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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.ComponentModel;
using System.Drawing;
using System.Drawing.Design;
using System.Globalization;
using System.Windows.Forms.Internal;
using System.Windows.Forms.Layout;
using Windows.Win32.UI.Accessibility;
namespace System.Windows.Forms;
/// <summary>
/// Displays text that can contain a hyperlink.
/// </summary>
[DefaultEvent(nameof(LinkClicked))]
[ToolboxItem($"System.Windows.Forms.Design.AutoSizeToolboxItem,{AssemblyRef.SystemDesign}")]
[SRDescription(nameof(SR.DescriptionLinkLabel))]
public partial class LinkLabel : Label, IButtonControl
{
private static readonly object s_eventLinkClicked = new();
private static Color s_iedisabledLinkColor = Color.Empty;
private static readonly LinkComparer s_linkComparer = new();
private DialogResult _dialogResult;
private Color _linkColor = Color.Empty;
private Color _activeLinkColor = Color.Empty;
private Color _visitedLinkColor = Color.Empty;
private Color _disabledLinkColor = Color.Empty;
private Font? _linkFont;
private Font? _hoverLinkFont;
private bool _textLayoutValid;
private bool _receivedDoubleClick;
private readonly List<Link> _links = new(2);
private Link? _focusLink;
private LinkCollection? _linkCollection;
private Region? _textRegion;
private Cursor? _overrideCursor;
private bool _processingOnGotFocus; // used to avoid raising the OnGotFocus event twice after selecting a focus link.
private LinkBehavior _linkBehavior = LinkBehavior.SystemDefault;
/// <summary>
/// Initializes a new default instance of the <see cref="LinkLabel"/> class.
/// </summary>
public LinkLabel() : base()
{
SetStyle(ControlStyles.AllPaintingInWmPaint
| ControlStyles.OptimizedDoubleBuffer
| ControlStyles.Opaque
| ControlStyles.UserPaint
| ControlStyles.StandardClick
| ControlStyles.ResizeRedraw,
value: true);
ResetLinkArea();
}
/// <summary>
/// Gets or sets the color used to display active links.
/// </summary>
[SRCategory(nameof(SR.CatAppearance))]
[SRDescription(nameof(SR.LinkLabelActiveLinkColorDescr))]
public Color ActiveLinkColor
{
get => _activeLinkColor.IsEmpty ? IEActiveLinkColor : _activeLinkColor;
set
{
if (_activeLinkColor != value)
{
_activeLinkColor = value;
InvalidateLink(null);
}
}
}
/// <summary>
/// Gets or sets the color used to display disabled links.
/// </summary>
[SRCategory(nameof(SR.CatAppearance))]
[SRDescription(nameof(SR.LinkLabelDisabledLinkColorDescr))]
public Color DisabledLinkColor
{
get => _disabledLinkColor.IsEmpty ? IEDisabledLinkColor : _disabledLinkColor;
set
{
if (_disabledLinkColor != value)
{
_disabledLinkColor = value;
InvalidateLink(null);
}
}
}
private Link? FocusLink
{
get => _focusLink;
set
{
if (_focusLink == value)
{
return;
}
if (_focusLink is not null)
{
InvalidateLink(_focusLink);
}
_focusLink = value;
if (_focusLink is not null)
{
InvalidateLink(_focusLink);
UpdateAccessibilityLink(_focusLink);
}
}
}
private static Color IELinkColor => LinkUtilities.IELinkColor;
private static Color IEActiveLinkColor => LinkUtilities.IEActiveLinkColor;
private static Color IEVisitedLinkColor => LinkUtilities.IEVisitedLinkColor;
private Color IEDisabledLinkColor
{
get
{
if (s_iedisabledLinkColor.IsEmpty)
{
s_iedisabledLinkColor = ControlPaint.Dark(DisabledColor);
}
return s_iedisabledLinkColor;
}
}
private Rectangle ClientRectWithPadding => LayoutUtils.DeflateRect(ClientRectangle, Padding);
[Browsable(false)]
[EditorBrowsable(EditorBrowsableState.Never)]
public new FlatStyle FlatStyle
{
get => base.FlatStyle;
set => base.FlatStyle = value;
}
/// <summary>
/// Gets or sets the range in the text that is treated as a link.
/// </summary>
[Editor($"System.Windows.Forms.Design.LinkAreaEditor, {AssemblyRef.SystemDesign}", typeof(UITypeEditor))]
[RefreshProperties(RefreshProperties.Repaint)]
[Localizable(true)]
[SRCategory(nameof(SR.CatBehavior))]
[SRDescription(nameof(SR.LinkLabelLinkAreaDescr))]
public LinkArea LinkArea
{
get => _links.Count == 0
? new LinkArea(0, 0)
: new LinkArea(_links[0].Start, _links[0].Length);
set
{
LinkArea pt = LinkArea;
_links.Clear();
if (!value.IsEmpty)
{
if (value.Start < 0)
{
throw new ArgumentOutOfRangeException(nameof(LinkArea), value, SR.LinkLabelAreaStart);
}
if (value.Length < -1)
{
throw new ArgumentOutOfRangeException(nameof(LinkArea), value, SR.LinkLabelAreaLength);
}
if (value.Start != 0 || !value.IsEmpty)
{
Links.Add(new Link(this));
// Update the link area of the first link.
_links[0].Start = value.Start;
_links[0].Length = value.Length;
}
}
UpdateSelectability();
if (!pt.Equals(LinkArea))
{
InvalidateTextLayout();
LayoutTransaction.DoLayout(ParentInternal, this, PropertyNames.LinkArea);
AdjustSize();
Invalidate();
}
}
}
/// <summary>
/// Gets ir sets a value that represents how the link will be underlined.
