TAdvOfficeTabSet vs Alternatives: Which Tab Control Wins?

Troubleshooting Common TAdvOfficeTabSet Issues and FixesTAdvOfficeTabSet is a versatile tab control commonly used in Delphi and C++Builder applications (especially with the TMS VCL UI Pack). It provides Office-style tabs with extensive customization, events, and visual features. Because it’s feature-rich, developers sometimes run into issues when integrating it into applications. This article covers common problems, diagnostic steps, and practical fixes — from visual glitches to event handling and performance.

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Table of contents

1. Quick checklist before troubleshooting
2. Visual rendering problems
3. Incorrect tab sizing or layout
4. Tab selection and event handling issues
5. Drag-and-drop and reordering problems
6. Performance and memory concerns
7. Theming and high-DPI issues
8. Compatibility with other controls and containers
9. Useful debugging techniques and test cases
10. Final checklist and best practices

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1 — Quick checklist before troubleshooting

• Ensure you use a supported TMS VCL UI Pack version. Many issues are fixed in newer releases.
• Confirm Delphi/C++Builder version compatibility with your version of TAdvOfficeTabSet.
• Test with a minimal reproducible project — isolate the control in a new form with only essential code.
• Check properties set at design-time and run-time. Sometimes design-time settings are overridden in code.
• Look for style or theme conflicts (VCL styles, third-party themes).

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2 — Visual rendering problems

Symptoms: flickering, incomplete drawing, clipped tabs, or tabs not updating when properties change.

Causes & fixes:

• Double-buffering:
  • Ensure the form and the control have appropriate double-buffering enabled. Set Form.DoubleBuffered := True and check TAdvOfficeTabSet.DoubleBuffered (if available). This reduces flicker.
• Repaint/Invalidate:
  • Call Invalidate or Refresh on the control after changing visual properties at runtime (e.g., colors, fonts, images). Example:

    
    AdvOfficeTabSet1.Invalidate; 

• Parent background and style clashes:
  • If using VCL styles, some custom painting routines may be affected. Try AdvOfficeTabSet1.StyleElements := [] or explicitly set StyleElements to include/exclude seFont/seClient/seBorder depending on the issue.
• Image list and icons:
  • If icons appear missing or offset, verify the ImageList’s properties (Width/Height, ColorDepth) match the images used. Assign the correct ImageList property of the tabset.
• Overlapping controls:
  • Ensure no other controls overlap the tab control. Z-order issues can hide parts of the tabs; use BringToFront/SendToBack appropriately.
• Owner-drawn conflicts:
  • If you handle custom painting (OnDrawTab or similar), make sure your code fully paints the background and borders. Leaving areas unpainted will show artifacts.

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3 — Incorrect tab sizing or layout

Symptoms: tabs too narrow/wide, text truncation, multi-line wrapping unexpected, tabs not filling available width.

Causes & fixes:

• Auto-size and style properties:
  • Check properties like TabSize, MultiLine, and AutoSize. To force equal-width tabs, enable an option like TabWidth or use TabStyle/Options that control distribution.
• DPI scaling:
  • On high-DPI monitors, text metrics may scale differently than control metrics. Ensure your application is DPI-aware (manifest or per-monitor VCL scaling in newer Delphi versions) and test with scaled fonts.
• Font and padding:
  • Font changes affect required tab width. Adjust Padding/Margin properties or set OwnerDraw and compute widths explicitly.
• Recalculating layout:
  • After changing tabs or font, call Update or a layout refresh method (Invalidate + RecreateWnd if necessary).
• Multi-row behavior:
  • If MultiLine is enabled and you get an unexpected number of lines, inspect the MaxRows or related properties controlling wrapping.

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4 — Tab selection and event handling issues

Symptoms: Clicks don’t select tabs, selection change events fire unexpectedly or not at all, keyboard navigation broken.

Causes & fixes:

• Enabled/Visible:
  • Ensure the control and tabs are Enabled and Visible. Disabled tabs won’t accept clicks.
• Event wiring:
  • Confirm event handlers (OnChange, OnClick, OnTabChanged) are assigned and not overridden later in code. Use breakpoint logging to verify firing.
• Modal or focused controls:
  • Modal dialogs or other controls capturing mouse/keyboard events might prevent clicks. Test selection in a simplified form.
• Hit-test areas:
  • If tabs have images or custom-drawn content, ensure your hit-testing logic (if custom) maps correctly to clickable areas.
• Programmatic selection:
  • When setting the TabIndex or SelectedTab programmatically, guard against recursive event calls. Use a boolean flag to suppress handler actions during programmatic changes:

    
    FChangingTabs := True; try AdvOfficeTabSet1.TabIndex := NewIndex; finally FChangingTabs := False; end; 

• Focus and keyboard:
  • Make sure TabStop is enabled if keyboard navigation is expected. Handle KeyDown/KeyUp if you need custom navigation.

