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Troubleshooting Common TLinkLabel Issues

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Troubleshooting Common TLinkLabel IssuesTLinkLabel is a component often used in Delphi and Lazarus applications to display clickable text that behaves like a hyperlink. While it’s simple in concept, developers can run into a variety of issues when integrating TLinkLabel into their projects: links that don’t respond, incorrect cursor behavior, styling problems, accessibility concerns, or unexpected runtime errors. This article walks through common problems, how to diagnose them, and practical solutions and workarounds.

Symptoms: Clicking the TLinkLabel has no effect; OnClick or OnLinkClick event handlers aren’t firing.

Possible causes and fixes:

  • Event handler not assigned. Confirm you assigned the event handler in the Object Inspector or in code. Example in Delphi: 
    
LinkLabel1.OnClick := LinkLabelClick; // or OnLinkClick for multiple links
  • Enabled property set to False. Ensure Enabled := True.
  • Transparent parent or overlapping controls. If another control sits above the label or the form uses complex layering, mouse events may be intercepted. Temporarily set the label’s Color to a visible color and its ParentBackground/ParentColor properties to test for overlaps.
  • Link area mismatch. Some TLinkLabel implementations use LinkRects or regions; verify the link text matches the defined link. Use the Link property (or Links collection) to ensure the correct substring/index is set.
  • Focus or modal dialog issues. If the application has a modal form or input capture, mouse events may be redirected. Test in a simple form to isolate.

2. Cursor doesn’t change to a hand pointer

Symptoms: Cursor remains default instead of changing to the hand pointer when hovered.

Possible causes and fixes:

  • ShowHint / Cursor settings. Ensure the label’s Cursor property is set to crHandPoint (or equivalent). In code: 
    
LinkLabel1.Cursor := crHandPoint;
  • Overridden OnMouseMove events. Custom mouse handling might reset the cursor. Check whether parent or other controls adjust the cursor globally.
  • OS or theme interference. Some platforms/themes may not show the hand cursor. Test with a different cursor or on another system.
  • Control not enabled. Disabled controls typically don’t change cursor; make sure Enabled is True.

Symptoms: Link appears as normal label text — no blue color or underline.

Possible causes and fixes:

  • Style properties not set. Check properties like Font.Color, Underline, LinkColor, and VisitedLinkColor. Example: 
    
LinkLabel1.Font.Color := clBlue; LinkLabel1.Style := LinkStyleUnderline; // if supported
  • Parent/Theme overrides. Visual themes or style engines (VCL styles, custom skins) may override control painting. Try disabling the theme or using style hooks to customize drawing.
  • Owner-drawn or custom paint events. If you handle OnPaint/OnDraw, ensure link-specific painting is preserved.
  • Multiple links with different styles. If using a Links collection, each link can have its own color/underline settings. Verify per-link properties are set correctly.

Symptoms: Links defined inside the label don’t match visual positions; clicks hit wrong link.

Possible causes and fixes:

  • Font and layout differences. Changes in font, size, or DPI scaling can shift text metrics. Ensure consistent font settings and recalculate LinkRects after font changes.
  • Use of tabs, spaces, or special characters. Invisible characters can misposition link rectangles. Clean the label text or explicitly set the substring indices when creating links.
  • Word wrapping. When word wrap is enabled, link rectangles may wrap to different lines. Update link regions when the control resizes: 
    
LinkLabel1.AutoSize := False; LinkLabel1.WordWrap := True; LinkLabel1.RecreateWnd; // forces layout recalculation
  • Bug in underlying implementation. If using a third-party or legacy TLinkLabel, check for known bugs or patches; consider switching to a maintained alternative component.

5. Accessibility and keyboard navigation issues

Symptoms: Users cannot activate links via keyboard; screen readers don’t announce links.

