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Panel.cs
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Panel.cs
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using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using MLEM.Extensions;
using MLEM.Graphics;
using MLEM.Misc;
using MLEM.Textures;
using MLEM.Ui.Style;
namespace MLEM.Ui.Elements {
/// <summary>
/// A panel element to be used inside of a <see cref="UiSystem"/>.
/// The panel is a complex element that displays a box as a background to all of its child elements.
/// Additionally, a panel can be set to scroll overflowing elements on construction, which causes all elements that don't fit into the panel to be hidden until scrolled to using a <see cref="ScrollBar"/>.
/// </summary>
public class Panel : Element {
/// <summary>
/// The scroll bar that this panel contains.
/// This is only nonnull if scrolling overflow was enabled in the constructor.
/// Note that some scroll bar styling is controlled by this panel, namely <see cref="StepPerScroll"/> and <see cref="ScrollerSize"/>.
/// </summary>
public readonly ScrollBar ScrollBar;
/// <summary>
/// The texture that this panel should have, or null if it should be invisible.
/// </summary>
public StyleProp<NinePatch> Texture;
/// <summary>
/// The color that this panel's <see cref="Texture"/> should be drawn with.
/// If this style property has no value, <see cref="Color.White"/> is used.
/// </summary>
public StyleProp<Color> DrawColor;
/// <summary>
/// The amount that the scrollable area is moved per single movement of the scroll wheel
/// This value is passed to the <see cref="ScrollBar"/>'s <see cref="Elements.ScrollBar.StepPerScroll"/>
/// </summary>
public StyleProp<float> StepPerScroll;
/// <summary>
/// The size that the <see cref="ScrollBar"/>'s scroller should have, in pixels.
/// The scroller size's height specified here is the minimum height, otherwise, it is automatically calculated based on panel content.
/// </summary>
public StyleProp<Vector2> ScrollerSize;
/// <summary>
/// The amount of pixels of room there should be between the <see cref="ScrollBar"/> and the rest of the content
/// </summary>
public StyleProp<float> ScrollBarOffset {
get => this.scrollBarOffset;
set {
this.scrollBarOffset = value;
this.SetAreaDirty();
}
}
private readonly List<Element> relevantChildren = new List<Element>();
private readonly HashSet<Element> scrolledChildren = new HashSet<Element>();
private readonly float[] scrollBarMaxHistory;
private readonly bool scrollOverflow;
private RenderTarget2D renderTarget;
private bool relevantChildrenDirty;
private float scrollBarChildOffset;
private StyleProp<float> scrollBarOffset;
private float lastScrollOffset;
private bool childrenDirtyForScroll;
/// <summary>
/// Creates a new panel with the given settings.
/// </summary>
/// <param name="anchor">The panel's anchor</param>
/// <param name="size">The panel's default size</param>
/// <param name="positionOffset">The panel's offset from its anchor point</param>
/// <param name="setHeightBasedOnChildren">Whether the panel should automatically calculate its height based on its children's size</param>
/// <param name="scrollOverflow">Whether this panel should automatically add a scroll bar to scroll towards elements that are beyond the area this panel covers</param>
/// <param name="autoHideScrollbar">Whether the scroll bar should be hidden automatically if the panel does not contain enough children to allow for scrolling. This only has an effect if <paramref name="scrollOverflow"/> is <see langword="true"/>.</param>
public Panel(Anchor anchor, Vector2 size, Vector2 positionOffset, bool setHeightBasedOnChildren = false, bool scrollOverflow = false, bool autoHideScrollbar = true) : base(anchor, size) {
this.PositionOffset = positionOffset;
this.SetHeightBasedOnChildren = setHeightBasedOnChildren;
this.scrollOverflow = scrollOverflow;
this.CanBeSelected = false;
if (scrollOverflow) {
this.ScrollBar = new ScrollBar(Anchor.TopRight, Vector2.Zero, 0, 0) {
OnValueChanged = (element, value) => this.ScrollChildren(),
CanAutoAnchorsAttach = false,
AutoHideWhenEmpty = autoHideScrollbar,
IsHidden = autoHideScrollbar
};
// handle automatic element selection, the scroller needs to scroll to the right location
this.OnSelectedElementChanged += (_, e) => {
if (!this.Controls.IsAutoNavMode)
return;
if (e == null || !e.GetParentTree().Contains(this))
return;
this.ScrollToElement(e);
};
this.AddChild(this.ScrollBar);
this.scrollBarMaxHistory = new float[3];
for (var i = 0; i < this.scrollBarMaxHistory.Length; i++)
this.scrollBarMaxHistory[i] = -1;
}
}
/// <summary>
/// Creates a new panel with the given settings.
