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tweak Grid repositioning code to be a little more O(N)

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This commit is contained in:
Paul Davis 2017-01-14 13:15:48 +00:00
parent 99b86f0f05
commit 04e346a3d8
1 changed files with 36 additions and 8 deletions
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44
libs/canvas/grid.cc
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@ -163,11 +163,20 @@ Grid::reposition_children ()
uint32_t max_row = 0;
uint32_t max_col = 0;
/* since we encourage dynamic and essentially random placement of
* children, begin by determining the maximum row and column given
* our current set of children and placements.
*/
for (CoordsByItem::const_iterator c = coords_by_item.begin(); c != coords_by_item.end(); ++c) {
max_col = max (max_col, (uint32_t) c->second.x);
max_row = max (max_row, (uint32_t) c->second.y);
}
/* Now compute the width of the widest child for each column, and the
* height of the tallest child for each row.
*/
vector<double> row_dimens;
vector<double> col_dimens;
@ -187,6 +196,32 @@ Grid::reposition_children ()
col_dimens[c->second.y] = max (col_dimens[c->second.y], bb.get().height());
}
/* now sum the row and column widths, so that row_dimens is transformed
* into the y coordinate of the upper left of each row, and col_dimens
* is transformed into the x coordinate of the left edge of each
* column.
*/
double prev = row_dimens[0];
row_dimens[0] = 0;
for (uint32_t n = 1; n < max_row; ++n) {
row_dimens[n] = row_dimens[n-1] + prev;
prev = row_dimens[n];
}
prev = col_dimens[0];
col_dimens[0] = 0;
for (uint32_t n = 1; n < max_col; ++n) {
col_dimens[n] = col_dimens[n-1] + prev;
prev = col_dimens[n];
}
/* position each item at the upper left of its (row, col) coordinate,
* given the width of all rows or columns before it.
*/
for (std::list<Item*>::iterator i = _items.begin(); ++i != _items.end(); ++i) {
CoordsByItem::const_iterator c = coords_by_item.find (*i);
@ -194,14 +229,7 @@ Grid::reposition_children ()
continue;
}
Duple pos (0,0);
for (uint32_t n = 0; n < c->second.x; ++n) {
pos.x += row_dimens[n];
pos.y += col_dimens[n];
}
(*i)->set_position (pos);
(*i)->set_position (Duple (col_dimens[c->second.x], row_dimens[c->second.y]));
}
_bounding_box_dirty = true;