`rasGetPageAt`

Hit-test a viewport device point against the cache's

int32_t __stdcall rasGetPageAt(IPGC CachePtr, int32_t ScrollX, int32_t ScrollY, int32_t X, int32_t Y);

Delphi

function rasGetPageAt(CachePtr: IPGC; ScrollX, ScrollY, X, Y: Integer): Integer; stdcall;

Purpose. Hit-test a viewport device point against the cache's current continuous-layout column to find which page it falls on.

Description. Walks pages in order from 1, accumulating each page's rendered height (Round(ph * z) + VBorder) starting from VBorder, and returns the first page whose accumulated vertical span contains Y + ScrollY. Only Y/ScrollY participate — X is accepted by the ABI but never read, consistent with a page-cache layout that is always a single vertical column (no side-by-side/grid page layout exists in this engine despite the parameter suggesting horizontal hit-testing might matter).

Parameters.

Parameter	Description
`CachePtr`	Target page cache.
`ScrollX`	Accepted but never read.
`ScrollY`	Added to `Y` to get the true document-space vertical position.
`X`	Accepted but never read.
`Y`	Viewport-relative vertical position to hit-test.

Return value. The 1-based page number at that position; 0 if none matches (position outside all pages, or CachePtr/document doesn't resolve).

C# (P/Invoke)

wrappers/dotnet/LumasPdf.cs

public static extern int rasGetPageAt(IntPtr CachePtr, int ScrollX, int ScrollY, int X, int Y);

Area

Rendering & Viewer