UI: Add a simple tween class.

CMakeLists.txt

@@ -955,6 +955,8 @@ add_library(native STATIC
 	ext/native/ui/ui_context.h
 	ext/native/ui/ui_screen.cpp
 	ext/native/ui/ui_screen.h
+	ext/native/ui/ui_tween.cpp
+	ext/native/ui/ui_tween.h
 	ext/native/ui/view.cpp
 	ext/native/ui/view.h
 	ext/native/ui/viewgroup.cpp

UWP/NativeUWP/NativeUWP.vcxproj

@@ -376,6 +376,7 @@
     <ClInclude Include="..\..\ext\native\ui\ui.h" />
     <ClInclude Include="..\..\ext\native\ui\ui_context.h" />
     <ClInclude Include="..\..\ext\native\ui\ui_screen.h" />
+    <ClInclude Include="..\..\ext\native\ui\ui_tween.h" />
     <ClInclude Include="..\..\ext\native\ui\view.h" />
     <ClInclude Include="..\..\ext\native\ui\viewgroup.h" />
     <ClInclude Include="..\..\ext\native\util\const_map.h" />
@@ -1290,6 +1291,7 @@
     <ClCompile Include="..\..\ext\native\ui\ui.cpp" />
     <ClCompile Include="..\..\ext\native\ui\ui_context.cpp" />
     <ClCompile Include="..\..\ext\native\ui\ui_screen.cpp" />
+    <ClCompile Include="..\..\ext\native\ui\ui_tween.cpp" />
     <ClCompile Include="..\..\ext\native\ui\view.cpp" />
     <ClCompile Include="..\..\ext\native\ui\viewgroup.cpp" />
     <ClCompile Include="..\..\ext\native\util\hash\hash.cpp" />

UWP/NativeUWP/NativeUWP.vcxproj.filters

@@ -154,6 +154,9 @@
     <ClCompile Include="..\..\ext\native\ui\ui_screen.cpp">
       <Filter>ui</Filter>
     </ClCompile>
+    <ClCompile Include="..\..\ext\native\ui\ui_tween.cpp">
+      <Filter>ui</Filter>
+    </ClCompile>
     <ClCompile Include="..\..\ext\native\ui\view.cpp">
       <Filter>ui</Filter>
     </ClCompile>
@@ -590,6 +593,9 @@
     <ClInclude Include="..\..\ext\native\ui\ui_screen.h">
       <Filter>ui</Filter>
     </ClInclude>
+    <ClInclude Include="..\..\ext\native\ui\ui_tween.h">
+      <Filter>ui</Filter>
+    </ClInclude>
     <ClInclude Include="..\..\ext\native\ui\view.h">
       <Filter>ui</Filter>
     </ClInclude>

ext/native/Android.mk

@@ -91,6 +91,7 @@ LOCAL_SRC_FILES :=\
     ui/viewgroup.cpp \
     ui/ui.cpp \
     ui/ui_screen.cpp \
+    ui/ui_tween.cpp \
     ui/ui_context.cpp \
     ui/screen.cpp \
     util/text/utf8.cpp \

ext/native/native.vcxproj

@@ -285,6 +285,7 @@
     <ClInclude Include="ui\ui.h" />
     <ClInclude Include="ui\ui_context.h" />
     <ClInclude Include="ui\ui_screen.h" />
+    <ClInclude Include="ui\ui_tween.h" />
     <ClInclude Include="ui\view.h" />
     <ClInclude Include="ui\viewgroup.h" />
     <ClInclude Include="util\random\rng.h" />
@@ -752,6 +753,7 @@
     <ClCompile Include="ui\ui.cpp" />
     <ClCompile Include="ui\ui_context.cpp" />
     <ClCompile Include="ui\ui_screen.cpp" />
+    <ClCompile Include="ui\ui_tween.cpp" />
     <ClCompile Include="ui\view.cpp" />
     <ClCompile Include="ui\viewgroup.cpp" />
     <ClCompile Include="util\hash\hash.cpp" />

ext/native/native.vcxproj.filters

@@ -329,6 +329,9 @@
     <ClInclude Include="thin3d\DataFormat.h">
       <Filter>thin3d</Filter>
     </ClInclude>
+    <ClInclude Include="ui\ui_tween.h">
+      <Filter>ui</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="gfx\gl_debug_log.cpp">
@@ -796,6 +799,9 @@
     <ClCompile Include="thin3d\VulkanRenderManager.cpp">
       <Filter>thin3d</Filter>
     </ClCompile>
+    <ClCompile Include="ui\ui_tween.cpp">
+      <Filter>ui</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <Filter Include="gfx">

