[Mac] GC#fillGradientRectangle don't color for y < 0

[csa-smt]

Describe the bug

When using GC#fillGradientRectangle with y < 0, color is not applied between y and 0.

By example, this causes a bug in the Eclipse Graphiti library, where you can create diagrams with elements with negative coordinates
https://gitlab.eclipse.org/eclipse/graphiti/graphiti

To Reproduce

In Eclipse SDK :

1. Help -> Install New Software
2. Select Graphiti Examples and install it
3. File -> New -> Other... -> Graphiti Example Diagram
4. Open the diagram created, and add EClass inside.
5. Move the EClass higher and scroll so that its y is < 0

Expected behavior

GC#fillGradientRectangle should also color with a y < 0, which is the case on Windows and Linux

Screenshots

In the above screenshot,

• the y of A is < 0 for its entire height
• the y of B is < 0 at the beginning then is > 0
• the y of C is > 0 for its entire height
  

Environment:

• • All OS
• • Windows
• • Linux
• • macOS

Additional context

This bug was introduced by commit 4f5f2dc

[Phillipus]

Could you provide a SWT stand-alone snippet that shows the problem? I would like to make sure that your PR doesn't cause other issues.

This bug was introduced by commit 4f5f2dc

So your PR reverses this and does that cause a regression for that fix?

[csa-smt]

Hi @Phillipus

Could you provide a SWT stand-alone snippet that shows the problem? I would like to make sure that your PR doesn't cause other issues.

Sorry, it’s not so easy to reproduce this with purely SWT code, and I don’t have enough time to do so.
That’s why I relied on examples from Eclipse Graphiti so that you can reproduce the issue yourself and verify that my commit fixes it.

So your PR reverses this and does that cause a regression for that fix?

I have not observed any regression on the bug described in https://bugs.eclipse.org/bugs/show_bug.cgi?id=564885 after applying my changes.
There is no white line in the Dark theme in Eclipse with my changes.
I assume that other changes have been made in Eclipse since commit 4f5f2dc, which means the bug no longer exists.

Additionally, I am questioning the relevance of the fix made in commit 4f5f2dc.
First, based on the discussion in the bug https://bugs.eclipse.org/bugs/show_bug.cgi?id=564885, this commit did not seem to fix the white line issue in all cases.
Second, why paint for x < 0 but not for y < 0? Why paint for y < 0 on Windows and Linux but not on Mac? I’m questioning the consistency of this.

[Phillipus]

I see a white line in the toolbar in our product's custom theme on Mac with your change: