CTRL+SCROLL -> layer up/down

3 files changed, 31 insertions, 2 deletions

diff --git a/src/main_gui.cpp b/src/main_gui.cpp
index 60cadfb31..6a84d778b 100644
--- a/src/main_gui.cpp
+++ b/src/main_gui.cpp
@@ -34,6 +34,9 @@
 #include "error.h"
 #include "news_gui.h"
 #include "misc_cmd.h"
+#include "gfx_func.h"
+#include "layer_gui.h"
+#include "landscape.h"
 
 #include "saveload/saveload.h"
 
@@ -153,6 +156,22 @@ void ZoomInOrOutToCursorWindow(bool in, Window *w)
 	}
 }
 
+void LayerUpOrDownToCursorWindow(bool in, Window *w)
+{
+	assert(w != NULL);
+
+	if (_game_mode != GM_MENU) {
+		int layer = calculateLayer(w->viewport) + (in ? -1 : 1);
+		if ((layer < 0) || (layer >= LayerCount())) return;
+
+		Point pt = RemapCoords(0, (in ? -1 : 1) * LayerSizeY() * TILE_SIZE, 0);
+		w->viewport->dest_scrollpos_x += pt.x;
+		w->viewport->dest_scrollpos_y += pt.y;
+		w->InvalidateData();
+
+	}
+}
+
 void FixTitleGameZoom(int zoom_adjust)
 {
 	if (_game_mode != GM_MENU) return;
@@ -422,7 +441,11 @@ struct MainWindow : Window
 	void OnMouseWheel(int wheel) override
 	{
 		if (_settings_client.gui.scrollwheel_scrolling != 2) {
-			ZoomInOrOutToCursorWindow(wheel < 0, this);
+			if (_ctrl_pressed) {
+				LayerUpOrDownToCursorWindow(wheel < 0, this);
+			} else {
+				ZoomInOrOutToCursorWindow(wheel < 0, this);
+			}
 		}
 	}
 
diff --git a/src/viewport_func.h b/src/viewport_func.h
index 58e1706eb..d8f2036aa 100644
--- a/src/viewport_func.h
+++ b/src/viewport_func.h
@@ -31,6 +31,7 @@ bool MarkAllViewportsDirty(int left, int top, int right, int bottom);
 
 bool DoZoomInOutWindow(ZoomStateChange how, Window *w);
 void ZoomInOrOutToCursorWindow(bool in, Window * w);
+void LayerUpOrDownToCursorWindow(bool in, Window * w);
 Point GetTileZoomCenterWindow(bool in, Window * w);
 void FixTitleGameZoom(int zoom_adjust = 0);
 void HandleZoomMessage(Window *w, const Viewport *vp, byte widget_zoom_in, byte widget_zoom_out);
diff --git a/src/viewport_gui.cpp b/src/viewport_gui.cpp
index 5047f04f3..3c02f9ab8 100644
--- a/src/viewport_gui.cpp
+++ b/src/viewport_gui.cpp
@@ -14,6 +14,7 @@
 #include "strings_func.h"
 #include "zoom_func.h"
 #include "window_func.h"
+#include "gfx_func.h"
 
 #include "widgets/viewport_widget.h"
 
@@ -137,7 +138,11 @@ public:
 	void OnMouseWheel(int wheel) override
 	{
 		if (_settings_client.gui.scrollwheel_scrolling != 2) {
-			ZoomInOrOutToCursorWindow(wheel < 0, this);
+			if (_ctrl_pressed) {
+				LayerUpOrDownToCursorWindow(wheel < 0, this);
+			} else {
+				ZoomInOrOutToCursorWindow(wheel < 0, this);
+			}
 		}
 	}