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Overlapping Windows And Window MenusWith the new functionality in 3.x of being able to attach a CUA compliant menu to each window individually, a whole new world opened up for lovers of overlapping windows! For those unaccustomed to such delights, imagine having a very large window, elements of which are only used occasionally. Thanks to the kindly auspices of VSPACE, one could just paint everything onto the one window and allow the user to pan to the bits they required. This works, but has the major disadvantage that ALL of the window is calculated before it is displayed, which makes window refresh that much slower. A better way is to overlay onto the main screen smaller subsets of the main data record in small windows. These overlays can be called from the window menu by a simple click with the mouse. There are a number of problems associated with this technique, but the largest is convincing the window processor that the record it is trying to call up in the smaller window (which has, of course, the same id as the record displayed in the main window), is not locked. The steps in achieving this can best be described as
Make the sub-windows non-locking
Pass the record back and forwards in labelled common, ensuring that the
integrity of data at different window levels is maintained
Update the labelled common areas with replace read/write processes
Remember of course, that the same technique might be used in multiple overlapping windows, so some way of keeping individual records separate must be incorporated. Rather than explain the process in depth, the code below shows just how this would be done. Note that the code is only installed in a Post Init hook on the window and from thereon in it installs itself. From within the commuter program called by the menu, the labelled common area would be loaded with the current record for the replace read process to pick up, the sub window would be called, and on return @Record would be updated from the labelled common area maintained by the replace write process on the sub window - i.e. (assuming that the labelled common area containing Record@ was declared earlier) 0001 Description: 0002 Record@(@Window.Level) = @Record 0003 Catalyst("W", "SKU_DESCRIPTION " : @Id) 0004 @Record = Record@(@Window.Level) 0005 Return 0001 Subroutine Overlay_Window(Branch) 0002 /* 0003 Author AMcA 0004 Date 10th April 1993 0005 Purpose Generic plug in for overlay windows 0006 Notes The labelled common area Overlay is used to pass the record 0007 between screens. It has been dimensioned to 20 to permit up to 0008 overlapped levels of window. 0009 */ 0010 0011 $Insert SysInclude, Window_Common% 0012 Common /Overlay/ Record@(20) 0013 Declare Subroutine Msg 0014 0015 Brnchs = "POST_INIT,REP_DEL,REP_QUERY,REP_READ," 0016 Brnchs:= "REP_REFRESH,REP_WRITE" 0017 Locate Branch in Brnchs using ',' setting POS then 0018 On Pos GoSub POST_INIT,REP_DEL,REP_QUERY,REP_READ,REP_REFRESH,REP_WRITE 0019 End Else 0020 Msg('Invalid Branch of %1%|Passed to %2%','','',BRANCH:@FM:WC_TEMPLATE%) 0021 End 0022 Return 0023 0024 Post_Init: 0025 /* 0026 Install the rep read/write/delete/refresh automatically. Note that for 0027 complete safety the program ought to check for pre-existing or 0028 duplicated processes so as not to overwrite them. 0029 */ 0030 Wc_Reproc%<3> = "S":@Vm:OVERLAY_WINDOW,REP_READ" Wc_Reproc%<4> = "S":@Vm:"OVERLAY_WINDOW,REP_WRITE" Wc_Reproc%<5> = "S":@Vm:"OVERLAY_WINDOW,REP_DEL" Wc_Reproc%<6> = "S":@Vm:"OVERLAY_WINDOW,REP_QUERY" Wc_Reproc%<7> = "S":@Vm:"OVERLAY_WINDOW,REP_REFRESH" Return Rep_Del: /* Remove those fields from the record that are contained in the current screen page. This is because a delete in a subwindow ought not to delete the main record, rather just that data in the subwindow. Note, do not attempt to remove key elements as they will be field 0 and therefore delete the record in its entirety. The same obtains for symbolics. */ For X = 2 To WC_W_Cnt% If WC_W%(X)<4> > 0 Then @Record<WC_W%(X)<4>> = "" End Next Record@(@Window.Level - 1) = @Record /* Now close the window and return to the calling program */ WC_Reset% = 6 Return Rep_Query: /* Do whatever you want to here */ Return Rep_Read: /* As the labelled common area was loaded at the previous window level, grab @Record from the array element one lower than the current window level */ @Record = Record@(@Window.Level - 1) WC_Orec% = @Record Return Rep_Refresh: /* Quit the screen */ WC_Reset% = 6 Return Rep_Write: Record@(@Window.Level - 1) = @Record WC_Reset% = 6 Return" (Volume 4, Issue 10, Pages 11-13) |
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