EM_SETSEL swaps parameters - c++

Question

I use EM_SETSEL message to select text in edit control. I need to select some text from the end to the middle, so that caret position is in the middle of the text.
MSDN documentation states the following:
The start value can be greater than the end value. The lower of the two values specifies the character position of the first character in the selection. The higher value specifies the position of the first character beyond the selection.
The start value is the anchor point of the selection, and the end value is the active end. If the user uses the SHIFT key to adjust the size of the selection, the active end can move but the anchor point remains the same.
But it seems that lesser value always becomes an anchor, e.g. I cannot achieve the desired behaviour.
Code sample (where "parent" is CWnd*):
TRACE("EM_SETSEL(%d, %d)\n", pos1, pos2);
parent->SendMessage(EM_SETSEL, pos1, pos2);
parent->SendMessage(EM_GETSEL, (WPARAM)&pos1, (LPARAM)&pos2);
TRACE("EM_GETSEL(%d, %d)\n", pos1, pos2);
produces the output:
EM_SETSEL(5, 1)
EM_GETSEL(1, 5)
Is there another way to get the desired selection?

Answer 1

Regarding EM_GETSEL/EM_SETSEL:
EM_GETSEL retrieves left/right positions
EM_SETSEL sets anchor/active positions
EM_SETSEL uses anchor/active positions, allowing you to easily place the caret at the left/right of the selection, so I'm not sure why a kludge was used in the other answer.
EM_GETSEL is the awkward window message, for which a kludge is necessary. This kludge temporarily changes the selection to 0 characters, in order to retrieve the active position, however, when I've used it I haven't seen any visible change.
To retrieve anchor/active positions:
use EM_GETSEL to retrieve the left/right positions
use EM_SETSEL to temporarily set the selection to 0 characters, leaving the caret at the active position
use EM_GETSEL to retrieve the active position
use EM_SETSEL to restore the original selection
Some example AutoHotkey code for setting the selection:
q:: ;Notepad - set active position (caret) at right
PostMessage, 0xB1, 5, 10, Edit1, A ;EM_SETSEL := 0xB1
return
w:: ;Notepad - set active position (caret) at left
PostMessage, 0xB1, 10, 5, Edit1, A ;EM_SETSEL := 0xB1
return
Some example AutoHotkey functions for getting/setting the selection:
JEE_EditGetRange(hCtl, ByRef vPos1, ByRef vPos2)
{
VarSetCapacity(vPos1, 4), VarSetCapacity(vPos2, 4)
SendMessage, 0xB0, % &vPos1, % &vPos2,, % "ahk_id " hCtl ;EM_GETSEL := 0xB0 ;(left, right)
vPos1 := NumGet(&vPos1, 0, "UInt"), vPos2 := NumGet(&vPos2, 0, "UInt")
}
;==================================================
JEE_EditSetRange(hCtl, vPos1, vPos2, vDoScroll:=0)
{
SendMessage, 0xB1, % vPos1, % vPos2,, % "ahk_id " hCtl ;EM_SETSEL := 0xB1 ;(anchor, active)
if vDoScroll
SendMessage, 0xB7, 0, 0,, % "ahk_id " hCtl ;EM_SCROLLCARET := 0xB7
}
;==================================================
;note: although this involves deselecting and selecting it seems to happen invisibly
JEE_EditGetRangeAnchorActive(hCtl, ByRef vPos1, ByRef vPos2)
{
;get selection
VarSetCapacity(vPos1, 4), VarSetCapacity(vPos2, 4)
SendMessage, 0xB0, % &vPos1, % &vPos2,, % "ahk_id " hCtl ;EM_GETSEL := 0xB0
vPos1 := NumGet(&vPos1, 0, "UInt"), vPos2 := NumGet(&vPos2, 0, "UInt")
if (vPos1 = vPos2)
return
vPos1X := vPos1, vPos2X := vPos2
;set selection to 0 characters and get active position
SendMessage, 0xB1, -1, 0,, % "ahk_id " hCtl ;EM_SETSEL := 0xB1
VarSetCapacity(vPos2, 4)
SendMessage, 0xB0, % &vPos2, 0,, % "ahk_id " hCtl ;EM_GETSEL := 0xB0
vPos2 := NumGet(&vPos2, 0, "UInt")
;restore selection
vPos1 := (vPos2 = vPos2X) ? vPos1X : vPos2X
SendMessage, 0xB1, % vPos1, % vPos2,, % "ahk_id " hCtl ;EM_SETSEL := 0xB1 ;(anchor, active)
}
LINKS:
The functions above that I originally posted at the AutoHotkey forums:
GUI COMMANDS: COMPLETE RETHINK - AutoHotkey Community
https://autohotkey.com/boards/viewtopic.php?f=5&t=25893&p=138292#p138292

Answer 2

#vafylec's answer is good. I've just rewritten it here Delphi, which is a little easier to parse and translate to other languages than AHK.
Basically, EM_SETSEL allows you to set the anchor at either end of the range, but EM_GETSEL only ever returns the first and last character, losing that information. With a little kludge, you can work around this:
procedure GetEditSelection(Handle: THandle; var Anchor, Start, Finish: Integer);
begin
SendMessage(Handle, EM_GETSEL, NativeUInt(#Start), NativeUInt(#Finish));
SendMessage(Handle, EM_SETSEL, -1, 0);
SendMessage(Handle, EM_GETSEL, NativeUInt(#Anchor), 0);
if Anchor = Start then
SendMessage(Handle, EM_SETSEL, Finish, Start)
else
SendMessage(Handle, EM_SETSEL, Start, Finish);
end;