Set global processing for string gadgets.
Source position: intuition.pas line 3540
function SetEditHook( |
Hook: PHook |
):PHook; |
Hook |
|
A pointer to a struct Hook which determines a function in your code to be called every time the user types a key. This is done before control is passed to the gadget custom editing hook, so affects all string gadgets. |
Returns previous global edit hook structure. You may need this hook if you wish to invoke the previous edit hook's behavior in addition to your own.
Sets new global editing hook for string gadgets.
Warning: The use and integration of this function has not been explored, and thus should be considered a risky function. Do not use this in a commercial product until further notice.
There are a few key differences between a global edit hook and the more famililar per-gadget StringExtend->EditHook field. In the case of the latter, the hook's creator supplies a WorkBuffer. Intuition's idea of the result of a keystroke is stored in the SGWork structure (which references the WorkBuffer). The state of the gadget before Intuition's hook acted is available in the TStringInfo.Buffer, .BufferPos, and .NumChars fields.
In the case of a global editing hook, your hook becomes Intuition's hook, which affects all gadgets, most of which do not have a WorkBuffer. This means that if you invoke Intuition's original hook (which you got as the result of this function), there isn't any easy way for you to "undo" that after the fact. This means that if Intuition's behavior for certain keystrokes is incompatible with your hook's objectives, then you must avoid calling Intuition's hook for those keys. One approach is to run through your hook's code first, acting on those keys you wish to recognize. Then, call Intuition's hook for those keys you do not recognize, or for those keys whose default actions you wish to add to.
Do not forget to set SGA_REDISPLAY when needed, and please be sure to give the TSGWork^.EditOp field a value which is as meaningful as possible.
Currently, only SGH_KEY messages are sent to the global edit hook, though custom edit hooks do receive SGH_CLICK messages in addition.
Finally, there is currently no arbitration between a global edit hook and a custom edit hook as to ownership of keystrokes. It would be fair to expect that a custom edit hook would be written to match the current Intuition edit hook. If your global edit hook acts on (say) up and down arrow keystrokes, an undesirable result may occur if some string gadget's custom hook also acts on these keystrokes. There is currently no easy way to resolve this issue.