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canvas: add a drawing-request-freeze/thaw API

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If queue_draw is "frozen", we simply accumulate drawing
requests in a (union) rectangle, and when finally "thawed"
the canvas submits a single redraw request for the entire
accumulated rect.

Although in theory this is all that GTK/GDK does for
draw requests, callgrind reveals significant costs
associated with the actual calltree for GtkWidget::queue_draw_area().

One potential cost is that GDK also maintains a list of
invalidated rectangles in addition to the union, and
for MIDI regions with thousands of notes, this can represent
real overhead. This approach dispenses with the rect list,
since our Canvas drawing model only uses the union rectangle
anyway.
This commit is contained in:
Paul Davis 2022-03-29 08:52:17 -06:00
parent 1769b20dd1
commit b6d0f8f661
2 changed files with 46 additions and 8 deletions
Download patch file Download diff file Expand all files Collapse all files

48
libs/canvas/canvas.cc
View file

@ -55,6 +55,7 @@ uint32_t Canvas::tooltip_timeout_msecs = 750;
/** Construct a new Canvas */
Canvas::Canvas ()
: _root (this)
, _queue_draw_frozen (0)
, _bg_color (Gtkmm2ext::rgba_to_color (0, 1.0, 0.0, 1.0))
, _last_render_start_timestamp(0)
, _use_intermediate_surface (false)
@ -230,6 +231,25 @@ Canvas::dump (ostream& o) const
_root.dump (o);
}
void
Canvas::freeze_queue_draw ()
{
_queue_draw_frozen++;
}
void
Canvas::thaw_queue_draw ()
{
if (_queue_draw_frozen) {
_queue_draw_frozen--;
if (_queue_draw_frozen == 0 && !frozen_area.empty()) {
request_redraw (frozen_area);
frozen_area = Rect();
}
}
}
/** Called when an item has been shown or hidden.
* @param item Item that has been shown or hidden.
*/
@ -238,6 +258,11 @@ Canvas::item_shown_or_hidden (Item* item)
{
Rect bbox = item->bounding_box ();
if (bbox) {
if (_queue_draw_frozen) {
frozen_area = frozen_area.extend (compute_draw_item_area (item, bbox));
return;
}
if (item->item_to_window (bbox).intersection (visible_area ())) {
queue_draw_item_area (item, bbox);
}
@ -416,41 +441,48 @@ Canvas::item_moved (Item* item, Rect pre_change_parent_bounding_box)
void
Canvas::queue_draw_item_area (Item* item, Rect area)
{
request_redraw (compute_draw_item_area (item, area));
}
Rect
Canvas::compute_draw_item_area (Item* item, Rect area)
{
Rect r;
if ((area.width()) > 1.0 && (area.height() > 1.0)) {
/* item has a rectangular bounding box, which may fall
* on non-integer locations. Expand it appropriately.
*/
Rect r = item->item_to_window (area, false);
r = item->item_to_window (area, false);
r.x0 = floor (r.x0);
r.y0 = floor (r.y0);
r.x1 = ceil (r.x1);
r.y1 = ceil (r.y1);
//std::cerr << "redraw box, adjust from " << area << " to " << r << std::endl;
request_redraw (r);
return;
} else if (area.width() > 1.0 && area.height() == 1.0) {
/* horizontal line, which may fall on non-integer
* coordinates.
*/
Rect r = item->item_to_window (area, false);
r = item->item_to_window (area, false);
r.y0 = floor (r.y0);
r.y1 = ceil (r.y1);
//std::cerr << "redraw HLine, adjust from " << area << " to " << r << std::endl;
request_redraw (r);
} else if (area.width() == 1.0 && area.height() > 1.0) {
/* vertical single pixel line, which may fall on non-integer
* coordinates
*/
Rect r = item->item_to_window (area, false);
r = item->item_to_window (area, false);
r.x0 = floor (r.x0);
r.x1 = ceil (r.x1);
//std::cerr << "redraw VLine, adjust from " << area << " to " << r << std::endl;
request_redraw (r);
} else {
/* impossible? one of width or height must be zero ... */
//std::cerr << "redraw IMPOSSIBLE of " << area << std::endl;
request_redraw (item->item_to_window (area, false));
r = item->item_to_window (area, false);
}
return r;
}
void