imgui-rs/imgui/src/drag_drop.rs
2021-10-15 16:47:24 -04:00

614 lines
26 KiB
Rust

//! Structs to create a Drag and Drop sequence. Almost all structs are re-exported
//! and can be accessed from the crate root; some additional utilities can be found in here.
//!
//! A DragDrop is a UI mechanism where users can appear to "drag"
//! some data from one [source](DragDropSource) to one [target](DragDropTarget).
//! A source and a target must both have some `name` identifier, which is declared when they
//! are created. If these names are equal, then a `payload` of some kind
//! will be given to the target caller whne the user releases their mouse button over
//! the target (additionally, the UI will reflect that the payload *can* be deposited
//! in the target).
//!
//! The complexity of this implementation is primarily in managing this payload. Users
//! can provide three different kinds of payloads:
//!
//! 1. Users can give an [empty payload](DragDropPayloadEmpty) with [begin](DragDropSource::begin).
//! This payload type is essentially just a notification system, but using some shared state,
//! this can be reasonably powerful, and is the safest way to transfer non-Copy data offered
//! right now.
//! 2. Users can give a [simple Copy payload](DragDropPayloadPod) with [begin](DragDropSource::begin_payload).
//! This allows users to copy data to Dear ImGui, which will take ownership over it, and then be given
//! it back to the Target. Please note: users are of course free to not drop any drag (cancel a drag),
//! so this data could easily be lost forever. Our `'static + Copy` bound is intended to keep users
//! to simplistic types.
//! 3. An unsafe implementation is provided which allows for any data to be unsafely copied. Note that once
//! you use this method, the safe implementations in #1 and #2 can create memory unsafety problems; notably,
//! they both assume that a payload has certain header information within it.
//!
//! For examples of each payload type, see [DragDropSource].
use std::{any, ffi, marker::PhantomData};
use crate::{sys, Condition, Ui};
use bitflags::bitflags;
bitflags!(
/// Flags for igBeginDragDropSource(), igAcceptDragDropPayload()
#[repr(transparent)]
pub struct DragDropFlags: u32 {
/// By default, a successful call to igBeginDragDropSource opens a tooltip so you can
/// display a preview or description of the source contents. This flag disable this
/// behavior.
const SOURCE_NO_PREVIEW_TOOLTIP = sys::ImGuiDragDropFlags_SourceNoPreviewTooltip;
/// By default, when dragging we clear data so that igIsItemHovered() will return false, to
/// avoid subsequent user code submitting tooltips. This flag disable this behavior so you
/// can still call igIsItemHovered() on the source item.
const SOURCE_NO_DISABLE_HOVER = sys::ImGuiDragDropFlags_SourceNoDisableHover;
/// Disable the behavior that allows to open tree nodes and collapsing header by holding
/// over them while dragging a source item.
const SOURCE_NO_HOLD_TO_OPEN_OTHERS = sys::ImGuiDragDropFlags_SourceNoHoldToOpenOthers;
/// Allow items such as igText(), igImage() that have no unique identifier to be used as
/// drag source, by manufacturing a temporary identifier based on their window-relative
/// position. This is extremely unusual within the dear imgui ecosystem and so we made it
/// explicit.
const SOURCE_ALLOW_NULL_ID = sys::ImGuiDragDropFlags_SourceAllowNullID;
/// External source (from outside of imgui), won't attempt to read current item/window
/// info. Will always return true. Only one Extern source can be active simultaneously.
const SOURCE_EXTERN = sys::ImGuiDragDropFlags_SourceExtern;
/// Automatically expire the payload if the source ceases to be submitted (otherwise
/// payloads are persisting while being dragged)
const SOURCE_AUTO_EXPIRE_PAYLOAD = sys::ImGuiDragDropFlags_SourceAutoExpirePayload;
/// igAcceptDragDropPayload() will returns true even before the mouse button is released.
