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How do VFP controls fake it?
Message
Information générale
Forum:
Visual FoxPro
Catégorie:
Autre
Versions des environnements
Visual FoxPro:
VFP 9
OS:
Windows XP SP2
Network:
Windows 2000 Server
Database:
Visual FoxPro
Divers
Thread ID:
01037136
Message ID:
01037763
Vues:
18
Hi Dawa,

I don't know why and when this was decided...it was before my time. My understanding is that there were serious challenges to using Win controls upfront and compatibility with 2.x issues but I don't know the details.

As to changing the cursor, I believe there's an API function that can do that and you can call it in the GotFocus of the control you want to effect. I don't know of any way to do it purely in VFP.

As to advantages to bitmaps over Win controls: There are many advantages. Early on in VFP there was concern that the runtimes were large; however, apps didn't consure that much GDI memory. Now, the 4-5MB VFP runtime seems little and we still have the advantage of very small footprints for VFP controls.

I've seen several non-VFP apps crash and burn because they became memory pigs because everything was a Win control.

You do lose some native control with controls not being Win controls (with an hwnd, etc) but what you gain in speed and memory conservation more than makes up for it IMHO.

Try this: Create a VFP form and add a 1000 textboxes to it (You can do it in code with ASELOBJ). Now, so the same thing in VB6 or VB.Net. Run each and then check system resources while running using Task Manager.

See?

>>There's an internal event handler that intercepts everything before it gets to Windows. So everything is completely internal to VFP (for the most part).
>
>John,
>
>Thanks for the reply.
>
>Could you explain the advantage of using bitmap representations as VFP controls over windowed controls?
>
>How and why was this decided?
>
>Were there technical challenges for using windowed controls?
>
>Is it possible to have a property named "Caret" or whatever for a text box or a edit box so one can change the image of a blinking caret?
>
>Is this event handling model the reason for "_vfp.AutoYield"?
------------------------------------------------
John Koziol, ex-MVP, ex-MS, ex-FoxTeam. Just call me "X"
"When the going gets weird, the weird turn pro" - Hunter Thompson (Gonzo) RIP 2/19/05
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