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GUI: Find the last visible item via binary search

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Store last visible item instead of an estimate of total items on screen
This commit is contained in:
av-dx 2021-08-04 21:27:01 +05:30 committed by Eugene Sandulenko
parent aa3ab57d8a
commit 0c59bb0801
2 changed files with 45 additions and 54 deletions
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97
gui/widgets/grid.cpp
View File

@ -373,7 +373,7 @@ GridWidget::GridWidget(GuiObject *boss, int x, int y, int w, int h)
_scrollBar->setTarget(this);
_scrollPos = 0;
_firstVisibleItem = 0;
_itemsOnScreen = 0;
_lastVisibleItem = 0;
_itemsPerRow = 0;
_innerHeight = 0;
@ -402,7 +402,7 @@ GridWidget::GridWidget(GuiObject *boss, const String &name)
_scrollBar->setTarget(this);
_scrollPos = 0;
_firstVisibleItem = 0;
_itemsOnScreen = 0;
_lastVisibleItem = 0;
_itemsPerRow = 0;
_innerHeight = 0;
@ -522,45 +522,49 @@ void GridWidget::sortGroups() {
}
}
bool GridWidget::calcVisibleEntries() {
bool needsReload = false;
int nFirstVisibleItem = 0, nItemsOnScreen = 0;
// Perform a binary search to find the last element before position yPos in arr.
int lastItemBeforeY(const Array<GridItemInfo> &arr, int yPos) {
// Binary search to find the last element whose y value is less
// than _scrollPos, i.e., the last item of the topmost visible row.
int start = 0;
int end = (int)_sortedEntryList.size() - 1;
int end = (int)arr.size() - 1;
int mid;
int ans = -1;
while (start <= end) {
mid = start + (end - start) / 2;
if (_sortedEntryList[mid].rect.top >= _scrollPos) {
if (arr[mid].rect.top >= yPos) {
end = mid - 1;
} else {
ans = mid;
start = mid + 1;
}
}
nFirstVisibleItem = ans;
return ans;
}
bool GridWidget::calcVisibleEntries() {
bool needsReload = false;
int nFirstVisibleItem = 0, nLastVisibleItem = 0;
int temp = lastItemBeforeY(_sortedEntryList, _scrollPos);
nFirstVisibleItem = temp;
// We want the leftmost item from the topmost visible row, so we traverse backwards
while ((nFirstVisibleItem >= 0) &&
(_sortedEntryList[nFirstVisibleItem].rect.top == _sortedEntryList[ans].rect.top)) {
(_sortedEntryList[nFirstVisibleItem].rect.top == _sortedEntryList[temp].rect.top)) {
nFirstVisibleItem--;
}
nFirstVisibleItem++;
nFirstVisibleItem = (nFirstVisibleItem < 0) ? 0 : nFirstVisibleItem;
nItemsOnScreen = (3 + (_scrollWindowHeight / (_gridItemHeight + _gridYSpacing))) * (_itemsPerRow);
nLastVisibleItem = lastItemBeforeY(_sortedEntryList, _scrollPos + _scrollWindowHeight);
nLastVisibleItem = (nLastVisibleItem < 0) ? 0 : nLastVisibleItem;
// TODO / FIXME: The previous if condition had to be removed as it can break on toggling groups.
// Find a proper if condition and put the below code under it.
{
if ((nFirstVisibleItem != _firstVisibleItem) || (nLastVisibleItem != _lastVisibleItem)) {
needsReload = true;
_itemsOnScreen = nItemsOnScreen;
_lastVisibleItem = nLastVisibleItem;
_firstVisibleItem = nFirstVisibleItem;
int toRender = MIN(_firstVisibleItem + _itemsOnScreen, (int)_sortedEntryList.size());
int toRender = MIN(_lastVisibleItem + 1, (int)_sortedEntryList.size());
_visibleEntryList.clear();
for (int ind = _firstVisibleItem; ind < toRender; ++ind) {
@ -651,35 +655,37 @@ void GridWidget::updateGrid() {
void GridWidget::assignEntriesToItems() {
// Assign entries from _visibleEntries to each GridItem in _gridItems
if (_visibleEntryList.empty() || _gridItems.empty())
if (_visibleEntryList.empty())
return;
Common::Array<GridItemInfo *>::iterator eit = _visibleEntryList.begin();
Common::Array<GridItemWidget *>::iterator it = _gridItems.begin();
for (int k = 0; k < _itemsOnScreen; ++k) {
GridItemWidget *item = *it;
GridItemInfo *entry = *eit;
if (eit != _visibleEntryList.end()) {
// Assign entry and update
item->setActiveEntry(*entry);
item->setPos(entry->rect.left, entry->rect.top - _scrollPos);
item->setSize(entry->rect.width(), entry->rect.height());
item->update();
if (k >= _itemsOnScreen - _itemsPerRow)
item->setVisible(false);
else
item->setVisible(true);
++eit;
} else {
// In case we have less ContainerWidgets than the number of visible entries
if (_visibleEntryList.size() > _gridItems.size()) {
for (uint l = _gridItems.size(); l < _visibleEntryList.size(); ++l) {
GridItemWidget *newItem = new GridItemWidget(this);
newItem->setVisible(false);
newItem->markAsDirty();
_gridItems.push_back(newItem);
}
}
for (uint k = 0; k < _gridItems.size(); ++k) {
GridItemWidget *item = _gridItems[k];
if (k >= _visibleEntryList.size()) {
// If we run out of visible entries to display.
// e.g., scrolled to the very bottom, we make items invisible,
// and move them out of view to keep them from registering mouse events.
item->setPos(_scrollWindowWidth, _scrollWindowHeight);
item->setVisible(false);
item->markAsDirty();
} else {
// Assign entry and update
item->setVisible(true);
GridItemInfo *entry = _visibleEntryList[k];
item->setActiveEntry(*entry);
item->setPos(entry->rect.left, entry->rect.top - _scrollPos);
item->setSize(entry->rect.width(), entry->rect.height());
item->update();
}
if (++it == _gridItems.end())
it = _gridItems.begin();
}
}
@ -827,21 +833,6 @@ void GridWidget::reflowLayout() {
reloadThumbnails();
}
int row = 0;
int col = 0;
for (int k = 0; k < _itemsOnScreen; ++k) {
GridItemWidget *newItem = new GridItemWidget(this);
newItem->setVisible(false);
_gridItems.push_back(newItem);
if (++col >= _itemsPerRow) {
++row;
col = 0;
}
}
assignEntriesToItems();
scrollBarRecalc();
markAsDirty();

2
gui/widgets/grid.h
View File

@ -142,7 +142,7 @@ protected:
int _rows;
int _itemsPerRow;
int _firstVisibleItem;
int _itemsOnScreen;
int _lastVisibleItem;
GridItemTray *_tray;
String _iconDir;