/// You can then call igIsDelivery() to test if the payload needs to be delivered.
const ACCEPT_BEFORE_DELIVERY = sys::ImGuiDragDropFlags_AcceptBeforeDelivery;
/// Do not draw the default highlight rectangle when hovering over target.
const ACCEPT_NO_DRAW_DEFAULT_RECT = sys::ImGuiDragDropFlags_AcceptNoDrawDefaultRect;
/// Request hiding the igBeginDragDropSource tooltip from the igBeginDragDropTarget site.
const ACCEPT_NO_PREVIEW_TOOLTIP = sys::ImGuiDragDropFlags_AcceptNoPreviewTooltip;
/// For peeking ahead and inspecting the payload before delivery. This is just a convenience
/// flag for the intersection of `ACCEPT_BEFORE_DELIVERY` and `ACCEPT_NO_DRAW_DEFAULT_RECT`
const ACCEPT_PEEK_ONLY = sys::ImGuiDragDropFlags_AcceptPeekOnly;
}
);
impl Ui {
/// Creates a new [DragDropSource] with the given name.
pub fn drag_drop_source_config<T: AsRef<str>>(&self, name: T) -> DragDropSource<'_, T> {
DragDropSource {
name,
flags: DragDropFlags::empty(),
cond: Condition::Always,
ui: self,
}
}
}
/// Creates a source for drag drop data out of the last ID created.
///
/// ```no_run
/// # use imgui::*;
/// fn show_ui(ui: &Ui) {
/// ui.button("Hello, I am a drag source!");
///
/// // Creates an empty DragSource with no tooltip
/// ui.drag_drop_source_config("BUTTON_DRAG").begin();
/// }
/// ```
///
/// Notice especially the `"BUTTON_DRAG"` name -- this is the identifier of this
/// DragDropSource; [DragDropTarget]'s will specify an identifier to *receive*, and these
/// names must match up. A single item should only have one [DragDropSource], though
/// a target may have multiple different targets.
///
/// DropDropSources don't do anything until you use one of the three `begin_` methods
/// on this struct. Each of these methods describes how you handle the Payload which ImGui
/// will manage, and then give to a [DragDropTarget], which will received the payload. The
/// simplest and safest Payload is the empty payload, created with [begin](Self::begin).
#[derive(Debug)]
pub struct DragDropSource<'ui, T> {
name: T,
flags: DragDropFlags,
cond: Condition,
ui: &'ui Ui,
}
impl<'ui, T: AsRef<str>> DragDropSource<'ui, T> {
/// Creates a new [DragDropSource] with the given name.
#[deprecated(since = "0.9.0", note = "use `ui.drag_drop_source_config` instead")]
pub fn new(name: T, ui: &'ui Ui) -> Self {
Self {
name,
flags: DragDropFlags::empty(),
cond: Condition::Always,
ui,
}
}
/// Sets the flags on the [DragDropSource]. Only the flags `SOURCE_NO_PREVIEW_TOOLTIP`,
/// `SOURCE_NO_DISABLE_HOVER`, `SOURCE_NO_HOLD_TO_OPEN_OTHERS`, `SOURCE_ALLOW_NULL_ID`,
/// `SOURCE_EXTERN`, `SOURCE_AUTO_EXPIRE_PAYLOAD` make semantic sense, but any other flags will
/// be accepted without panic.
#[inline]
pub fn flags(mut self, flags: DragDropFlags) -> Self {
self.flags = flags;
self
}
/// Sets the condition on the [DragDropSource]. Defaults to [Always](Condition::Always).
#[inline]
pub fn condition(mut self, cond: Condition) -> Self {
self.cond = cond;
self
}
/// Creates the source of a drag and returns a handle on the tooltip.
/// This handle can be immediately dropped without binding it, in which case a default empty
/// circle will be used for the "blank" tooltip as this item is being dragged around.
///
/// Otherwise, use this tooltip to add data which will display as this item is dragged.
/// If `SOURCE_NO_PREVIEW_TOOLTIP` is enabled, however, no preview will be displayed
/// and this returned token does nothing. Additionally, a given target may use the flag
/// `ACCEPT_NO_PREVIEW_TOOLTIP`, which will also prevent this tooltip from being shown.
///
/// This drag has no payload, but is still probably the most useful way in imgui-rs to handle payloads.
