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| Alt-Tab Problem |
| mtsmox
Global user (4/4/00 10:13:28 am) Reply ALT-TAB problem -------------------------------------------------------------------------------- I have a problem with ALT-TAB: If my game is running and the user presses ALT-TAB my program crashes. That is because my program hasn't got the focus anymore, so I can't blit to it. Also my DI devices are unaqcuired, because of the focus loss. How can I tell if my program lost focus, are do you know another solution for my problem? I was curious: how does alphablitting work? Ofcourse I could use the vbDABL dll, but I would like to know how it is done... thanks
MetalWarrior Global user (4/4/00 4:39:59 pm) Reply Re: ALT-TAB problem -------------------------------------------------------------------------------- The easiest way to tell if you lose focus is by using the Form_LostFocus event. Or you could use Subclassing, which is exampled in the DI mouse tutorial in the SDK. Alphablitting is basically finding a color that is a given percentage difference between the source color and destination color for each pixel. That's what gives it that "see-through" look.
black eyez Global user (4/4/00 4:51:06 pm) Reply Alphablending -------------------------------------------------------------------------------- Yeah, basically alphablending (blitting) is taking the source and destination colors and combining them to create an in-between color like this: finalcolor = (sourcecolor * alphavalue) + (destinationcolor * (1 - alphavalue)) where alphavalue is a number
between 0 and 1. This is the most basic form of alphablending (and the
most common) called 'additive blending'. There are others like subtractitive,
multiplicative, etc etc. I could get into much more detail if you want
about simplifying the formula to make it faster etc if you want, but I
won't for now
david goodlad
Lucky Unregistered User (4/4/00 6:51:22 pm) Reply ALT-TAB solution -------------------------------------------------------------------------------- These are the (somewhat cheesy) functions that I use to detect and handle loss of exclusivity: Public Function LostSurfaces() As Boolean 'This
function will tell if we should reload our bitmaps or not
'If
we did lose our bitmaps, restore the surfaces and return 'true'
End Function Private Function ExclusiveMode() As Boolean Dim TestExMode As Long 'This
function tests if we're still in exclusive mode
If
(TestExMode = DD_OK) Then
End
Function
Call the "LostSurfaces" function..
if it returns "True" then you need to reload your bitmaps onto their surfaces.
If it returns "False" then just carry on your merry way. Also note, this
function repeatedly checks for a return to exclusivity (by calling the
"ExclusiveMode" function) and won't return its value until we have the
focus again. This prevents any potential errors caused by attempted blits
of lost surfaces.
Lucky
mtsmox Global user (4/6/00 10:07:40 am) Reply Re: ALT-TAB solution -------------------------------------------------------------------------------- Thanks for your replies, but I still had a few problems: The Form_LostFocus event
isn't called if the form loses focus and the Form_GotFocus event is only
called if there are no objects on the form and only at startup.
Thanks for your help,
Daniel Netz Unregistered User (4/6/00 2:39:27 pm) Reply _ -------------------------------------------------------------------------------- Subclassing is a way of getting into the Windows Procedures that's hidden in VB. If you program Win32 for C++ you have to take care of the windows messages yourself while VB does that for you, that is, if you're not using subclassing. I use the Form_Resize function to check what state the window is in. If you put a Select procedure there that checks what WindowState the form is in, you can easily keep track of when to restore your surfaces and when to pause the rendering.
MetalWarrior Global user (4/6/00 7:14:05 pm) Reply Re: _ -------------------------------------------------------------------------------- Hey, that's a good idea. Now why didn't I think of that? Don't answer that. ;-)
Daniel Netz Global user (4/7/00 12:39:17 am) Reply Re: _ -------------------------------------------------------------------------------- I think I'll do that anyway, if you don't mind I would never have thought
about it either, if I didn't learn that the Form_Resize event is triggered
not just when the window resizes, but also when the WindowState has changed.
mtsmox Global user (4/7/00 10:44:35 am) Reply Re: _ -------------------------------------------------------------------------------- But Form_Resize isn't triggered if a form loses focus. So If you bring another form to the foreground, the programme happely continues. I tried Screen.ActiveForm but that only returns forms you use yourself, so if another programme is on top, it still returns a form you own... so you can't check if your application is running on top or not This obviously isn't that
important, but those little things really annoy me
Joren
MetalWarrior Global user (4/7/00 1:53:26 pm) Reply Re: _ -------------------------------------------------------------------------------- If you're running in FullScreen mode, Form_Resize is all you need. If, however, you're running in Windowed mode, then the Form_LostFocus event should be triggered. Are you sure that doesn't work?
mtsmox Global user (4/9/00 5:48:08 am) Reply Re: _ -------------------------------------------------------------------------------- Form_LostFocus is only called if you switch from one form to another within your own application, not if you switch between apps. And if I test Form_Resize by putting a stop command in it and make a fullscreen form and switch between apps with ALT-TAB, Form_Resize isn't called... but if you minimize or maximize it is called. But I'm testing it without DX, perhaps if you have setup DX and then use ALT-TAB the WindowState IS changed. Getting back to my first
post: I would like to know how to use alpha blitting in a FAST way... I've
seen the tutorial on this page but that was for DX6. Isn't setpixel and
getpixel in DX7 fast enough for alpha blitting, so you don't have to use
CopyMemory?
thanks
Voodoo VB Administrator (4/9/00 6:51:31 am) Reply Well -------------------------------------------------------------------------------- Well, no, it isn't fast enough really. If you would like to see, dl the BiohazrdDD library from the source code page. It uses setpixel/getpixel for alpha-blending. Peter
black eyez Global user (4/9/00 10:50:34 am) Reply Re: Well -------------------------------------------------------------------------------- Yeah, doing it in native vb code is.. err... shall we say really slow? :P Even with copymemory it can be quite slow. *shameless plug* so if ya wanna do it fast, use some assembly like my dll 'vbDABL' hehehe It's at my website: blackhole.thenexus.bc.ca/ under the downloads section. David david goodlad
CoryP Global user (4/9/00 1:59:03 pm) Reply Re: ALT-TAB -------------------------------------------------------------------------------- You could try to use the GetActiveWindow API function which returns a handle to the active window. The declaration is Public Declare Function GetActiveWindow Lib "user32" () As Long Edited by CoryP at: 4/9/00
1:59:03 pm
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