Check for an annotation containing the specified point.
PDFAnnotHandle pdfOnAnnot(PDFViewerHandle viewer, int page, double x, double y)
If the specified coordinates on the specified page are inside (over) an annotation, this function returns an annotation handle. If the coordinates are not inside an annotation, it returns NULL.

The coordinates are in the PDF coordinate space.

void mouseDownCbk(void *data, int button, int shift, int page, double x, double y) { PDFAnnotHandle annot; char *type, *content; int contentLength; annot = pdfOnAnnot(viewer, page, x, y); type = pdfGetAnnotType(annot); if (!strcmp(type, "Text")) { content = pdfGetAnnotContent(annot, &contentLength); /* ... display the popup text annotation content ... */ pdfFreeMemory(content); } }