PDFium: Lazarus and Free Pascal viewer integration in Delphi

Integrera PDFium VCL Component-flöden i Delphi- och C++Builder-applikationer, eller PDFium LCL Component-flöden i Lazarus/FPC, med källkodskomponenter för visning, rendering, formulär, utskrift, preflight-rapporter och standardinriktad validering.

Den här artikeln är skriven för teams sharing PDF viewing code between Delphi, Lazarus, and Free Pascal applications. Den behandlar Lazarus and Free Pascal viewer integration som produktionsnära dokumentteknik, inte som ett isolerat komponentanrop.

Den praktiska risken är att a viewer can compile in multiple IDEs yet fail in deployment because widget-set behavior, binary loading, calling conventions, and resource paths differ. Därför behöver flödet ett skrivet kontrakt, observerbar diagnostik och realistiska regressionsfiler.

Arkitekturbeslut

Treat the viewer layer as portable infrastructure. supported IDEs, compiler versions, CPU architectures, and widget sets / PDFium binary location, bitness, load failure message, and update policy

• supported IDEs, compiler versions, CPU architectures, and widget sets
• PDFium binary location, bitness, load failure message, and update policy
• high-DPI scaling, mouse wheel, keyboard, and focus behavior across frameworks
• feature parity expectations for thumbnails, search, forms, printing, and annotations

Implementeringsflöde

Stabilize runtime loading before adding UI features. Ordningen nedan gör arbetsflödet granskbart för Delphi- och C++Builder-team.

1. create a small viewer shell that loads the PDFium runtime before opening documents
2. normalize paths and binary names for each supported deployment layout
3. exercise zoom, scroll, selection, and focus events on every widget set
4. separate shared PDF logic from framework-specific panels and dialogs
5. package diagnostics that identify missing binaries and architecture mismatches

Valideringsbevis

Deployment evidence for mixed-toolchain support. Behåll dessa fält tillsammans med utdata eller supportunderlaget.

• compiler, widget set, target architecture, PDFium binary path, and runtime version
• load success or failure reason before the first document is opened
• input-event test results for wheel, drag, keyboard, focus, and high-DPI scaling
• feature matrix showing which viewer actions are supported in each build

Portability is a packaging decision

A Lazarus and FPC integration should define how the PDFium binary is found, which widget sets are supported, how DPI and input events are normalized, and which viewer features are guaranteed across platforms.

Operational metrics to watch

The first release should expose enough metrics to prove the workflow is healthy under real files, not only under curated samples.

• count and rate for compiler, widget set, target architecture, PDFium binary path, and runtime version
• warning trend for a 32-bit application cannot load a 64-bit PDFium binary
• latency of the stage that must create a small viewer shell that loads the PDFium runtime before opening documents
• profile usage for supported IDEs, compiler versions, CPU architectures, and widget sets

Tekniska granskningsnoteringar för Lazarus and Free Pascal viewer integration

Använd dessa granskningsnoteringar för att säkerställa att funktionen har passerat demo-nivån och kan försvaras under leverans, support och kundeskalering.

• Beslut: supported IDEs, compiler versions, CPU architectures, and widget sets. Implementeringspresspunkt: normalize paths and binary names for each supported deployment layout. Acceptansbevis: input-event test results for wheel, drag, keyboard, focus, and high-DPI scaling. Regressionsutlösare: printing and file dialogs may need framework-specific wrappers
• Beslut: PDFium binary location, bitness, load failure message, and update policy. Implementeringspresspunkt: exercise zoom, scroll, selection, and focus events on every widget set. Acceptansbevis: feature matrix showing which viewer actions are supported in each build. Regressionsutlösare: a 32-bit application cannot load a 64-bit PDFium binary
• Beslut: high-DPI scaling, mouse wheel, keyboard, and focus behavior across frameworks. Implementeringspresspunkt: separate shared PDF logic from framework-specific panels and dialogs. Acceptansbevis: compiler, widget set, target architecture, PDFium binary path, and runtime version. Regressionsutlösare: relative paths often work in the IDE and fail from installed shortcuts

Gränsfall

• a 32-bit application cannot load a 64-bit PDFium binary
• relative paths often work in the IDE and fail from installed shortcuts
• widget-set differences can alter focus behavior in docked panes
• printing and file dialogs may need framework-specific wrappers

Delphi / C++Builder notes

PDFium Component should sit behind a small service boundary that receives files, streams, profiles, and credentials, then returns output paths, warnings, metrics, and validation status. Important terms include Lazarus, Free Pascal, LCL, PDFium, widget set, runtime loading.

Delphi-kodexempel

Följande Delphi-skiss visar en praktisk servicegräns för detta ämne. Håll policykontroller, loggning och validering utanför det smala produktanropet så att arbetsflödet går att testa.

procedure TMainForm.OpenDocument(const FileName: string);
begin
  PdfView.LoadFromFile(FileName);
  TrackDocumentLifetime(FileName, PdfView.PageCount);
  PageSpinEdit.MaxValue := PdfView.PageCount;
  RenderCurrentPage;
  UpdateToolbarState;
end;

Produktionschecklista

• Kör arbetsflödet på en tom fil, en normal kundfil och en värstafallfil
• Öppna den genererade PDF-filen med rätt visare, validator, skrivare eller nedströmsapplikation
• Logga produktversion, profilversion, inmatningshash, utdatasökväg, förfluten tid och antal varningar
• Håll lösenord, certifikat, tillfälliga filer och kunddata under tydliga lagringsregler
• Lägg till regressionsdokument när en kundfil avslöjar ett nytt gränsfall

Produktdokumentation

PDFium Component

Fler kodexempel

procedure TViewerForm.FormCreate(Sender: TObject);
begin
  Pdf := TPdf.Create(Self);

  PdfView := TPdfView.Create(Self);
  PdfView.Parent := Self;
  PdfView.Align := alClient;
  PdfView.Pdf := Pdf;
  PdfView.FitMode := pfmFitWidth;

  if ParamCount > 0 then
  begin
    Pdf.FileName := ParamStr(1);
    Pdf.Active := True;   // opens the document; PageCount valid after this
  end;
end;