* Part of https://github.com/emilk/egui/issues/4535
* Closes https://github.com/emilk/egui/issues/3974
This adds a special `sizing_pass` mode to `Ui`, in which we have no
centered or justified layouts, and everything is hidden. This is used by
`Area` to use the first frame to measure the size of its contents so
that it can then set the perfectly correct size the subsequent frames.
For menus, where buttons are justified (span the full width), this
finally the problem of auto-sizing. Before you would have to pick a
width manually, and all buttons would expand to that width. If it was
too wide, it looked weird. If it was too narrow, text would wrap. Now
all menus are exactly the width they need to be. By default menus will
wrap at `Spacing::menu_width`.
This affects all situations when you have something that should be as
small as possible, but still span the full width/height of the parent.
For instance: the `egui::Separator` widget now checks the
`ui.is_sizing_pass` flag before deciding on a size. In the sizing pass a
horizontal separator is always 0 wide, and only in subsequent passes
will it span the full width.
* Closes https://github.com/emilk/egui/issues/3444
* Closes https://github.com/emilk/egui/issues/865
On a touch screen, if you press down on a widget and hold for 0.6
seconds (`MAX_CLICK_DURATION`), it will now trigger a secondary click,
i.e. `Response::secondary_clicked` will be `true`. This means you can
now open context menus on touch screens.
Thanks to `impl From<bool> for Vec2b` one can now shorten some builder
calls, like:
Previous:
```rust
egui::ScrollArea::vertical()
.auto_shrink([false; 2])
```
New:
```rust
egui::ScrollArea::vertical()
.auto_shrink(false)
```
I encountered a case where I needed to know if an egui context menu was
open, even if the mouse cursor was not in an egui area (full details in
discord). I found that every resource I needed to detect that the menu
was open was either private, or pub(crate). While it is possible to
wrap the `Response::context_menu()` in code to do state-tracking, it
becomes necessary to duplicate that code in every place you use a
context menu.
In this commit, I add `Context::is_context_menu_open()`. Named similarly
to `Context::is_pointer_over_area()`, this method will return true if
any context menu is open. This is possible because the context menu
uses a temp var with a fixed Id to store its state. This method just
fetches the state, and interrogates it to see if there is a menu
present.
One helper method, `BarState::has_root()`, was added as all the fields
needed to perform the check were private to the `menu` module.
I've also updated the Context Menu demo to show the result of
`is_context_menu_open()` to verify the code functions as expected.
Andreas Reich
Emil Ernerfeldt
rustbasic
David M. Lary