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avoid recursing through the entire canvas when scrolling - only scroll explicitly identified ScrollGroups

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This commit is contained in:
Paul Davis 2014-05-21 10:25:28 -04:00
parent a551181842
commit c9f890bd7c
3 changed files with 32 additions and 13 deletions
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29
libs/canvas/canvas.cc
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@ -33,6 +33,7 @@
#include "canvas/canvas.h"
#include "canvas/debug.h"
#include "canvas/line.h"
#include "canvas/scroll_group.h"
using namespace std;
using namespace ArdourCanvas;
@ -40,7 +41,6 @@ using namespace ArdourCanvas;
/** Construct a new Canvas */
Canvas::Canvas ()
: _root (this)
, _global_scroll (true)
{
set_epoch ();
}
@ -48,19 +48,29 @@ Canvas::Canvas ()
void
Canvas::scroll_to (Coord x, Coord y)
{
Duple d (x, y);
_scroll_offset = d;
_scroll_offset = Duple (x, y);
_root.scroll_to (d);
/* We do things this way because we do not want to recurse through
the canvas for every scroll. In the presence of large MIDI
tracks this means traversing item lists that include
thousands of items (notes).
This design limits us to moving only those items (groups, typically)
that should move in certain ways as we scroll. In other terms, it
becomes O(1) rather than O(N).
*/
for (list<ScrollGroup*>::iterator i = scrollers.begin(); i != scrollers.end(); ++i) {
(*i)->scroll_to (_scroll_offset);
}
pick_current_item (0); // no current mouse position
}
void
Canvas::set_global_scroll (bool yn)
Canvas::add_scroller (ScrollGroup& i)
{
_global_scroll = yn;
scrollers.push_back (&i);
}
void
@ -602,6 +612,11 @@ GtkCanvas::item_going_away (Item* item, boost::optional<Rect> bounding_box)
_focused_item = 0;
}
ScrollGroup* sg = dynamic_cast<ScrollGroup*>(item);
if (sg) {
scrollers.remove (sg);
}
if (_current_item == item) {
/* no need to send a leave event to this item, since it is going away
*/