/// </summary>
[DefaultValue(LinkBehavior.SystemDefault)]
[SRCategory(nameof(SR.CatBehavior))]
[SRDescription(nameof(SR.LinkLabelLinkBehaviorDescr))]
public LinkBehavior LinkBehavior
{
get => _linkBehavior;
set
{
// Valid values are 0x0 to 0x3
SourceGenerated.EnumValidator.Validate(value);
if (value != _linkBehavior)
{
_linkBehavior = value;
InvalidateLinkFonts();
InvalidateLink(null);
}
}
}
/// <summary>
/// Gets or sets the color used to display links in normal cases.
/// </summary>
[SRCategory(nameof(SR.CatAppearance))]
[SRDescription(nameof(SR.LinkLabelLinkColorDescr))]
public Color LinkColor
{
get => _linkColor.IsEmpty
? SystemInformation.HighContrast ? SystemColors.HotTrack : IELinkColor
: _linkColor;
set
{
if (_linkColor != value)
{
_linkColor = value;
InvalidateLink(null);
}
}
}
/// <summary>
/// Gets the collection of links used in a <see cref="LinkLabel"/>.
/// </summary>
[Browsable(false)]
[DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
public LinkCollection Links => _linkCollection ??= new LinkCollection(this);
/// <summary>
/// Gets or sets a value indicating whether the link should be displayed as if it was visited.
/// </summary>
[DefaultValue(false)]
[SRCategory(nameof(SR.CatAppearance))]
[SRDescription(nameof(SR.LinkLabelLinkVisitedDescr))]
public bool LinkVisited
{
get => _links.Count != 0 && _links[0].Visited;
set
{
if (value == LinkVisited)
{
return;
}
if (_links.Count == 0)
{
Links.Add(new Link(this));
}
_links[0].Visited = value;
}
}
internal override bool OwnerDraw => true;
protected Cursor? OverrideCursor
{
get => _overrideCursor;
set
{
if (_overrideCursor == value)
{
return;
}
_overrideCursor = value;
if (IsHandleCreated)
{
// We want to instantly change the cursor if the mouse is within our bounds.
// This includes the case where the mouse is over one of our children
PInvoke.GetCursorPos(out Point p);
PInvoke.GetWindowRect(this, out var r);
if ((r.left <= p.X && p.X < r.right && r.top <= p.Y && p.Y < r.bottom) || PInvoke.GetCapture() == HWND)
{
PInvoke.SendMessage(this, PInvoke.WM_SETCURSOR, (WPARAM)HWND, (LPARAM)(int)PInvoke.HTCLIENT);
}
}
}
}
[Browsable(true)]
[EditorBrowsable(EditorBrowsableState.Always)]
public new event EventHandler? TabStopChanged
{
add => base.TabStopChanged += value;
remove => base.TabStopChanged -= value;
}
[Browsable(true)]
[EditorBrowsable(EditorBrowsableState.Always)]
public new bool TabStop
{
get => base.TabStop;
set => base.TabStop = value;
}
[RefreshProperties(RefreshProperties.Repaint)]
[AllowNull]
public override string Text
{
get => base.Text;
set => base.Text = value;
}
[RefreshProperties(RefreshProperties.Repaint)]
public new Padding Padding
{
get => base.Padding;
set => base.Padding = value;
}
/// <summary>
/// Gets or sets the color used to display the link once it has been visited.
/// </summary>
[SRCategory(nameof(SR.CatAppearance))]
[SRDescription(nameof(SR.LinkLabelVisitedLinkColorDescr))]
public Color VisitedLinkColor
{
get => _visitedLinkColor.IsEmpty
? SystemInformation.HighContrast ? LinkUtilities.GetVisitedLinkColor() : IEVisitedLinkColor
: _visitedLinkColor;
set
{
if (_visitedLinkColor != value)
{
_visitedLinkColor = value;
InvalidateLink(null);
}
}
}
/// <summary>
/// Occurs when the link is clicked.
/// </summary>
[WinCategory("Action")]
[SRDescription(nameof(SR.LinkLabelLinkClickedDescr))]
public event LinkLabelLinkClickedEventHandler? LinkClicked
{
add => Events.AddHandler(s_eventLinkClicked, value);
remove => Events.RemoveHandler(s_eventLinkClicked, value);
}
internal static Rectangle CalcTextRenderBounds(Rectangle textRect, Rectangle clientRect, ContentAlignment align)
{
int xLoc, yLoc, width, height;
if ((align & WindowsFormsUtils.AnyRightAlign) != 0)
{
xLoc = clientRect.Right - textRect.Width;
}
else if ((align & WindowsFormsUtils.AnyCenterAlign) != 0)
{
xLoc = (clientRect.Width - textRect.Width) / 2;
}
else
{
xLoc = clientRect.X;
}
if ((align & WindowsFormsUtils.AnyBottomAlign) != 0)
{
yLoc = clientRect.Bottom - textRect.Height;
}
else if ((align & WindowsFormsUtils.AnyMiddleAlign) != 0)
{
yLoc = (clientRect.Height - textRect.Height) / 2;
}
else
{
yLoc = clientRect.Y;
}
// If the text rect does not fit in the client rect, make it fit.
