Sandro Begashvili / Perfil

The article presents CPdfBuffer and CPdfWriter, a minimal MQL5 pair that derives all offsets from the output buffer instead of hand-maintaining numbers. CPdfWriter records object starts, writes a fixed-width cross-reference table and trailer, and ensures structural consistency. The result passes Part 2's validator, and a ready-to-use script converts arbitrary text to a paginated PDF.

This part finishes the geometry layer: arcs use a sagitta‑based angular step tied to the pixel tolerance, so segment counts are computed, not guessed. The path gains ArcTo, AddCircle, AddEllipse and AddRoundRect with per‑corner radii, enabling common UI shapes such as tabs, pills, badges, rings, gauges and donut wedges.

This part introduces cubic Bézier curves and a quadratic verb, flattened on append by recursive midpoint splitting (De Casteljau). A conservative flatness test sums distances of control points to the chord and stops within a pixel-based tolerance, adapting detail to curvature. The design keeps downstream code intact while giving you efficient, scale-independent curve quality.

Learn how a viewer opens a PDF backwards, why xref entries must be exactly 20 bytes, and how a two-character change falsifies multiple offsets. We reproduce three typical failures, compare results in PDFium and pypdf, and extract four strict checks a generator must pass. The included PdfValidate.mqh class for MQL5 applies these checks and returns actionable offsets and object numbers for reliable testing beyond “it opens”.