Make a pinch zoom the grid and nothing else

Two faults left over from making the gesture reach the grid at all.

**It still opened photographs.** Checking the finger id stops the
synthetic release Slint emits when the *second* finger lands, but not the
other end of the gesture: lifting one finger of two leaves the other one
down, and Slint replays that survivor as a fresh `Pressed` on whatever is
under it — which is how it hands the pointer back to ordinary handling.
Under it is a cell. So the cell was selected, and lifting that last finger
was a complete, well-formed click on the same finger that pressed. No
part of the event stream distinguishes it from a real tap, so the grid now
remembers that a pinch just happened: a latch raised when the gesture
starts and lowered a beat after it ends, during which cells take neither
presses nor clicks.

The press that *opens* a pinch is undone rather than suppressed — it has
already happened by the time a second finger makes it a pinch. Undoing it
has to be exact, or a cancel that restored the selection but left the
anchor moved would make the next shift-click select a run from a cell
nobody pointed at, so capture and restore are a tested pair.

**And it was not smooth.** Two reasons. The pinch was thresholded into ±1
steps of 25%, so the grid lurched and then sat still; it now takes the
ratio since the last update and tracks the fingers, with the drawn cell
still landing on whole column counts because the columns divide the
width. And `zoom-cells` was the one geometry change still reloading
inline — a full catalog re-read, 360-row model rebuild and thumbnail
batch per step, on the thread drawing the frame. It goes through the same
settle timer as the rest now.
This commit is contained in:
2026-08-21 22:03:46 +02:00
parent 6ae0af3f72
commit 2fba685e16
4 changed files with 241 additions and 20 deletions
+116
View File
@@ -45,6 +45,47 @@ use slint::{ComponentHandle, Model as _};
use crate::{AppWindow, CollectionRow};
/// The selection as it stood before a press, for [`cancel_press`].
struct PressUndo {
selection: BTreeSet<ImageId>,
anchor: Option<usize>,
previous_anchor: Option<usize>,
cursor: Option<usize>,
}
impl PressUndo {
/// Everything [`press_remembering_anchor`] is about to change.
///
/// The four are the whole of what a press touches, which is the property
/// the restore depends on and the reason it is worth a test of its own: an
/// press that grew a fifth piece of state would leave that piece behind
/// after a cancel, silently.
fn capture(
selection: &BTreeSet<ImageId>,
anchor: Option<usize>,
previous_anchor: Option<usize>,
cursor: Option<usize>,
) -> Self {
Self {
selection: selection.clone(),
anchor,
previous_anchor,
cursor,
}
}
/// Put it all back. Returns the two the caller holds in `Cell`s.
fn restore(
self,
selection: &mut BTreeSet<ImageId>,
anchor: &mut Option<usize>,
) -> (Option<usize>, Option<usize>) {
*selection = self.selection;
*anchor = self.anchor;
(self.previous_anchor, self.cursor)
}
}
/// Selection, drag, and tree state for the running window.
///
/// Everything is `RefCell` because Slint callbacks are `Fn`, not `FnMut`, and
@@ -80,6 +121,19 @@ pub struct CollectionsController {
/// double tap — which lands on the cell that is already the anchor — leaves
/// it pointing where the first tap left it.
previous_anchor: std::cell::Cell<Option<usize>>,
/// TRACES: FR-UI-4
/// What the selection was immediately before the most recent press, so a
/// gesture that turns out not to have been a press can put it back.
///
/// A press has to act immediately — the drag that may follow reads the
/// selection to build its payload, so deciding on release is too late.
/// That is right for a drag and wrong for a pinch, which begins as an
/// ordinary one-finger press and only becomes a pinch when the second
/// finger lands. By then a cell has been selected that the user never
/// meant to touch; they were reaching for the grid with two fingers.
///
/// Cheap to keep: a few hundred ids at most, cloned once per press.
press_undo: RefCell<Option<PressUndo>>,
/// Where the keyboard is, as an image ordinal.
///
/// Distinct from the anchor, and it has to be: shift+arrow grows a range
@@ -452,6 +506,15 @@ pub fn select_row(
ctrl: bool,
shift: bool,
) {
// Before anything moves — see `press_undo`. A press that turns out to be
// the opening finger of a pinch is undone from here.
*ctl.press_undo.borrow_mut() = Some(PressUndo::capture(
&ctl.selection.borrow(),
*ctl.anchor.borrow(),
ctl.previous_anchor.get(),
ctl.cursor(),
));
let mut previous = ctl.previous_anchor.get();
press_remembering_anchor(
&mut ctl.selection.borrow_mut(),
@@ -471,6 +534,27 @@ pub fn select_row(
sync_selection(window, ctl, ids);
}
/// TRACES: FR-UI-4
/// Put the selection back as it was before the most recent press.
///
/// For the gesture that begins as a press and turns out to be something else.
