Re: Strange bug (?) when painting/cropping recording surface to PDF surface

On 2016-04-10 09:28, Adrian Johnson wrote:
> On 10/04/16 03:25, Bernhard R. Fischer wrote:
>> Hi!
>>
>> _Background_
>> In my project a record all drawing operations to a recording surface.
>> Finally, to output files I create surfaces of specific backends (PNG,
>> PDF, and SVG) and "crop" (the final surface is smaller than the
>> recording source surface), rotate, and paint the recording surface to it.
>>
>>
>> _Strange Behavior_
>> When using PDF as backend, not everything is painted from the source
>> (recording) surface to the PDF surface. On PNG and SVG it works as expected.
>>
>>
>> _Examples_
>> There is a PNG and PDF example to show the behavior. Look at the right
>> lower corner: right of the string "015°30" the short black lines in the
>> axis are missing compared to the PNG.
>> http://www.abenteuerland.at/download/eagle/output.pdf
>> http://www.abenteuerland.at/download/eagle/output.png
>>
>>
>> _Trigger_
>> I observed, that this behavior is triggered as soon as the PDF surface
>> is smaller than the recording surface.
>>
>>
>> _Code Snippet_
>> The following code snippets shows how I create the PDF and PNG surface
>> from the recording surface (sfc_).
>>
>>
>> 	/* create PDF from sfc_ */
>> 	sfc = cairo_pdf_surface_create("output.pdf", width*.7, height*1.3);
>> 	dst = cairo_create(sfc);
>> 	cairo_rotate(dst, DEG2RAD(15));
>> 	cairo_set_source_surface(dst, sfc_, 0, 0);
>>         cairo_paint(dst);
>>         cairo_show_page(dst);
>>         cairo_destroy(dst);
>>         cairo_surface_destroy(sfc);
>>
>>
>> 	/* create PNG from sfc_ */
>>          sfc = cairo_image_surface_create(CAIRO_FORMAT_RGB24, width*.7,
>> height*1.3);
>>          dst = cairo_create(sfc);
>>          cairo_rotate(dst, DEG2RAD(15));
>>          cairo_set_source_surface(dst, sfc_, 0, 0);
>>          cairo_paint(dst);
>>          cairo_show_page(dst);
>>          cairo_destroy(dst);
>>          cairo_surface_write_to_png(sfc, "output.png");
>>          cairo_surface_destroy(sfc);
>>
>>
>> Any hints appreciated.
> 
> If you can provide a simple test case that reproduces the bug with the
> current version of cairo I can look into it.
> 

Hi!

Please find attached a simple test program which demonstrates it.
I tested it on Cairo 1.14.6 and 1.14.0.


Bernhard

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/*! Simple example demonstrating that painting to PDF surface from recording
 * surface leads to Cairo dropping some elements.
 *
 * @author Bernhard R. Fischer
 *
 * Compile with:
 * gcc -Wall -lm `pkg-config --cflags --libs cairo` rec_test.c
 */
#include <stdio.h>
#include <math.h>
#include <cairo.h>
#include <cairo-pdf.h>

#define MAXSIZE 800.0
#define PDFSIZEX 500.0
#define PDFSIZEY 800.0

#define RADIUS 200


/*! Draw something to (recording) surface. */
void draw_to_surface(cairo_surface_t *dst)
{
   cairo_t *ctx;
   double a;

   ctx = cairo_create(dst);
   // draw rectangle of PDF size
   cairo_set_source_rgb(ctx, 0, 1, 0);
   cairo_rectangle(ctx, 0, 0, PDFSIZEX, PDFSIZEY);
   cairo_stroke(ctx);

   // draw a circle with ticks
   cairo_set_source_rgb(ctx, 1, 0, 0);
   for (a = 0; a < 2 * M_PI; a += M_PI / 90)
   {
      cairo_move_to(ctx, MAXSIZE / 2 + RADIUS * cos(a), MAXSIZE / 2 + RADIUS * sin(a));
      cairo_line_to(ctx, MAXSIZE / 2 + 0.9 * RADIUS * cos(a), MAXSIZE / 2 + 0.9 * RADIUS * sin(a));
      cairo_stroke(ctx);
   }
   cairo_destroy(ctx);
}


/*! Copy (and rotate) one surface to another one. */
void copy_rec_to_surface(cairo_surface_t *src, cairo_surface_t *dst)
{
   cairo_t *ctx;
   ctx = cairo_create(dst);
   cairo_rotate(ctx, 45 * M_PI / 180); // with the rotation the missing elements get visible
   cairo_set_source_surface(ctx, src, 0, 0);
   cairo_paint(ctx);
   cairo_show_page(ctx);
   cairo_destroy(ctx);
}


int main(int argc, char **argv)
{
   cairo_surface_t *srec, *sfc;

   // create recording surface
   srec = cairo_recording_surface_create(CAIRO_CONTENT_COLOR_ALPHA, NULL);

   // draw something to surface
   draw_to_surface(srec);

   // create PDF surface
   sfc = cairo_pdf_surface_create("rec_test.pdf", PDFSIZEX, PDFSIZEY);
   copy_rec_to_surface(srec, sfc);
   cairo_surface_destroy(sfc);

   // create image surface
   sfc = cairo_image_surface_create(CAIRO_FORMAT_RGB24, PDFSIZEX, PDFSIZEY);
   copy_rec_to_surface(srec, sfc);
   cairo_surface_write_to_png(sfc, "rec_test.png");
   cairo_surface_destroy(sfc);

   // finally destroy recording surface
   cairo_surface_destroy(srec);

   return 0;
}