(2020-05-28, 8:45)Merlijn Wissink Wrote: It's been a little while since I last used buffer exchange, but I'm pretty sure everything after the STORE command is what is buffered.
And of course, the fact that it's not clear to a bunch of us which way it works is exactly why the topic's come up. :-)
For whatever it's worth, the MLCad spec is a bit vague, but describes it this way:
The buffer command either stores an image or retrieves a stored image. The image is taken from the actual view and when restored put in there.
[…]
You first create the model completely without the [hovering part]. Then you save an image of the current view, and after that you put the [hovering part] above the model. When the user continues drawing you retrieve the previously saved image and redraw the [hovering part] in it’s[sic] final position.
In his tutorial, which I'm pretty sure is where I first learned about buffer excahnge, Willy says:
MLCad allows to save up to 26 display states during the View Mode and to retrieve them at a later moment. Selecting A from the drop-down box [to insert the STORE command] and hitting OK will save the display state up to this point in an internal memory named A.
But, I should add that I've never used either MLCad or LPub, and other programs might process the buffer exchange commands a different way than by placing a saved view state into a memory buffer. And of course, from the user's perspective, the real action is what happens between the commands, and it is the user's experience that we're exploring, after all!
Quote:In any case, an example for the problem described there. Imagine you're making instructions for which need a part in a temporary positions for a certain number of steps. Everything after the STORE command will be removed once RETRIEVE is called. So, if you add temporary part in step 20, then in steps 21-24 you add other ('normal') parts and then call RETRIEVE in step 25 to place the temporary part in the final positions, all the other parts in steps 21-24 will be removed too, because the STORE command never ends (until RETRIEVE).
Oh yes, I see what you mean now. I agree that it would be nice not to have to re-insert any parts, including the ones that are being moved. My FLOAT method would do that, since it only affects the next line. And it works similarly to your END idea, except that FLOAT automatically lasts for just a single step, unless you specify otherwise with the n parameter.