/// </summary>
/// <param name="anchor">The panel's anchor</param>
/// <param name="size">The panel's default size</param>
/// <param name="setHeightBasedOnChildren">Whether the panel should automatically calculate its height based on its children's size</param>
/// <param name="scrollOverflow">Whether this panel should automatically add a scroll bar to scroll towards elements that are beyond the area this panel covers</param>
/// <param name="autoHideScrollbar">Whether the scroll bar should be hidden automatically if the panel does not contain enough children to allow for scrolling. This only has an effect if <paramref name="scrollOverflow"/> is <see langword="true"/>.</param>
public Panel(Anchor anchor, Vector2 size, bool setHeightBasedOnChildren = false, bool scrollOverflow = false, bool autoHideScrollbar = true) : this(anchor, size, Vector2.Zero, setHeightBasedOnChildren, scrollOverflow, autoHideScrollbar) {}
/// <inheritdoc />
public override void ForceUpdateArea() {
if (this.scrollOverflow) {
// sanity check
if (this.SetHeightBasedOnChildren)
throw new NotSupportedException("A panel can't both set height based on children and scroll overflow");
foreach (var child in this.Children) {
if (child != this.ScrollBar && !child.Anchor.IsAuto())
throw new NotSupportedException($"A panel that handles overflow can't contain non-automatic anchors ({child})");
}
}
base.ForceUpdateArea();
if (this.scrollOverflow) {
for (var i = 0; i < this.scrollBarMaxHistory.Length; i++)
this.scrollBarMaxHistory[i] = -1;
}
this.SetScrollBarStyle();
}
/// <inheritdoc />
public override void SetAreaAndUpdateChildren(RectangleF area) {
base.SetAreaAndUpdateChildren(area);
this.ScrollChildren();
this.ScrollSetup();
}
/// <inheritdoc />
public override void ForceUpdateSortedChildren() {
base.ForceUpdateSortedChildren();
if (this.scrollOverflow)
this.ForceUpdateRelevantChildren();
}
/// <inheritdoc />
public override void RemoveChild(Element element) {
if (element == this.ScrollBar)
throw new NotSupportedException("A panel that scrolls overflow cannot have its scroll bar removed from its list of children");
base.RemoveChild(element);
// when removing children, our scroll bar might have to be hidden
// if we don't do this before adding children again, they might incorrectly assume that the scroll bar will still be visible and adjust their size accordingly
this.childrenDirtyForScroll = true;
}
/// <inheritdoc />
public override T AddChild<T>(T element, int index = -1) {
// if children were recently removed, make sure to update the scroll bar before adding new ones so that they can't incorrectly assume the scroll bar will be visible
if (this.childrenDirtyForScroll && this.System != null)
this.ScrollSetup();
return base.AddChild(element, index);
}
/// <inheritdoc />
public override void RemoveChildren(Func<Element, bool> condition = null) {
base.RemoveChildren(e => e != this.ScrollBar && (condition == null || condition(e)));
}
/// <inheritdoc />
public override void Draw(GameTime time, SpriteBatch batch, float alpha, SpriteBatchContext context) {
// draw children onto the render target if we have one
if (this.scrollOverflow && this.renderTarget != null) {
this.UpdateAreaIfDirty();
batch.End();
// force render target usage to preserve so that previous content isn't cleared
var lastUsage = batch.GraphicsDevice.PresentationParameters.RenderTargetUsage;
batch.GraphicsDevice.PresentationParameters.RenderTargetUsage = RenderTargetUsage.PreserveContents;
using (batch.GraphicsDevice.WithRenderTarget(this.renderTarget)) {
batch.GraphicsDevice.Clear(Color.Transparent);
// offset children by the render target's location
var area = this.GetRenderTargetArea();
// do the usual draw, but within the render target
var trans = context;
trans.TransformMatrix = Matrix.CreateTranslation(-area.X, -area.Y, 0);
batch.Begin(trans);
base.Draw(time, batch, alpha, trans);
batch.End();
}
batch.GraphicsDevice.PresentationParameters.RenderTargetUsage = lastUsage;
batch.Begin(context);
}
if (this.Texture.HasValue())
batch.Draw(this.Texture, this.DisplayArea, this.DrawColor.OrDefault(Color.White) * alpha, this.Scale);
// if we handle overflow, draw using the render target in DrawUnbound
if (!this.scrollOverflow || this.renderTarget == null) {
base.Draw(time, batch, alpha, context);
} else {
// draw the actual render target (don't apply the alpha here because it's already drawn onto with alpha)
batch.Draw(this.renderTarget, this.GetRenderTargetArea(), Color.White);
}
}
/// <inheritdoc />
public override Element GetElementUnderPos(Vector2 position) {
// if overflow is handled, don't propagate mouse checks to hidden children
var transformed = this.TransformInverse(position);
if (this.scrollOverflow && !this.GetRenderTargetArea().Contains(transformed))
return !this.IsHidden && this.CanBeMoused && this.DisplayArea.Contains(transformed) ? this : null;
return base.GetElementUnderPos(position);
}
/// <summary>
/// Scrolls this panel's <see cref="ScrollBar"/> to the given <see cref="Element"/> in such a way that its center is positioned in the center of this panel.
