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Fix focus handling in multi-window applications #489

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Fix focus handling in multi-window applications #489

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57adef1
Expose `View::default_compute_layout`
timboudreau Jun 3, 2024
1f05c20
Fix focus handling in multi-window applications
timboudreau Jun 5, 2024
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18 changes: 15 additions & 3 deletions src/id.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,7 @@ use crate::{
view::{IntoView, View},
view_state::{ChangeFlags, StackOffset, ViewState},
view_storage::VIEW_STORAGE,
window_tracking::window_id_for_root,
window_tracking::{is_known_root, window_id_for_root},
ScreenLayout,
};

Expand All @@ -37,6 +37,9 @@ impl ViewId {

pub fn remove(&self) {
VIEW_STORAGE.with_borrow_mut(|s| {
// Remove the cached root, in the (unlikely) case that this view is
// re-added to a different window
s.root.remove(*self);
if let Some(Some(parent)) = s.parent.get(*self) {
if let Some(children) = s.children.get_mut(*parent) {
children.retain(|c| c != self);
Expand Down Expand Up @@ -155,11 +158,20 @@ impl ViewId {
pub(crate) fn root(&self) -> Option<ViewId> {
VIEW_STORAGE.with_borrow_mut(|s| {
if let Some(root) = s.root.get(*self) {
// The cached value will be cleared on remove() above
return *root;
}
let root_view_id = s.root_view_id(*self);
s.root.insert(*self, root_view_id);
root_view_id
// root_view_id() always returns SOMETHING. If the view is not yet added
// to a window, it can be itself or its nearest ancestor, which means we
// will store garbage permanently.
if let Some(root) = root_view_id {
if is_known_root(&root) {
s.root.insert(*self, root_view_id);
return Some(root);
}
}
None
})
}

Expand Down
69 changes: 69 additions & 0 deletions src/update.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -96,3 +96,72 @@ pub(crate) enum UpdateMessage {
},
WindowVisible(bool),
}

impl std::fmt::Debug for UpdateMessage {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
UpdateMessage::Focus(id) => f.write_fmt(format_args!("Focus({:?})", id)),
UpdateMessage::ClearFocus(id) => f.write_fmt(format_args!("ClearFocus({:?})", id)),
UpdateMessage::Active(id) => f.write_fmt(format_args!("Active({:?})", id)),
UpdateMessage::ClearActive(id) => f.write_fmt(format_args!("ClearActive({:?})", id)),
UpdateMessage::WindowScale(scale) => {
f.write_fmt(format_args!("WindowScale({})", scale))
}
UpdateMessage::Disabled { id, is_disabled } => {
f.write_fmt(format_args!("Disabled({:?}:{})", id, is_disabled))
}
UpdateMessage::RequestPaint => f.write_str("RequestPaint"),
UpdateMessage::State { id, state: _ } => {
f.write_fmt(format_args!("State({:?}:???)", id))
}
UpdateMessage::KeyboardNavigable { id } => {
f.write_fmt(format_args!("KeyboardNavigable({:?})", id))
}
UpdateMessage::Draggable { id } => f.write_fmt(format_args!("Draggable({:?})", id)),
UpdateMessage::ToggleWindowMaximized => f.write_str("ToggleWindowMaximized"),
UpdateMessage::SetWindowMaximized(maximized) => {
f.write_fmt(format_args!("SetWindowMaximized({})", maximized))
}
UpdateMessage::MinimizeWindow => f.write_str("MinimizeWindow"),
UpdateMessage::DragWindow => f.write_str("DragWindow"),
UpdateMessage::DragResizeWindow(direction) => {
f.write_fmt(format_args!("DragResizeWindow({:?})", direction))
}
UpdateMessage::SetWindowDelta(delta) => {
f.write_fmt(format_args!("SetWindowDelta({}, {})", delta.x, delta.y))
}
UpdateMessage::Animation { id, animation: _ } => {
f.write_fmt(format_args!("Animation({:?})", id))
}
UpdateMessage::ShowContextMenu { menu: _, pos } => {
f.write_fmt(format_args!("ShowContextMenu({:?})", pos))
}
UpdateMessage::WindowMenu { menu: _ } => f.write_str("WindowMenu"),
UpdateMessage::SetWindowTitle { title } => {
f.write_fmt(format_args!("SetWindowTitle({:?})", title))
}
UpdateMessage::AddOverlay {
id,
position,
view: _,
} => f.write_fmt(format_args!("AddOverlay({:?} : {:?})", id, position)),
UpdateMessage::RemoveOverlay { id } => {
f.write_fmt(format_args!("RemoveOverlay({:?})", id))
}
UpdateMessage::Inspect => f.write_str("Inspect"),
UpdateMessage::ScrollTo { id, rect } => {
f.write_fmt(format_args!("ScrollTo({:?}:{:?})", id, rect))
}
UpdateMessage::FocusWindow => f.write_str("FocusWindow"),
UpdateMessage::SetImeAllowed { allowed } => {
f.write_fmt(format_args!("SetImeAllowed({})", allowed))
}
UpdateMessage::SetImeCursorArea { position, size } => {
f.write_fmt(format_args!("SetImeCursorArea({:?}, {:?})", position, size))
}
UpdateMessage::WindowVisible(visible) => {
f.write_fmt(format_args!("WindowVisible({})", visible))
}
}
}
}
22 changes: 11 additions & 11 deletions src/view_storage.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -52,18 +52,18 @@ impl ViewStorage {
}
}