if (textRect.Width > clientRect.Width)
{
xLoc = clientRect.X;
width = clientRect.Width;
}
else
{
width = textRect.Width;
}
if (textRect.Height > clientRect.Height)
{
yLoc = clientRect.Y;
height = clientRect.Height;
}
else
{
height = textRect.Height;
}
return new Rectangle(xLoc, yLoc, width, height);
}
protected override AccessibleObject CreateAccessibilityInstance() => new LinkLabelAccessibleObject(this);
internal override void ReleaseUiaProvider(HWND handle)
{
base.ReleaseUiaProvider(handle);
if (OsVersion.IsWindows8OrGreater())
{
foreach (Link link in _links)
{
if (link.IsAccessibilityObjectCreated)
{
PInvoke.UiaDisconnectProvider(link.AccessibleObject, skipOSCheck: true);
}
}
}
}
protected override void CreateHandle()
{
base.CreateHandle();
InvalidateTextLayout();
}
internal override bool CanUseTextRenderer
{
get
{
// The Gdi library doesn't currently have a way to calculate character ranges so we cannot use it for
// painting link(s) within the text, but if the link are is null or covers the entire text we are ok
// since it is just one area with the same size of the text binding area.
return LinkArea.Start == 0 && (LinkArea.IsEmpty || LinkArea.Length == new StringInfo(Text).LengthInTextElements);
}
}
internal override bool UseGDIMeasuring() => !UseCompatibleTextRendering;
/// <summary>
/// Converts the character index into char index of the string.
/// </summary>
/// <remarks>
/// <para>
/// This method mainly deal with surrogate. Suppose we have a string consisting of 3 surrogates, and we want the
/// second character, then the index we need should be 2 instead of 1, and this method returns the correct index.
/// </para>
/// </remarks>
private static int ConvertToCharIndex(int index, string text)
{
// This method is copied in LinkCollectionEditor. Update the other one as well if you change this method.
if (index <= 0)
{
return 0;
}
if (string.IsNullOrEmpty(text))
{
Debug.Assert(text is not null, "string should not be null");
// Do no conversion, just return the original value passed in.
return index;
}
// Dealing with surrogate characters in some languages, characters can expand over multiple
// chars, using StringInfo lets us properly deal with it.
StringInfo stringInfo = new(text);
int numTextElements = stringInfo.LengthInTextElements;
if (index > numTextElements)
{
// Pretend all the characters after are ASCII characters
return index - numTextElements + text.Length;
}
// Return the length of the substring which has specified number of characters.
string sub = stringInfo.SubstringByTextElements(0, index);
return sub.Length;
}
/// <summary>
/// Ensures that we have analyzed the text run so that we can render each segment and link.
/// </summary>
private Region? EnsureRun(Graphics g)
{
Debug.Assert(g is not null);
if (_textLayoutValid)
{
return _textRegion;
}
string text = Text;
if (text.Length == 0)
{
Links.Clear();
Links.Add(new Link(0, -1)); // default 'magic' link.
_textLayoutValid = true;
return null;
}
using StringFormat textFormat = CreateStringFormat();
using Font alwaysUnderlined = new Font(Font, Font.Style | FontStyle.Underline);
if (UseCompatibleTextRendering)
{
Region[] textRegions = g.MeasureCharacterRanges(text, alwaysUnderlined, ClientRectWithPadding, textFormat);
int regionIndex = 0;
for (int i = 0; i < Links.Count; i++)
{
Link link = Links[i];
int charStart = ConvertToCharIndex(link.Start, text);
int charEnd = ConvertToCharIndex(link.Start + link.Length, text);
if (LinkInText(charStart, charEnd - charStart))
{
Links[i].VisualRegion = textRegions[regionIndex];
regionIndex++;
}
}
Debug.Assert(regionIndex == (textRegions.Length - 1), "Failed to consume all link label visual regions");
_textRegion = textRegions[^1];
}
else
{
// Use TextRenderer.MeasureText to see the size of the text
Rectangle clientRectWithPadding = ClientRectWithPadding;
Size clientSize = new(clientRectWithPadding.Width, clientRectWithPadding.Height);
TextFormatFlags flags = CreateTextFormatFlags(clientSize);
Size textSize = TextRenderer.MeasureText(text, alwaysUnderlined, clientSize, flags);
// We need to take into account the padding that GDI adds around the text.
int iLeftMargin, iRightMargin;
TextPaddingOptions padding = default;
if ((flags & TextFormatFlags.NoPadding) == TextFormatFlags.NoPadding)
{
padding = TextPaddingOptions.NoPadding;
}
else if ((flags & TextFormatFlags.LeftAndRightPadding) == TextFormatFlags.LeftAndRightPadding)
{
padding = TextPaddingOptions.LeftAndRightPadding;
}
using var hfont = GdiCache.GetHFONTScope(Font);
DRAWTEXTPARAMS dtParams = hfont.GetTextMargins(padding);
iLeftMargin = dtParams.iLeftMargin;
iRightMargin = dtParams.iRightMargin;
Rectangle visualRectangle = new(
clientRectWithPadding.X + iLeftMargin,
clientRectWithPadding.Y,
textSize.Width - iRightMargin - iLeftMargin,
textSize.Height);
visualRectangle = CalcTextRenderBounds(visualRectangle, clientRectWithPadding, RtlTranslateContent(TextAlign));
Region visualRegion = new(visualRectangle);
if (_links is not null && _links.Count == 1)
{
Links[0].VisualRegion = visualRegion;
}
_textRegion = visualRegion;
}
_textLayoutValid = true;
return _textRegion;
}
internal override StringFormat CreateStringFormat()
{
StringFormat stringFormat = base.CreateStringFormat();
if (string.IsNullOrEmpty(Text))
{
return stringFormat;
}
CharacterRange[] regions = AdjustCharacterRangesForSurrogateChars();
stringFormat.SetMeasurableCharacterRanges(regions);
return stringFormat;
}
/// <summary>
/// Calculate character ranges taking into account the locale. Provided for surrogate chars support.
