set_vec3
Description:
Sets the value of the uniform idx.
Note:
GTK's new Vulkan-focused rendering does not support this feature. Use [GtkGLArea](../gtk4/class.GLArea.html) for OpenGL rendering.
The uniform must be of vec3 type.
Parameters:
| this |
a `GskShaderArgsBuilder` |
| idx |
index of the uniform |
| value |
value to set the uniform too |