QCard DLL Lesson 9

Lesson 8 Lesson 10

See Lesson 1 for QCard DLL and WAV files needed for the demo code.

Dragging a Card

QCard has features that allows us to drag a single card or a block of cards. We'll start with dragging a single card.

Mouse Click Starts Drag

We can start the dragging event when the user presses a mouse button down. We'll use the right button for this. Once the button is down, we'll activate the mouse move event for the right button and call on QCard to intialize the dragging procedure. Since InitDrag returns the index of the clicked card, we'll write that on the display so we can see what's happening. We need to send the graphicbox handle and MouseX and MouseY to the function.

 #1.g "when rightButtonDown [initDrag]" 
 wait 
 
 [initDrag] 
 cardIndex=InitDrag(hBox,MouseX,MouseY) 
 #1.g "place 10 420;\Drag Card Index is ";cardIndex;space$(100) 
 #1.g "when rightButtonMove [doDrag]" 
 wait

InitDrag

Here is the documentation from QCard for InitDrag.

Use this function in a MouseDown event to start a drag operation. The function searches through all cards to determine if the mouse cursor is over any card whose IsBlocked property is FALSE. If it finds one, it returns the number of that card. If it does not find one, it searches through all the cards in the deck to see if the mouse lies in the top 16 (or User-Defined OffSet) pixels of any card, blocked or not. If it does, it returns the number of that card.

By checking the IsBlocked property of this returned card, you can tell if the user wants to carry out a single drag or a block drag. If InitDrag returns a value of 0, the mouse is not currently located over any card. The InitDrag function should always be followed by a corresponding AbortDrag, an EndDrag or an EndBlockDrag call. This is due to that fact that InitDrag "captures" all mouse input, and requires one of these corresponding calls to release the capture. The values nx and ny are the current mouse coordinates.

Here is the InitDrag function, wrapped in a Liberty BASIC function.

 Function InitDrag(hndle, x, y) 
 calldll #qc, "InitDrag",_ 
 hndle as ulong, x as long, y as long,_ 
 InitDrag as long 
 end function

AbortDrag

QCard DLL captures mouse events while dragging. If mouse event capture is not released, the program will crash. Mouse event capture is released by EndDrag, but if something goes amiss, we can assure a stable program by calling AbortDrag to release mouse event capture.

 calldll #qc, "AbortDrag",re as void

DoDrag

DoDrag is the subroutine used by QCard to move the card. It requires the handle of the graphicbox and MouseX and MouseY.

 [doDrag] 
 call DoDrag hBox, MouseX, MouseY 
 #1.g "when rightButtonUp [endDrag]" 
 wait

The documentation tells us that DoDrag, "Carries out the drag operation which was initiated by InitDrag call. DoDrag moves the current Source Card to its new location. Values nx and ny are the current mouse coordinates." It does not return a value.

 Sub DoDrag hndle,x,y 
 calldll #qc, "DoDrag",hndle as ulong,_ 
 x as long, y as long, r as void 
 end sub

EndDrag

We stop the dragging operation and drop the card at the current location when the right mouse button is released. The EndDrag function requires the handle of the graphicbox and MouseX and MouseY. We also cancel the "rightButtonUp" event in our code.

 [endDrag] 
 #1.g "when rightButtonUp" 
 cardIndex=EndDrag(hBox,MouseX,MouseY) 
 #1.g "place 10 420;\Destination Card Index is ";cardIndex;space$(100) 
 wait

Qcard tells us this about EndDrag, "EndDrag ends a single drag operation and returns the number of the Destination card (that is, the card it is being dropped on), if any. It searches the deck for any card which overlaps the Source Card and whose IsBlocked property is FALSE. If it finds one, it returns the number of that card. The function also releases the mouse which was captured by the InitDrag call."

 Function EndDrag(hndle,x,y) 
 calldll #qc, "EndDrag",hndle as ulong,_ 
 x as long, y as long, EndDrag as long 
 end function

DEMO

See Lesson 1 for QCard DLL and WAV files needed for the demo code.

The demo uses the foundation of our Memory card game. It invites the user to right click and drag a card.

 'An open project card game, begun by Alyce Watson, May 27, 2003. 
 'Uses Qcard32.dll, a freeware library of playing card images. 
 'DLL by Stephen Murphy. Qcard32.DLL website: 
 'http://www.telusplanet.net/public/stevem/ 
 
 dim card(24) 'array to hold cards 
 gosub [fillCardArray] 'fill array with card values 
 newIndex=0 'used when shuffling 
 tempCard=0 'temp var used when shuffling 
 
 [varSetup] 
 i=0 'i will be our counter var in for/next loops 
 design=1 'default design is circles 
 
 nomainwin 
 WindowWidth=640:WindowHeight=480 
 UpperLeftX=1:UpperLeftY=1 
 
 menu #1, "&File", "&New",[new],"E&xit", [quit] 
 graphicbox #1.g, 0, 0, 640, 440 
 open "Card Dragging" for window_nf as #1 
 #1 "trapclose [quit]" 
 
 'get graphicbox handle 
 hBox=hwnd(#1.g) 
 
 'open the dll 
 open "qcard32.dll" for dll as #qc 
 'initialize the deck 
 Call InitializeDeck hBox 
 
