Found an error in cairo.mod

BlitzMax Forums/Brucey's Modules/Found an error in cairo.mod

Midimaster

(Posted 2011) [#1]

Is this is a bug report?

I use CAIRO.MOD to build PDF documents. But I use the it too to build the preview screenshots of this PDF.

Everything works fine, but if I build a preview document, which has a lot of...

cairo.ShowText

...it builds 3 or 4 times the complete 2 pages document. But then it crashes with this error message: t

Assertion failed: !unscaled->from_face, file C:/BlitzMax/mod/BaH.mod/cairo.mod/src/cairo-ft-font.c, line 558
This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.

Now I don't know, whether this a a CAIRO bug or a bug of the CAIRO.MOD? Or a bug of me :) . I am not really firm in C and a noobie in CAIRO.

This it what I do in cairo:

Type PDF_TYP
	Global cairo:TCairo , normalizeMat:TCairoMatrix
	Global CairoBild:TImage[9] , Page%=0 , AktScale#=1

	Function CreateFirstPreview(Scale#)
		Print "FUNKTION CreateFirstPreview"
		AktScale=Scale
		CreateNextPreview
	End Function



	Function CreateNextPreview()
		Print "FUNKTION CreateNextPreview Next Page"
		cairo = TCairo.Create(TCairoImageSurface.CreateForPixmap(TCairoPaperSize.PAPER_A4.width, TCairoPaperSize.PAPER_A4.height))
		normalizeMat = TCairoMatrix.CreateScale(AktScale , AktScale )
		cairo.SetMatrix(normalizeMat)
	End Function
	


	Function CheckNewLine(Y#)
		If Y>TCairoPaperSize.PAPER_A4.Height/AktScale Then
			'new page
			cairo.destroy()
			CairoBild[page] = LoadImage(TCairoImageSurface(cairo.getTarget()).pixmap())
			CreateNextPreview()
			Page:+1
		EndIf
	End Function
	 
	Function FinishPDF()
		Print "FUNKTION FinishPDF " + AlsPreview
		cairo.destroy()
		CairoBild[Page] = LoadImage(TCairoImageSurface(cairo.getTarget()).pixmap())
	End Function
	
	
	
	Function TextOut (x#,y#,t$)
		cairo.Save()
		Print "cairo textout X=" + x + " Y=" + y + " T=" + t +"!"
		cairo.Translate(x, y)
		cairo.SelectFontFace( "arial", CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_NORMAL)
		cairo.SetFontSize(25)
		cairo.ShowText t
		cairo.Restore()
	End Function

End Type

In the complete code I do much more than this on the document: images, paintings,... but they are not relevant for reproducing the bug. The bug appears after third or fourth document refresh. Each document I call ~100-200 times TextOut(), in total >400.

Maybe it is only a stupid mistake by me? Maybe I forget to "Delete" any object, is it only a stack overrun?

Perhaps someone can help me?

Midimaster

(Posted 2011) [#2]

here is a little work-around, which reduces the problem...

This makes clear, that the problem is in one of these four lines:

cairo.Save()
...
cairo.SelectFontFace( "arial", CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_NORMAL)
....
cairo.SetFontSize(25)
....
cairo.Restore()

This causes less crashes, because I'm now collecting all TextOut()-Calls and sending them in one package to CAIRO.

At first I print al elements as usuall.
Then I open the surface , "print" all texts, and after this I close the surface.

This makes it more unflexible, but it is working. Nevertheless we should find the reason for the crash and send a bug report to cairographics.org

'first all other elements
For Local loc:BildElement = EachIn BildListe	
	If (loc.Typ<>105)
		PDF_Typ.Male loc.X , loc.Y  loc.T
	EndIf 
Next
	
'now the strings:
PDF_Typ.WorkAroundTextStart 
For Local loc:BildElement = EachIn BildListe	
	If (loc.Typ=105)
		PDF_Typ.WorkAroundTextOut loc.X , loc.Y loc.T
	EndIf 
Next	
PDF_Typ.WorkAroundTextFinish 



Type PDF_Typ
	....

	Function WorkAroundTextStart()
		cairo.Save()
		cairo.SelectFontFace( "arial", CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_NORMAL)
		cairo.SetFontSize(25)
	End Function
	
	
	
	
	Function WorkAroundTextOut (x#,y#,t$)
		cairo.Translate(x, y)
		cairo.MoveTo( -0, 24)
		cairo.ShowText t
		cairo.MoveTo( -0, -24)
		cairo.Translate(-x, -y)
	End Function
	
	
	Function WorkAroundTextFinish()
		cairo.Restore()	
	End Function

	...
End Type

Brucey

(Posted 2011) [#3]

I've just released 1.24 of BaH.Cairo.

Main changes to the module are :
* Cairo update to 1.10.2.
* Pixman update to 0.22.2.
* Added support for TStream surface writing (PDF, PS, etc)
* Fixed CopyPath and CopyPathFlat not returning value.
* Added TCairoRegion and TCairoRectangleInt.

Hopefully this makes things a bit better in general.