/// Using `once_cell` or some shared data, this pattern can be very powerful:
///
/// ```no_run
/// # use imgui::*;
/// fn show_ui(ui: &Ui, drop_message: &mut Option<String>) {
/// ui.button("Drag me!");
///
/// let drag_drop_name = "Test Drag";
///
/// // drag drop SOURCE
/// if ui.drag_drop_source_config(drag_drop_name).begin().is_some() {
/// // warning -- this would allocate every frame if `DragDropSource` has
/// // condition `Always`, which it does by default. We're okay with that for
/// // this example, but real code probably wouldn't want to allocate so much.
/// *drop_message = Some("Test Payload".to_string());
/// }
///
/// ui.button("Target me!");
///
/// // drag drop TARGET
/// if let Some(target) = ui.drag_drop_target() {
/// if target
/// .accept_payload_empty(drag_drop_name, DragDropFlags::empty())
/// .is_some()
/// {
/// let msg = drop_message.take().unwrap();
/// assert_eq!(msg, "Test Payload");
/// }
///
/// target.pop();
/// }
/// }
/// ```
///
/// In the above, you'll see how the payload is really just a message passing service.
/// If you want to pass a simple integer or other "plain old data", take a look at
/// [begin_payload](Self::begin_payload).
#[inline]
pub fn begin(self) -> Option<DragDropSourceToolTip<'ui>> {
self.begin_payload(())
}
/// Creates the source of a drag and returns a handle on the tooltip.
/// This handle can be immediately dropped without binding it, in which case a default empty
/// circle will be used for the "blank" tooltip as this item is being dragged around.
///
/// Otherwise, use this tooltip to add data which will display as this item is dragged.
/// If `SOURCE_NO_PREVIEW_TOOLTIP` is enabled, however, no preview will be displayed
/// and this returned token does nothing. Additionally, a given target may use the flag
/// `ACCEPT_NO_PREVIEW_TOOLTIP`, which will also prevent this tooltip from being shown.
///
/// This function also takes a payload in the form of `T: Copy + 'static`. ImGui will
/// memcpy this data immediately to an internally held buffer, and will return the data
/// to [DragDropTarget].
///
/// ```no_run
/// # use imgui::*;
/// fn show_ui(ui: &Ui) {
/// ui.button("Drag me!");
///
/// let drag_drop_name = "Test Drag";
/// let msg_to_send = "hello there sailor";
///
/// // drag drop SOURCE
/// if let Some(tooltip) = ui.drag_drop_source_config(drag_drop_name).begin_payload(msg_to_send) {
/// ui.text("Sending message!");
/// tooltip.end();
/// }
///
/// ui.button("Target me!");
///
/// // drag drop TARGET
/// if let Some(target) = ui.drag_drop_target() {
/// if let Some(Ok(payload_data)) = target
/// .accept_payload::<&'static str, _>(drag_drop_name, DragDropFlags::empty())
/// {
/// let msg = payload_data.data;
/// assert_eq!(msg, msg_to_send);
/// }
///
/// target.pop();
/// }
/// }
/// ```
#[inline]
pub fn begin_payload<P: Copy + 'static>(
self,
payload: P,
) -> Option<DragDropSourceToolTip<'ui>> {
unsafe {
let payload = TypedPayload::new(payload);
self.begin_payload_unchecked(
&payload as *const _ as *const ffi::c_void,
std::mem::size_of::<TypedPayload<P>>(),
)
}
}
/// Creates the source of a drag and returns a handle on the tooltip.
/// This handle can be immediately dropped without binding it, in which case a default empty
/// circle will be used for the "blank" tooltip as this item is being dragged around.
///
/// Otherwise, use this tooltip to add data which will display as this item is dragged.
/// If `SOURCE_NO_PREVIEW_TOOLTIP` is enabled, however, no preview will be displayed
/// and this returned token does nothing. Additionally, a given target may use the flag
/// `ACCEPT_NO_PREVIEW_TOOLTIP`, which will also prevent this tooltip from being shown.
///
/// This function also takes a payload of any `*const T`. ImGui will
/// memcpy this data immediately to an internally held buffer, and will return the data
/// to [DragDropTarget].
