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egui_extras: clean up visible table bounds calculation a little

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This commit is contained in:
Wayne Warren 2022-04-04 08:09:10 -06:00
parent 1d7f698669
commit 603ce062b3
1 changed files with 11 additions and 14 deletions
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25
egui_extras/src/table.rs
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@ -412,30 +412,26 @@ impl<'a> TableBody<'a> {
heights: impl Iterator<Item = f32>, heights: impl Iterator<Item = f32>,
mut populate_row: impl FnMut(usize, TableRow<'_, '_>), mut populate_row: impl FnMut(usize, TableRow<'_, '_>),
) { ) {
// VIRTUAL_EXTENSION represents how far above and below the limits of the visible rectangle
// that we should consider when determining which rows to actually populate. this provides
// the illusion of table rows sliding out of view (rather than disappearing abruptly)
const VIRTUAL_EXTENSION: f32 = 30.0;
// in order for each row to retain its striped color as the table is scrolled, we need an // in order for each row to retain its striped color as the table is scrolled, we need an
// iterator with the boolean built in based on the enumerated index of the iterator element // iterator with the boolean built in based on the enumerated index of the iterator element
let mut striped_heights = heights let mut striped_heights = heights
.enumerate() .enumerate()
.map(|(index, height)| (index, index % 2 == 0, height)); .map(|(index, height)| (index, index % 2 == 0, height));
let max_height = self.end_y - self.start_y + VIRTUAL_EXTENSION; let max_height = self.end_y - self.start_y;
let y_progress = self.y_progress() - VIRTUAL_EXTENSION; let y_progress = self.y_progress();
// cumulative height of all rows above those being displayed // cumulative height of all rows above those being displayed
let mut height_above_visible: f64 = 0.0; let mut height_above_visible: f64 = 0.0;
// cumulative height of all rows below those being displayed // cumulative height of all rows below those being displayed
let mut height_below_visible: f64 = 0.0; let mut height_below_visible: f64 = 0.0;
// calculate height above visible table range // calculate height above visible table range and populate the first non-virtual row.
// because this row is meant to slide under the top bound of the visual table we calculate
// height_of_first_row + height_above_visible >= y_progress as our break condition rather
// than just height_above_visible >= y_progress
while let Some((row_index, striped, height)) = striped_heights.next() { while let Some((row_index, striped, height)) = striped_heights.next() {
// when y_progress is greater than height above 0, we need to increment the row index if height as f64 + height_above_visible >= y_progress as f64 {
// and update the height above visble with the current height then continue
if height_above_visible >= y_progress as f64 {
self.add_buffer(height_above_visible as f32); self.add_buffer(height_above_visible as f32);
let tr = TableRow { let tr = TableRow {
layout: &mut self.layout, layout: &mut self.layout,
@ -450,10 +446,11 @@ impl<'a> TableBody<'a> {
height_above_visible += height as f64; height_above_visible += height as f64;
} }
// populate visible rows // populate visible rows, including the final row that should slide under the bottom bound
let mut current_height: f64 = 0.0; // used to track height of visible rows // of the visible table.
let mut current_height: f64 = 0.0;
while let Some((row_index, striped, height)) = striped_heights.next() { while let Some((row_index, striped, height)) = striped_heights.next() {
if current_height > max_height as f64 { if height as f64 + current_height > max_height as f64 {
break; break;
} }
let tr = TableRow { let tr = TableRow {