UI: Add a simple means of persisting data.

ext/native/ui/ui_screen.cpp

@@ -1,3 +1,4 @@
+#include <map>
 #include "base/display.h"
 #include "input/input_state.h"
 #include "input/keycodes.h"
@@ -19,13 +20,23 @@ UIScreen::~UIScreen() {
 
 void UIScreen::DoRecreateViews() {
 	if (recreateViews_) {
+		UI::PersistMap persisted;
+		bool persisting = root_ != nullptr;
+		if (persisting) {
+			root_->PersistData(UI::PERSIST_SAVE, persisted);
+		}
+
 		delete root_;
-		root_ = 0;
+		root_ = nullptr;
 		CreateViews();
 		if (root_ && root_->GetDefaultFocusView()) {
 			root_->GetDefaultFocusView()->SetFocus();
 		}
 		recreateViews_ = false;
+
+		if (persisting) {
+			root_->PersistData(UI::PERSIST_RESTORE, persisted);
+		}
 	}
 }
 

ext/native/ui/view.h

@@ -9,6 +9,7 @@
 
 #include <string>
 #include <vector>
+#include <map>
 #include <cmath>
 #include <cstdio>
 #include <memory>
@@ -203,9 +204,15 @@ enum FocusFlags {
 	FF_GOTFOCUS = 2
 };
 
-class ViewGroup;
+enum PersistStatus {
+	PERSIST_SAVE,
+	PERSIST_RESTORE,
+};
 
-void Fill(UIContext &dc, const Bounds &bounds, const Drawable &drawable);
+typedef std::vector<int> PersistBuffer;
+typedef std::map<std::string, UI::PersistBuffer> PersistMap;
+
+class ViewGroup;
 
 struct MeasureSpec {
 	MeasureSpec(MeasureSpecType t, float s = 0.0f) : type(t), size(s) {}
@@ -339,6 +346,7 @@ public:
 	virtual std::string Describe() const;
 
 	virtual void FocusChanged(int focusFlags) {}
+	virtual void PersistData(PersistStatus status, PersistMap &storage) {}
 
 	void Move(Bounds bounds) {
 		bounds_ = bounds;

ext/native/ui/viewgroup.cpp

@@ -70,11 +70,18 @@ void ViewGroup::Clear() {
 	lock_guard guard(modifyLock_);
 	for (size_t i = 0; i < views_.size(); i++) {
 		delete views_[i];
-		views_[i] = 0;
+		views_[i] = nullptr;
 	}
 	views_.clear();
 }
 
+void ViewGroup::PersistData(PersistStatus status, PersistMap &storage) {
+	lock_guard guard(modifyLock_);
+	for (size_t i = 0; i < views_.size(); i++) {
+		views_[i]->PersistData(status, storage);
+	}
+}
+
 void ViewGroup::Touch(const TouchInput &input) {
 	lock_guard guard(modifyLock_);
 	for (auto iter = views_.begin(); iter != views_.end(); ++iter) {

ext/native/ui/viewgroup.h

@@ -64,6 +64,7 @@ public:
 	virtual void SetBG(const Drawable &bg) { bg_ = bg; }
 
 	virtual void Clear();
+	void PersistData(PersistStatus status, PersistMap &storage) override;
 	View *GetViewByIndex(int index) { return views_[index]; }
 	int GetNumSubviews() const { return (int)views_.size(); }
 	void SetHasDropShadow(bool has) { hasDropShadow_ = has; }