Okay, finally, (I should have done this immediately), here is the best and most brief explanation: So load the code of the attached UPDATED scrap-mode.el. Then do `M-x scrap-expand-overlays`. It will print 1000, but I expect it to print the number of overlays you are actually seeing on screen, because the function calls (print (length (overlays-in (window-start) (window-end))))) after adding the 'space' display properties/expanding the overlays. So although the display properties have been added, they seem to not have taken effect at the time (print (length (overlays-in (window-start) (window-end))))) is evaluated. If you uncomment the `sit-for` in `scrap-expand-overlays`, then you will see it prints a different (i.e. the correct/expected) number. Another way to get the expected number, is to now do M-: (length (overlays-in (window-start) (window-end))) On Tue, 21 Feb 2023 at 14:57, dalanicolai wrote: > B.t.w. I am using Emacs 29 (and 30), and the overlay-recenter is still > there. > Maybe it would be handy to remove it then? > > On Tue, 21 Feb 2023 at 14:50, dalanicolai wrote: > >> Let me, additionally, very briefly explain what the code is doing, and >> what I am expecting (as an attempt to make it immediately clear what I >> mean). >> >> So the code is first simply creating (for my dir) 108 overlays. Then >> in 'scrap-dir-images' are made to display the images from the >> directory. Immediately, after the >> '(seq-do-indexed (lambda (im n) (overlay-put ... 'display ...)' >> the function print the value of '(overlays-in (window-start) >> (window-end))', >> which return 108. However, I expect it to print 2, as the overlays should >> have the size of the images now (and I see only two images simultaneously >> on >> screen). Indeed when doing 'M-: (overlays-in (window-start) (window-end))' >> immediately after creating the 'image gallery', it returns 2. >> >> On Tue, 21 Feb 2023 at 14:39, dalanicolai wrote: >> >>> In this example code, I am simply displaying all images at once, >>> because I am assuming that the images in the directory are not too >>> many and that they are small (which is not a very reasonable >>> assumption, but this is just my personal 'test' function). >>> >>> Indeed, the example does not call sit-for, because it should show that >>> the printed number of overlays, is the number of all images in the >>> directory (instead of only the number of images currently on the >>> screen, i.e. within '(overlays-in (window-start) (window-end))' ). >>> >>> For example, I have a directory with 108 images, when I run 'M-x >>> scrap-dir-images' it print 108, although it should print the number of >>> images on screen i.e. by '(overlays-in (window-start) (window-end))', >>> which value is what 'scrap-dir-images' prints. However, the images >>> are normal 'foto' size, so that I only see two images on screen, and >>> indeed doing 'M-: (overlays-in (window-start) (window-end))' manually >>> now prints 2. If I had added the '(sit-for)' in the example >>> code, then I would have 'fixed' the problem, and 'scrap-dir-images' >>> would have printed 2 immediately because the display property >>> ('expansion of the overlays') got enough time to take effect. >>> >>> I hope this clears things up, but of course I would be happy to try >>> another explanation (e.g. sending by adding an animated gif). >>> >>> But this function is a no-op in Emacs 29 and later, since the overlays >>>> were reimplemented in a way that makes it unnecessary to "center" the >>>> list of overlays. So you can forget about that and ignore this >>>> function. >>>> >>> >>> Thanks, that is indeed handy to know. >>> >>> On Tue, 21 Feb 2023 at 14:21, Eli Zaretskii wrote: >>> >>>> > From: dalanicolai >>>> > Date: Tue, 21 Feb 2023 13:46:56 +0100 >>>> > >>>> > So now here are the questions: >>>> > >>>> > - when displaying multiple pages in columns, I would like to use the >>>> > overlays-in function to determine which overlays should display >>>> > images. So I am creating a full 'book roll' by giving the overlays a >>>> > size via the 'space' display property, after which I use overlays-in >>>> > to determine which overlays are actually visible. However, after it >>>> > takes some time for the 'space' display property to take effect, so I >>>> > am manuall adding a 'sit-for' with some reasonable delay >>>> > time. However, I would like to ask if there is someone has an idea for >>>> > a 'better' mechanism to wait until/detect if the 'overlay expansion' >>>> > has finished. >>>> > >>>> > If the explanation is not clear then please load the following file >>>> > and do 'M-x scrap-dir-images' on a directory that contains enough >>>> > images to not fit all on a single screen. It will print the number of >>>> > overlays found via 'overlays-in' directly after 'displaying the >>>> > images' (here by assigning the image as display property instead of >>>> > space). You will find it prints all overlays in the buffer (instead of >>>> > only the ones on screen). To find what I expect it to print now >>>> > (again) do 'M-: (overlays-in (window-start) (window-end))'. >>>> >>>> I did all that, and I still don't understand the question. In >>>> particular, your code doesn't call sit-for, so I'm unsure what exactly >>>> is the problem you are asking about here. >>>> >>>> > My second question is about the function 'overlay-recenter' I don't >>>> > really understand its docstring. What kind of 'overlay lookup' would >>>> > go faster? What is 'overlay-lookup' anyway? >>>> >>>> Looking up overlays that are relevant to a particular buffer position. >>>> >>>> But this function is a no-op in Emacs 29 and later, since the overlays >>>> were reimplemented in a way that makes it unnecessary to "center" the >>>> list of overlays. So you can forget about that and ignore this >>>> function. >>>> >>>