/// </summary>
private CharacterRange[] AdjustCharacterRangesForSurrogateChars()
{
string text = Text;
if (string.IsNullOrEmpty(text))
{
return [];
}
StringInfo stringInfo = new(text);
int textLen = stringInfo.LengthInTextElements;
List<CharacterRange> ranges = new(Links.Count + 1);
foreach (Link link in Links)
{
int charStart = ConvertToCharIndex(link.Start, text);
int charEnd = ConvertToCharIndex(link.Start + link.Length, text);
if (LinkInText(charStart, charEnd - charStart))
{
int length = Math.Min(link.Length, textLen - link.Start);
ranges.Add(new CharacterRange(charStart, ConvertToCharIndex(link.Start + length, text) - charStart));
}
}
ranges.Add(new CharacterRange(0, text.Length));
return [.. ranges];
}
/// <summary>
/// Determines whether the whole link label contains only one link,
/// and the link runs from the beginning of the label to the end of it.
/// </summary>
private bool IsLabelFilledByOneLink()
{
if (_links is null || _links.Count != 1 || Text is null)
{
return false;
}
StringInfo stringInfo = new(Text);
if (LinkArea.Start == 0 && LinkArea.Length == stringInfo.LengthInTextElements)
{
return true;
}
return false;
}
/// <summary>
/// Determines if the given client coordinates is contained within a portion of a link area.
/// </summary>
protected Link? PointInLink(int x, int y)
{
using Graphics g = CreateGraphicsInternal();
Link? hit = null;
EnsureRun(g);
foreach (Link link in _links)
{
if (link.VisualRegion is not null && link.VisualRegion.IsVisible(x, y, g))
{
hit = link;
break;
}
}
return hit;
}
/// <summary>
/// Invalidates only the portions of the text that is linked to the specified link. If link is null, then
/// all linked text is invalidated.
/// </summary>
private void InvalidateLink(Link? link)
{
if (IsHandleCreated)
{
if (link is null || link.VisualRegion is null || IsLabelFilledByOneLink())
{
Invalidate();
}
else
{
Invalidate(link.VisualRegion);
}
}
}
/// <summary>
/// Invalidates the current set of fonts we use when painting links. The fonts will be recreated when needed.
/// </summary>
private void InvalidateLinkFonts()
{
_linkFont?.Dispose();
if (_hoverLinkFont is not null && _hoverLinkFont != _linkFont)
{
_hoverLinkFont.Dispose();
}
_linkFont = null;
_hoverLinkFont = null;
}
private void InvalidateTextLayout()
{
_textLayoutValid = false;
_textRegion?.Dispose();
_textRegion = null;
}
private bool LinkInText(int start, int length) => start >= 0 && start < Text.Length && length > 0;
/// <summary>
/// Gets or sets a value that is returned to the parent form when the link label is clicked.
/// </summary>
DialogResult IButtonControl.DialogResult
{
get => _dialogResult;
set
{
// Valid values are 0x0 to 0x7
SourceGenerated.EnumValidator.Validate(value);
_dialogResult = value;
}
}
void IButtonControl.NotifyDefault(bool value)
{
}
protected override void OnGotFocus(EventArgs e)
{
if (!_processingOnGotFocus)
{
base.OnGotFocus(e);
_processingOnGotFocus = true;
}
try
{
Link? focusLink = FocusLink;
if (focusLink is null)
{
// Set focus on first link.
// This will raise the OnGotFocus event again but it will not be processed because processingOnGotFocus is true.
Select(directed: true, forward: true);
}
else
{
InvalidateLink(focusLink);
UpdateAccessibilityLink(focusLink);
}
}
finally
{
if (_processingOnGotFocus)
{
_processingOnGotFocus = false;
}
}
}
protected override void OnLostFocus(EventArgs e)
{
base.OnLostFocus(e);
if (FocusLink is not null)
{
InvalidateLink(FocusLink);
}
}
protected override void OnKeyDown(KeyEventArgs e)
{
base.OnKeyDown(e);
if (e.KeyCode == Keys.Enter)
{
if (FocusLink is not null && FocusLink.Enabled)
{
OnLinkClicked(new LinkLabelLinkClickedEventArgs(FocusLink));
}
}
}
protected override void OnMouseLeave(EventArgs e)
{
base.OnMouseLeave(e);
if (!Enabled)
{
return;
}
foreach (Link link in _links)
{
if ((link.State & LinkState.Hover) == LinkState.Hover
|| (link.State & LinkState.Active) == LinkState.Active)
{
bool activeChanged = (link.State & LinkState.Active) == LinkState.Active;
link.State &= ~(LinkState.Hover | LinkState.Active);
if (activeChanged || _hoverLinkFont != _linkFont)
{
InvalidateLink(link);
}
OverrideCursor = null;
}
}
}
protected override void OnMouseDown(MouseEventArgs e)
{
base.OnMouseDown(e);
if (!Enabled || e.Clicks > 1)
{
_receivedDoubleClick = true;
return;
}
for (int i = 0; i < _links.Count; i++)
{
if ((_links[i].State & LinkState.Hover) == LinkState.Hover)
{
_links[i].State |= LinkState.Active;
Focus();
if (_links[i].Enabled)
{
FocusLink = _links[i];
InvalidateLink(FocusLink);
}
Capture = true;
break;
}
}
}
protected override void OnMouseUp(MouseEventArgs e)
{
base.OnMouseUp(e);
if (Disposing || IsDisposed)
{
return;
}
if (!Enabled || e.Clicks > 1 || _receivedDoubleClick)
{
_receivedDoubleClick = false;
return;
}
for (int i = 0; i < _links.Count; i++)
{
if ((_links[i].State & LinkState.Active) == LinkState.Active)
{
_links[i].State &= ~LinkState.Active;
InvalidateLink(_links[i]);
Capture = false;
Link? clicked = PointInLink(e.X, e.Y);
if (clicked is not null && clicked == FocusLink && clicked.Enabled)
{
OnLinkClicked(new LinkLabelLinkClickedEventArgs(clicked, e.Button));
}
}
}
}
protected override void OnMouseMove(MouseEventArgs e)
{
base.OnMouseMove(e);
if (!Enabled)
{
return;
}
Link? hoverLink = null;
foreach (Link link in _links)
{
if ((link.State & LinkState.Hover) == LinkState.Hover)
{
hoverLink = link;
break;
}
}
Link? pointIn = PointInLink(e.X, e.Y);
if (pointIn == hoverLink)
{
return;
}
if (hoverLink is not null)
{
hoverLink.State &= ~LinkState.Hover;
}
if (pointIn is not null)
{
pointIn.State |= LinkState.Hover;
if (pointIn.Enabled)
{
OverrideCursor = Cursors.Hand;
}
}
else
{
OverrideCursor = null;
}
if (_hoverLinkFont != _linkFont)
{
if (hoverLink is not null)
{
InvalidateLink(hoverLink);
}
if (pointIn is not null)
{
InvalidateLink(pointIn);
}
}
}
/// <summary>
/// Raises the <see cref="OnLinkClicked"/> event.
