
https://codereview.chromium.org/1304793002/

- Adds LayoutRectMake constructor.

- Adds LayoutRectZero constant.

- Renames fields: 'contextWidth' -> 'boundingWidth',
                  'yOrigin' -> 'originY'

- Renames function LayoutRectForRectInRectUsingDirection() ->
		   LayoutRectForRectInBoundingRectUsingDirection()

- Renames function LayoutRectForRectInRect() ->
		   LayoutRectForRectInBoundingRect()

- Renames function LayoutRectGetTrailing() ->
		   LayoutRectGetTrailingEdge()

- Corrects parameter name errors in comments.

BUG=

Review URL: https://codereview.chromium.org/1305013002

Cr-Commit-Position: refs/heads/master@{#345587}

ios/chrome/browser/ui/ui_util.h

@@ -30,16 +30,28 @@ base::i18n::TextDirection LayoutDirection();
 // may not be flipped if positioned in RTL or LTR contexts. |leading| is the
 // distance from the leading edge that the final rect's edge should be; in LTR
 // this will be the x-origin, in RTL it will be used to compute the x-origin.
-// |contextWidth| is the width of whatever element the rect will be used to
-// frame a subview of. |yOrigin| will be origin.y of the rect, and |size| will
+// |boundingWidth| is the width of whatever element the rect will be used to
+// frame a subview of. |originY| will be origin.y of the rect, and |size| will
 // be the size of the rect.
 struct LayoutRect {
   CGFloat leading;
-  CGFloat contextWidth;
-  CGFloat yOrigin;
+  CGFloat boundingWidth;
+  CGFloat originY;
   CGSize size;
 };
 
+// The null LayoutRect, with leading, boundingWidth and originY of 0.0, and
+// a size of CGSizeZero.
+extern const LayoutRect LayoutRectZero;
+
+// Returns a new LayoutRect; |height| and |width| are used to construct the
+// |size| field.
+LayoutRect LayoutRectMake(CGFloat leading,
+                          CGFloat boundingWidth,
+                          CGFloat originY,
+                          CGFloat width,
+                          CGFloat height);
+
 // Given |layout|, returns the rect for that layout in text direction
 // |direction|.
 CGRect LayoutRectGetRectUsingDirection(LayoutRect layout,
@@ -60,19 +72,23 @@ CGPoint LayoutRectGetPositionForAnchorUsingDirection(
     LayoutRect layout,
     CGPoint anchor,
     base::i18n::TextDirection direction);
+
+// As above, using |direction| == RIGHT_TO_LEFT if UseRTLLayout(), LEFT_TO_RIGHT
+// otherwise.
 CGPoint LayoutRectGetPositionForAnchor(LayoutRect layout, CGPoint anchor);
 
-// Given |layout|, a rect, and |contextRect|, a rect whose bounds are the
-// context in which |layout|'s frame is interpreted, return the layout that
-// defines |layout|.
-LayoutRect LayoutRectForRectInRectUsingDirection(
+// Given |rect|, a rect, and |boundingRect|, a rect whose bounds are the
+// context in which |rect|'s frame is interpreted, return the layout that
+// defines |rect|, assuming |direction| is the direction |rect| was positioned
+// under.
+LayoutRect LayoutRectForRectInBoundingRectUsingDirection(
     CGRect rect,
-    CGRect contextRect,
+    CGRect boundingRect,
     base::i18n::TextDirection direction);
 
 // As above, using |direction| == RIGHT_TO_LEFT if UseRTLLayout(), LEFT_TO_RIGHT
 // otherwise.
-LayoutRect LayoutRectForRectInRect(CGRect rect, CGRect contextRect);
+LayoutRect LayoutRectForRectInBoundingRect(CGRect rect, CGRect boundingRect);
 
 // Given a layout |layout|, return the layout that defines the leading area up
 // to |layout|.
@@ -83,7 +99,7 @@ LayoutRect LayoutRectGetLeadingLayout(LayoutRect layout);
 LayoutRect LayoutRectGetTrailingLayout(LayoutRect layout);
 
