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Fix clickable widgets blocking scrolling on touch screens (#3815) 

Currently, when you try dragging a ScrollArea and start over a button,
the button blocks the ScrollArea from receiving the drag event.

This PR updates layer_rects_this_frame and layer_rects_prev_frame to
include the Sense and will use it to check if the previous layer has a
sense that would be a conflict.

<details><summary>Videos</summary>
<p>
(In both videos I'm clicking and dragging)

Before: 


https://github.com/emilk/egui/assets/8009393/83cc5a8a-2283-46d6-9337-164e1289f701

After (I modified the WidgetGallery to be scrollable, as you can see you
can now scroll over buttons and dragging the slider still blocks the
scroll):


https://github.com/emilk/egui/assets/8009393/be634cf8-3af2-4520-ba1c-bb8bfcc82997

Scrolling in the sidebar also works now:


https://github.com/emilk/egui/assets/8009393/d4309bec-22e1-4fb4-a425-7b029237849b


</p>
</details>

---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
This commit is contained in:
lucasmerlin 2024-01-15 10:08:41 +01:00 committed by GitHub
parent ce6876e5bd
commit 4c8b95f365
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1 changed files with 25 additions and 5 deletions
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30
crates/egui/src/context.rs
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@ -112,6 +112,14 @@ impl ContextImpl {
// ----------------------------------------------------------------------------
/// Used to store each widgets [Id], [Rect] and [Sense] each frame.
/// Used to check for overlaps between widgets when handling events.
struct WidgetRect {
id: Id,
rect: Rect,
sense: Sense,
}
/// State stored per viewport
#[derive(Default)]
struct ViewportState {
@ -138,10 +146,10 @@ struct ViewportState {
used: bool,
/// Written to during the frame.
layer_rects_this_frame: HashMap<LayerId, Vec<(Id, Rect)>>,
layer_rects_this_frame: HashMap<LayerId, Vec<WidgetRect>>,
/// Read
layer_rects_prev_frame: HashMap<LayerId, Vec<(Id, Rect)>>,
layer_rects_prev_frame: HashMap<LayerId, Vec<WidgetRect>>,
/// State related to repaint scheduling.
repaint: ViewportRepaintInfo,
@ -865,17 +873,29 @@ impl Context {
.layer_rects_this_frame
.entry(layer_id)
.or_default()
.push((id, interact_rect));
.push(WidgetRect {
id,
rect: interact_rect,
sense,
});
if hovered {
let pointer_pos = viewport.input.pointer.interact_pos();
if let Some(pointer_pos) = pointer_pos {
if let Some(rects) = viewport.layer_rects_prev_frame.get(&layer_id) {
for &(prev_id, prev_rect) in rects.iter().rev() {
for &WidgetRect {
id: prev_id,
rect: prev_rect,
sense: prev_sense,
} in rects.iter().rev()
{
if prev_id == id {
break; // there is no other interactive widget covering us at the pointer position.
}
if prev_rect.contains(pointer_pos) {
// We don't want a click-only button to block drag-events to a `ScrollArea`:
let has_conflicting_sense = (prev_sense.click && sense.click)
|| (prev_sense.drag && sense.drag);
if prev_rect.contains(pointer_pos) && has_conflicting_sense {
// Another interactive widget is covering us at the pointer position,
// so we aren't hovered.