 [new] 
 Call SetDefaultValues 
 Call SetCurrentBack design 
 
 'draw a nice background 
 #1.g "down; fill 10 190 225" 
 #1.g "backcolor 10 190 225" 
 'temp message for this demo only 
 #1.g "place 10 420" 
 #1.g "\Right-click on a card, then move mouse to drag and drop it." 
 gosub [shuffleCards] 
 
 'set xy location to start deal 
 x=10:y=2 
 for i = 1 to 24 
 'set status of all cards to 0, which is face down 
 ' - we won't do this yet, so we can see the results 
 'of our deal 
 'call SetCardStatus card(i), 0 
 
 Call DealCard hBox,card(i),x,y 
 x=x+100 
 if x>510 then 'move to next row 
 x=10 
 y=y+100 
 end if 
 playwave "card.wav",sync 
 
 'pause 100 milliseconds between cards 
 call Pause 100 
 scan 
 next 
 #1.g "when rightButtonDown [initDrag]" 
 wait 
 
 [initDrag] 
 cardIndex=InitDrag(hBox,MouseX,MouseY) 
 #1.g "place 10 420;\Drag Card Index is ";cardIndex;space$(100) 
 #1.g "when rightButtonMove [doDrag]" 
 wait 
 
 [doDrag] 
 call DoDrag hBox, MouseX, MouseY 
 #1.g "when rightButtonUp [endDrag]" 
 wait 
 
 [endDrag] 
 #1.g "when rightButtonUp" 
 cardIndex=EndDrag(hBox,MouseX,MouseY) 
 #1.g "place 10 420;\Destination Card Index is ";cardIndex;space$(100) 
 wait 
 
 [fillCardArray] 
 'fill card array 
 'cards 1 to 52 are in the first deck 
 'cards 53 to 104 are in the second deck 
 'use cards Jack through King in each suit, first deck 
 card(1)=11 'jack of clubs 
 card(2)=12 'queen 
 card(3)=13 'king 
 card(4)=24 'jack of diamonds 
 card(5)=25 'queen 
 card(6)=26 'king 
 card(7)=37 'jack of hearts 
 card(8)=38 'queen 
 card(9)=39 'king 
 card(10)=50 'jack of spades 
 card(11)=51 'queen 
 card(12)=52 'king 
 
 'now use second deck, to fill second half of array 
 for i = 1 to 12 
 card(i+12)=card(i)+52 
 next 
 RETURN 
 
 
 [shuffleCards] 
 playwave "shuffle.wav",async 
 'now shuffle cards 
 for i = 1 to 24 
 newIndex=int(rnd(0)*24)+1 
 tempCard=card(i) 'temp var to allow switching values 
 card(i)=card(newIndex) 'this index now contains value from random index 
 card(newIndex)=tempCard 'random index now contains value from other index 
 'now card(i) has switched values with a random card in the array 
 next 
 playwave "shuffle.wav",sync 
 RETURN 
 
 [quit] close #qc:close #1:end 
 
 
 '''''''''''''''''''' 
 'subs and functions: 
 Sub Pause ms 
 'pause ms number of milliseconds 
 calldll #kernel32,"Sleep",_ 
 ms as long, re as void 
 End Sub 
 
 Function InitDrag(hndle, x, y) 
 calldll #qc, "InitDrag",_ 
 hndle as ulong, x as long, y as long,_ 
 InitDrag as long 
 end function 
 
 Sub DoDrag hndle,x,y 
 calldll #qc, "DoDrag",hndle as ulong,_ 
 x as long, y as long, r as void 
 end sub 
 
 Function EndDrag(hndle,x,y) 
 calldll #qc, "EndDrag",hndle as ulong,_ 
 x as long, y as long, EndDrag as long 
 end function 
 
 Sub InitializeDeck hndle 
 calldll #qc, "InitializeDeck",_ 
 hndle as ulong,r as long 
 End Sub 
 
 Sub SetCardStatus nC,face 
 'nC is number of card - 1-52 in first deck and 
 '53-104 in second deck, if used 
 'face: 0=facedown,1=faceup 
 calldll #qc, "SetCardStatus",nC as long,_ 
 face as long,r as void 
 End Sub 
 
 Sub DealCard hndle,nC,x,y 
 'places card on window whose handle is hndle at x,y 
 'nC is number of card - 1-52 in first deck and 
 '53-104 in second deck, if used 
 calldll #qc, "DealCard",hndle as ulong,nC as long,_ 
 x as long,y as long,r as void 
 End Sub 
 
 Sub DrawBack hndle, nV, x, y 
 'nV can be 1,2,3,4,5,6 for 6 possible designs 
 'draws a cardback image on screen 
 calldll #qc, "DrawBack",hndle as ulong,_ 
 nV as long,x as long,y as long,r as void 
 End Sub 
 
 Sub SetCurrentBack nV 
 'nV can be 1,2,3,4,5,6 for 6 possible designs 
 calldll #qc, "SetCurrentBack",nV as long,r as void 
 End Sub 
 
 Sub SetDefaultValues 
 'reset all card properties back to their default values. 
 calldll #qc, "SetDefaultValues",r as void 
 End Sub

Lesson 7 ~~Lesson9~~ 8 Lesson 10

QCard09