/// A pinch is the case that matters: it starts as one finger on a cell, which
/// selects it, and only becomes a pinch when the second finger lands — by
/// which point the user has selected a photograph they were not reaching for.
///
/// Idempotent, and a no-op when there is nothing to undo, so it is safe to
/// call on every gesture start rather than only on the ones that need it.
pub fn cancel_press(window: &AppWindow, ctl: &Rc<CollectionsController>, ids: &[ImageId]) {
let Some(undo) = ctl.press_undo.borrow_mut().take() else {
return;
};
let (previous_anchor, cursor) =
undo.restore(&mut ctl.selection.borrow_mut(), &mut ctl.anchor.borrow_mut());
ctl.previous_anchor.set(previous_anchor);
ctl.set_cursor(cursor);
sync_selection(window, ctl, ids);
}
/// Rebuild the sidebar from the catalog.
///
/// Called after every edit. The whole tree rather than a patch: a rename can
@@ -2581,6 +2665,38 @@ mod tests {
assert_eq!(sel.len(), 3, "the selection survived the press");
}
#[test]
fn a_press_undone_leaves_the_selection_exactly_as_it_was() {
// A pinch opens as one finger on a cell, so by the time it is known to
// be a pinch a photograph has been selected that the user was only
// reaching past. Undoing it has to be *exact*: a cancel that restored
// the selection but left the anchor moved would make the next
// shift-click select a run from a cell nobody pointed at.
let all = ids(6);
let mut sel = BTreeSet::new();
let mut anchor = None;
// A selection built the ordinary way, and the state it leaves behind.
apply_press(&mut sel, &mut anchor, &all, 0, 1, false, false);
apply_press(&mut sel, &mut anchor, &all, 0, 3, true, false);
let before = (sel.clone(), anchor);
// The finger that opens a pinch.
let undo = PressUndo::capture(&sel, anchor, Some(1), Some(3));
apply_press(&mut sel, &mut anchor, &all, 0, 5, false, false);
assert_ne!(
(sel.clone(), anchor),
before,
"the press has to change something, or this proves nothing"
);
let (previous_anchor, cursor) = undo.restore(&mut sel, &mut anchor);
assert_eq!((sel, anchor), before, "selection and anchor are back");
assert_eq!(previous_anchor, Some(1), "and so is the shift-click origin");
assert_eq!(cursor, Some(3), "and the keyboard cursor");
}
#[test]
fn a_press_past_the_end_of_the_window_is_ignored() {
// The grid is windowed and a stale row index can arrive after a scrub.
+51 -1
View File
@@ -3607,7 +3607,57 @@ pub fn wire<F>(
// of the request key, so cells that now want the large resolution
// simply miss and ask for it, while the 256px ones they already
// hold stay served.
load_window(&w, &ctl);
//
// Deferred, like every other geometry change. This one was still
// reloading inline — a full catalog re-read and model rebuild per
// step, which is what a wheel spun through six steps paid six
// times over.
schedule_reload(&w, &ctl);
});
}
// TRACES: FR-UI-4
// A pinch, which is continuous where the wheel is stepped.
//
// Given the ratio since the last update rather than a direction, so the
// grid tracks the fingers instead of jumping a fixed 25% per threshold
// crossing. What the user is setting is the size class — how big they want
// a thumbnail to be — and the drawn cell follows from it by dividing the
// width, so the visible result still lands on whole column counts. Feeding
// a continuous value in is what decides *when* it crosses.
{
let weak = window.as_weak();
let ctl = ctl.clone();
window.on_library_pinch_cells(move |ratio| {
let Some(w) = weak.upgrade() else { return };
if !(ratio.is_finite() && ratio > 0.0) {
return;
}
let current = w.get_library_cell_size();
let next = (current * ratio).clamp(MIN_CELL_SIZE, MAX_CELL_SIZE);
if (next - current).abs() < 0.5 {
return;
}
w.set_library_cell_size(next);
schedule_reload(&w, &ctl);
});
}
// TRACES: FR-UI-4
// A pinch has begun, so the press that started it was not a press.
//
// A pinch opens as one finger on a cell — which selects it — and only
// becomes a pinch when the second lands. Without this the user is left
// holding a selection they never made, on a photograph they were only
// reaching past.
{
let weak = window.as_weak();
let ctl = ctl.clone();
let coll = coll_ctl.clone();
window.on_library_pinch_started(move || {
let Some(w) = weak.upgrade() else { return };
crate::collections_ui::cancel_press(&w, &coll, &ctl.visible_ids());
});
}
+6
View File
@@ -508,6 +508,10 @@ export component AppWindow inherits Window {
in property <bool> library-syncing: false;
in-out property <length> library-cell-size: 180px;
callback library-zoom-cells(int);
/// A pinch step on the grid: the ratio since the last update.
callback library-pinch-cells(float);
/// A pinch on the grid has begun, so the press that opened it was not one.