ext/native/ui/ui_tween.cpp

@@ -0,0 +1,31 @@
+#include "base/colorutil.h"
+#include "ui/ui_tween.h"
+#include "ui/view.h"
+
+namespace UI {
+
+uint32_t ColorTween::Current() {
+	return colorBlend(to_, from_, Position());
+}
+
+void TextColorTween::Apply(View *view) {
+	// TODO: No validation without RTTI?
+	TextView *tv = (TextView *)view;
+	tv->SetTextColor(Current());
+}
+
+void VisibilityTween::Apply(View *view) {
+	view->SetVisibility(Current());
+}
+
+Visibility VisibilityTween::Current() {
+	// Prefer V_VISIBLE over V_GONE/V_INVISIBLE.
+	float p = Position();
+	if (from_ == V_VISIBLE && p < 1.0f)
+		return from_;
+	if (to_ == V_VISIBLE && p > 0.0f)
+		return to_;
+	return p >= 1.0f ? to_ : from_;
+}
+
+}  // namespace

ext/native/ui/ui_tween.h

@@ -0,0 +1,118 @@
+#pragma once
+
+#include <algorithm>
+#include <cstdint>
+#include "base/timeutil.h"
+#include "ui/view.h"
+
+namespace UI {
+
+// This is the class to use in Update().
+class Tween {
+public:
+	Tween(float duration, float (*curve)(float)) : duration_(duration), curve_(curve) {
+		start_ = time_now();
+	}
+	virtual ~Tween() {
+	}
+
+	// Actually apply the tween to a view.
+	virtual void Apply(View *view) = 0;
+
+	bool Finished() {
+		return time_now() >= start_ + duration_;
+	}
+
+protected:
+	float DurationOffset() {
+		return time_now() - start_;
+	}
+
+	float Position() {
+		return curve_(std::min(1.0f, DurationOffset() / duration_));
+	}
+
+	float start_;
+	float duration_;
+	float (*curve_)(float);
+};
+
+// This is the class all tweens inherit from.  Shouldn't be used directly, see below.
+template <typename Value>
+class TweenBase: public Tween {
+public:
+	TweenBase(Value from, Value to, float duration, float (*curve)(float) = [](float f) { return f; })
+		: Tween(duration, curve), from_(from), to_(to) {
+	}
+
+	// Use this to change the destination value.
+	// Useful when a state flips while the tween is half-way through.
+	void Divert(const Value &newTo) {
+		const Value newFrom = Current();
+
+		// Are we already part way through another transition?
+		if (!Finished()) {
+			if (newTo == to_) {
+				// Already on course.  Don't change.
+			} else if (newTo == from_) {
+				// Reversing, adjust start_ to be smooth from the current value.
+				float newOffset = duration_ - DurationOffset();
+				start_ = time_now() - newOffset;
+			} else {
+				// Otherwise, start over.
+				start_ = time_now();
+			}
+		} else {
+			// Already finished, so restart.
+			start_ = time_now();
+		}
+
+		from_ = newFrom;
+		to_ = newTo;
+	}
+
+	// Stop animating the value.
+	void Stop() {
+		Reset(Current());
+	}
+
+	// Use when the value is explicitly reset.  Implicitly stops the tween.
+	void Reset(const Value &newFrom) {
+		from_ = newFrom;
+		to_ = newFrom;
+	}
+
+protected:
+	virtual Value Current() = 0;
+
+	Value from_;
+	Value to_;
+};
+
+// Generic - subclass this for specific color handling.
+class ColorTween : public TweenBase<uint32_t> {
+public:
+	using TweenBase::TweenBase;
+
+protected:
+	uint32_t Current() override;
+};
+
+class TextColorTween : public ColorTween {
+public:
+	using ColorTween::ColorTween;
+
+	void Apply(View *view) override;
+};
+
+class VisibilityTween : public TweenBase<Visibility> {
+public:
+	using TweenBase::TweenBase;
+
+	void Apply(View *view) override;
+
+protected:
+	Visibility Current() override;
+};
+
+}  // namespace