From 7c4fb8b08404d4153211d5d38bb08dbc4c3ad8bc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Henrik=20Rydg=C3=A5rd?= <hrydgard@gmail.com>
Date: Thu, 16 Apr 2026 13:15:22 -0600
Subject: [PATCH] Add basic modifier key tracking to UIScreen

---
 Common/Input/InputState.h |  6 ++++++
 Common/UI/UIScreen.cpp    | 32 ++++++++++++++++++++++++++++++++
 Common/UI/UIScreen.h      | 17 +++++++++++++++++
 3 files changed, 55 insertions(+)

diff --git a/Common/Input/InputState.h b/Common/Input/InputState.h
index bdbec037d7..c48737cb84 100644
--- a/Common/Input/InputState.h
+++ b/Common/Input/InputState.h
@@ -171,7 +171,13 @@ enum class KeyInputFlags {
 	HAS_WHEEL_DELTA = 1 << 2,
 	IS_REPEAT = 1 << 3,
 	CHAR = 1 << 4,  // Unicode character input. Cannot detect keyups of these so KeyInputFlags::DOWN and KeyInputFlags::UP are zero when this is set.
+
+	// NOTE: These are only available in sync input.
+	MOD_CTRL = 1 << 5,
+	MOD_SHIFT = 1 << 6,
+	MOD_ALT = 1 << 7,
 };
+
 ENUM_CLASS_BITOPS(KeyInputFlags);
 
 struct KeyInput {
diff --git a/Common/UI/UIScreen.cpp b/Common/UI/UIScreen.cpp
index 8566822af6..f223c02185 100644
--- a/Common/UI/UIScreen.cpp
+++ b/Common/UI/UIScreen.cpp
@@ -130,9 +130,41 @@ bool UIScreen::UnsyncKey(const KeyInput &key) {
 		}
 	}
 
+	// Track modifier keys.
+	if (key.flags & KeyInputFlags::DOWN) {
+		switch (key.keyCode) {
+		case NKCODE_CTRL_LEFT: modifiersPressed_ |= Modifier::LCTRL; break;
+		case NKCODE_CTRL_RIGHT: modifiersPressed_ |= Modifier::RCTRL; break;
+		case NKCODE_SHIFT_LEFT: modifiersPressed_ |= Modifier::LSHIFT; break;
+		case NKCODE_SHIFT_RIGHT: modifiersPressed_ |= Modifier::RSHIFT; break;
+		case NKCODE_ALT_LEFT: modifiersPressed_ |= Modifier::LALT; break;
+		case NKCODE_ALT_RIGHT: modifiersPressed_ |= Modifier::RALT; break;
+		}
+	}
+	if (key.flags & KeyInputFlags::UP) {
+		switch (key.keyCode) {
+		case NKCODE_CTRL_LEFT: modifiersPressed_ &= ~Modifier::LCTRL; break;
+		case NKCODE_CTRL_RIGHT: modifiersPressed_ &= ~Modifier::RCTRL; break;
+		case NKCODE_SHIFT_LEFT: modifiersPressed_ &= ~Modifier::LSHIFT; break;
+		case NKCODE_SHIFT_RIGHT: modifiersPressed_ &= ~Modifier::RSHIFT; break;
+		case NKCODE_ALT_LEFT: modifiersPressed_ &= ~Modifier::LALT; break;
+		case NKCODE_ALT_RIGHT: modifiersPressed_ &= ~Modifier::RALT; break;
+		}
+	}
+
 	QueuedEvent ev{};
 	ev.type = QueuedEventType::KEY;
 	ev.key = key;
+
+	if (modifiersPressed_ & (Modifier::LCTRL | Modifier::RCTRL)) {
+		ev.key.flags |= KeyInputFlags::MOD_CTRL;
+	}
+	if (modifiersPressed_ & (Modifier::LSHIFT | Modifier::RSHIFT)) {
+		ev.key.flags |= KeyInputFlags::MOD_SHIFT;
+	}
+	if (modifiersPressed_ & (Modifier::LALT | Modifier::RALT)) {
+		ev.key.flags |= KeyInputFlags::MOD_ALT;
+	}
 	std::lock_guard<std::mutex> guard(eventQueueLock_);
 	eventQueue_.push_back(ev);
 	return retval;
diff --git a/Common/UI/UIScreen.h b/Common/UI/UIScreen.h
index e319b097d2..8732752067 100644
--- a/Common/UI/UIScreen.h
+++ b/Common/UI/UIScreen.h
@@ -32,6 +32,17 @@ struct QueuedEvent {
 	};
 };
 
+enum class Modifier {
+	NONE = 0,
+	LCTRL = 1,
+	RCTRL = 2,
+	LSHIFT = 4,
+	RSHIFT = 8,
+	LALT = 16,
+	RALT = 32,
+};
+ENUM_CLASS_BITOPS(Modifier);
+
 class UIScreen : public Screen {
 public:
 	UIScreen();
@@ -61,6 +72,10 @@ public:
 
 	virtual UI::Margins RootMargins() const { return UI::Margins(0); }
 
+	virtual void focusChanged(ScreenFocusChange focusChange) {
+		modifiersPressed_ = Modifier::NONE;
+	}
+
 protected:
 	virtual void CreateViews() = 0;
 
@@ -90,6 +105,8 @@ protected:
 private:
 	std::mutex eventQueueLock_;
 	std::deque<QueuedEvent> eventQueue_;
+
+	Modifier modifiersPressed_{};
 };
 
 class UIDialogScreen : public UIScreen {