pinta crashes on creating gradients

[pleabargain]

please see video showing the bug in action
http://youtu.be/s81tNpP9pMs

steps to create
create new drawing
use select lasso tool
draw
then fill lasso selection with gradient
CRASHES sometines

but
during the video you will see pinta crashing 3x

[grofaty (grofaty)]

I can reproduce this problem every time on Pinta 1.7.0.191 on Windows 7 by the following steps:
1. New Image: 800 x 600.
2. Rectangle Select and select top half of the canvas.
3. Gradient and click somewhere in selected rectangle and move mouse from left to right to draw a gradient.
4. Ellipse Select and draw selection on canvas.
5. Gradient and fill gradient inside selection. Crash appears. But if you look closely this is not Pinta crash, but some of the upper component. Don't know GTK or something even from operating system itself. But as seen on pleabargain's movie he also has just window closed without proper Pinta crash dialog.

Following above steps crash appears in all of the cases on my test scenario.

[grofaty (grofaty)]

It looks like I have even manage to reproduce a problem in way simpler steps:
1. Open Pinta.
2. Ellipse Select.
3. Draw selection on UPPER HALF!!! of the image.
4. Gradient.
5. Click inside selection and draw gradient from left to right.
What happens? Nothing, everything works fine.

Now do we are going to do something very similar:
1. Open Pinta.
2. Ellipse Select.
3. Draw selection on LOWER HALF!!! of the image.
4. Gradient.
5. Click inside selection and draw gradient from left to right.
What happens? Crash.

That is probably why the problem is not always reproducible, because you have to draw selection on bottom half of the cavnas.

[grofaty (grofaty)]

Ahhh forgot to write exactly the same problem is with Rectangle Select and Lasso Select if selection is performed on bottom half of the canvas - always reproducible. But as above if selection is done on upper half of canvas then crash never appears.

[Jonathan Pobst (jpobst)]

Thanks for the repo steps, here's the exception:

System.AccessViolationException occurred
  HResult=-2147467261
  Message=Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
  Source=Pinta.Core
  StackTrace:
       at Pinta.Core.GradientRenderer.ProcessGradientLine(Byte startAlpha, Byte endAlpha, Int32 y, Rectangle rect, ImageSurface surface, ColorBgra* src_data_ptr, Int32 src_width) in c:\Users\Jonathan\Documents\Visual Studio 2013\Projects\PintaPobst2\Pinta.Core\Classes\GradientRenderer.cs:line 216
  InnerException:

[Cameron White (cameronwhite91)]

Fixed: https://github.com/PintaProject/Pinta/commit/30253dd7

[grofaty (grofaty)]

I tested this on 1.7.0.194 from http://forge.pinta-project.com/ zip file on Ubuntu 14.04 and I can confirm problem from #4 and #5 is fixed. Thanks.