move pan input into an InputMapper

src/ui/InputMapper.h

@@ -0,0 +1,44 @@
+#pragma once
+
+#include "WorldCamera.h"
+
+class QKeyEvent;
+
+// Turns raw key events into the game's semantic actions and publishes them
+// (REQ-UI-HOTKEYS). Widgets react to the action, never to the key, so the two can
+// be rebound independently later; the bindings themselves are still hard-coded
+// here for now.
+//
+// Two output shapes, chosen by the nature of the action rather than by taste:
+//
+//  * Discrete actions — one press, one thing happens — fire an event as they
+//    always have.
+//  * Continuous actions, currently just panning, are held state. They also travel
+//    as events, but level-triggered ones carrying the complete current value (see
+//    PanDirectionChangedEvent), so a receiver never has to reconstruct state from
+//    edges.
+//
+// Holding the state here rather than in the widgets is what makes releaseAll()
+// possible: one call clears every held action at once, which is how a lost key-up
+// (focus moving to a modal mid-pan) stops being a stuck input.
+class InputMapper
+{
+public:
+    // Both return true when the key was consumed; the caller passes anything else
+    // on to its base class so unrelated shortcuts keep working.
+    bool handleKeyPress(QKeyEvent* event);
+    bool handleKeyRelease(QKeyEvent* event);
+
+    // Drops all held-key state, publishing the resulting change. Call when the
+    // receiving widget can no longer expect key-up events.
+    void releaseAll();
+
+private:
+    // Recomputes the pan direction from the held keys and publishes it if it
+    // changed. Holding both keys cancels out.
+    void updatePanDirection();
+
+    bool         m_panLeftHeld   = false;
+    bool         m_panRightHeld  = false;
+    PanDirection m_panDirection  = PanDirection::None;
+};