Rendering problem - angled lines appear during mouse interaction

[bukkideme]

Describe the bug
When the docked ScottPlot.FormsPlot is maximized together with the parent Form's window, strange angled lines appear at top right during middle mouse button pushed down. Same artifact happens when we use the right mouse button for zoom.

To Reproduce
VS Community 2019, Version 16.5.5.
ScottPlot 4.0.32 (previous version also has the same bug)

Steps to reproduce:

Create a new Winform project.
Drop a ScottPlot.FormsPlot user control into the Form, and set it as "Dock - Fill".
Run the project.
Maximize the Form window.
Start to use the mouse buttons for the different zoom options.
Bug appears visible.

Another info, if you set the grid line width to value 2 or higher (i did it in the Form's constructor), the bug seems to disappear:
formsPlot1.plt.Grid(lineWidth: 2);

Screenshots
I set the Grid color to red to make the bug more visible!

[Ichibot200]

I have the same issue.
Unfortunately, I have not taken a closer look at the issue myself yet.

[swharden]

This is so frustrating! This is an error in System.Drawing when rendering non-anti-aliased perfectly horizontal lines that touch the edge of the bitmap described in #327

This issue may have re-emerged from recent work on the grid system a63eba9

I'll take a closer look!

strange angled lines appear at top right during middle mouse button pushed down

This is because mouse interactions enable anti-aliasing mode

[swharden]

This should be fixed in ScottPlot 4.0.33 now on NuGet. I'd appreciate your feedback to confirm it works on your machines!

[swharden]

FWIW it's not just System.Drawing, this also happens with System.Drawing.Common in .NET Core 2.0 🤔

var plt = new ScottPlot.Plot(400, 300);
plt.Grid(xSpacing: 2, ySpacing: 2, color: Color.Red);
plt.Axis(-13, 13, -10, 10);
plt.GetSettings(false).misc.antiAliasData = false;
plt.GetSettings(false).misc.correctGridRenderingBug = false;
plt.SaveFig("microsoftPleaseExplain.png");

but enabling anti-aliasing fixes it 🙈

plt.GetSettings(false).misc.antiAliasData = true;

[swharden]

SOLVED: Never create a solid Pen.DashPattern (set Pen.DashStyle to Solid instead)

Assigning a dash pattern (even a solid one) automatically switches a pen's DashPattern from Solid to Custom. Custom dash patterns produce rendering artifacts when anti-aliasing is off. They're also less performant.

I searched the code and removed all instances where the DashPattern was manually set.
https://github.com/swharden/ScottPlot/search?q=dashpattern&unscoped_q=dashpattern

I created a helper function to safely make pens:
https://github.com/swharden/ScottPlot/blob/f9c1c8bedc8c0c6da98084867b949178c3036f38/src/ScottPlot/Drawing/GDI.cs#L63-L97