Internal drawing bug

[ghost]

Hello,

So after investigating a lot, I have found that there is still some internal drawing problems on nuklear.

E.g. #347, #401, #409, #424, #479, #480

On a separate note, the commit 9a9f4f0 is introducing breaking changes on the D3D9 backend, and probably many others.

As this is a serious issue, I am thinking and gathering a maximum of information, before doing a pull request.

I am working on many nuklear project for some time now, and expect some fixes from me.

[ghost]

Note about the D3D9/OpenGL backend:

For a 500 x 500 pixels window,

When I revert the commit 9a9f4f0:

with NK_ANTI_ALIASING_OFF
The window is drawn at the correct size.
Bottom lines and right lines are not drawn like getting -0.5f offsets.
> result in a 500px x 500px window.

with NK_ANTI_ALIASING_ON
The window is drawn with anti-aliasing (with 0.5f offsets), but the lines are drawn without anti-aliasing.
> result in a 501px x 501px window.

When I use the commit 9a9f4f0:

with NK_ANTI_ALIASING_OFF
The window is drawn with the 0.5f offsets (1px more).
Top lines and left lines are not drawn like getting -0.5f offsets.
> result in a 501px x 501px window.

with NK_ANTI_ALIASING_ON
The window is drawn without anti-aliasing (buttons too), only lines get anti-aliased.
> result in a 500px x 500px window.

Note about other drawing bugs:

with NK_ANTI_ALIASING_OFF
When we draw with nk_stroke_rect, and that float line_thickness > 1.0f there is a bug.
float line_thickness = 0, it is not drawing our rectangle. correct.
float line_thickness = 1, it is drawing our rectange with a 1px thickness. correct.
float line_thickness > 1, it is drawing four broken edges (-1px). not correct.
When config.line_AA is set to NK_ANTI_ALIASING_ON, the bug is gone. (but it doesn't matter as we don't want anti-aliasing)

Exemple with float line_thickness = 2, at bottom right,

Note 1: regardless of whether the anti-aliasing is enabled or not, the window should always be the same specified size.

Note 2: when disabling anti-aliasing lines, you'll probably want to disable borders in your style as well (same as Dear ImGui).

---

Updates:

1. I have fixed the lines not being drawn due to getting -0.5f on offset.x and offset.y.

2. About the problem with line_thickness > 1 when NK_ANTI_ALIASING_OFF is set, well this is really tricky because of too many factors (different backends as well as with/without AA), I will end up using my own function.
If you want additional information, have a look here:

• AddRect() without AntiAliasedLines missing a pixel ocornut/imgui#1646
• AddRect vs. 4x AddLine - 1 pixel width/height difference? ocornut/imgui#2441

[dumblob]

Hey, we're glad you're using Nuklear in many projects.

Regarding 1px off, feel free to make a pull request with the improvement. I'm actually quite confident we shouldn't just blindly revert the commit, but come up with a better solution - any ideas? Maybe add the "anti-aliasing" also to other parts of Nuklear?