///
/// ## Safety
/// This function itself will not cause a panic, but using it directly opts you into
/// managing the lifetime of the pointer provided yourself. Dear ImGui will execute a memcpy on
/// the data passed in with the size (in bytes) given, but this is, of course, just a copy,
/// so if you pass in an `&String`, for example, the underlying String data will not be cloned,
/// and could easily dangle if the `String` is dropped.
///
/// Moreover, if `Condition::Always` is set (as it is by default), you will be copying in your data
/// every time this function is ran in your update loop, which if it involves an allocating and then
/// handing the allocation to ImGui, would result in a significant amount of data created.
///
/// Overall, users should be very sure that this function is needed before they reach for it, and instead
/// should consider either [begin](Self::begin) or [begin_payload](Self::begin_payload).
#[inline]
pub unsafe fn begin_payload_unchecked(
&self,
ptr: *const ffi::c_void,
size: usize,
) -> Option<DragDropSourceToolTip<'ui>> {
let should_begin = sys::igBeginDragDropSource(self.flags.bits() as i32);
if should_begin {
sys::igSetDragDropPayload(self.ui.scratch_txt(&self.name), ptr, size, self.cond as i32);
Some(DragDropSourceToolTip::push())
} else {
None
}
}
}
/// A helper struct for RAII drap-drop support.
pub struct DragDropSourceToolTip<'ui>(PhantomData<&'ui Ui>);
impl DragDropSourceToolTip<'_> {
/// Creates a new tooltip internally.
#[inline]
fn push() -> Self {
Self(PhantomData)
}
/// Ends the tooltip directly. You could choose to simply allow this to drop
/// by not calling this, which will also be fine.
#[inline]
pub fn end(self) {
// left empty to invoke drop...
}
}
impl Drop for DragDropSourceToolTip<'_> {
fn drop(&mut self) {
unsafe { sys::igEndDragDropSource() }
}
}
impl Ui {
/// Creates a new DragDropTarget, which gives methods for handling
/// accepting payloads.
#[doc(alias = "BeginDragDropTarget")]
pub fn drag_drop_target(&self) -> Option<DragDropTarget<'_>> {
let should_begin = unsafe { sys::igBeginDragDropTarget() };
if should_begin {
Some(DragDropTarget(self))
} else {
None
}
}
}
/// Creates a target for drag drop data out of the last ID created.
///
/// ```no_run
/// # use imgui::*;
/// fn show_ui(ui: &Ui) {
/// // Drop something on this button please!
/// ui.button("Hello, I am a drag Target!");
///
/// if let Some(target) = DragDropTarget::new(ui) {
/// // accepting an empty payload (which is really just raising an event)
/// if let Some(_payload_data) = target.accept_payload_empty("BUTTON_DRAG", DragDropFlags::empty()) {
/// println!("Nice job getting on the payload!");
/// }
///
/// // and we can accept multiple, different types of payloads with one drop target.
/// // this is a good pattern for handling different kinds of drag/drop situations with
/// // different kinds of data in them.
/// if let Some(Ok(payload_data)) = target.accept_payload::<usize, _>("BUTTON_ID", DragDropFlags::empty()) {
/// println!("Our payload's data was {}", payload_data.data);
/// }
/// }
/// }
/// ```
///
/// Notice especially the `"BUTTON_DRAG"` and `"BUTTON_ID"` name -- this is the identifier of this
/// DragDropTarget; [DragDropSource]s will specify an identifier when they send a payload, and these
/// names must match up. Notice how a target can have multiple acceptances on them -- this is a good
/// pattern to handle multiple kinds of data which could be passed around.
///
/// DropDropTargets don't do anything until you use one of the three `accept_` methods
/// on this struct. Each of these methods will spit out a _Payload struct with an increasing
/// amount of information on the Payload. The absolute safest solution is [accept_payload_empty](Self::accept_payload_empty).
#[derive(Debug)]
pub struct DragDropTarget<'ui>(&'ui Ui);
impl<'ui> DragDropTarget<'ui> {
/// Creates a new DragDropTarget, which gives methods for handling
/// accepting payloads.
