; Description: How to use hooks in Blitz. This one is an example for the ASL ; screenmode requester and it works. Working parts by Paul "Mildred" ; West. ; You need amigalibsii.res resident. ; ; Note that some things aren't explained fully (i.e. the tags ; for the screenmode requester). You should look at the Autodocs ; for these. ; ; Type: SYSTEM ; ; Author: David McMinn (dmcminn@house-of-mojo.freeserve.co.uk) ; ; Requires: amigalibs.res ; ; History: ; 20 Oct 1999 Removed the pointless LEA from the hook (I'm sure it used to crash when I used JSR 6(a3)???) ; Global variable base is now stored in some reserved memory, not the h_UserData field ; ; ?? ??? ???? Written. Thanks to Paul West who got it working (Runerrsoff/on and jump to label+6) ; MOVE.l a5,globalbase ; Store a copy of Blitz's global variable base pointer ; This should always be done somewhere before using the ; hooks, and only needs to be done once ; These defines should be in amigalibsii.res, but they appear not to be #DTAG_DISP=$80000000 #DTAG_DIMS=$80001000 #DTAG_MNTR=$80002000 #DTAG_NAME=$80003000 ; The initial values for the width and height when opening the screenmode ; requester (silly really, as we won't see them - see later in code) PrefDisplayWidth.w=320 PrefDisplayHeight.w=240 ; Define a hook, and set it DEFTYPE.Hook myhook ; The hook for ASL tag as &myhook myhook\h_Entry=?hook ; Set address of hook stub which sorts out registers and calls Blitz function ; the hook stub in this code can be used as an all purpose hook ; as long as you set the address of the function in the hook h_SubEntry ; field and you set up this function so that it returns a long, and takes ; three long parameters (standard for a hook function). The three ; parameters will be as specified in the Autodocs for the hook ; callback you are trying to use except the parameters will arrive ; as parameter 1 instead of a0, parameter 2 instead of a1 and parameter 3 ; instead of a2. myhook\h_SubEntry = ?hook_jump ; Set address of Blitz function that you want to use as hook callback ; function ; NB That you must have a label directly before the function ; Set up some tags for the ASL screenmode requester Dim SMRtags.TagItem(18) SMRtags(0)\ti_Tag=#ASLSM_InitialLeftEdge,160 ; Initial left edge of requester SMRtags(1)\ti_Tag=#ASLSM_InitialTopEdge,0 ; Initial top edge of requester SMRtags(2)\ti_Tag=#ASLSM_InitialWidth,300 ; Initial width of requester SMRtags(3)\ti_Tag=#ASLSM_InitialHeight,600 ; Initial height of requester SMRtags(4)\ti_Tag=#ASLSM_InitialDisplayID,$21000 ; Initial screenmode (if present, PAL:Lowres) SMRtags(5)\ti_Tag=#ASLSM_InitialDisplayDepth,8 ; Initial depth of screen (in bitplanes/bits per pixel) SMRtags(6)\ti_Tag=#ASLSM_InitialDisplayWidth,PrefDisplayWidth ; Initial width of desired screen SMRtags(7)\ti_Tag=#ASLSM_InitialDisplayHeight,PrefDisplayHeight ; Initial height of desired screen SMRtags(8)\ti_Tag=#ASLSM_InitialOverscanType,2 ; Initial overscan type in cycle gadget (2 = #OSCAN_STANDARD) SMRtags(9)\ti_Tag=#ASLSM_InitialInfoOpened,1 ; Set information box to open SMRtags(10)\ti_Tag=#ASLSM_InitialInfoLeftEdge,350 ; Initial left edge of info box SMRtags(11)\ti_Tag=#ASLSM_InitialInfoTopEdge,50 ; Initial top edge of info box SMRtags(12)\ti_Tag=#ASLSM_DoDepth,0 ; Don't show depth requester to user SMRtags(13)\ti_Tag=#ASLSM_DoOverscanType,1 ; Show overscan cycle gadget to user SMRtags(14)\ti_Tag=#ASLSM_DoWidth,1 ; Show width gadget to user SMRtags(15)\ti_Tag=#ASLSM_DoHeight,1 ; Show height gadget to user SMRtags(16)\ti_Tag=#ASLSM_FilterFunc,&myhook ; Set hook for this function SMRtags(17)\ti_Tag=#TAG_END ; End of tag list ; Initialise and allocate a requester for the screenmode *sreq.ScreenModeRequester=0 *sreq=AllocAslRequest_(#ASL_ScreenModeRequest,&SMRtags(0)\ti_Tag) ; Display the requester ok.b=AslRequest_(*sreq,&SMRtags(0)\ti_Tag) ; If the return value was not 0 (therefore a success) If ok<>0 ; Display