THPDFLoadedPageRenderSession Class

Retains page render state and a live partial bitmap so a loaded page can be rendered over multiple bounded calls

声明

THPDFLoadedPageRenderSession = class(TObject)
public
  function ContinueRender(MaxMilliseconds: Cardinal = 0;
    MaxObjects: Integer = 0): THPDFProgressiveRenderStatus;
  function TakeBitmap: TBitmap;
  property Bitmap: TBitmap read GetBitmap;
  property ObjectsProcessed: Integer read GetObjectsProcessed;
  property TotalObjects: Integer read GetTotalObjects;
  property ProgressiveJPEGScansDecoded: Integer
    read GetProgressiveJPEGScansDecoded;
  property ProgressiveJPEGImagesDecoded: Integer
    read GetProgressiveJPEGImagesDecoded;
  property Status: THPDFProgressiveRenderStatus read GetStatus;
  property IsRegionRender: Boolean read FIsRegionRender;
  property RegionLeft: Single read FRegionLeft;
  property RegionBottom: Single read FRegionBottom;
  property RegionRight: Single read FRegionRight;
  property RegionTop: Single read FRegionTop;
  property RegionVisiblePaintObjects: Integer
    read GetRegionVisiblePaintObjects;
  property RegionCulledPaintObjects: Integer
    read GetRegionCulledPaintObjects;
  property OnProgress: THPDFProgressiveRenderProgressEvent
    read FOnProgress write SetOnProgress;
  property OnProgressiveJPEGScan: THPDFProgressiveJPEGScanEvent
    read FOnProgressiveJPEGScan write SetOnProgressiveJPEGScan;
end;

单元

HPDFDoc

Status values

• prsReady means the page is initialised and no content operator has run
• prsPaused means a budget ended before all operators completed
• prsCompleted means the complete page bitmap is available
• prsCancelled means the callback or token stopped the session at an operator boundary

使用说明

• Either budget can be zero for unlimited work, while both zero values run to a terminal state in one call
• Bitmap remains owned by the session and is intended for read-only preview access
• TakeBitmap is valid only in a terminal state and transfers ownership to the caller
• ProgressiveJPEGScansDecoded 和 ProgressiveJPEGImagesDecoded count successful incremental image work, while OnProgressiveJPEGScan can cancel after a visible scan
• IsRegionRender identifies ROI sessions; the region properties retain the requested user-space bounds and the visible and culled counters describe display-list paint selection
• The loaded THotPDF instance and cancellation token must remain alive until the session is freed

相关 API

• THotPDF.BeginLoadedPageProgressiveRender
• THotPDF.BeginLoadedPageProgressiveRegionRender
• THPDFCancellationToken
• 渐进式渲染与取消