/// Returns the deepest view ID encountered traversing parents. It does *not* guarantee
/// that it is a real window root; any caller should perform the same test
/// of `window_tracking::is_known_root()` that `ViewId.root()` does before
/// assuming the returned value is really a window root.
pub(crate) fn root_view_id(&self, id: ViewId) -> Option<ViewId> {
let mut parent = self.parent.get(id).cloned().flatten();
while let Some(parent_id) = parent {
match self.parent.get(parent_id).cloned().flatten() {
Some(id) => {
parent = Some(id);
}
None => {
return parent;
}
}
// Rewritten from the original looping version - unless we anticipate view ids
// deeper than the possible stack depth, this should be more efficient and
// require less cloning.
if let Some(p) = self.parent.get(id).unwrap_or(&None) {
self.root_view_id(*p)
} else {
Some(id)
Comment on lines +60 to +66

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Happy to leave it as-is too. Though I think if you have enough view ids to exhaust the stack, you might have some UI usability problems far worse than hitting that limit :-)

}
parent
}
}
63 changes: 59 additions & 4 deletions src/window_handle.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -310,6 +310,9 @@ impl WindowHandle {
}
}
if was_focused != cx.app_state.focus {
// What is this for? If you call ViewId.request_focus(), this
// causes focus to be set to your view, then briefly set to
// None here and then back. Why?
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the app_state focus will taken from it's option before a pointer down even is propagated. Once event propagation is done, if another view has set itself to have focus because of the pointer down event the focus_changed function will notify the old was_focused that it's focus has been lost and the new app state focus that it has gained focus

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What I found (I added dumping the stack to the focus method it calls if the value was None) is that, when someViewId.request_focus() was called with an existing focus target, focus goes old_id -> None -> new_id.

I didn't check if events were fired for focus going to None, since event propagation wasn't working at that point. As long as we're not doubling up event notifications, it's probably fine - just peculiar.

