EditTable Cookbook - How to get cell coordinates
Published 22 SEP 2009 at 09:00:00AM by Captain C
Many of the applications we write need to display things like option dialog boxes near a specific control. In most cases this is quite easy to handle as we can easily obtain the SIZE property of a control and work out our positioning from that. A slightly more difficult task is to position something relative to an EditTable cell because OpenInsight doesn't expose this information as a property or a method.
We've seen many attempts to calculate cell coordinates in Basic+ - we've even done it a few times ourselves and it's quite a pain, having to take into account all the different styles of the edit table, the width of columns, which columns are hidden and so forth.
Well, there's a really easy way to do this, and that's by asking the EditTable itself what the coordinates are via the standard Windows API SendMessage function. We just need to know what message to send to the EditTable.
DTM_READCELLRECT
The message we need is called DTM_READCELLRECT, and it returns the coordinates of the cell identified via the ACCESSPOS property. All we need to do is pass it the address of a RECT structure to fill in, which we then translate into a dynamic array which we can use further.
Here's a simple function to demonstrate this:
0001 compile function edt_GetCellRect( edtID, colNo, rowNo ) 0002 /* 0003 Author : Darth C, Sprezzatura Actual 0004 Date : Sep 09 0005 Purpose : Function to return edit table cell coordinates 0006 0007 Parameters 0008
0009 0010 edtID → Fully qualified name of the edit table 0011 0012 colNo → Column number of the target cell. Defaults 0013 to currentPos 0014 0015 rowNo → Row number of the target cell. Defaults to 0016 currentPos 0017 0018 Returns 0019
0020 0021 Returns the edit table cell coordinates as per the RECT 0022 structure layout, i.e. 0023 0024 <1> Left 0025 <2> Top 0026 <3> Right 0027 <4> Bottom 0028 0029 Note these coordinates are relative to the Edit Table 0030 CLIENT area, NOT the desktop/screen! 0031 0032 */ 0033 declare function sendMessage, blank_Struct, struct_To_Var 0034 declare function get_Property 0035 0036 equ DTM_READCELLRECT$ to 1079 ; * // (WM_USER + 55) 0037 equ DTA_ACCESS$ to 0x0000 0038 0039 if assigned( edtID ) else edtID = "" 0040 if assigned( colNo ) else colNo = "" 0041 if assigned( rowNo ) else rowNo = "" 0042 0043 if len( edtID ) else 0044 return "" 0045 end 0046 0047 if len( colNo ) and len( rowNo ) then 0048 call set_Property( edtID, "ACCESSPOS", colNo : @fm : rowNo ) 0049 end else 0050 * // Use the current "caret" position - ensure ACCESSPOS 0051 * // is sync'd with CARETPOS 0052 call set_Property( edtID, "ACCESSPOS", | 0053 get_Property( edtID, "CARETPOS" ) ) 0054 end 0055 0056 * // Create a blank RECT structure for the edit table 0057 * // to fill for us and lock it 0058 rc = blank_Struct( "RECT" ) 0059 lockVariable rc as BINARY 0060 0061 * // Send the DTM_READCELLRECT message. 0062 * // 0063 * // The third parameter (wParam) contains a value that 0064 * // tells the edittable which cell we want. DTA_ACCESS 0065 * // means "use the ACCESSPOS property". 0066 * // 0067 * // We send the address of the RECT structure to fill in 0068 * // as the last parameter (lParam). 0069 call sendMessage( get_Property( edtID, "HANDLE" ), | 0070 DTM_READCELLRECT$, | 0071 DTA_ACCESS$, | 0072 getPointer( rc ) ) 0073 0074 * // Unlock and translate the structure to a 0075 * // dynamic array 0076 unlockVariable rc 0077 rc = struct_To_Var( rc, "RECT" ) 0078 0079 return rc
(The more pedantic amongst you may notice that we didn't reset ACCESSPOS after we updated it. The reason for this is simple - every low-level function in the EditTable updates ACCESSPOS to the required coordinates before executing, and you should never assume ACCESSPOS is at the correct coordinates - always set it yourself before use!)
You can download a text version of edt_GetCellRect here