Anchors property

Questa voce API conserva identificatori, firme, blocchi di codice e termini PDF nella forma originale.

Specifies which edges of the viewer remain a fixed distance from the corresponding edges of its parent when the parent is resized.

Anchors are an alternative to Align that give pixel-accurate control over how the PDF viewer follows its parent container. Each element of the set (akLeft, akTop, akRight, akBottom) locks that edge of the viewer to the same edge of the parent — if both opposing edges are anchored, the viewer stretches when the parent resizes; if only one is anchored, the viewer keeps its size and slides.

The most common layout for a PDF reader inside a fixed-width inspector pane or a wizard step is [akLeft, akTop, akRight, akBottom], which is functionally equivalent to alClient but leaves the design-time bounding rectangle intact and lets you nest other controls around the viewer without z-order surprises.

Whenever an anchor causes the viewer to grow or shrink, the inherited resize handler recomputes the scrolling area; the active FitMode (when not pfmNone) is re-applied so the page artwork keeps its visual relationship with the viewport.

• Anchors and Align are mutually exclusive on the same control. Setting Align to anything other than alNone overrides anchors at run-time.
• Persistent property — the set value is saved to the form file and restored at run-time. Works identically under VCL and Lazarus LCL.
• If you only anchor one edge of an axis, the viewer's size on that axis is frozen; use Constraints.MinWidth / MinHeight to keep the viewport usable.
• Anchor-driven resizes still fire OnResize, so any custom scrollbar wiring or zoom calculations triggered from that event continue to run.

Align, Constraints, OnResize, FitMode