/// </summary>
protected virtual void OnLinkClicked(LinkLabelLinkClickedEventArgs e)
{
((LinkLabelLinkClickedEventHandler?)Events[s_eventLinkClicked])?.Invoke(this, e);
}
protected override void OnPaddingChanged(EventArgs e)
{
base.OnPaddingChanged(e);
InvalidateTextLayout();
}
protected override void OnPaint(PaintEventArgs e)
{
Animate();
ImageAnimator.UpdateFrames(Image);
Graphics g = e.GraphicsInternal;
Region? textRegion = EnsureRun(g);
// We can't call base.OnPaint because labels paint differently from link labels,
// but we still need to raise the Paint event.
if (textRegion is null)
{
Debug.Assert(Text.Length == 0);
PaintLinkBackground(g);
RaisePaintEvent(this, e);
return;
}
if (AutoEllipsis)
{
Rectangle clientRect = ClientRectWithPadding;
Size preferredSize = GetPreferredSize(new Size(clientRect.Width, clientRect.Height));
_showToolTip = clientRect.Width < preferredSize.Width || clientRect.Height < preferredSize.Height;
}
else
{
_showToolTip = false;
}
if (Enabled)
{
PaintEnabled();
}
else
{
PaintDisabled();
}
RaisePaintEvent(this, e);
void PaintEnabled()
{
// Control.Enabled not to be confused with Link.Enabled
bool optimizeBackgroundRendering = !GetStyle(ControlStyles.OptimizedDoubleBuffer);
using var foreBrush = ForeColor.GetCachedSolidBrushScope();
using var linkBrush = LinkColor.GetCachedSolidBrushScope();
if (!optimizeBackgroundRendering)
{
PaintLinkBackground(g);
}
Debug.Assert((_linkFont is null && _hoverLinkFont is null)
|| (_linkFont is not null && _hoverLinkFont is not null));
LinkUtilities.EnsureLinkFonts(Font, LinkBehavior, ref _linkFont, ref _hoverLinkFont);
using GraphicsStateScope graphicsScope = new(g);
Region originalClip = g.Clip;
// The focus rectangle if there is only one link
RectangleF focusRectangle = RectangleF.Empty;
if (!IsLabelFilledByOneLink())
{
foreach (Link link in _links)
{
if (link.VisualRegion is not null)
{
g.ExcludeClip(link.VisualRegion);
}
}
// When there is only one link in link label, this step is not necessary as it will be overlapped
// by the rest of the rendering.
PaintLink(
e,
link: null,
foreBrush,
linkBrush,
_linkFont,
_hoverLinkFont,
optimizeBackgroundRendering,
focusRectangle,
textRegion);
}
else if (_links[0].VisualRegion?.GetRegionScans(e.GraphicsInternal.Transform) is { } regionRectangles
&& regionRectangles.Length > 0)
{
// Exclude the area to draw the focus rectangle.
if (UseCompatibleTextRendering)
{
focusRectangle = new RectangleF(regionRectangles[0].Location, SizeF.Empty);
foreach (RectangleF rect in regionRectangles)
{
focusRectangle = RectangleF.Union(focusRectangle, rect);
}
}
else
{
focusRectangle = ClientRectWithPadding;
Size finalRectSize = focusRectangle.Size.ToSize();
Size requiredSize = MeasureTextCache.GetTextSize(Text, Font, finalRectSize, CreateTextFormatFlags(finalRectSize));
focusRectangle.Width = requiredSize.Width;
if (requiredSize.Height < focusRectangle.Height)
{
focusRectangle.Height = requiredSize.Height;
}
focusRectangle = CalcTextRenderBounds(Rectangle.Round(focusRectangle), ClientRectWithPadding, RtlTranslateContent(TextAlign));
}
using Region region = new(focusRectangle);
g.ExcludeClip(region);
}
foreach (Link link in _links)
{
PaintLink(
e,
link,
foreBrush,
linkBrush,
_linkFont,
_hoverLinkFont,
optimizeBackgroundRendering,
focusRectangle,
textRegion);
}
if (optimizeBackgroundRendering)
{
g.Clip = originalClip;
g.ExcludeClip(textRegion);
PaintLinkBackground(g);
}
}
void PaintDisabled()
{
// Paint disabled link label (disabled control, not to be confused with disabled link).
using GraphicsStateScope graphicsScope = new(g);
// We need to paint the background first before clipping to textRegion because it is calculated using
// ClientRectWithPadding which in some cases is smaller that ClientRectangle.
