Update the audio scroll position at most once every 50ms when dragging markers

Originally committed to SVN as r6736.

aegisub/src/audio_display.cpp

@@ -591,6 +591,7 @@ AudioDisplay::AudioDisplay(wxWindow *parent, AudioController *controller, agi::C
 	Bind(wxEVT_MOTION, &AudioDisplay::OnMouseEvent, this);
 	Bind(wxEVT_ENTER_WINDOW, &AudioDisplay::OnMouseEvent, this);
 	Bind(wxEVT_LEAVE_WINDOW, &AudioDisplay::OnMouseEvent, this);
+	scroll_timer.Bind(wxEVT_TIMER, &AudioDisplay::OnScrollTimer, this);
 }
 
 
@@ -1026,6 +1027,7 @@ void AudioDisplay::OnMouseEvent(wxMouseEvent& event)
 	{
 		if (!dragged_object->OnMouseEvent(event))
 		{
+			scroll_timer.Stop();
 			SetDraggedObject(0);
 			SetCursor(wxNullCursor);
 		}
@@ -1234,6 +1236,31 @@ void AudioDisplay::OnSelectionChanged()
 
 	if (audio_marker)
 	{
+		if (!scroll_timer.IsRunning())
+		{
+			// If the dragged object is outside the visible area, start the
+			// scroll timer to shift it back into view
+			int rel_x = RelativeXFromTime(audio_marker->GetPosition());
+			if (rel_x < 0 || rel_x >= GetClientSize().GetWidth())
+			{
+				// 50ms is the default for this on Windows (hardcoded since
+				// wxSystemSettings doesn't expose DragScrollDelay etc.)
+				scroll_timer.Start(50, true);
+			}
+		}
+	}
+	else if (OPT_GET("Audio/Auto/Scroll")->GetBool() && sel.end() != 0)
+	{
+		ScrollTimeRangeInView(sel);
+	}
+
+	RefreshRect(scrollbar->GetBounds(), false);
+}
+
+void AudioDisplay::OnScrollTimer(wxTimerEvent &event)
+{
+	if (!audio_marker) return;
+
 	int rel_x = RelativeXFromTime(audio_marker->GetPosition());
 	int width = GetClientSize().GetWidth();
 
@@ -1247,13 +1274,6 @@ void AudioDisplay::OnSelectionChanged()
 	{
 		ScrollBy(rel_x - width + width / 20);
 	}
-	}
-	else if (OPT_GET("Audio/Auto/Scroll")->GetBool() && sel.end() != 0)
-	{
-		ScrollTimeRangeInView(sel);
-	}
-
-	RefreshRect(scrollbar->GetBounds(), false);
 }
 
 void AudioDisplay::OnStyleRangesChanged()

aegisub/src/audio_display.h

@@ -41,6 +41,7 @@
 
 #include <wx/gdicmn.h>
 #include <wx/string.h>
+#include <wx/timer.h>
 #include <wx/window.h>
 #endif
 
@@ -131,6 +132,9 @@ class AudioDisplay: public wxWindow {
 	void SetDraggedObject(AudioDisplayInteractionObject *new_obj);
 
 
+	/// Timer for scrolling when markers are dragged out of the displayed area
+	wxTimer scroll_timer;
+
 	/// Leftmost pixel in the virtual audio image being displayed
 	int scroll_left;
 
@@ -213,6 +217,7 @@ class AudioDisplay: public wxWindow {
 	void OnFocus(wxFocusEvent &event);
 	/// wxWidgets keypress event
 	void OnKeyDown(wxKeyEvent& event);
+	void OnScrollTimer(wxTimerEvent &event);
 
 	// AudioControllerAudioEventListener implementation
 	void OnAudioOpen(AudioProvider *provider);