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5 — Drag-and-drop and reordering problems

Symptoms: Can’t drag tabs to reorder, drop target visual not visible, drag ghost image missing.

Causes & fixes:

• Allowing drag/reorder:
  • Confirm properties like AllowDrag, AllowReorder, or similar are enabled.
• Mouse capture and events:
  • Ensure OnMouseDown/OnMouseMove/OnMouseUp are not interfering with internal drag logic. If you handle these events, call inherited or implement the required behavior.
• Drag image/list:
  • If the control should show a drag image, make sure its DragImages property and global DragManager settings are correct. Assign a TDragImageList with appropriate size.
• Container interactions:
  • Parent controls that intercept drag/drop can prevent tabset drag operations. Test with a bare form.

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6 — Performance and memory concerns

Symptoms: slow tab switching, UI freezes when many tabs present, increasing memory use.

Causes & fixes:

• Excessive controls per tab:
  • Each tab may host many controls. Creating/destroying many controls on tab change is expensive. Use a frame/list virtualization or create controls on demand.
• Images and resources:
  • Large or many images in an imagelist can impact memory. Optimize images, use appropriate color depth, and share imagelists when possible.
• Event-heavy handlers:
  • Avoid heavy processing directly in selection/change events. Offload expensive work to a background thread or perform lazy loading.
• Low-level leaks:
  • Use FastMM (if using Delphi) and memory leak reporting to see if repeated tab creation causes leaks. Ensure you free dynamically created components.
• Redraw frequency:
  • Minimize unnecessary Invalidate/Refresh calls during rapid changes. Use BeginUpdate/EndUpdate if the component exposes them.

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7 — Theming and high-DPI issues

Symptoms: blurry text/icons, misaligned elements with VCL styles or per-monitor DPI.

Causes & fixes:

• VCL Styles:
  • Some custom controls don’t automatically integrate with VCL styles. Test with styles disabled, or tweak StyleElements/StyleName settings. Update TMS components—newer versions add better style support.
• Per-monitor DPI:
  • Enable per-monitor DPI awareness in project options (Delphi) and test on multiple scale factors. Consider scaling fonts and images manually if automatic scaling produces poor results.
• Image scaling:
  • Use vector graphics (SVG) support if available or provide multiple image sizes in an imagelist. Ensure Transparent color and ColorDepth settings are correct.

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8 — Compatibility with other controls and containers

Symptoms: Embedded tabset behaves incorrectly inside panels, toolbars, or complex layouts; anchoring/docking not working.

Causes & fixes:

• Parent alignment:
  • Docking/Anchoring: ensure Align, Anchors, and parent container properties are set to match intended behavior. A mismatched Align may cause clipping.
• Toolbars and custom non-client areas:
  • Controls placed on toolbars or non-client regions may require special handling; test placement on a simple panel first.
• Scrollable containers:
  • If inside a TScrollBox, ensure the tab control responds to scrolling; you might need to adjust its AlignWithMargins or update scroll settings.
• Frame embedding:
  • When used inside frames, components may not behave as expected until frame parent is set. Call Frame.Parent := SomeParent early and adjust Align after parent assignment.

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9 — Useful debugging techniques and test cases

• Minimal reproduction:
  • Create a new project with only a form and TAdvOfficeTabSet. Reproduce the issue there before hunting in the full app.
• Property bisecting:
  • Change groups of properties to narrow which setting causes the issue.
• Replace with native control:
  • Temporarily swap to a standard TPageControl. If problem disappears, it confirms component-specific behavior.
• Logging:
  • Log event calls, property changes, and redraw counts to find unexpected behavior.
• Version compare:
  • Test with older/newer versions of the TMS VCL UI Pack to see if a regression or bugfix is involved.
• Ask the vendor:
  • TMS has support forums and issue tracking; if you find a bug, prepare a small reproducible project and report it.

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10 — Final checklist and best practices

• Keep TMS VCL and RAD Studio updated to compatible versions.
• Use minimal reproducible examples to isolate issues.
• Prefer lazy creation of heavy controls and resources per tab.
• Be explicit with DPI and style settings in modern multi-monitor environments.
• Use BeginUpdate/EndUpdate or similar when making many changes.
• If you modify painting behavior, always handle all painting steps (background, border, content).
• When in doubt, revert to default properties and reintroduce changes incrementally.

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If you want, I can:

• Review a snippet of your code or a small project to pinpoint the issue;
• Provide a minimal reproducible example demonstrating a fix for a specific symptom;
• Suggest exact property names and code samples tailored to your Delphi/C++Builder and TMS VCL UI Pack versions.