PaintLinkBackground(g);
if (UseCompatibleTextRendering)
{
// The clipping only applies when rendering through GDI+.
g.IntersectClip(textRegion);
StringFormat stringFormat = CreateStringFormat();
ControlPaint.DrawStringDisabled(g, Text, Font, DisabledColor, ClientRectWithPadding, stringFormat);
}
else
{
Color foreColor;
using (DeviceContextHdcScope scope = new(e, applyGraphicsState: false))
{
foreColor = scope.HDC.FindNearestColor(DisabledColor);
}
Rectangle clientRectWidthPadding = ClientRectWithPadding;
ControlPaint.DrawStringDisabled(
g,
Text,
Font,
foreColor,
clientRectWidthPadding,
CreateTextFormatFlags(clientRectWidthPadding.Size));
}
}
}
protected override void OnPaintBackground(PaintEventArgs e)
{
if (Image is not { } image)
{
base.OnPaintBackground(e);
return;
}
Rectangle imageBounds = CalcImageRenderBounds(image, ClientRectangle, RtlTranslateAlignment(ImageAlign));
using (GraphicsStateScope backgroundPaintScope = new(e.Graphics))
{
e.Graphics.ExcludeClip(imageBounds);
base.OnPaintBackground(e);
}
using GraphicsStateScope imagePaintScope = new(e.Graphics);
e.Graphics.IntersectClip(imageBounds);
base.OnPaintBackground(e);
DrawImage(e.Graphics, image, ClientRectangle, RtlTranslateAlignment(ImageAlign));
}
protected override void OnFontChanged(EventArgs e)
{
base.OnFontChanged(e);
InvalidateTextLayout();
InvalidateLinkFonts();
Invalidate();
}
protected override void OnAutoSizeChanged(EventArgs e)
{
base.OnAutoSizeChanged(e);
InvalidateTextLayout();
}
internal override void OnAutoEllipsisChanged()
{
base.OnAutoEllipsisChanged();
InvalidateTextLayout();
}
protected override void OnEnabledChanged(EventArgs e)
{
base.OnEnabledChanged(e);
if (!Enabled)
{
for (int i = 0; i < _links.Count; i++)
{
_links[i].State &= ~(LinkState.Hover | LinkState.Active);
}
OverrideCursor = null;
}
InvalidateTextLayout();
Invalidate();
}
protected override void OnTextChanged(EventArgs e)
{
base.OnTextChanged(e);
InvalidateTextLayout();
UpdateSelectability();
}
protected override void OnTextAlignChanged(EventArgs e)
{
base.OnTextAlignChanged(e);
InvalidateTextLayout();
UpdateSelectability();
}
private void PaintLink(
PaintEventArgs e,
Link? link,
SolidBrush foreBrush,
SolidBrush linkBrush,
Font linkFont,
Font hoverLinkFont,
bool optimizeBackgroundRendering,
RectangleF focusRectangle,
Region textRegion)
{
Graphics g = e.GraphicsInternal;
Debug.Assert(g is not null, "Must pass valid graphics");
Debug.Assert(foreBrush is not null, "Must pass valid foreBrush");
Debug.Assert(linkBrush is not null, "Must pass valid linkBrush");
if (link is not null)
{
PaintLink();
}
else
{
PaintNoLink();
}
void PaintLink()
{
if (link.VisualRegion is null)
{
// Don't paint anything if we are given a link with no visual region.
return;
}
Color brushColor = Color.Empty;
LinkState linkState = link.State;
Font font = (linkState & LinkState.Hover) == LinkState.Hover ? hoverLinkFont : linkFont;
if (link.Enabled)
{
// Not to be confused with Control.Enabled.
if ((linkState & LinkState.Active) == LinkState.Active)
{
brushColor = ActiveLinkColor;
}
else if ((linkState & LinkState.Visited) == LinkState.Visited)
{
brushColor = VisitedLinkColor;
}
}
else
{
brushColor = DisabledLinkColor;
}
g.Clip = IsLabelFilledByOneLink() ? new Region(focusRectangle) : link.VisualRegion;
if (optimizeBackgroundRendering)
{
PaintLinkBackground(g);
}
if (brushColor == Color.Empty)
{
brushColor = linkBrush.Color;
}
if (UseCompatibleTextRendering)
{
using var useBrush = brushColor.GetCachedSolidBrushScope();
StringFormat stringFormat = CreateStringFormat();
g.DrawString(Text, font, useBrush, ClientRectWithPadding, stringFormat);
}
else
{
brushColor = g.FindNearestColor(brushColor);
Rectangle clientAreaMinusPadding = ClientRectWithPadding;
TextRenderer.DrawText(
g,
Text,
font,
clientAreaMinusPadding,
brushColor,
CreateTextFormatFlags(clientAreaMinusPadding.Size)
#if DEBUG
// Skip the asserts in TextRenderer because the DC has been modified
| TextRenderer.SkipAssertFlag
#endif
);
}
if (Focused
&& ShowFocusCues
&& FocusLink == link
&& link.VisualRegion.GetRegionScans(g.Transform) is { } regionRectangles && regionRectangles.Length > 0)
{
// Get the rectangles making up the visual region, and draw each one.