Possible causes and fixes:

  • TabStop not enabled. Make sure TabStop := True so the link can receive focus via Tab.
  • No keyboard handler. Implement OnKeyDown or set proper default handling so Enter/Space activates the link.
  • Accessibility info missing. For screen readers, ensure the control’s AccessibleName/AccessibleDescription properties are set, or implement accessibility interfaces if available.
  • Focus rectangle hidden by style. Visual styles might hide focus cues; ensure keyboard focus is visually identifiable or provide alternate cues.

6. Runtime errors or access violations

Symptoms: Application crashes when interacting with TLinkLabel; access violations occur.

Possible causes and fixes:

  • Uninitialized Links collection. Ensure the Links collection or link objects are properly created before use.
  • Handler uses freed objects. Event handlers referencing objects that have been freed will cause AVs. Use safe checks (Assigned) and guard code: 
    
if Assigned(SomeObject) then SomeObject.DoSomething;
  • Threading issues. UI components must be accessed from the main thread. Wrap background-to-UI calls via Synchronize/Queue or PostMessage.
  • Mismatched component versions. Using third-party components built for a different compiler/runtime may cause crashes. Rebuild components with the current IDE or use compatible versions.

7. Links not working after localization or Unicode text

Symptoms: Links that worked with ASCII stop working after adding Unicode or translated text.

Possible causes and fixes:

  • Incorrect substring indices. Localization may change string lengths; ensure Links refer to correct start/length positions or use text search instead of hard-coded indices.
  • Unicode vs ANSI API mismatch. Ensure the component and project use Unicode-aware methods (Delphi 2009+ is Unicode). If using older libraries, convert text properly.
  • Right-to-left layouts. RTL languages can affect link direction and hit testing; verify support for BiDi and adjust link rectangles accordingly.

8. Opening URLs fails or blocked

Symptoms: Clicking a link fails to open a browser or returns an error.

Possible causes and fixes:

  • Incorrect URL format. Ensure URLs include scheme (http:// or https://). Use ShellExecute or equivalent properly: 
    
ShellExecute(0, 'open', PChar(URL), nil, nil, SW_SHOWNORMAL);
  • Security or OS policies. Corporate policies or antivirus may block shell commands. Test on another machine or check group policies.
  • Default browser not set. Some systems require a default handler for HTTP; verify system settings.
  • Escape characters. Ensure URL is properly encoded; spaces and non-ASCII chars need percent-encoding.

9. Visual artifacts when repainting or resizing

Symptoms: Flicker, trailing text, or incorrect redraws when the form repaints.

Possible causes and fixes:

  • Double-buffering not used. Enable DoubleBuffered on the form or control to reduce flicker: 
    
Form1.DoubleBuffered := True;
  • Inefficient OnPaint handling. Avoid heavy operations inside paint handlers; invalidate only necessary regions.
  • Not handling WM_ERASEBKGND. If owner-drawing, properly handle background erasure to avoid artifacts.

10. Compatibility with different frameworks or versions

Symptoms: Behavior differs between Delphi versions, Lazarus, or between Windows versions.

Possible causes and fixes:

  • API or property differences. Review documentation for the specific TLinkLabel implementation you use (VCL, LCL, third-party). Adjust code to conditional-compile where necessary: 
    
{$IFDEF FPC} // Lazarus-specific code {$ELSE} // Delphi-specific code {$ENDIF}
  • Recompile third-party packages with current compiler. Binary packages built with another compiler version may misbehave.
  • Feature gaps. Some implementations lack features (e.g., multiple links). Consider custom components or updated libraries.

Debugging checklist

  • Confirm event handlers are assigned and the control is Enabled/Visible.
  • Test the control in a minimal form to exclude external interference.
  • Check font, DPI, and word-wrap settings that affect layout.
  • Verify URLs and use ShellExecute with proper encoding.
  • Rebuild third-party components with the current IDE; check for known bugs or patches.
  • Use logging or breakpoints in event handlers to see if they’re reached.

If you share code snippets or describe the exact behavior (Delphi/Lazarus version, runtime OS, properties set, whether Links collection is used), I can point out the precise fix.

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