the returned values in the structure allocated earlier ; and wait for 3 seconds NPrint *sreq\sm_DisplayID NPrint *sreq\sm_DisplayWidth NPrint *sreq\sm_DisplayHeight Delay_ 150 EndIf If (*sreq) Then FreeAslRequest_(*sreq) ; If the screenmode allocation succeeded, then free theallocated memory ;************************************************************************* ; This is the Function that the hook will call. Put the label before ; the Statement/Function you want To jump To. Note that you need to put ; Runnerrsoff and Runerrson around the statement or function. ; ; In this implementation, the ASL screenmode requester uses a hook to decide ; which screenmodes to display in the selection list. This function returns ; true for ASL to display the screenmode and false to not display the screenmode. ; The hook (and therefore this function) are called for every screenmode that ; ASL screenmode requester finds. Runerrsoff hook_jump: Function.l hook{*dahook.Hook, modeID.l, *smr.ScreenModeRequester} DEFTYPE.DisplayInfo DisInfoBuf ; Buffer to receive information about mode display DEFTYPE.DimensionInfo DimInfoBuf ; Buffer to receive information about mode dimensions DEFTYPE.MonitorInfo MonInfoBuf ; Buffer to receive information about monitor (driver) DEFTYPE.NameInfo NamInfoBuf ; Buffer to receive information about mode name ; Gets a handle to a record of display information for the screenmode in question IDhandle.l=FindDisplayInfo_(modeID) ; Fill in the various buffers about this screenmode, using the newly ; gotten handle GetDisplayInfoData_ IDhandle,&DisInfoBuf,SizeOf.DisplayInfo,#DTAG_DISP,0 GetDisplayInfoData_ IDhandle,&DimInfoBuf,SizeOf.DimensionInfo,#DTAG_DIMS,0 GetDisplayInfoData_ IDhandle,&MonInfoBuf,SizeOf.MonitorInfo,#DTAG_MNTR,0 GetDisplayInfoData_ IDhandle,&NamInfoBuf,SizeOf.NameInfo,#DTAG_NAME,0 ; Do tests. True=Mode is valid, False=mode is invalid. In these test, any mode ; with a maximum horizontal width of less than 400 is rejected (i.e. PAL and ; NTSC Lowres modes) If DimInfoBuf\Nominal\MaxX < 400 Function Return False Else Function Return True End If End Function Runerrson ;************************************************************************* ;************************************************************************* Goto HookSkip ; This is done so that hook code does not get ; executed out of place ; Code for calling the higher level hook functions. This piece of code is used ; for all hooks. Basically it puts whats in A0 (usually the *hook structure) into ; D0, A1 into D1 and A2 into D2. What this means is that within your high level ; function, you should have three parameters. These parameters must match up with ; what the Autodocs say will be passed in the address registers (given that they ; are put into the data registers). Remember that in Blitz, the parameters ; are in order of data register D0 first parameter, and so on. ; This hook will also return a value in D0, which is the value returned by the ; high level function. Some hook applications may need this, others may not, ; but I think it is pretty standard to return a value, even if it is a dummy ; value. hook: MOVEM.l d1-d7/a0-a6,-(a7) ; Save registers to stack (NOT D0!!!) MOVE.l a0,d0 ; These three moves put the hook parameters MOVE.l a1,d1 ; (which are in A0-A2) into the data registers, MOVE.l a2,d2 ; so that the Blitz function can access them MOVEA.l globalbase(pc),a5 ; Restore the global variable base MOVEA.l 12(a0),a3 ; Get the address pointed to by the h_SubEntry field of the Hook structure JSR 6(a3) ; Get address of Blitz function and jump to it! ; The value is returned in d0 from the function. As this is where ; we want it, nothing is done, and the hook returns. MOVEM.l (a7)+,d1-d7/a0-a6 ; Restore registers from stack (NOT D0, we want to keep the return value) RTS globalbase: Ds.l 1 ; Reserve 1 longword for storing Blitz's global variable base pointer HookSkip End