VR: Reuse more common size and layout logic in LinearLayout

This change reduces the amount of custom code in LinearLayout to the
minimum, reducing duplication and keeping things more consistent.

BUG=
R=acondor

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_vr
Change-Id: I11a9c0a766845f9b5b7a86378a12b5e0b6202115
Reviewed-on: https://chromium-review.googlesource.com/1053754Reviewed-by: Tibor Goldschwendt <tiborg@chromium.org>
Commit-Queue: Christopher Grant <cjgrant@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557688}

chrome/browser/vr/elements/linear_layout.cc

@@ -23,35 +23,23 @@ float GetExtent(const UiElement& element, bool horizontal) {
 LinearLayout::LinearLayout(Direction direction) : direction_(direction) {}
 LinearLayout::~LinearLayout() {}
 
-bool LinearLayout::SizeAndLayOut() {
-  if (!IsVisible())
-    return false;
-
-  bool changed = false;
-  if (layout_length > 0.0f) {
-    UiElement* element_to_resize = nullptr;
-    for (auto& child : children()) {
-      if (child->resizable_by_layout()) {
-        DCHECK_EQ(nullptr, element_to_resize);
-        element_to_resize = child.get();
-      } else {
-        changed |= child->SizeAndLayOut();
-      }
-    }
-    DCHECK_NE(element_to_resize, nullptr);
-    changed |= element_to_resize->SizeAndLayOut();
-    changed |= AdjustResizableElement(element_to_resize);
-    changed |= element_to_resize->SizeAndLayOut();
-  } else {
-    for (auto& child : children()) {
-      changed |= child->SizeAndLayOut();
+bool LinearLayout::SizeAndLayOutChildren() {
+  bool changed = UiElement::SizeAndLayOutChildren();
+  if (layout_length_ == 0.0f)
+    return changed;
+
+  // We need to adjust one of the elements' size to ensure a fixed total layout
+  // width.  Find that element, set its size, and lay it out again.
+  UiElement* element_to_resize = nullptr;
+  for (auto& child : children()) {
+    if (child->resizable_by_layout()) {
+      element_to_resize = child.get();
+      break;
     }
   }
-
-  changed |= PrepareToDraw();
-  set_update_phase(kUpdatedSize);
-  DoLayOutChildren();
-  set_update_phase(kUpdatedLayout);
+  DCHECK_NE(element_to_resize, nullptr);
+  changed |= AdjustResizableElement(element_to_resize);
+  changed |= element_to_resize->SizeAndLayOut();
   return changed;
 }
 
@@ -141,7 +129,7 @@ bool LinearLayout::AdjustResizableElement(UiElement* element_to_resize) {
   float minor = 0;
   GetTotalExtent(element_to_resize, &minimum_total, &minor);
 
-  float extent = layout_length - minimum_total;
+  float extent = layout_length_ - minimum_total;
   extent = std::max(extent, 0.f);
 
   auto new_size = element_to_resize->size();

chrome/browser/vr/elements/linear_layout.h

@@ -18,10 +18,10 @@ class LinearLayout : public UiElement {
 
   void set_margin(float margin) { margin_ = margin; }
   void set_direction(Direction direction) { direction_ = direction; }
-  void set_layout_length(float extent) { layout_length = extent; }
+  void set_layout_length(float extent) { layout_length_ = extent; }
 
   // UiElement overrides.
-  bool SizeAndLayOut() override;
+  bool SizeAndLayOutChildren() override;
   void LayOutChildren() override;
 
  private:
@@ -39,12 +39,14 @@ class LinearLayout : public UiElement {
   bool AdjustResizableElement(UiElement* element_to_resize);
 
   Direction direction_;
+
+  // The spacing between elements.
   float margin_ = 0.0f;
 
   // If non-zero, LinearLayout will look for an element tagged as allowing
   // sizing by its parent, and set that element's size such that the total
   // layout's length is attained.
-  float layout_length = 0.0f;
+  float layout_length_ = 0.0f;
 };
 
 }  // namespace vr

chrome/browser/vr/elements/ui_element.cc

@@ -799,9 +799,10 @@ bool UiElement::IsAnimatingProperty(TargetProperty property) const {
 bool UiElement::SizeAndLayOut() {
   if (!IsVisible() && kEnableOptimizedTreeWalks)
     return false;
-  bool changed = false;
-  for (auto& child : children_)
-    changed |= child->SizeAndLayOut();
+
+  // May be overridden by layout elements.
+  bool changed = SizeAndLayOutChildren();
+
   changed |= PrepareToDraw();
   set_update_phase(kUpdatedSize);
   DoLayOutChildren();
@@ -809,6 +810,13 @@ bool UiElement::SizeAndLayOut() {
   return changed;
 }
 
+bool UiElement::SizeAndLayOutChildren() {
+  bool changed = false;
+  for (auto& child : children_)
+    changed |= child->SizeAndLayOut();
+  return changed;
+}
+
 void UiElement::DoLayOutChildren() {
   LayOutChildren();
   if (!bounds_contain_children_) {

chrome/browser/vr/elements/ui_element.h

@@ -397,9 +397,12 @@ class UiElement : public cc::AnimationTarget {
   void RemoveKeyframeModels(int target_property);
   bool IsAnimatingProperty(TargetProperty property) const;
 
-  // Recursive method that sizes and lays out element subtrees. This method may
-  // be overridden by elements that have custom layout requirements.
-  virtual bool SizeAndLayOut();
+  // Recursive method that sizes and lays out element subtrees.
+  bool SizeAndLayOut();
+
+  // This method may be overridden by elements that have custom layout
+  // requirements.
+  virtual bool SizeAndLayOutChildren();
 
   void DoLayOutChildren();