/// </summary>
/// <param name="element">The element to scroll to.</param>
public void ScrollToElement(Element element) {
this.ScrollToElement(element.Area.Center.Y);
}
/// <summary>
/// Scrolls this panel's <see cref="ScrollBar"/> to the given <paramref name="elementY"/> coordinate in such a way that the coordinate is positioned in the center of this panel.
/// </summary>
/// <param name="elementY">The y coordinate to scroll to, which should have this element's <see cref="Element.Scale"/> applied.</param>
public void ScrollToElement(float elementY) {
var highestValidChild = this.Children.FirstOrDefault(c => c != this.ScrollBar && !c.IsHidden);
if (highestValidChild == null)
return;
this.ScrollBar.CurrentValue = (elementY - this.Area.Height / 2 - highestValidChild.Area.Top) / this.Scale + this.ChildPadding.Value.Height / 2;
}
/// <inheritdoc />
protected override void InitStyle(UiStyle style) {
base.InitStyle(style);
this.Texture = this.Texture.OrStyle(style.PanelTexture);
this.DrawColor = this.DrawColor.OrStyle(style.PanelColor);
this.StepPerScroll = this.StepPerScroll.OrStyle(style.PanelStepPerScroll);
this.ScrollerSize = this.ScrollerSize.OrStyle(style.PanelScrollerSize);
this.ScrollBarOffset = this.ScrollBarOffset.OrStyle(style.PanelScrollBarOffset);
this.ChildPadding = this.ChildPadding.OrStyle(style.PanelChildPadding);
this.SetScrollBarStyle();
}
/// <inheritdoc />
protected override IList<Element> GetRelevantChildren() {
var relevant = base.GetRelevantChildren();
if (this.scrollOverflow) {
if (this.relevantChildrenDirty)
this.ForceUpdateRelevantChildren();
relevant = this.relevantChildren;
}
return relevant;
}
/// <inheritdoc />
protected override void OnChildAreaDirty(Element child, bool grandchild) {
base.OnChildAreaDirty(child, grandchild);
if (grandchild && !this.AreaDirty) {
// we only need to scroll when a grandchild changes, since all of our children are forced
// to be auto-anchored and so will automatically propagate their changes up to us
this.ScrollChildren();
// we also need to re-setup here in case the child is involved in a special GetTotalCoveredArea
this.ScrollSetup();
}
}
/// <inheritdoc />
protected internal override void RemovedFromUi() {
base.RemovedFromUi();
// we dispose our render target when removing so that it doesn't cause a memory leak
// if we're added back afterwards, it'll be recreated in ScrollSetup anyway
this.renderTarget?.Dispose();
this.renderTarget = null;
}
/// <summary>
/// Prepares the panel for auto-scrolling, creating the render target and setting up the scroll bar's maximum value.
