UI: Make PopupScreens animate in just a bit.

ext/native/math/curves.cpp

@@ -45,6 +45,27 @@ float ease(int t, int fadeLength)
 	return ease((float)t / (float)fadeLength);
 }
 
+float bezierEaseInOut(float val) {
+	static const float x1 = 0.42f, x2 = 0.58f;
+	static const float a = 1.0f - 3.0f * x2 + 3.0f * x1;
+	static const float b = 3.0f * x2 - 6.0f * x1;
+	static const float c = 3.0f * x1;
+
+	float guess = val;
+	for (int i = 0; i < 4; ++i) {
+		float slope = 3.0f * a * guess * guess + 2.0f * b * guess + c;
+		if (slope == 0.0f) {
+			break;
+		}
+
+		float x = ((a * guess + b) * guess + c) * guess - val;
+		guess -= x / slope;
+	}
+
+
+	return (-2.0f * guess + 3.0f) * guess * guess;
+}
+
 float sawtooth(int t, int period) {
 	return (t % period) * (1.0f / (period - 1));
 }

ext/native/math/curves.h

@@ -14,6 +14,8 @@ float linearOut(int t, int fadeInLength);
 float ease(float val);
 float ease(int t, int fadeLength);
 
+float bezierEaseInOut(float val);
+
 // need a bouncy ease
 
 // waveforms [0, 1]

ext/native/ui/ui_screen.cpp

@@ -1,7 +1,9 @@
+#include <algorithm>
 #include <map>
 #include "base/display.h"
 #include "input/input_state.h"
 #include "input/keycodes.h"
+#include "math/curves.h"
 #include "ui/ui_screen.h"
 #include "ui/ui_context.h"
 #include "ui/screen.h"
@@ -213,6 +215,8 @@ PopupScreen::PopupScreen(std::string title, std::string button1, std::string but
 		button1_ = di->T(button1.c_str());
 	if (!button2.empty())
 		button2_ = di->T(button2.c_str());
+
+	alpha_ = 0.0f;
 }
 
 bool PopupScreen::touch(const TouchInput &touch) {
@@ -238,6 +242,24 @@ bool PopupScreen::key(const KeyInput &key) {
 	return UIDialogScreen::key(key);
 }
 
+void PopupScreen::update() {
+	UIDialogScreen::update();
+
+	static const int FRAMES_LEAD_IN = 6;
+	if (++frames_ < FRAMES_LEAD_IN) {
+		float leadIn = bezierEaseInOut(frames_ * (1.0f / (float)FRAMES_LEAD_IN));
+		alpha_ = leadIn;
+		scale_.x = 0.9f + leadIn * 0.1f;
+		scale_.y =  0.9f + leadIn * 0.1f;
+		translation_.y = -dp_yres * (1.0f - leadIn) * 0.5f;
+	} else {
+		alpha_ = 1.0f;
+		scale_.x = 1.0f;
+		scale_.y = 1.0f;
+		translation_.y = 0.0f;
+	}
+}
+
 void PopupScreen::CreateViews() {
 	using namespace UI;
 
@@ -255,6 +277,8 @@ void PopupScreen::CreateViews() {
 	root_->Add(box_);
 	box_->SetBG(UI::Drawable(0xFF303030));
 	box_->SetHasDropShadow(true);
+	// Since we scale a bit, make the dropshadow bleed past the edges.
+	box_->SetDropShadowExpand(std::max(dp_xres, dp_yres));
 
 	View *title = new PopupHeader(title_);
 	box_->Add(title);

ext/native/ui/ui_screen.h

@@ -76,6 +76,8 @@ protected:
 	virtual bool ShowButtons() const { return true; }
 	virtual void OnCompleted(DialogResult result) {}
 
+	virtual void update() override;
+
 private:
 	UI::EventReturn OnOK(UI::EventParams &e);
 	UI::EventReturn OnCancel(UI::EventParams &e);
@@ -85,6 +87,8 @@ private:
 	std::string title_;
 	std::string button1_;
 	std::string button2_;
+
+	int frames_ = 0;
 };
 
 class ListPopupScreen : public PopupScreen {

ext/native/ui/viewgroup.cpp

@@ -118,8 +118,8 @@ void ViewGroup::Axis(const AxisInput &input) {
 void ViewGroup::Draw(UIContext &dc) {
 	if (hasDropShadow_) {
 		// Darken things behind.
-		dc.FillRect(UI::Drawable(0x60000000), dc.GetBounds());
-		float dropsize = 30;
+		dc.FillRect(UI::Drawable(0x60000000), dc.GetBounds().Expand(dropShadowExpand_));
+		float dropsize = 30.0f;
 		dc.Draw()->DrawImage4Grid(dc.theme->dropShadow4Grid,
 			bounds_.x - dropsize, bounds_.y,
 			bounds_.x2() + dropsize, bounds_.y2()+dropsize*1.5, 0xDF000000, 3.0f);

ext/native/ui/viewgroup.h

@@ -69,6 +69,7 @@ public:
 	View *GetViewByIndex(int index) { return views_[index]; }
 	int GetNumSubviews() const { return (int)views_.size(); }
 	void SetHasDropShadow(bool has) { hasDropShadow_ = has; }
+	void SetDropShadowExpand(float s) { dropShadowExpand_ = s; }
 
 	void Lock() { modifyLock_.lock(); }
 	void Unlock() { modifyLock_.unlock(); }
@@ -81,6 +82,7 @@ protected:
 	std::vector<View *> views_;
 	View *defaultFocusView_;
 	Drawable bg_;
+	float dropShadowExpand_ = 0.0f;
 	bool hasDropShadow_;
 	bool clip_;
 };