To be dependable, the entity must also be stable.
Formal protocols have the advantage that the entity stay stable by design.
Thus, when they are available and the applications support them, they usually provide the most dependable solution. When formal protocols are not sufficient, there are other entities that can fill the role, even those not originally designed for interprocess communication. Many can be found in the operating system, and since all applications share the operating system, these can sometimes be used for interprocess communication for a wide range of applications. Pixel data access fits into this category because it uses the display buffer, which is managed by the operating system.