#[doc(alias = "BeginDragDropTarget")]
#[deprecated(since = "0.9.0", note = "Use `ui.drag_drop_target() instead")]
pub fn new(ui: &'ui Ui) -> Option<Self> {
ui.drag_drop_target()
}
/// Accepts an empty payload. This is the safest option for raising named events
/// in the DragDrop API. See [DragDropSource::begin] for more information on how you
/// might use this pattern.
///
/// Note: If you began this operation with `begin_payload_unchecked` it always incorrect
/// to use this function. Use `accept_payload_unchecked` instead
pub fn accept_payload_empty(
&self,
name: impl AsRef<str>,
flags: DragDropFlags,
) -> Option<DragDropPayloadEmpty> {
self.accept_payload(name, flags)?
.ok()
.map(|payload_pod: DragDropPayloadPod<()>| DragDropPayloadEmpty {
preview: payload_pod.preview,
delivery: payload_pod.delivery,
})
}
/// Accepts a payload with plain old data in it. This returns a Result, since you can specify any
/// type. The sent type must match the return type (via TypeId) to receive an `Ok`.
///
/// Note: If you began this operation with `begin_payload_unchecked` it always incorrect
/// to use this function. Use `accept_payload_unchecked` instead
pub fn accept_payload<T: 'static + Copy, Name: AsRef<str>>(
&self,
name: Name,
flags: DragDropFlags,
) -> Option<Result<DragDropPayloadPod<T>, PayloadIsWrongType>> {
let output = unsafe { self.accept_payload_unchecked(name, flags) };
// convert the unsafe payload to our Result
output.map(|unsafe_payload| {
// sheering off the typeid...
let received =
unsafe { (unsafe_payload.data as *const TypedPayloadHeader).read_unaligned() };
let expected = any::TypeId::of::<T>();
if received.type_id == expected {
let data =
unsafe { (unsafe_payload.data as *const TypedPayload<T>).read_unaligned() }
.data;
Ok(DragDropPayloadPod {
data,
preview: unsafe_payload.preview,
delivery: unsafe_payload.delivery,
})
} else {
Err(PayloadIsWrongType {
received,
expected: TypedPayloadHeader::new::<T>(),
})
}
})
}
/// Accepts a drag and drop payload which contains a raw pointer to [c_void](std::ffi::c_void)
/// and a size in bytes. Users should generally avoid using this function
/// if one of the safer variants is acceptable.
///
/// ## Safety
///
/// Because this pointer comes from ImGui, absolutely no promises can be made on its
/// contents, alignment, or lifetime. Interacting with it is therefore extremely unsafe.
/// **Important:** a special note needs to be made to the [ACCEPT_BEFORE_DELIVERY](DragDropFlags::ACCEPT_BEFORE_DELIVERY) flag --
/// passing this flag will make this function return `Some(DragDropPayload)` **even before
/// the user has actually "dropped" the payload by release their mouse button.**
///
/// In safe functions, this works just fine, since the data can be freely copied
/// (or doesn't exist at all!). However, if you are working with your own data, you must
/// be extremely careful with this data, as you may, effectively, only have immutable access to it.
///
/// Moreover, if the `DragDropSource` has also used `Condition::Once` or similar when they sent the data,
/// ImGui will assume its data is still valid even after your preview, so corrupting that data could
/// lead to all sorts of unsafe behvaior on ImGui's side. In summary, using this function for any data
/// which isn't truly `Copy` or "plain old data" is difficult, and requires substantial knowledge
/// of the various edge cases.
pub unsafe fn accept_payload_unchecked(
&self,
name: impl AsRef<str>,
flags: DragDropFlags,
) -> Option<DragDropPayload> {
let inner = sys::igAcceptDragDropPayload(self.0.scratch_txt(name), flags.bits() as i32);
if inner.is_null() {
None
} else {
let inner = *inner;
// @fixme: there are actually other fields on `inner` which I have shorn -- they're
// considered internal to imgui (such as id of who sent this), so i've left it for
// now this way.
