Fix copy-paste errors in compile_shaders() error messages and comments

[RajdeepKushwaha5]

Summary of Changes

Fix 6 copy-paste errors in Basic_viewer/include/CGAL/Qt/Basic_viewer.h compile_shaders() that were carried over from the clipping plane shader section when the sphere, cylinder, normal, and triangle shader blocks were added:

4 incorrect error messages — the fragment shader std::cerr messages for sphere (line 989), cylinder (line 1022), normal (line 1054), and triangle (line 1086) all incorrectly said "Adding fragment shader for clipping plane FAILED" instead of naming the actual shader. Fixed each to reference the correct shader name.

1 stale comment — line 997 had // clipping plane shader at the start of the Cylinder shader block. Removed it.

1 wrong section comment — line 1059 had // Normal shader as the section header for the Triangle shader block. Changed to // Triangle shader.

Release Management

• Affected package(s): Basic_viewer
• Issue(s) solved (if any): fix Basic_viewer: Copy-paste errors in compile_shaders() — wrong error messages and stale comments #9392
• Feature/Small Feature (if any): N/A
• License and copyright ownership: N/A

[Copilot]

Pull request overview

Fixes misleading compile_shaders() debug output and section comments in Basic_viewer so shader compilation/linking failures are attributed to the correct shader blocks (per issue #9392).

Changes:

• Corrected 4 fragment-shader failure messages to reference sphere/cylinder/normal/triangle instead of “clipping plane”.
• Removed a stale “clipping plane shader” comment that was incorrectly placed in the cylinder shader block.
• Corrected the section header comment for the triangle shader block.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.