Chinese vertical text renders incorrectly after rotation with Graphics.DrawString in WinForms

[vimalrajsf5014]

Description :

When rendering Chinese text in a WinForms application by using Graphics.DrawString with StringFormatFlags.DirectionVertical, and then applying a rotation transform, the text is displayed in an unexpected orientation and reading order.
The expected behavior is that the text remains logically ordered and readable as a vertically oriented string, while the entire text block is rotated as a single unit. Instead, individual CJK glyphs appear rotated and/or repositioned in a way that changes the intended visual representation and may affect the meaning.
This appears to be related to the underlying text rendering behavior in System.Drawing / GDI+, rather than to any specific WinForms control.
The issue occurs in both .NET Framework and .NET Core / .NET.

Screenshots :

Observed output :

Expected Output :

Alphabet Output :

SimpleSample :

TextSample.zip

Steps to Reproduce :

Step 1 : Run the attached sample application.
Step 2 : Click the Rotate button.
Step 3 : Observe how the Chinese text is rendered after rotation.

Actual Behavior :

• Chinese characters are displayed with an unexpected orientation.
• The text flow changes after rotation.
• The rendered result is not readable as intended.

Expected Behavior :

• The text should remain readable after rotation.
• The entire text block should rotate as a single unit.
• Chinese characters should retain their proper orientation and logical reading order.

Questions :

• Is this a known limitation of GDI+ or System.Drawing when rendering vertical CJK text?
• Is this the expected behavior of Graphics.DrawString in this scenario?
• Are there any recommended alternatives for correctly rendering vertical Chinese text?

Environment :

Framework: .NET Framework / .NET
OS: Windows 11

[LeafShi1]

Thank you for submitting this issue, however, this is not a WinForms bug. The behavior comes from the GDI+/System.Drawing text rendering pipeline used by Graphics.DrawString, not from WinForms itself, and WinForms only calls into that pipeline. Chinese characters and numerals follow different vertical rendering rules, which leads to the observed result.

For this scenario, we recommend implementing a custom rendering solution, For example:

• rotate the canvas as needed,
• layout and draw by text element (grapheme cluster),
• apply per-element rotation when required

[smourier]

IMHO, I think it's by design see Analyzing character orientation for explanation (about Direct Write but probably the same behavior for GDI+)

Every character has a preferred character orientation, or the direction that the character should be oriented in any directional layout. For example, in traditional horizontal layout, both the Latin text and the Chinese text are oriented vertically. On the other hand, in a vertical layout, the Chinese text remains upright, and the Latin text is rotated 90 degrees