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Add ZOrdering to SpriteBatches #1139

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3fcfe95
Add ZOrdering to SpriteBatches
distantforest1 Mar 16, 2023
adb42f6
Minor code style tweaks
distantforest1 Mar 16, 2023
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177 changes: 172 additions & 5 deletions h2d/SpriteBatch.hx
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,9 @@ package h2d;
import h2d.RenderContext;
import h2d.impl.BatchDrawState;

/**
Iterates through the BatchElement linked list.
**/
private class ElementsIterator {
var e : BatchElement;
public inline function new(e) {
Expand All @@ -18,6 +21,28 @@ private class ElementsIterator {
}
}

/**
Iterates through the BatchElement linked list in reverse (from the last element backwards to the first element).
**/

private class ReversedElementsIterator {
var e:BatchElement;

public inline function new(e) {
this.e = e;
}

public inline function hasNext() {
return e != null;
}

public inline function next() {
var p = e;
e = @:privateAccess e.prev;
return p;
}
}

/**
A base class for `SpriteBatch` elements which can be extended with custom logic.

Expand Down Expand Up @@ -80,6 +105,12 @@ class BatchElement {
as `SpriteBatch.tile` used as a source of rendered texture.
**/
public var t : Tile;
/**
The order it is drawn on screen.

The `hasZOrder` bool must be `true` on `SpriteBatch` for this to take effect.
**/
public var zOrder(default,set) : Float;
/**
Alpha value of the element.
Alias of `BatchElement.a`.
Expand Down Expand Up @@ -117,10 +148,28 @@ class BatchElement {
return a = v;
}


/**
Set the zOrder. The `SpriteBatch.hasZOrder` must be `true` for this to work as intended.
@param v The z-order of the `BatchElement`. The higher the z-order the closer it is to the screen.
**/
function set_zOrder(v) {
this.zOrder = v;
if (this.batch == null)
return v;

// Remove and re-insert the item back into the batch sorted
if (this.batch.hasZOrder) {
this.batch.delete(this);
this.batch.add(this);
}
return v;
}

/**
Override this method to perform custom logic per batch element.
Update method called only if `SpriteBatch.hasUpdate` is set to `true`.
@param dt The elapsed time in seconds since last update from `RenderContext.elapsedTime`.
@param et The elapsed time in seconds since last update from `RenderContext.elapsedTime`.
@returns If method returns `false`, element will be removed from the SpriteBatch.
**/
@:dox(show)
Expand Down Expand Up @@ -204,13 +253,22 @@ class SpriteBatch extends Drawable {
Enables usage of `update` method in SpriteBatch elements.
**/
public var hasUpdate : Bool = false;
/**
Enables z-ordering on added BatchElements.

Makes use of `BatchElement.zOrder`. Higher numbers of zOrder means the sprites will be drawn on top.
**/
public var hasZOrder : Bool = false;
/**
Get number of elements in this SpriteBatch
**/
public var length(get, null):Int;
var first : BatchElement;
var last : BatchElement;
var tmpBuf : hxd.FloatBuffer;
var buffer : h3d.Buffer;
var state : BatchDrawState;
var empty : Bool;

/**
Create new SpriteBatch instance.
@param t The Tile used as a base Texture to draw contents with.
Expand All @@ -225,10 +283,50 @@ class SpriteBatch extends Drawable {
/**
Adds a new BatchElement to the SpriteBatch.
@param e The element to add.
@param before When set, element will be added to the beginning of the element chain (rendered first).
@param before When set, element will be added to the beginning of the element chain (rendered first). If `hasZOrder` is enabled, this is ignored.
**/
public function add(e:BatchElement,before=false) {
public function add(e:BatchElement, before=false) {
e.batch = this;

// If hasZOrder=true insert it in the correct spot in the linked list.
if (hasZOrder) {
insertByZOrder(e);
return e;
}

// Default behaviour
addDefault(e);
return e;
}
/**
Add element by their z-order.

If the values are the same it will add it to front of the elements with the same values.
@param e The element to insert into the linked list sorted by z-order.
**/
function insertByZOrder(e:BatchElement) {
var inserted = false;

for (e1 in this.getElementsReversed()) {
if (e1.zOrder <= e.zOrder) {
this.insertAfter(e, e1);
inserted = true;
break;
}
}

if (inserted == false) {
addDefault(e, true);
}
return e;
}
/**
Add element to the end (or beginning) of the element chain.
@param e The element to add.
@param before When set, element will be added to the beginning of the element chain (rendered first).
*/
inline function addDefault(e:BatchElement, before=false) {

if( first == null ) {
first = last = e;
e.prev = e.next = null;
Expand All @@ -245,7 +343,6 @@ class SpriteBatch extends Drawable {
}
return e;
}

/**
Removes all elements from the SpriteBatch.

Expand All @@ -264,6 +361,59 @@ class SpriteBatch extends Drawable {
return add(new BatchElement(t));
}

/**
Insert element before a certain element
@param e The element to insert
@param before The element to insert before
**/
public function insertBefore(e:BatchElement, before:BatchElement) {
e.batch = this;

if (first == null) { // List is likely empty
first = last = e;
e.prev = e.next = null;
} else if (before.prev == null) { // First element
before.prev = e;
e.prev = null;
e.next = before;
first = e;
} else { // Insert between 'before' and 'before.prev'
var tmp = before.prev;
e.prev = tmp;
tmp.next = e;

e.next = before;
before.prev = e;
}
return e;
}

/**
Insert element after a certain element.
@param e The element to insert
@param after The element to insert after.
**/
public function insertAfter(e:BatchElement, after:BatchElement) {
e.batch = this;
if (first == null) { // List is likely empty
first = last = e;
e.prev = e.next = null;
} else if (after.next == null) { // Last element
after.next = e;
e.prev = after;
e.next = null;
last = e;
} else { // Insert between 'after' and 'after.next'
var tmp = after.next;
e.next = tmp;
tmp.prev = e;

e.prev = after;
after.next = e;
}
return e;
}

@:allow(h2d.BatchElement)
function delete(e : BatchElement) {
if( e.prev == null ) {
Expand Down Expand Up @@ -469,6 +619,23 @@ class SpriteBatch extends Drawable {
return new ElementsIterator(first);
}

/**
Iterates through the elements in reverse from the end to the beginning.

Adding or removing the elements will affect the Iterator results.
**/
public inline function getElementsReversed() {
return new ReversedElementsIterator(last);
}

/**
Get number of elements in SpriteBatch
@return Int
**/
function get_length():Int {
return [for (e in this.getElements()) e].length;
}

override function onRemove() {
super.onRemove();
if( buffer != null ) {
Expand Down