if (IsLabelFilledByOneLink())
{
// Draw one merged focus rectangle
Debug.Assert(focusRectangle != RectangleF.Empty, "focusRectangle should be initialized");
ControlPaint.DrawFocusRectangle(g, Rectangle.Ceiling(focusRectangle), ForeColor, BackColor);
}
else
{
foreach (RectangleF rect in regionRectangles)
{
ControlPaint.DrawFocusRectangle(g, Rectangle.Ceiling(rect), ForeColor, BackColor);
}
}
}
return;
}
void PaintNoLink()
{
// Painting with no link.
g.IntersectClip(textRegion);
if (optimizeBackgroundRendering)
{
PaintLinkBackground(g);
}
if (UseCompatibleTextRendering)
{
StringFormat stringFormat = CreateStringFormat();
g.DrawString(Text, Font, foreBrush, ClientRectWithPadding, stringFormat);
return;
}
Color color;
using (DeviceContextHdcScope hdc = new(g, applyGraphicsState: false))
{
color = ColorTranslator.FromWin32(
(int)PInvoke.GetNearestColor(hdc, (COLORREF)(uint)ColorTranslator.ToWin32(foreBrush.Color)).Value);
}
Rectangle clientRectWithPadding = ClientRectWithPadding;
TextRenderer.DrawText(
g,
Text,
Font,
clientRectWithPadding,
color,
CreateTextFormatFlags(clientRectWithPadding.Size));
}
}
private void PaintLinkBackground(Graphics g)
{
using PaintEventArgs e = new(g, ClientRectangle);
InvokePaintBackground(this, e);
}
void IButtonControl.PerformClick()
{
// If a link is not currently focused, focus on the first link.
if (FocusLink is null && Links.Count > 0)
{
string text = Text;
foreach (Link link in Links)
{
int charStart = ConvertToCharIndex(link.Start, text);
int charEnd = ConvertToCharIndex(link.Start + link.Length, text);
if (link.Enabled && LinkInText(charStart, charEnd - charStart))
{
FocusLink = link;
break;
}
}
}
// Act as if the focused link was clicked.
if (FocusLink is not null)
{
OnLinkClicked(new LinkLabelLinkClickedEventArgs(FocusLink));
}
}
protected override bool ProcessDialogKey(Keys keyData)
{
if ((keyData & (Keys.Alt | Keys.Control)) != Keys.Alt)
{
Keys keyCode = keyData & Keys.KeyCode;
switch (keyCode)
{
case Keys.Tab:
if (TabStop)
{
bool forward = (keyData & Keys.Shift) != Keys.Shift;
if (FocusNextLink(forward))
{
return true;
}
}
break;
case Keys.Up:
case Keys.Left:
if (FocusNextLink(false))
{
return true;
}
break;
case Keys.Down:
case Keys.Right:
if (FocusNextLink(true))
{
return true;
}
break;
}
}
return base.ProcessDialogKey(keyData);
}
private bool FocusNextLink(bool forward)
{
int focusIndex = -1;
if (_focusLink is not null)
{
for (int i = 0; i < _links.Count; i++)
{
if (_links[i] == _focusLink)
{
focusIndex = i;
break;
}
}
}
focusIndex = GetNextLinkIndex(focusIndex, forward);
if (focusIndex != -1)
{
FocusLink = Links[focusIndex];
return true;
}
else
{
FocusLink = null;
return false;
}
}
private int GetNextLinkIndex(int focusIndex, bool forward)
{
Link? test;
string text = Text;
int charStart = 0;
int charEnd = 0;
if (forward)
{
do
{
focusIndex++;
if (focusIndex < Links.Count)
{
test = Links[focusIndex];
charStart = ConvertToCharIndex(test.Start, text);
charEnd = ConvertToCharIndex(test.Start + test.Length, text);
}
else
{
test = null;
}
}
while (test is not null
&& !test.Enabled
&& LinkInText(charStart, charEnd - charStart));
}
else
{
do
{
focusIndex--;
if (focusIndex >= 0)
{
test = Links[focusIndex];
charStart = ConvertToCharIndex(test.Start, text);
charEnd = ConvertToCharIndex(test.Start + test.Length, text);
}
else
{
test = null;
}
}
while (test is not null
&& !test.Enabled
&& LinkInText(charStart, charEnd - charStart));
}
return focusIndex < 0 || focusIndex >= _links.Count ? -1 : focusIndex;
}
private void ResetLinkArea() => LinkArea = new LinkArea(0, -1);
internal void ResetActiveLinkColor() => _activeLinkColor = Color.Empty;
internal void ResetDisabledLinkColor() => _disabledLinkColor = Color.Empty;
internal void ResetLinkColor()
{
_linkColor = Color.Empty;
InvalidateLink(null);
}
private void ResetVisitedLinkColor() => _visitedLinkColor = Color.Empty;
protected override void SetBoundsCore(int x, int y, int width, int height, BoundsSpecified specified)
{
// We cache too much state to try and optimize this (regions, etc). It is best to always relayout here.
// If we want to resurrect this code in the future, remember that we need to handle a word wrapped top
// aligned text that will become newly exposed (and therefore layed out) when we resize.
InvalidateTextLayout();
Invalidate();
base.SetBoundsCore(x, y, width, height, specified);
}
protected override void Select(bool directed, bool forward)
{
// In a multi-link label, if the tab came from another control, we want to keep the currently
// focused link, otherwise, we set the focus to the next link.
if (directed && _links.Count > 0)
{
// Find which link is currently focused
int focusIndex = -1;
if (FocusLink is not null)
{
focusIndex = _links.IndexOf(FocusLink);
}
// We could be getting focus from ourself, so we must invalidate each time.
