RenderPageToDC in thread

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   Hi everybody.

Two weeks ago I post an issue with rendering in separate thread: 
https://quickpdf.fogbugz.com/default.asp?18390_auaga7jpi7kq2ihs
Unfortunately it is leaved without response and I wonder is there anyone who could help me. I mean to at least to test this project on your environment and confirm that problem exists (it is also possible that I somehow incorrectly use the library but I not found any "thread" related topics except that it should work).
You can download test project from the issue attach (url above). Also I repeat a bug explanation:
I use TDebenuPDFLibrary in TThread execute for pages render. And
 sometimes the result page is blank (when rendering runs in the main
 thread all ok).

 When page renders simply by call:

    RenderPageToDC(72, 1, Bitmap.Canvas.Handle);

 then offen exception raises in TCanvas.GetHandle where Self = Nil (It
 comes from TPDFPicasso.BeginPath where seems Canvas is Nil). But this
 exception handles somewhere inside QuickPDF and RenderPageToDC just
 returns 1 and blank bitmap. If this call wrap with this:

     Bitmap.Canvas.Lock;
   try
       . . .
  finally
       Bitmap.Canvas.Unlock;
  end;
exceptions not occurs but blank pages still exists (to increase a
 chance to catch it just move the mouse cursor over main window; it
 generates repaint calls in main thread that seems significant).

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goobit Members Profile Find Members Posts Beginner Joined: 20 Apr 13 Status: Offline Points: 1	Post Options Post Reply Quote goobit Report Post Thanks(0) Quote Reply Topic: RenderPageToDC in thread Posted: 20 Apr 13 at 4:56PM
	Hi everybody. Two weeks ago I post an issue with rendering in separate thread: https://quickpdf.fogbugz.com/default.asp?18390_auaga7jpi7kq2ihs Unfortunately it is leaved without response and I wonder is there anyone who could help me. I mean to at least to test this project on your environment and confirm that problem exists (it is also possible that I somehow incorrectly use the library but I not found any "thread" related topics except that it should work). You can download test project from the issue attach (url above). Also I repeat a bug explanation: I use TDebenuPDFLibrary in TThread execute for pages render. And sometimes the result page is blank (when rendering runs in the main thread all ok). When page renders simply by call: RenderPageToDC(72, 1, Bitmap.Canvas.Handle); then offen exception raises in TCanvas.GetHandle where Self = Nil (It comes from TPDFPicasso.BeginPath where seems Canvas is Nil). But this exception handles somewhere inside QuickPDF and RenderPageToDC just returns 1 and blank bitmap. If this call wrap with this: Bitmap.Canvas.Lock; try . . . finally Bitmap.Canvas.Unlock; end; exceptions not occurs but blank pages still exists (to increase a chance to catch it just move the mouse cursor over main window; it generates repaint calls in main thread that seems significant).