Better mechanism to fade out the side bar when not on EmuScreen

Common/Math/math_util.h

@@ -67,6 +67,13 @@ inline T clamp_value(T val, T floor, T cap) {
 		return val;
 }
 
+// Very common operation, familiar from shaders.
+inline float saturatef(float x) {
+	if (x > 1.0f) return 1.0f;
+	else if (x < 0.0f) return 0.0f;
+	else return x;
+}
+
 #define ROUND_UP(x, a)   (((x) + (a) - 1) & ~((a) - 1))
 #define ROUND_DOWN(x, a) ((x) & ~((a) - 1))
 

Common/System/OSD.cpp

@@ -3,6 +3,7 @@
 #include "Common/System/OSD.h"
 #include "Common/TimeUtil.h"
 #include "Common/Log.h"
+#include "Common/Math/math_util.h"
 
 OnScreenDisplay g_OSD;
 
@@ -50,6 +51,17 @@ std::vector<OnScreenDisplay::ProgressBar> OnScreenDisplay::ProgressBars() {
 	return bars_;  // makes a copy.
 }
 
+void OnScreenDisplay::NudgeSidebar() {
+	sideBarShowTime_ = time_now_d();
+}
+
+float OnScreenDisplay::SidebarAlpha() const {
+	double timeSinceNudge = time_now_d() - sideBarShowTime_;
+
+	// Fade out in 1/4 second, 0.1s after the last nudge.
+	return saturatef(1.0f - ((float)timeSinceNudge - 0.1f) * 4.0f);
+}
+
 void OnScreenDisplay::Show(OSDType type, const std::string &text, const std::string &text2, const std::string &icon, float duration_s, const char *id) {
 	// Automatic duration based on type.
 	if (duration_s <= 0.0f) {

Common/System/OSD.h

@@ -53,9 +53,9 @@ public:
 	void SetProgressBar(std::string id, std::string &&message, int minValue, int maxValue, int progress);
 	void RemoveProgressBar(std::string id);
 
-	// Show stuff on the side or now, like the challenge indicators etc.
-	void SetShowSidebar(bool show) { showSidebar_ = show; }
-	bool ShowSidebar() const { return showSidebar_; }
+	// Call every frame to keep the sidebar visible. Otherwise it'll fade out.
+	void NudgeSidebar();
+	float SidebarAlpha() const;
 
 	// Fades out everything related to achievements. Should be used on game shutdown.
 	void ClearAchievementStuff();
@@ -92,7 +92,7 @@ private:
 	std::vector<ProgressBar> bars_;
 	std::mutex mutex_;
 
-	bool showSidebar_ = true;
+	double sideBarShowTime_ = 0.0;
 };
 
 extern OnScreenDisplay g_OSD;

UI/EmuScreen.cpp

@@ -197,7 +197,6 @@ EmuScreen::EmuScreen(const Path &filename)
 	// Usually, we don't want focus movement enabled on this screen, so disable on start.
 	// Only if you open chat or dev tools do we want it to start working.
 	UI::EnableFocusMovement(false);
-	g_OSD.SetShowSidebar(true);
 }
 
 bool EmuScreen::bootAllowStorage(const Path &filename) {
@@ -1480,6 +1479,8 @@ void EmuScreen::render() {
 	if (!thin3d)
 		return;  // shouldn't really happen but I've seen a suspicious stack trace..
 
+	g_OSD.NudgeSidebar();
+
 	if (invalid_) {
 		// Loading, or after shutdown?
 		if (loadingTextView_->GetVisibility() == UI::V_VISIBLE)

UI/OnScreenDisplay.cpp

@@ -230,7 +230,9 @@ void OnScreenMessagesView::Draw(UIContext &dc) {
 
 	const float fadeoutCoef = 1.0f / OnScreenDisplay::FadeoutTime();
 
-	if (g_OSD.ShowSidebar()) {
+	float sidebarAlpha = g_OSD.SidebarAlpha();
+
+	if (sidebarAlpha > 0.0f) {
 		// Draw side entries. Top entries should apply on top of them if there's a collision, so drawing
 		// these first makes sense.
 		const std::vector<OnScreenDisplay::Entry> sideEntries = g_OSD.SideEntries();
@@ -268,6 +270,7 @@ void OnScreenMessagesView::Draw(UIContext &dc) {
 				continue;
 			}
 			Bounds b(10.0f, y, tw, th);
+			// We don't multiply in sidebarAlpha here because it shouldn't drive the below animation.
 			float alpha = Clamp((float)(entry.endTime - now) * fadeoutCoef, 0.0f, 1.0f);
 			// OK, render the thing.
 
@@ -275,11 +278,11 @@ void OnScreenMessagesView::Draw(UIContext &dc) {
 			case OSDType::ACHIEVEMENT_PROGRESS:
 			case OSDType::ACHIEVEMENT_CHALLENGE_INDICATOR:
 			{
-				RenderAchievement(dc, achievement, style, b, alpha, entry.startTime, now);
+				RenderAchievement(dc, achievement, style, b, alpha * sidebarAlpha, entry.startTime, now);
 				break;
 			}
 			case OSDType::LEADERBOARD_TRACKER:
-				RenderLeaderboardTracker(dc, b, entry.text, alpha);
+				RenderLeaderboardTracker(dc, b, entry.text, alpha * sidebarAlpha);
 				break;
 			default:
 				continue;

UI/PauseScreen.cpp

@@ -263,12 +263,10 @@ void GamePauseScreen::update() {
 
 GamePauseScreen::GamePauseScreen(const Path &filename)
 	: UIDialogScreenWithGameBackground(filename) {
-	g_OSD.SetShowSidebar(false);
 }
 
 GamePauseScreen::~GamePauseScreen() {
 	__DisplaySetWasPaused();
-	g_OSD.SetShowSidebar(true);
 }
 
 void GamePauseScreen::CreateSavestateControls(UI::LinearLayout *leftColumnItems, bool vertical) {