FocusLink = null;
int newFocus = GetNextLinkIndex(focusIndex, forward);
if (newFocus == -1)
{
if (forward)
{
// -1, so "next" will be 0
newFocus = GetNextLinkIndex(-1, forward);
}
else
{
// Count, so "next" will be Count-1
newFocus = GetNextLinkIndex(_links.Count, forward);
}
}
if (newFocus != -1)
{
FocusLink = _links[newFocus];
}
}
base.Select(directed, forward);
}
/// <summary>
/// Determines if the color for active links should remain the same.
/// </summary>
internal bool ShouldSerializeActiveLinkColor() => !_activeLinkColor.IsEmpty;
/// <summary>
/// Determines if the color for disabled links should remain the same.
/// </summary>
internal bool ShouldSerializeDisabledLinkColor() => !_disabledLinkColor.IsEmpty;
/// <summary>
/// Determines if the range in text that is treated as a link should remain the same.
/// </summary>
private bool ShouldSerializeLinkArea()
{
if (_links.Count == 1)
{
// use field access to find out if "length" is really -1
return Links[0].Start != 0 || Links[0]._length != -1;
}
return true;
}
/// <summary>
/// Determines if the color of links in normal cases should remain the same.
/// </summary>
internal bool ShouldSerializeLinkColor() => !_linkColor.IsEmpty;
/// <summary>
/// Determines whether designer should generate code for setting the UseCompatibleTextRendering or not.
/// DefaultValue(false)
/// </summary>
private bool ShouldSerializeUseCompatibleTextRendering()
{
// Serialize code if LinkLabel cannot support the feature or the property's value is not the default.
return !CanUseTextRenderer || UseCompatibleTextRendering != UseCompatibleTextRenderingDefault;
}
/// <summary>
/// Determines if the color of links that have been visited should remain the same.
/// </summary>
private bool ShouldSerializeVisitedLinkColor() => !_visitedLinkColor.IsEmpty;
/// <summary>
/// Update accessibility with the currently focused link.
/// </summary>
private void UpdateAccessibilityLink(Link focusLink)
{
if (!IsHandleCreated)
{
return;
}
int focusIndex = -1;
for (int i = 0; i < _links.Count; i++)
{
if (_links[i] == focusLink)
{
focusIndex = i;
}
}
AccessibilityNotifyClients(AccessibleEvents.Focus, focusIndex);
if (IsAccessibilityObjectCreated)
{
focusLink.AccessibleObject?.RaiseAutomationEvent(UIA_EVENT_ID.UIA_AutomationFocusChangedEventId);
}
}
/// <summary>
/// Validates that no links overlap. This will throw an exception if they do.
/// </summary>
private void ValidateNoOverlappingLinks()
{
for (int x = 0; x < _links.Count; x++)
{
Link left = _links[x];
if (left.Length < 0)
{
throw new InvalidOperationException(SR.LinkLabelOverlap);
}
for (int y = x; y < _links.Count; y++)
{
if (x != y)
{
Link right = _links[y];
int maxStart = Math.Max(left.Start, right.Start);
int minEnd = Math.Min(left.Start + left.Length, right.Start + right.Length);
if (maxStart < minEnd)
{
throw new InvalidOperationException(SR.LinkLabelOverlap);
}
}
}
}
}
/// <summary>
/// Updates the label's ability to get focus. If there are any links in the label, then the label can get
/// focus, else it can't.
/// </summary>
private void UpdateSelectability()
{
LinkArea pt = LinkArea;
bool selectable = false;
string text = Text;
int charStart = ConvertToCharIndex(pt.Start, text);
int charEnd = ConvertToCharIndex(pt.Start + pt.Length, text);
if (LinkInText(charStart, charEnd - charStart))
{
selectable = true;
}
else
{
// If a link is currently focused, de-select it
if (FocusLink is not null)
{
FocusLink = null;
}
}
OverrideCursor = null;
TabStop = selectable;
SetStyle(ControlStyles.Selectable, selectable);
}
[RefreshProperties(RefreshProperties.Repaint)]
[SRCategory(nameof(SR.CatBehavior))]
[SRDescription(nameof(SR.UseCompatibleTextRenderingDescr))]
public new bool UseCompatibleTextRendering
{
get
{
Debug.Assert(CanUseTextRenderer || base.UseCompatibleTextRendering, "Using GDI text rendering when CanUseTextRenderer reported false.");
return base.UseCompatibleTextRendering;
}
set
{
if (base.UseCompatibleTextRendering != value)
{
// Cache the value so it is restored if CanUseTextRenderer becomes true and the designer can undo changes to this as side effect.
base.UseCompatibleTextRendering = value;
InvalidateTextLayout();
}
}
}
internal override bool SupportsUiaProviders => true;
/// <summary>
/// Handles the WM_SETCURSOR message.
/// </summary>
private void WmSetCursor(ref Message m)
{
// Accessing through the Handle property has side effects that break this logic. You must use InternalHandle.
if ((HWND)m.WParamInternal == InternalHandle && m.LParamInternal.LOWORD == PInvoke.HTCLIENT)
{
Cursor.Current = OverrideCursor ?? Cursor;
}
else
{
DefWndProc(ref m);
}
}
protected override void WndProc(ref Message msg)
{
switch (msg.MsgInternal)
{
case PInvoke.WM_SETCURSOR:
WmSetCursor(ref msg);
break;
default:
base.WndProc(ref msg);
break;
}
}
protected override void Dispose(bool disposing)
{
if (disposing)
{
InvalidateTextLayout();
InvalidateLinkFonts();
}
base.Dispose(disposing);
}
}
|