Fix special handling of 'zoom vertical' scroll wheel modifier key.

gtkmm2ext/keyboard.cc has a special case to emit a signal on the key-up of
the modifier key used to adjust track heights in conjunction with the
scroll wheel, so that the same track continues to be resized even when
it's shrunk to no longer be under the mouse cursor. However, this code
assumed that the modifier key for this was <Shift>.

Fix it to use the event->state bit corresponding to
ScrollZoomVerticalModifier instead, and rename the relevant functions to
clarify that it's the 'zoom vertical' modifier key they're dealing with.

Partially fixes #5610.

2 files changed, 8 insertions, 5 deletions

diff --git a/libs/gtkmm2ext/gtkmm2ext/keyboard.h b/libs/gtkmm2ext/gtkmm2ext/keyboard.h
index 84988e1525..2c6b026a42 100644
--- a/libs/gtkmm2ext/gtkmm2ext/keyboard.h
+++ b/libs/gtkmm2ext/gtkmm2ext/keyboard.h
@@ -164,7 +164,7 @@ class Keyboard : public sigc::trackable, PBD::Stateful
 	    }
 	};
 
-	sigc::signal0<void> ShiftReleased;
+	sigc::signal0<void> ZoomVerticalModifierReleased;
 
   protected:
 	static Keyboard* _the_keyboard;
diff --git a/libs/gtkmm2ext/keyboard.cc b/libs/gtkmm2ext/keyboard.cc
index f694471d9a..5087f61a23 100644
--- a/libs/gtkmm2ext/keyboard.cc
+++ b/libs/gtkmm2ext/keyboard.cc
@@ -248,12 +248,15 @@ Keyboard::snooper (GtkWidget *widget, GdkEventKey *event)
 		keyval = event->keyval;
 	}
 
-	if (keyval == GDK_Shift_L) {
+	if (event->state & ScrollZoomVerticalModifier) {
 		/* There is a special and rather hacky situation in Editor which makes
-		   it useful to know when a shift key has been released, so emit a signal
-		   here (see Editor::_stepping_axis_view)
+		   it useful to know when the modifier key for vertical zoom has been
+		   released, so emit a signal here (see Editor::_stepping_axis_view).
+		   Note that the state bit for the modifier key is set for the key-up
+		   event when the modifier is released, but not the key-down when it
+		   is pressed, so we get here on key-up, which is what we want.
 		*/
-		ShiftReleased (); /* EMIT SIGNAL */
+		ZoomVerticalModifierReleased (); /* EMIT SIGNAL */
 	}
 
 	if (event->type == GDK_KEY_PRESS) {