Support scroll-rotate in Atlas

Split mouse wheel scroll handling into horizontal and vertical. Keep
vertical scroll for zooming and use horizontal to rotate around the y
axis replicating the behaviour of the main game.

Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>

source/tools/atlas/AtlasUI/ScenarioEditor/ScenarioEditor.cpp

@@ -272,11 +272,19 @@ private:
 		// Global mouse event handlers (for camera motion)
 
 		if (evt.GetWheelRotation())
+		{
+			if (evt.GetWheelAxis() == wxMOUSE_WHEEL_VERTICAL)
 			{
 				float speed = 16.f * ScenarioEditor::GetSpeedModifier();
 				POST_MESSAGE(SmoothZoom, (eRenderView::GAME, evt.GetWheelRotation() * speed / evt.GetWheelDelta()));
 			}
 			else
+			{
+				float speed = ScenarioEditor::GetSpeedModifier();
+				POST_MESSAGE(RotateY, (evt.GetWheelRotation() * speed / evt.GetWheelDelta()));
+			}
+		}
+		else
 		{
 			if (evt.MiddleIsDown())
 			{

source/tools/atlas/GameInterface/GameLoop.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2012 Wildfire Games.
+/* Copyright (C) 2026 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -41,7 +41,8 @@ struct GameLoopState
 	struct Input
 	{
 		float scrollSpeed[6]; // [fwd, bwd, left, right, cw-rotation, ccw-rotation]. 0.0f for disabled.
-		float zoomDelta;
+		float zoomDelta{0.f};
+		float rotateDelta{0.f};
 	} input;
 };
 

source/tools/atlas/GameInterface/Handlers/CameraCtrlHandlers.cpp

@@ -199,6 +199,14 @@ MESSAGEHANDLER(RotateAround)
 	}
 }
 
+MESSAGEHANDLER(RotateY)
+{
+	if (!g_Game || g_Game->GetView()->GetCinema()->IsPlaying())
+		return;
+
+	g_AtlasGameLoop->input.rotateDelta = msg->angle;
+}
+
 MESSAGEHANDLER(LookAt)
 {
 	// TODO: different camera depending on msg->view

source/tools/atlas/GameInterface/InputProcessor.cpp

@@ -117,6 +117,35 @@ bool InputProcessor::ProcessInput(GameLoopState* state)
 		moved = true;
 	}
 
+	if (state->input.rotateDelta != 0.f)
+	{
+		float angle{4 * state->realFrameLength};
+		if (input.rotateDelta > 0 )
+		{
+			if (angle > input.rotateDelta)
+			{
+				angle = input.rotateDelta;
+				input.rotateDelta = 0.f;
+			}
+			else
+				input.rotateDelta -= angle;
+		}
+		else
+		{
+			angle *= -1;
+			if (angle < input.rotateDelta)
+			{
+				angle = input.rotateDelta;
+				input.rotateDelta = 0.f;
+			}
+			else
+				input.rotateDelta -= angle;
+		}
+		Rotate(camera, angle);
+
+		moved = true;
+	}
+
 	if (moved)
 	{
 		camera.UpdateFrustum();

source/tools/atlas/GameInterface/Messages.h

@@ -456,6 +456,10 @@ MESSAGE(RotateAround,
 		((Position, pos))
 		);
 
+MESSAGE(RotateY,
+		((float, angle))
+		);
+
 MESSAGE(LookAt,
 		((int, view)) // eRenderView
 		((Position, pos))