Only compute and render the visible portion of crossfades. Fixes #3498.

[ardour.git] / gtk2_ardour / crossfade_view.cc

diff --git a/gtk2_ardour/crossfade_view.cc b/gtk2_ardour/crossfade_view.cc
index bc8521dbc2c44c72fb5e33207ac54987230fb479..81f5f4173feb00814d686e809b8a21be5180a364 100644 (file)
--- a/gtk2_ardour/crossfade_view.cc
+++ b/gtk2_ardour/crossfade_view.cc
@@ -55,7 +55,8 @@ CrossfadeView::CrossfadeView (ArdourCanvas::Group *parent,
                            xf->length(), false, false, TimeAxisViewItem::Visibility (TimeAxisViewItem::ShowFrame)),
          crossfade (xf),
          left_view (lview),
-         right_view (rview)    
+         right_view (rview),
+         _all_in_view (false)
 {
        _valid = true;
        _visible = true;
@@ -144,13 +145,12 @@ CrossfadeView::crossfade_changed (const PropertyChange& what_changed)
        }
 }
 
+/** Set up our fade_in and fade_out curves to contain points for the currently visible portion
+ *  of the crossfade.
+ */
 void
 CrossfadeView::redraw_curves ()
 {
-       Points* points;
-       int32_t npoints;
-       float* vec;
-
        if (!crossfade->following_overlap()) {
                /* curves should not be visible */
                fade_in->hide ();
@@ -163,9 +163,22 @@ CrossfadeView::redraw_curves ()
                return;
        }
 
-       npoints = get_time_axis_view().editor().frame_to_pixel (crossfade->length());
-       // npoints = std::min (gdk_screen_width(), npoints);
+       PublicEditor& editor = get_time_axis_view().editor ();
+
+       framepos_t const editor_left = editor.leftmost_position ();
+       framepos_t const editor_right = editor_left + editor.current_page_frames ();
+       framepos_t const xfade_left = crossfade->position ();
+       framepos_t const xfade_right = xfade_left + crossfade->length ();
+
+       /* Work out the range of our frames that are visible */
+       framepos_t const min_frames = std::max (editor_left, xfade_left);
+       framepos_t const max_frames = std::min (editor_right, xfade_right);
+
+       _all_in_view = (editor_left <= xfade_left && editor_right >= xfade_right);
 
+       /* Hence the number of points that we will render */
+       int32_t const npoints = editor.frame_to_pixel (max_frames - min_frames);
+       
        if (!_visible || !crossfade->active() || npoints < 3) {
                fade_in->hide();
                fade_out->hide();
@@ -175,24 +188,30 @@ CrossfadeView::redraw_curves ()
                fade_out->show();
        }
 
-       points = get_canvas_points ("xfade edit redraw", npoints);
-       vec = new float[npoints];
+       Points* points = get_canvas_points ("xfade edit redraw", npoints);
+       float* vec = new float[npoints];
+
+       crossfade->fade_in().curve().get_vector (min_frames - crossfade->position(), max_frames - crossfade->position(), vec, npoints);
 
-       crossfade->fade_in().curve().get_vector (0, crossfade->length(), vec, npoints);
+       /* Work out the offset from the start of the crossfade to the visible part, in pixels */
+       double xoff = 0;
+       if (crossfade->position() < editor.leftmost_position()) {
+               xoff = editor.frame_to_pixel (min_frames) - editor.frame_to_pixel (crossfade->position ());
+       }
 
        for (int i = 0, pci = 0; i < npoints; ++i) {
                Art::Point &p = (*points)[pci++];
-               p.set_x (i + 1);
+               p.set_x (xoff + i + 1);
                p.set_y (_height - ((_height - 2) * vec[i]));
        }
 
        fade_in->property_points() = *points;
 
-       crossfade->fade_out().curve().get_vector (0, crossfade->length(), vec, npoints);
+       crossfade->fade_out().curve().get_vector (min_frames - crossfade->position(), max_frames - crossfade->position(), vec, npoints);
 
        for (int i = 0, pci = 0; i < npoints; ++i) {
                Art::Point &p = (*points)[pci++];
-               p.set_x (i + 1);
+               p.set_x (xoff + i + 1);
                p.set_y (_height - ((_height - 2) * vec[i]));
        }
        
@@ -269,3 +288,17 @@ CrossfadeView::crossfade_fades_changed ()
 {
        redraw_curves ();
 }
+
+void
+CrossfadeView::horizontal_position_changed ()
+{
+       /* If the crossfade curves are entirely within the editor's visible space, there is
+          no need to redraw them here as they will be completely drawn (as distinct from
+          the other case where the horizontal position change will uncover `undrawn'
+          sections).
+       */
+       
+       if (!_all_in_view) {
+               redraw_curves ();
+       }
+}