Factor out the mouse wheel forwarding code in the audio display to a function used by the audio display, video display and subtitles grid, and make it actually work

Originally committed to SVN as r5781.

aegisub/src/audio_display.cpp

@@ -1003,30 +1003,8 @@ void AudioDisplay::OnMouseEvent(wxMouseEvent& event)
 	// Check for mouse wheel scrolling
 	if (event.GetWheelRotation() != 0)
 	{
-		// First check if the cursor is inside or outside the display.
-		// If it's outside, we want to send the event to the control it's over instead.
-		/// @todo Factor this into a reusable function
-		{
-			wxWindow *targetwindow = wxFindWindowAtPoint(event.GetPosition());
-			if (targetwindow && targetwindow != this)
-			{
-				wxWindow *parent = GetParent();
-				while (parent && parent != targetwindow)
-				{
-					parent = parent->GetParent();
-				}
-
-				// Don't forward scroll wheel events to parents of this as the
-				// target is sometimes reported as a parent even when the mouse
-				// is over the audio display
-				if (!parent)
-				{
-					targetwindow->GetEventHandler()->ProcessEvent(event);
-					event.Skip(false);
+		if (!ForwardMouseWheelEvent(this, event))
 			return;
-				}
-			}
-		}
 
 		bool zoom = event.CmdDown();
 		if (OPT_GET("Audio/Wheel Default to Zoom")->GetBool()) zoom = !zoom;

aegisub/src/base_grid.cpp

@@ -714,8 +714,10 @@ void BaseGrid::OnMouseEvent(wxMouseEvent &event) {
 
 	// Mouse wheel
 	if (event.GetWheelRotation() != 0) {
+		if (ForwardMouseWheelEvent(this, event)) {
 			int step = 3 * event.GetWheelRotation() / event.GetWheelDelta();
 			ScrollTo(yPos - step);
+		}
 		return;
 	}
 

aegisub/src/utils.cpp

@@ -448,4 +448,18 @@ void RestartAegisub() {
 #endif
 }
 
+bool ForwardMouseWheelEvent(wxWindow *source, wxMouseEvent &evt) {
+	wxWindow *target = wxFindWindowAtPoint(wxGetMousePosition());
+	if (!target || target == source) return true;
 
+	// If the mouse is over a parent of the source window just pretend it's
+	// over the source window, so that the mouse wheel works on borders and such
+	wxWindow *parent = source->GetParent();
+	while (parent && parent != target) parent = parent->GetParent();
+	if (parent == target) return true;
+
+	// Otherwise send it to the new target
+	target->GetEventHandler()->ProcessEvent(evt);
+	evt.Skip(false);
+	return false;
+}

aegisub/src/utils.h

@@ -69,6 +69,12 @@ int AegiStringToFix(const wxString &str,size_t decimalPlaces,int start=0,int end
 wxIcon BitmapToIcon(wxBitmap bmp);
 void RestartAegisub();
 
+/// Forward a mouse wheel event to the window under the mouse if needed
+/// @param source The initial target of the wheel event
+/// @param evt The event
+/// @return Should the calling code process the event?
+bool ForwardMouseWheelEvent(wxWindow *source, wxMouseEvent &evt);
+
 
 /// @brief Templated abs() function
 template <typename T> T tabs(T x) { return x < 0 ? -x : x; }

aegisub/src/video_display.cpp

@@ -65,6 +65,7 @@
 #include "ass_file.h"
 #include "main.h"
 #include "threaded_frame_source.h"
+#include "utils.h"
 #include "video_out_gl.h"
 #include "video_box.h"
 #include "video_context.h"
@@ -420,8 +421,10 @@ void VideoDisplay::OnMouseLeave(wxMouseEvent& event) {
 }
 
 void VideoDisplay::OnMouseWheel(wxMouseEvent& event) {
-	if (int wheel = event.GetWheelRotation())
+	if (int wheel = event.GetWheelRotation()) {
+		if (ForwardMouseWheelEvent(this, event))
 			SetZoom (zoomValue + .125 * (wheel / event.GetWheelDelta()));
+	}
 }
 
 void VideoDisplay::OnContextMenu(wxContextMenuEvent&) {