callback library-pinch-started();
in property <int> library-scroll-to: 0;
in property <int> library-scroll-token: 0;
/// Which row of the loaded window is the photograph currently open in
@@ -1130,6 +1134,8 @@ in property <bool> panel-visible: true;
syncing: root.library-syncing;
requested-cell-size: root.library-cell-size;
zoom-cells(d) => { root.library-zoom-cells(d); }
pinch-cells(r) => { root.library-pinch-cells(r); }
pinch-started() => { root.library-pinch-started(); }
scroll-to: root.library-scroll-to;
scroll-token: root.library-scroll-token;
sync-now() => { root.library-sync-now(); }
+68 -19
View File
@@ -860,6 +860,11 @@ export component LibraryGrid inherits Rectangle {
/// Ctrl+wheel or pinch over the grid: resize the cells. A signed step,
/// not a size, so Rust owns the bounds.
callback zoom-cells(int);
/// A pinch step: the ratio since the last update, above 1 spreading. The
/// continuous counterpart of `zoom-cells`, which the wheel steps.
callback pinch-cells(float);
/// A pinch has begun, so the press that opened it was not a press.
callback pinch-started();
callback columns-changed(int);
callback sync-now();
/// The grid scrolled: the first visible image's ordinal in the library.
@@ -1167,6 +1172,30 @@ export component LibraryGrid inherits Rectangle {
changed columns => { root.columns-changed(root.columns); }
property <int> row-count: ceil(root.cells.length / max(1, columns));
// --- while a pinch is happening, and just after -----------------------
//
// **A pinch does not end cleanly.** Lifting one finger of two leaves the
// other one down, and Slint replays that survivor as a *fresh* `Pressed`
// on whatever is under it — that is how it hands the pointer back to
// ordinary handling. Under it is a cell. So the cell was selected, and
// then lifting that last finger was a complete, well-formed click and the
// photograph opened. Checking the finger id, which is what stops the
// *second* finger's synthetic release from opening anything, cannot help
// here: this press and this release are genuinely the same finger.
//
// Nothing in the event stream distinguishes that survivor from a real tap,
// so the grid has to remember that a pinch just happened. The latch is
// raised when the gesture starts and lowered a beat after it ends.
property <bool> pinching: false;
settle := Timer {
interval: 350ms;
running: false;
triggered => {
root.pinching = false;
self.running = false;
}
}
// How many cells the viewport holds, plus a screenful either side so
// scrolling has loaded rows to move into rather than blank ones.
//
@@ -1884,21 +1913,34 @@ export component LibraryGrid inherits Rectangle {
property <float> last-scale: 1.0;
started => { self.last-scale = 1.0; }
updated => {
// A quarter-step either way is enough to act on: cell
// size is continuous, unlike the timeline's discrete
// zoom levels.
if (self.scale / max(0.01, self.last-scale) > 1.15) {
root.zoom-cells(1);
self.last-scale = self.scale;
} else if (self.scale / max(0.01, self.last-scale) < 0.87) {
root.zoom-cells(-1);
self.last-scale = self.scale;
}
started => {
self.last-scale = 1.0;
root.pinching = true;
settle.running = false;
// The finger that opened this gesture landed on a cell
// and selected it. It was reaching for the grid, not
// for that photograph.
root.pinch-started();
}
// Continuous, not stepped. Thresholding this into ±1 zoom
// steps meant the grid lurched 25% at a time and sat still
// in between, which is the whole of "pinching is not
// smooth". The ratio since the last update is what tracks
// the fingers; where the drawn cell lands is still a whole
// number of columns, because the columns divide the width.
updated => {
root.pinch-cells(self.scale / max(0.01, self.last-scale));
self.last-scale = self.scale;
}
// The latch outlives the gesture — see `pinching`.
ended => {
self.last-scale = 1.0;
settle.running = true;
}
cancelled => {
self.last-scale = 1.0;
settle.running = true;
}
ended => { self.last-scale = 1.0; }
cancelled => { self.last-scale = 1.0; }
}
// Follow a requested position. Without this a scrub moves the
@@ -2160,11 +2202,17 @@ export component LibraryGrid inherits Rectangle {
if (ev.kind == PointerEventKind.down) {
self.down-finger = ev.touch-finger-id;
self.click-pending = false;
root.cell-pressed(
i,
ev.modifiers.control || root.select-mode,
ev.modifiers.shift,
);
// Not while the grid is being pinched, nor in
// the moment after: this is the finger left
// over from the gesture, handed back as a new
// press. See `pinching`.
if (!root.pinching) {
root.cell-pressed(
i,
ev.modifiers.control || root.select-mode,
ev.modifiers.shift,
);
}
}
if (ev.kind == PointerEventKind.up) {
// A *plain* click opens the image; a modified
@@ -2176,6 +2224,7 @@ export component LibraryGrid inherits Rectangle {
// is only honoured when the press was
// unmodified.
if (self.click-pending
&& !root.pinching
&& ev.touch-finger-id == self.down-finger) {
root.cell-clicked(i);
}