Properly release GL resource when unmapping a window and detect stale
cache indices using a generation count. This fixes the disappearing
images (GL textures would be invalid and need to be re-created) as well
as the panics when an item's cache index ended up being re-used because
some other item was drawn first and allocated that indices. The latter
is fixed by using a generational counter on the cache that's bumped when
clearing, instead of a single "cache_ok" bool.
The follow basic example reproduces the issue that the items remain around
but the item cache has been destroyed and re-created, which causes get_mut() to fail:
```
let app = App::new();
loop {
app.run(); // now close the window via the close button in the window decoration
}
```
This replaces the box gradient with a new implementation that
behaves like the HTML Canvas element, by applying a gaussian
blur to the alpha of the rectangle to shadow.
The drop-shadow-blur property is changed to be now just a "level", like
the HTML Canvas shadowBlur property, which is defined to be half of the
standard deviation of the gaussian blur to be applied.
We don't need a property reference anymore, a plain image reference is fine AFAICS.
Dirtyness of the source is tracked on the caller side of layouting_info()
or in the draw_image_impl anyway.
Use slab instead of the deprecated vec_arena, both of which appear to
use the same Vec based storage of an enum that's either the entry or an
index to the next free slot.
Instead of using a solve_layout function in the component, use property to hold
a layout cache.
This commit only implement the GridLayout and only the interpreter part
According to llvm-lines, MaybeAnimatedPropertyInfoWrapper::set_binding was
in the top 5 of functions with 15971 lines over 46 copies.
Split the code that does not depend on the Item parameter in a different function
Pass everything needed for delayed evaluation for
`PlatformWindow::font_metrics()` to permit caching the font matching
result in the Text/TextInput's rendering cache.
We query text metrics frequently for text items, for example when in
layouts. This requires font resolution, which is about to become more
much more expensive due to analysis of the underlying text. To speed
this up, the objective is to use the item rendering cache. Making that
work in turn requires querying all related properties inside a property
tracker. That means we need to delay querying anything related to that,
including the font request needed for the `font_metrics()` function on
the PlatformWindow trait.
Commit 843f52b3c5 erroneously applied the cross-axis
preferred size, which breaks the
images in buttons in the printer demo.
Also use the same value for shrink as for flex-grow, as advised by Olivier :-)