/// </summary>
protected virtual void ScrollSetup() {
this.childrenDirtyForScroll = false;
if (!this.scrollOverflow || this.IsHidden)
return;
float childrenHeight;
if (this.Children.Count > 1) {
var highestValidChild = this.Children.FirstOrDefault(c => c != this.ScrollBar && !c.IsHidden);
var lowestChild = this.GetLowestChild(c => c != this.ScrollBar && !c.IsHidden, true);
childrenHeight = lowestChild.GetTotalCoveredArea(false).Bottom - highestValidChild.Area.Top;
} else {
// if we only have one child (the scroll bar), then the children take up no visual height
childrenHeight = 0;
}
// the max value of the scroll bar is the amount of non-scaled pixels taken up by overflowing components
var scrollBarMax = Math.Max(0, (childrenHeight - this.ChildPaddedArea.Height) / this.Scale);
if (!this.ScrollBar.MaxValue.Equals(scrollBarMax, Element.Epsilon)) {
// avoid a show/hide oscillation that occurs while updating our area with children that can lose height when the scroll bar is shown (like long paragraphs)
if (!this.scrollBarMaxHistory[0].Equals(this.scrollBarMaxHistory[2], Element.Epsilon) || !this.scrollBarMaxHistory[1].Equals(scrollBarMax, Element.Epsilon)) {
this.scrollBarMaxHistory[0] = this.scrollBarMaxHistory[1];
this.scrollBarMaxHistory[1] = this.scrollBarMaxHistory[2];
this.scrollBarMaxHistory[2] = scrollBarMax;
this.ScrollBar.MaxValue = scrollBarMax;
this.relevantChildrenDirty = true;
}
}
// update child padding based on whether the scroll bar is visible
var childOffset = this.ScrollBar.IsHidden ? 0 : this.ScrollerSize.Value.X + this.ScrollBarOffset;
var childOffsetDelta = childOffset - this.scrollBarChildOffset;
if (!childOffsetDelta.Equals(0, Element.Epsilon)) {
this.scrollBarChildOffset = childOffset;
this.ChildPadding += new Padding(0, childOffsetDelta, 0, 0);
}
// the scroller height has the same relation to the scroll bar height as the visible area has to the total height of the panel's content
var scrollerHeight = Math.Min(this.ChildPaddedArea.Height / childrenHeight / this.Scale, 1) * this.ScrollBar.Area.Height;
this.ScrollBar.ScrollerSize = new Vector2(this.ScrollerSize.Value.X, Math.Max(this.ScrollerSize.Value.Y, scrollerHeight));
// update the render target
var area = (Rectangle) this.GetRenderTargetArea();
if (area.Width <= 0 || area.Height <= 0) {
this.renderTarget?.Dispose();
this.renderTarget = null;
return;
}
if (this.renderTarget == null || area.Width != this.renderTarget.Width || area.Height != this.renderTarget.Height) {
this.renderTarget?.Dispose();
this.renderTarget = new RenderTarget2D(this.System.Game.GraphicsDevice, area.Width, area.Height, false, SurfaceFormat.Color, DepthFormat.None, 0, RenderTargetUsage.PreserveContents);
this.relevantChildrenDirty = true;
}
}
private void SetScrollBarStyle() {
if (this.ScrollBar == null)
return;
this.ScrollBar.StepPerScroll = this.StepPerScroll;
this.ScrollBar.Size = new Vector2(this.ScrollerSize.Value.X, 1);
this.ScrollBar.PositionOffset = new Vector2(-this.ScrollerSize.Value.X - this.ScrollBarOffset, 0);
}
private void ForceUpdateRelevantChildren() {
this.relevantChildrenDirty = false;
this.relevantChildren.Clear();
var visible = this.GetRenderTargetArea();
foreach (var child in this.SortedChildren) {
if (child.Area.Intersects(visible)) {
this.relevantChildren.Add(child);
} else {
foreach (var c in child.GetChildren(regardGrandchildren: true)) {
if (c.Area.Intersects(visible)) {
this.relevantChildren.Add(child);
break;
}
}
}
}
}
private RectangleF GetRenderTargetArea() {
var area = this.ChildPaddedArea.OffsetCopy(this.ScaledScrollOffset);
area.X = this.DisplayArea.X;
area.Width = this.DisplayArea.Width;
return area;
}
private void ScrollChildren() {
if (!this.scrollOverflow)
return;
var currentChildren = new HashSet<Element>();
// scroll all our children (and cache newly added ones)
// we ignore false grandchildren so that the children of the scroll bar stay in place
foreach (var child in this.GetChildren(c => c != this.ScrollBar, true, true)) {
// if a child was newly added later, the last scroll offset was never applied
if (this.scrolledChildren.Add(child))
child.ScrollOffset.Y -= this.lastScrollOffset;
child.ScrollOffset.Y += (this.lastScrollOffset - this.ScrollBar.CurrentValue);
currentChildren.Add(child);
}
// remove cached scrolled children that aren't our children anymore
this.scrolledChildren.IntersectWith(currentChildren);
this.lastScrollOffset = this.ScrollBar.CurrentValue;
this.relevantChildrenDirty = true;
}
}
}