Extend lines
Usual, I drag a line perpendicular to another line (X/Y values)
Then I want to drag it 200mm further.
But if I select the end point, drag it further and enter 200, then Bricscad gives the line a total lengt of 200 instead of adding 200mm.
Is it possible to switch it so that Bricscad uses the selected point coördinate to drag it X distance further?
Then I want to drag it 200mm further.
But if I select the end point, drag it further and enter 200, then Bricscad gives the line a total lengt of 200 instead of adding 200mm.
Is it possible to switch it so that Bricscad uses the selected point coördinate to drag it X distance further?
Comments

Since a while we are experimenting with additional snaps and dynamic dimensions, which is a slow process of trying out and finetuning.
As it happens, you may be interested to give the following a try (assuming you use a recent V15 release):
set DYNDIVIS to 2 (it controls the number of dynamic dimensions that are offered) and
set DYNMODE at least to 3 ( set it to 7 if you want to see more tracking dynamic dimensions)
Now when you drag the endpoint of a line to a new location, not only the distance to the startpoint will be displayed, but also the distance from the previous location of the endpoint. Hit TAB to move the focus to the desired dimension field. To ease dragging in one of the tracking directions, tapping the Shift key while a tracking line is displayed will lock the cursor to this tracking line, which tends to become a slightly addictive habit... 
For me, it works the way I think you're saying you want it to. I set Osnap = PER, then grab endpoint B of line AB and drag it toward line CD until I see the perpendicular symbol at the appropriate point on CD. Instead of clicking there, I continue dragging beyond CD in a direction approximately perpendicular to CD, along an xline that appears temporarily. At the same time, I type 10 on the numeric keypad and hit Enter. The result is that AB is now perpendicular to CD, with B 10" beyond CD. See image.
The same thing happens if I draw a new line starting at A and dragging the second endpoint to CD. The only way I can get a line of total length 10" is if I enter 10 while only the perpendicular symbol is showing, i.e. before dragging it beyond CD to make the xline appear.Drag.png 
Anthony thanks I never noticed this but it works for me to. Actually partially answered one of my ´quesstions the other day.

Reading your post again though I type 10 and get distans from A to B at 10 both in V13 and V15 BUT only if I create the AB line. If I change the AB line from another angle it will not be perpendicular at all. ???

Patrick, if I try to make line AB have a total length of 10" I get the same result as you. That is, if I try to stretch AB by dragging B to the perpendicular point on CD (and not going beyond it) and then entering a length, nothing happens. AB remains unchanged.
But if I offset CD through A, creating temporary line EF, then I can use EF in the same way that I used CD in the screenshot above. A is the perpendicular point on EF, so if I first drag B to A, and then drag away from it along the inferred xline, whatever distance I enter will be the new total length of AB perpendicular to both CD and EF. 
This also works (Bricscad V14.2.17; DYNMODE=3; DYNDIGRIP=31):
1. Drag the point you want to move.
2. Hit Tab 3 times: a dyn dimension for the angle between the old line and the modified line can now be entered.
3. Enter 0 (zero) but do not hit the Enter key.
4. Hit Tab 3 times: a dyn dimension for the additional length can now be entered.
5. Enter the desired length and hit Enter.
Done! 
A can not make it work (not shure I can follow you) but ROY YESS what sort of manual do you have ! It works after 10 tries ( do not enter zero, but enter first the distance then enter at the given angle V15 and V13) NICE ONE

I might be misunderstanding the requirement, but if you want to move the B end of AB to be an amount beyond the perpendicular of CD all you need to do is turn DYN off and hover over the perpendicular point to pick it up and then move the mouse in the direction you want and type your length.
If you want to draw a new line; with DYN still turned off, start the new line and type TT (TK also works but you need to press Enter to end the temporary tracking) and click on the perpendicular point when it is activated, again move the mouse in the direction you want and type your length.
Hope this helps,
David 
@ Patrik:
What you suggest is better because it requires fewer clicks (Bricscad V14.2.17; DYNMODE=3; DYNDIGRIP=31):
1. Drag the point you want to move.
2. Hit Tab 2 times: a dyn dimension for the additional length can now be entered.
3. Enter the desired length but do not hit the Enter key.
4. Hit Tab once: a dyn dimension for the angle between the old line and the modified line can now be entered.
5. Enter 0 (zero) and hit Enter.
Done!
Note: Steps 4 and 5 are not required if the line is orthogonal.
@ Patrik:
My manual is entitled "Trial and Error"...
@ David:
Your suggestion works just fine if the line is orthogonal. Judging from the original question I am inclined to think this is indeed the case, but I am not completely sure.
Finally an alternative:
Use the SegmentDist snap from my BKG_AdditionalSnaps (freeware). 
Why make iit so complicated.
line AB: select A and drag it up or down to give it's direction to go to and a distance.
Direction can be up/down, leftright depending where the endpoint is dragged.
Autocad does it, okay, for that price.... but the free draftsight does it too and zw*** also.
So Bricssys? 
Stefaan same for bricscad BUT the trick was to extend a specific amount beyond a perpendicular line.

not exactly same, but I do this at Command Line by typing LEN then I (increase amount  Enter amount)) and select the end of that line.
Its quick. 
That's indeed an approach.
Thanks Richard. 
@ Stefaan:
Am I right in thinking that your original post and your post #11 are based on tests with DYNMODE switched on? In other words: with DYNMODE switched off (see posts #9 and #12.), BricsCAD works the same as the other software products you have mentioned?
This discussion has been closed.
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