Problems rendering bitmaps in Linux
lazarus / 32-Linux

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Grahame Grieve · 2021-11-01 02:07

I'm porting PDFium to Lazarus (again). There's an older port, but it's
windows only, and doesn't do some things I wanted. And it's not in
Git. So: https://github.com/grahamegrieve/PdfiumLib

It compiles for Windows, Linux and OSX, and the example works fine on
Windows. But on linux, I get an exception rendering the PDF. The
source of the exception is in gtk2widgetset.inc, line 4285:

  if SrcDevContext.Drawable = nil then RaiseSrcDrawableNil;

SrcDevContext is indeed nil. I don't know why - should it be? or what
should I do to make it not nil? The code that sets up the error is in
PDFiumCtrl (line 750):

    PageDC := CreateCompatibleDC(DC);
    OldPageBmp := SelectObject(PageDC, FPageBitmap);
    try
      if FRenderedPageIndex <> PageIndex then
      begin
        FRenderedPageIndex := PageIndex;
        Draw(PageDC, 0, 0, Page);
      end;
      BitBlt(DC, FDrawX, FDrawY, FDrawWidth, FDrawHeight, PageDC, 0,
0, SRCCOPY);     

There's a whole set of things going on here that I'm not familar with
around DCs and bitmaps, and it all works on windows, but not linux. is
it me doing something wrong?

Lazarus Version: 2.3.0, trunk 25th Oct, revision =
main-2_3-520-gcff7d7fdb8. To reproduce,
https://github.com/bblanchon/pdfium-binaries tag
c854f3e80a81e0999b68596d40c6b1f99a34ee1a , compile the example and
open any PDF (I think)

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VTwin · 2022-01-17 22:17

May be a bug. Perhaps you might consider a more cross-platform
solution? See felipemdc's comments:

https://forum.lazarus.freepascal.org/index.php?topic=3383.0

I have had great success using BGRABitmap on several flavors of
Windows, maxOS, and Linux.