 // Return the trailing extent of |layout| (its leading plus its width).
-CGFloat LayoutRectGetTrailing(LayoutRect layout);
+CGFloat LayoutRectGetTrailingEdge(LayoutRect layout);
 
 // Is the screen of the device a high resolution screen, i.e. Retina Display.
 bool IsHighResScreen();

ios/chrome/browser/ui/ui_util.mm

@@ -29,17 +29,29 @@ bool UseRTLLayout() {
   return UseRTLLayout() ? base::i18n::RIGHT_TO_LEFT : base::i18n::LEFT_TO_RIGHT;
 }
 
+const LayoutRect LayoutRectZero = {0.0, 0.0, 0.0, CGSizeMake(0.0, 0.0)};
+
+LayoutRect LayoutRectMake(CGFloat leading,
+                          CGFloat boundingWidth,
+                          CGFloat originY,
+                          CGFloat width,
+                          CGFloat height) {
+  LayoutRect layout = {leading, boundingWidth, originY,
+                       CGSizeMake(width, height)};
+  return layout;
+}
+
 CGRect LayoutRectGetRectUsingDirection(LayoutRect layout,
                                        base::i18n::TextDirection direction) {
   CGRect rect;
   if (direction == base::i18n::RIGHT_TO_LEFT) {
     CGFloat trailing =
-        layout.contextWidth - (layout.leading + layout.size.width);
-    rect = CGRectMake(trailing, layout.yOrigin, layout.size.width,
+        layout.boundingWidth - (layout.leading + layout.size.width);
+    rect = CGRectMake(trailing, layout.originY, layout.size.width,
                       layout.size.height);
   } else {
     DCHECK_EQ(direction, base::i18n::LEFT_TO_RIGHT);
-    rect = CGRectMake(layout.leading, layout.yOrigin, layout.size.width,
+    rect = CGRectMake(layout.leading, layout.originY, layout.size.width,
                       layout.size.height);
   }
   return rect;
@@ -77,8 +89,8 @@ LayoutRect LayoutRectForRectInRectUsingDirection(
   } else {
     layout.leading = CGRectGetMinX(rect);
   }
-  layout.contextWidth = contextRect.size.width;
-  layout.yOrigin = rect.origin.y;
+  layout.boundingWidth = contextRect.size.width;
+  layout.originY = rect.origin.y;
   layout.size = rect.size;
   return layout;
 }
@@ -91,24 +103,24 @@ LayoutRect LayoutRectForRectInRect(CGRect rect, CGRect contextRect) {
 LayoutRect LayoutRectGetLeadingLayout(LayoutRect layout) {
   LayoutRect leadingLayout;
   leadingLayout.leading = 0;
-  leadingLayout.contextWidth = layout.contextWidth;
-  leadingLayout.yOrigin = layout.yOrigin;
+  leadingLayout.boundingWidth = layout.boundingWidth;
+  leadingLayout.originY = leadingLayout.originY;
   leadingLayout.size = CGSizeMake(layout.leading, layout.size.height);
   return leadingLayout;
 }
 
 LayoutRect LayoutRectGetTrailingLayout(LayoutRect layout) {
   LayoutRect leadingLayout;
-  CGFloat trailing = LayoutRectGetTrailing(layout);
+  CGFloat trailing = LayoutRectGetTrailingEdge(layout);
   leadingLayout.leading = trailing;
-  leadingLayout.contextWidth = layout.contextWidth;
-  leadingLayout.yOrigin = layout.yOrigin;
+  leadingLayout.boundingWidth = layout.boundingWidth;
+  leadingLayout.originY = leadingLayout.originY;
   leadingLayout.size =
-      CGSizeMake((layout.contextWidth - trailing), layout.size.height);
+      CGSizeMake((layout.boundingWidth - trailing), layout.size.height);
   return leadingLayout;
 }
 
-CGFloat LayoutRectGetTrailing(LayoutRect layout) {
+CGFloat LayoutRectGetTrailingEdge(LayoutRect layout) {
   return layout.leading + layout.size.width;
 }