Support smooth scrolling (part 2)

Fix scrolling when smooth scrolling is enabled /
allow to scroll smoothly for:
- canvas palette
- node selection in path tool
- selection cycling in select tool while holding Alt key
- spraying in spray tool with mouse wheel
- adjusting color by scrolling in lower left stroke/fill fields

1 files changed, 4 insertions, 1 deletions

diff --git a/src/ui/widget/rotateable.cpp b/src/ui/widget/rotateable.cpp
index 64b37a07f..6c2056da1 100644
--- a/src/ui/widget/rotateable.cpp
+++ b/src/ui/widget/rotateable.cpp
@@ -34,7 +34,7 @@ Rotateable::Rotateable():
     signal_button_press_event().connect(sigc::mem_fun(*this, &Rotateable::on_click));
     signal_motion_notify_event().connect(sigc::mem_fun(*this, &Rotateable::on_motion));
     signal_button_release_event().connect(sigc::mem_fun(*this, &Rotateable::on_release));
-    gtk_widget_add_events(GTK_WIDGET(gobj()), GDK_SCROLL_MASK);
+    gtk_widget_add_events(GTK_WIDGET(gobj()), GDK_SCROLL_MASK | GDK_SMOOTH_SCROLL_MASK);
     signal_scroll_event().connect(sigc::mem_fun(*this, &Rotateable::on_scroll));
 
 }
@@ -139,6 +139,9 @@ bool Rotateable::on_scroll(GdkEventScroll* event)
         change = 1.0;
     } else if (event->direction == GDK_SCROLL_DOWN) {
         change = -1.0;
+    } else if (event->direction == GDK_SCROLL_SMOOTH) {
+        double delta_y_clamped = CLAMP(event->delta_y, -1.0, 1.0); // values > 1 result in excessive changes
+        change = 1.0 * -delta_y_clamped;
     } else {
         return FALSE;
     }