Enum zaplib::Area

pub enum Area {
    Empty,
    View(ViewArea),
    InstanceRange(InstanceRangeArea),
}

An Area can be thought of as a “pointer” into the draw tree. You typically get one as the result of a draw command, like Cx::add_instances, or View::end_view.

Note that an Area might point to an old element in the draw tree, so use Area::is_valid to check if it points to the latest version.

You can use an Area pointer to write fields, e.g. using Area::get_slice_mut, Area::write_user_uniforms, and so on. You can also use it for checking if an event was fired on a certain part of the draw tree (using Event::hits_pointer, Cx::key_focus, etc), and more.

TODO(JP): this can currently point to a View/CxView that isn’t actually in the draw tree anymore (ie. there the corresponding CxView is never referenced in the draw tree), or which just doesn’t exist at all any more (ie. the View object has also been removed). There is currently no was of telling if any of this is the case, since there is no “garbage collection” of views. CxView just sticks around in Cx::views forever.

Variants

Empty

A “null pointer”, doesn’t point to anything yet.

View(ViewArea)

See ViewArea.

InstanceRange(InstanceRangeArea)

See InstanceRangeArea.

Implementations

impl Area

pub fn is_empty(&self) -> bool

Shorthand for if let Area::Empty = area.

pub fn is_first_instance(&self) -> bool

Check if this is an Area::InstanceRange that points to the first instance in its corresponding DrawCall. Useful for setting uniforms on a DrawCall only once, when handling the first instance.

pub fn get_scroll_pos(&self, cx: &Cx) -> Vec2

The scroll position of an Area is the cumulative offset of all scroll containers (compared to if there had not been scrolling at all).

pub fn get_rect_for_first_instance(&self, cx: &Cx) -> Option<Rect>

Returns the final screen Rect for the first instance of the Area.

TODO(JP): The “first instance” bit is confusing; in most (if not all) cases you’d want to get something that covers the entire Area. Maybe returning a single Rect isn’t the right thing then, since the individual rectangles can be all over the place. We could return a Vec instead?

TODO(JP): Specifically, this seems to return very weird values for crate::TextIns (only the first character, and offset to the bottom it seems).

pub fn get_slice<T: 'static + Copy>(&self, cx: &Cx) -> &[T]

Get an immutable slice for an Area::InstanceRange.

This is not safe when T cannot be initialized with arbitrary data, so be careful. See also crate::cast.

pub fn get_first<'a, T: 'static + Copy + Default>(
    &'a self,
    cx: &'a mut Cx
) -> &'a T

Get an immutable reference to the first element.

If no such element exists, then a default element is returned.

Example:

let glyph = area.get_first::<TextIns>(cx);

TODO(JP): It would be nice if we can eliminate the default fallback altogether; see Cx::temp_default_data for ideas.

This is not safe when T cannot be initialized with arbitrary data, so be careful. See also crate::cast.

pub fn get_slice_mut<T: 'static + Copy>(&self, cx: &mut Cx) -> &mut [T]

Get a mutable slice for an Area::InstanceRange.

This is not safe when T cannot be initialized with arbitrary data, so be careful. See also crate::cast.

pub fn get_first_mut<'a, T: 'static + Copy + Default>(
    &'a self,
    cx: &'a mut Cx
) -> &'a mut T

Get a mutable reference to the first element.

If no such element exists, then a default element is returned. Mutating such a default element won’t do anything, but it also won’t hurt.

Note that in general you can’t rely on these mutations to last very long, since they’ll be cleared on the next redraw.

Example:

let glyph = area.get_first_mut::<TextIns>(cx);

TODO(JP): It would be nice if we can eliminate the default fallback altogether; see Cx::temp_default_data for ideas.

This is not safe when T cannot be initialized with arbitrary data, so be careful. See also crate::cast.

pub fn write_user_uniforms<T: 'static>(&self, cx: &mut Cx, uniforms: T)

Get a write user-level uniforms for the DrawCall that this Area points to.

It can be useful to wrap this in Area::is_first_instance to avoid having to write this multiple times for the same DrawCall.

pub fn write_texture_2d(
    &self,
    cx: &mut Cx,
    name: &str,
    texture_handle: TextureHandle
)

Write a Texture value into the the DrawCall associated with this Area::InstanceRange.

TODO(JP): Fix bug: https://github.com/Zaplib/zaplib/issues/156

Trait Implementations

impl Clone for Area

fn clone(&self) -> Area

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Area

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Area

fn default() -> Area

Returns the “default value” for a type.

impl Hash for Area

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher, 

Feeds a slice of this type into the given Hasher.

impl Ord for Area

fn cmp(&self, other: &Area) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

Restrict a value to a certain interval.

impl PartialEq<Area> for Area

fn eq(&self, other: &Area) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Area) -> bool

This method tests for !=.

impl PartialOrd<Area> for Area

fn partial_cmp(&self, other: &Area) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl Copy for Area

impl Eq for Area

impl StructuralEq for Area

impl StructuralPartialEq for Area