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canvas: add a method to prevent extensive item coordinate math during ::prepare_for_render_children()

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Also, auto-ify a loop in Item::prepare_for_render_children()
This commit is contained in:
Paul Davis
2025-07-29 11:02:32 -06:00
parent 9f49e6379d
commit 6c499b180b
2 changed files with 12 additions and 11 deletions
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1
libs/canvas/canvas/item.h
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@@ -82,6 +82,7 @@ public:
* @param area Area to draw, in **window** coordinates
*/
virtual void prepare_for_render (Rect const & area) const { }
virtual bool needs_prepare_for_render () const { return false; }
/** Adds one or more items to the vector \p items based on their
* covering \p point which is in window coordinates

22
libs/canvas/item.cc
View File

@@ -975,27 +975,27 @@ Item::prepare_for_render_children (Rect const & area) const
ensure_lut ();
std::vector<Item*> items = _lut->get (area);
for (std::vector<Item*>::const_iterator i = items.begin(); i != items.end(); ++i) {
for (auto const & item : items) {
if (!(*i)->visible ()) {
if (!item->needs_prepare_for_render()) {
continue;
}
Rect item_bbox = (*i)->bounding_box ();
if (!item->visible ()) {
continue;
}
Rect item_bbox = item->bounding_box ();
if (!item_bbox) {
continue;
}
Rect item = (*i)->item_to_window (item_bbox, false);
Rect d = item.intersection (area);
if (d) {
Rect draw = d;
if (draw.width() && draw.height()) {
(*i)->prepare_for_render (area);
}
Rect item_rect = item->item_to_window (item_bbox, false);
Rect draw = item_rect.intersection (area);
if (draw.width() && draw.height()) {
item->prepare_for_render (area);
} else {
// Item does not intersect with visible canvas area
}