cx.app_state.focus_changed(was_focused, cx.app_state.focus);
}

Expand Down Expand Up @@ -701,11 +704,28 @@ impl WindowHandle {
CENTRAL_UPDATE_MESSAGES.with_borrow_mut(|central_msgs| {
if !central_msgs.is_empty() {
UPDATE_MESSAGES.with_borrow_mut(|msgs| {
let central_msgs = std::mem::take(&mut *central_msgs);
for (id, msg) in central_msgs {
// We need to retain any messages which are for a view that either belongs
// to a different window, or which does not yet have a root
let removed_central_msgs =
std::mem::replace(central_msgs, Vec::with_capacity(central_msgs.len()));
for (id, msg) in removed_central_msgs {
if let Some(root) = id.root() {
let msgs = msgs.entry(root).or_default();
msgs.push(msg);
} else {
// Messages that are not for our root get put back - they may
// belong to another window, or may be construction-time messages
// for a View that does not yet have a window but will momentarily.
//
// Note that if there is a plethora of events for ids which were created
// but never assigned to any view, they will probably pile up in here,
// and if that becomes a real problem, we may want a garbage collection
// mechanism, or give every message a max-touch-count and discard it
// if it survives too many iterations through here. Unclear if there
// are real-world app development patterns where that could actually be
// an issue. Since any such mechanism would have some overhead, there
// should be a proven need before building one.
central_msgs.push((id, msg));
}
}
});
Expand All @@ -716,11 +736,17 @@ impl WindowHandle {
if !central_msgs.borrow().is_empty() {
DEFERRED_UPDATE_MESSAGES.with(|msgs| {
let mut msgs = msgs.borrow_mut();
let central_msgs = std::mem::take(&mut *central_msgs.borrow_mut());
for (id, msg) in central_msgs {
let removed_central_msgs = std::mem::replace(
&mut *central_msgs.borrow_mut(),
Vec::with_capacity(msgs.len()),
);
let unprocessed = &mut *central_msgs.borrow_mut();
for (id, msg) in removed_central_msgs {
if let Some(root) = id.root() {
let msgs = msgs.entry(root).or_default();
msgs.push((id, msg));
} else {
unprocessed.push((id, msg));
}
}
});
Expand Down Expand Up @@ -748,11 +774,40 @@ impl WindowHandle {
if cx.app_state.focus != Some(id) {
let old = cx.app_state.focus;
cx.app_state.focus = Some(id);

// Fix: Focus events were never dispatched to views' own
// event_before_children / event_after_children.
//
// This is a bit messy; could it be done in ViewId.apply_event()
// instead? Are there other cases of dropped events?
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Other events are from winit, so they would be dispatched by the event method, while Event::FocusGained and Event::FocusLost is kind of an "internal" event.

let mut ec = EventCx {
app_state: cx.app_state,
};

if let Some(old) = old.as_ref() {
ec.unconditional_view_event(*old, Event::FocusLost, true);
}
ec.unconditional_view_event(id, Event::FocusGained, true);

cx = UpdateCx {
app_state: ec.app_state,
};

cx.app_state.focus_changed(old, cx.app_state.focus);
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unconditional_view_event probably needs to called in focus_changed.

E.g. when the focus got changed due to pointer click.

}
}
UpdateMessage::ClearFocus(id) => {
let old = cx.app_state.focus;
cx.app_state.clear_focus();
if let Some(old) = old {
let mut ec = EventCx {
app_state: cx.app_state,
};
ec.unconditional_view_event(old, Event::FocusLost, true);
cx = UpdateCx {
app_state: ec.app_state,
};
}
cx.app_state.focus_changed(Some(id), None);
}
UpdateMessage::Active(id) => {
Expand Down
16 changes: 15 additions & 1 deletion src/window_tracking.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -72,7 +72,17 @@ impl WindowMapping {
}

fn window_id_for_root(&self, id: &ViewId) -> Option<WindowId> {
self.window_id_for_root_view_id.get(id).copied()
let result = self.window_id_for_root_view_id.get(id).copied();
// We are called by ViewId.window_id(), which should no longer ever return a
// ViewId from root() that is not actually a root - so if we get here with a
// window id that has gained a parent since it was determined to be a root,
// something is very wrong.
debug_assert!(
id.parent().is_none(),
"Not a root view id: {:?} - check the logic in ViewId.window_id().",
id
);
result
}

fn root_view_id_for(&self, window_id: &WindowId) -> Option<ViewId> {
Expand All @@ -94,6 +104,10 @@ pub fn with_window_id_and_window<F: FnOnce(&WindowId, &Window) -> T, T>(
.unwrap_or(None)
}

pub fn is_known_root(id: &ViewId) -> bool {
with_window_map(|map| map.window_id_for_root_view_id.contains_key(id)).unwrap_or(false)
}

fn with_window_map_mut<F: FnMut(&mut WindowMapping)>(mut f: F) -> bool {
let map = WINDOW_FOR_WINDOW_AND_ROOT_IDS.get_or_init(|| RwLock::new(Default::default()));
if let Ok(mut map) = map.write() {
Expand Down