Allow doubleclick-and-drag and tripleclick-and-drag#8166
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Implements egui issue emilk#2550: when the user double-clicks and keeps the button held while dragging, the selection now extends word-by-word, and triple-click-and-drag extends line-by-line. Plain click-and-drag still selects character-by-character. egui only computes a click `count` on release, but to know the drag granularity we need that count while the button is still held. So `PointerState` now computes a `press_click_count` at press time using the same double-/triple-click logic the release path uses. `TextCursorState` gains a `SelectionMode` (Char/Word/Line) and an anchor unit so dragging back and forth across the anchor re-derives the selection correctly. `pointer_interaction` picks the mode from `press_click_count` on the start of a drag and, while dragging in Word/Line mode, takes the union of the anchor word/line and the word/line under the pointer. `LabelSelectionState` carries the same mode and anchor so label drag respects word/line granularity too. The single-galley case is fully correct; cross-galley label drags snap each galley's moving end to a word/line boundary. Existing single/double/triple-click behavior is preserved. Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>
Fix 1: In multi-widget label selection, a word/line drag anchored in one galley failed to keep the anchor unit selected when dragged upward into a previous label. `selection.secondary` was set once at drag start to the anchor unit's MIN, which is only correct for forward/downward drags. `cursor_for` now recomputes `selection.secondary` every frame it processes the anchor galley (matched via the stored `drag_anchor` widget Id) whenever the primary is in a different galley. The far end of the anchor unit is chosen by `anchor_secondary_index` based on whether the primary has been dragged before the anchor in document order (compared via screen position). The single-galley case still flows through `combine_units` unchanged. Fix 2: `extend_word_line_drag` ran an O(n) word/line scan every frame while dragging. A `last_drag_pointer` cache on `TextCursorState` now stores the pointer char index and resulting range from the previous frame, skipping the scan while the pointer stays on the same character. `begin_drag` clears the cache so a new drag never reuses a stale range. Adds unit tests for the secondary-flip direction logic and the cache. Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>
Fix 1 (behavior regression): label shift-click now resets the drag-selection granularity to Char. Previously a shift-click in a label left `selection_mode` at whatever a prior word/line drag had set, so a later shift-click extended by whole words/lines instead of by character, diverging from `TextEdit` and from `main`. Fix 2 (performance): add a stationary-pointer cache (`last_drag_unit`) to `LabelSelectionState`, mirroring `TextCursorState::last_drag_pointer`. The label word/line drag path called `unit_bounds_at` every frame, running an O(n) scan and heap-allocating a line-sized `String` even when the pointer was stationary. The cache (widget Id + pointer char index -> unit bounds) skips the scan while the pointer stays put, and is cleared on `drag_started` so no stale reuse. Fix 3 (API hygiene): `SelectionMode` and `SelectionMode::from_click_count` were accidentally `pub`, enlarging egui's public API; they are now `pub(crate)`. The unused `TextCursorState::selection_mode()` accessor (no callers anywhere) is removed. The three drag-transient fields (`selection_mode`, `drag_anchor_unit`, `last_drag_pointer`) now carry `#[serde(skip)]` so ephemeral drag state is not persisted. Fix 4 (cleanup): the double-/triple-click-count arithmetic that was duplicated between the press and release paths in `input_state/mod.rs` is extracted into a single private `PointerState::compute_click_count` helper. Tests: add `test_from_click_count` and `test_shift_click_resets_to_char_mode`; existing cache test still holds. `cargo test -p egui`, clippy (`--all-features`), fmt, and both default / `--no-default-features` builds are clean. Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>
Follow-up to the double-/triple-click-and-drag feature (egui issue emilk#2550). Edge case 1 (FIXED): cache not invalidated on mid-drag text change. `TextCursorState::last_drag_pointer` was keyed only on the pointer char index, so an IME composition or programmatic edit that changed the galley text while the pointer stayed on the same char returned a stale range. The cache key now also includes `text.len()`; a differing length is treated as a miss. A new unit test covers this. Edge case 2 (INVESTIGATED, no code change needed): stale selection mode when a drag starts without a hovered press. Confirmed unreachable: the `is_being_dragged` branch in `pointer_interaction` can only run for a widget whose id equals `dragged_id()`, which requires `potential_drag_id` to have been set from a press-time drag hit, on a frame where the widget is also in the `hovered` set and `any_pressed()` is true -- so the press branch is guaranteed to have run first and overwritten `selection_mode`/ `drag_anchor_unit`. (Labels never reach this branch; they always pass `is_being_dragged = false`.) Added an explanatory comment instead of dead defensive code. Edge case 3 (PRE-EXISTING egui LIMITATION, documented): anchor galley scrolled out of view. The cross-galley secondary-flip can only run on the frame the anchor galley is visited. If it scrolls out, `selection.secondary` freezes at its last valid value. Verified there is no crash, panic or cross-galley index misuse; this degrades no worse than `main`'s char-mode multi-widget selection, which has the identical failure mode. Documented precisely in a code comment; a proper fix needs a multi-widget-selection rewrite, out of scope. Edge case 4 (FIXED): one-frame flicker on fast direction reversal. The cross-galley secondary-flip decided drag direction from `selection.primary.pos`, which is one frame stale when the anchor galley is processed before the pointer's galley. It now uses the live pointer position from `pointer_interact_pos()`, removing the lag at its source. Tests: `cargo test -p egui` all pass (38 unit + 166 doctests). `cargo clippy -p egui --all-features`, `cargo fmt`, `cargo build -p egui` and `cargo build -p egui --no-default-features` all clean. Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>
egui's CONTRIBUTING.md asks for each type in its own file unless trivial. Move the `SelectionMode` enum and its impl out of `text_cursor_state.rs` into a new `selection_mode.rs`, and make the `select_word_at`, `select_line_at` and `range_bounds` helpers `pub(crate)` so the new module can use them. The `from_click_count` test moves along with it. No behavior change. Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>
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Preview available at https://egui-pr-preview.github.io/pr/8166-featureclick-drag-selection View snapshot changes at kitdiff |
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Fix for the current behaviour where a double-click selects a word and a triple-click selects a line, but dragging with multi-click looses the initial selection and then extends the selection character by character.
The fix works for both
TextEditand selectableLabels (single- and multi-widget selection). Plain single-click drag, double/triple-click without dragging, and shift-click are all unchanged.How
The click count (1/2/3) is normally only known on pointer release, but a double-/triple-click-and-drag needs it while the button is still held. So
PointerStatenow also computes the click count at press time (press_click_count), reusing the same double/triple-click logic the release path already used.TextCursorState(shared byTextEditandLabel) gains aSelectionMode(Char/Word/Line) and an anchored unit, so the selection extends and shrinks in whole words/lines as the pointer moves back and forth.Known limitation
For multi-widget label selection, if the anchor widget (where the drag started) is scrolled out of view, the selection endpoint freezes at its last valid value. This is a limitation of egui's multi-widget text selection (char-mode selection on
mainhas the same failure mode).This PR addresses #2550
cargo test -p eguipasses (added unit tests for the new logic)cargo clippy -p egui --all-featuresis cleancargo fmtis cleanserdefeature