alt Hacker NewsI'm genuinely surprised Microsoft's attitude towards "wndprocs don't have a context pointer" was "let's JIT compile a trampoline to hold the context pointer" and not to add support for a five-parameter wndproc into USER.dll, or have a wrapper that grabs GWLP_USERDATA and copies it to the register this lives in.
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pjc50 • yesterday at 6:46 AM
Doesn't x32 only have four registers available in the calling convention, AX-DX?
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> I'm genuinely surprised Microsoft's attitude towards "wndprocs don't have a context pointer"
They designed windows classes to be reusable, and assumed many developers going to reuse windows classes across windows.
Consider the following use case. Programmer creates a window class for a custom control, registers the class. Designs a dialog template with multiple of these custom controls in a single dialog. Then creates the dialog by calling DialogBoxW or similar.
These custom controls are created automatically multiple at once, hard to provide context pointers for each control.