Slidy Sliders - help please (skid?)

Okay, so how do I make sliders "slidy"? See the example below. I want it to be the case that when I drag the slider, the panel moves with it. At present, it just moves once I release the mouse button.

I *know* this is possible, because skid did it in his maxedit code editor. But despite rummaging in that code, I can't see how! Any ideas? Anyone? Am I being really stupid?

SuperStrict

Local win:TGadget = CreateWindow("test" , 0 , 0 , 200 , 200 , Null , WINDOW_TITLEBAR) 
Local tab:TGadget = CreateTabber(0 , 0 , 150 , 150 , win)
Local panel:TGadget = CreatePanel(0 , 0 , 130 , 500 , tab)
Local slider_v:TGadget = CreateSlider(ClientWidth(tab) - 20 , 0 , 20 , ClientHeight(tab) , tab)
SetSliderRange slider_v , ClientHeight(tab) , 500

For Local i:Int = 0 To 20
	CreateButton "test " + i , 10 , 10 + i * 20 , 110 , 15 , panel
Next

Local t:TTimer = CreateTimer(60)

Repeat
	WaitEvent() 
	Select EventSource() 
		Case win
			If EventID() = EVENT_WINDOWCLOSE Then End
		Case slider_v
			If EventID() = EVENT_GADGETACTION Then
				SetGadgetShape panel,0,-EventData(),GadgetWidth(panel),GadgetHeight(panel)
			EndIf
		Case t
			SetGadgetShape panel,0,-SliderValue(slider_v),GadgetWidth(panel),GadgetHeight(panel)
	End Select
Forever

Two words - event hooks! ;-)

The basic idea is that the scrollbar generates events as you move the knob, but they are only added to the Blitz Event Queue after you release. To make matters worse, the action causes the program to go into a modal loop, one which is not left until you release the mouse button, at which point the program is allowed to carry on with its processing. If you want to catch all the events (as they happen) you need to use an Event Hook - which basically involves adding your own function to the internal Blitz list that Blitz calls when it catches an event.

SuperStrict

Global win:TGadget = CreateWindow("test" , 0 , 0 , 200 , 200 , Null , WINDOW_TITLEBAR) 
Global tab:TGadget = CreateTabber(0 , 0 , 150 , 150 , win)
Global panel:TGadget = CreatePanel(0 , 0 , 130 , 500 , tab)
Global slider_v:TGadget = CreateSlider(ClientWidth(tab) - 20 , 0 , 20 , ClientHeight(tab) , tab)
SetSliderRange slider_v , ClientHeight(tab) , 500

For Local i:Int = 0 To 20
	CreateButton "test " + i , 10 , 10 + i * 20 , 110 , 15 , panel
Next

Global t:TTimer = CreateTimer(60)

AddHook EmitEventHook, eventHook

Repeat
	WaitSystem
Forever


Function eventHook:Object(pID%, pData:Object, pContext:Object)

	Local pEvent:TEvent = TEvent(pData)
	If Not pEvent Then Return pData
	
	Select pEvent.source 
		Case win
			If pEvent.id = EVENT_WINDOWCLOSE Then End
		Case slider_v
			If pEvent.id = EVENT_GADGETACTION Then
				SetGadgetShape panel,0,-pEvent.data,GadgetWidth(panel),GadgetHeight(panel)
			EndIf
		Case t
			SetGadgetShape panel,0,-SliderValue(slider_v),GadgetWidth(panel),GadgetHeight(panel)
	EndSelect

EndFunction

Quick example for you that should hopefully show you what I mean. Check out Assari's EventHook MaxGUI Tutorial for more information.

Ah, I did wonder whether event hooks might be the difference.

Is there any real reason why the slider events can't be posted to the queue in real-time? i.e. in the same way that mouse move events are?

Mainly because on Windows, as the user is changing a slider's value, the OS enters a modal loop, which means that normal program execution isn't performed - however, event hooks are called from within the modal look and therefore can be used to intercept these events. Only when the mouse is released is normal execution resumed (i.e. your main program flow continues) and Blitz just posts the final slider value in the queue.

It would be practical if each slider has 3 events it can send out: startsliding, sliding, stopsliding (or comparible names). Currently the only "event" we have is stopsliding, which can be read using a hook to mimic a 'sliding' event.

From what Seb says, I don't think that's quite true.

In polled mode (using WaitEvent), you're right, there is no extra event. But in when using EventHooks and WaitSystem, it seems that the events do come through.

Which still seems bizarre to me, but hey, that'll be Microsoft...