Some(DragDropPayload {
data: inner.Data,
size: inner.DataSize as usize,
preview: inner.Preview,
delivery: inner.Delivery,
})
}
}
/// Ends the current target. Ironically, this doesn't really do anything in ImGui
/// or in imgui-rs, but it might in the future.
pub fn pop(self) {
// omitted...exists just to run Drop.
}
}
impl Drop for DragDropTarget<'_> {
fn drop(&mut self) {
unsafe { sys::igEndDragDropTarget() }
}
}
/// An empty DragDropPayload. It has no data in it, and just includes
/// two bools with status information.
#[derive(Debug, Clone, Copy)]
#[non_exhaustive]
pub struct DragDropPayloadEmpty {
/// Set when [`accept_payload_empty`](DragDropTarget::accept_payload_empty) was called
/// and mouse has been hovering the target item.
pub preview: bool,
/// Set when [`accept_payload_empty`](DragDropTarget::accept_payload_empty) was
/// called and mouse button is released over the target item.
pub delivery: bool,
}
/// A DragDropPayload with status information and some POD, or plain old data,
/// in it.
#[derive(Debug, Copy, Clone)]
#[non_exhaustive]
pub struct DragDropPayloadPod<T: 'static + Copy> {
/// The kind data which was requested.
pub data: T,
/// Set when [`accept_payload`](DragDropTarget::accept_payload) was called
/// and mouse has been hovering the target item.
pub preview: bool,
/// Set when [`accept_payload`](DragDropTarget::accept_payload) was
/// called and mouse button is released over the target item.
pub delivery: bool,
}
#[derive(Debug)]
#[non_exhaustive]
pub struct DragDropPayload {
/// Data which is copied and owned by ImGui. If you have accepted the payload, you can
/// take ownership of the data; otherwise, view it immutably. Interacting with `data` is
/// very unsafe.
pub data: *const ffi::c_void,
/// The size of the data in bytes.
pub size: usize,
/// Set when [`accept_payload_unchecked`](DragDropTarget::accept_payload_unchecked) was called
/// and mouse has been hovering the target item.
pub preview: bool,
/// Set when [`accept_payload_unchecked`](DragDropTarget::accept_payload_unchecked) was
/// called and mouse button is released over the target item. If this is set to false, then you
/// set DragDropFlags::ACCEPT_BEFORE_DELIVERY and shouldn't mutate `data`.
pub delivery: bool,
}
/// A typed payload.
#[derive(Debug, Clone, Copy)]
#[repr(C)]
struct TypedPayload<T> {
header: TypedPayloadHeader,
data: T,
}
impl<T: Copy + 'static> TypedPayload<T> {
/// Creates a new typed payload which contains this data.
fn new(data: T) -> Self {
Self {
header: TypedPayloadHeader::new::<T>(),
data,
}
}
}
/// A header for a typed payload.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Ord, PartialOrd)]
#[repr(C)]
struct TypedPayloadHeader {
type_id: any::TypeId,
#[cfg(debug_assertions)]
type_name: &'static str,
}
impl TypedPayloadHeader {
#[cfg(debug_assertions)]
fn new<T: 'static>() -> Self {
Self {
type_id: any::TypeId::of::<T>(),
type_name: any::type_name::<T>(),
}
}
#[cfg(not(debug_assertions))]
fn new<T: 'static>() -> Self {
Self {
type_id: any::TypeId::of::<T>(),
}
}
}
/// Indicates that an incorrect payload type was received. It is opaque,
/// but you can view useful information with Debug formatting when
/// `debug_assertions` are enabled.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Ord, PartialOrd)]
pub struct PayloadIsWrongType {
expected: TypedPayloadHeader,
received: TypedPayloadHeader,
}
#[cfg(debug_assertions)]
impl std::fmt::Display for PayloadIsWrongType {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(
f,
"Payload is {} -- expected {}",
self.received.type_name, self.expected.type_name
)
}
}
#[cfg(not(debug_assertions))]
impl std::fmt::Display for PayloadIsWrongType {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.pad("Payload is wrong type")
}
}
impl std::error::Error for PayloadIsWrongType {}