Open Bug 64926 Opened 20 years ago Updated 3 years ago
Page is not rescrolled after text zoom (font size changed) (page position) (increase text size)
From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux 2.2.16 i686; en-US; 0.7) Gecko/20010105 BuildID: 2001010517 Not sure whether this is fixable, knowing that Mozilla depends on X for fonts, but nevertheless: If you're in the middle of a lengthy page and you change your font size by doing View->Text size, the fonts change, but your page doesn't acommodate for the newer font sizes, showing either the part of the page you've already read through (if you made fonts bigger), or the part you're not into yet (if you made them smaller). This is really annoying, since you have to scroll looking for where you left off. Reproducible: Always Steps to Reproduce: Scroll to the middle of a long page. View->Font Size->; Change setting Actual Results: You're elsewhere in the page. Expected Results: You should see the same fragment of the text. Mozilla should re-calculate font sizes and then re-scroll to show you the same portion of text which you were viewing before you changed the size of your fonts.
An afterthought: This can be done by grabbing a portion of the visible text or anchoring the visible part of the page somehow, then changing the font size and looking for the grabbed text/anchor, which should be then scrolled into view. Thus no font calculations are necessary.
yes this is important.
Assignee: asa → ben
Severity: normal → enhancement
Status: UNCONFIRMED → NEW
Component: Browser-General → XP Apps: GUI Features
Ever confirmed: true
OS: Linux → All
QA Contact: doronr → sairuh
Hardware: PC → All
Perhaps this could reuse the code currently used to remember the current position on a page when going back/forward?
Triaging the Most doomed (which Happens to Ben right now :)
*** Bug 72099 has been marked as a duplicate of this bug. ***
Assignee: ben → attinasi
Component: XP Apps: GUI Features → Layout
QA Contact: sairuh → petersen
Does anybody know where the current scroll-to logic is? I am not familiar with it...
Priority: -- → P4
Target Milestone: --- → mozilla1.0
This seems like a duplicate of Bug 136564
*** Bug 136564 has been marked as a duplicate of this bug. ***
*** Bug 167368 has been marked as a duplicate of this bug. ***
Summary: [RFE] Page does not rescroll after font size is changed → Page does not rescroll after font size is changed
*** Bug 180024 has been marked as a duplicate of this bug. ***
Assignee: attinasi → other
QA Contact: petersen → ian
*** Bug 167007 has been marked as a duplicate of this bug. ***
This is not an enhancement. It is a defect in our existing implementation. This bug makes text zoom problematic to use on long pages. Normal severity. Changing summary to make this easier to find. The feature in question is no longer called font size, but now it's called "text zoom." This bug should be very easy to fix. First, this bug has the following symptoms. You're scrolling down in a page, let's say Slashdot's front page, that has several screenfuls worth of information. You decide to text zoom. It doesn't matter whether you increase or decrease the size of the text. When the text size is changed, the vertical scrollbar moves. As a result, the position on the page that you were just reading is not on the screen anymore. All we have to do to fix this bug is to not move the scrollbar. A potential fix would be this. Before changing the text size, we should figure out how far the user has scrolled down, figured as a percentage of the page size or length taken as a whole. Then the text size should be changed. Then, after that, we should move the scroll bar up to or down to the same percentage of the page as was figured before.
Another potential solution would involve determining what element is displayed in the top left corner of the screen and then repositioning so that the same element is there after the zoom. I'm not familliar with the code, but intuitively it seems like this could use a lot of the same stuff that's used for the 'view selection source' feature on the context menu. I'll be very happy to see this bug fixed :)
See also bug 139832 (for resizing windows), which suggests an approximate method of getting the right scroll position that involves keeping the scroll percent rather than the number of pixels.
*** Bug 171297 has been marked as a duplicate of this bug. ***
I was just thinking while text zooming at the osnews.com forum, it would be great to do this not just for vertical scroll position, but also for horizontal scroll position. The same algorithm should work for both.
*** Bug 229108 has been marked as a duplicate of this bug. ***
Another bug which should be really easy to fix, and would contribute a lot to the browsing experience. BTW, for whoever fixes this: I suggest that the center of the viewport will remain fixed, that is to say if the middle character in the line closest to the middle of the viewport is the X%'th character on the page, this should remain the case (give or take 1 line) after the font resize as well.
I would say the top of viewport should be fixed, not the middle. If I can't read the top line and I increase the size, I wouldn't want it vanishing on me. It's also the way IE does it.
But,alanjstr, think that, usually, before the actual text on a page there are headers, titles, etc. - plus you usually start reading a few lines, then give up and zoom in. That's why I think the center is better. I also think zooming into the center has a generally-less-disorienting effect.
I fear comment #16 wouldn't, as work lots of sites use some form of menu along the left border that is way narrower and shorter than the actual page body -- using this for an anchor may lock the view to the wrong part of the page. Therefore, I too vote to use the percentage of the whole page (as measured by the scrollbars or however, so that the topmost line stays more ore less in place). Most user interfaces are anchored in top-left, and especially for text displays this would (imho) make the most sense. And yes, it's only natural to handle the horizontal position as well.
Summary: Page does not rescroll after text zoom (font size changed) (page position) → Page is not rescrolled after text zoom (font size changed) (page position)
I can think of one class of cases where this is well defined. Where you have just gone to a location with a named anchor, the right place to rebind the viewport to would be to rerun the logic for showing the named anchor. The rest of the cases are plainly quite tricky, but it may be useful to handle this set separately anyway.
*** Bug 243879 has been marked as a duplicate of this bug. ***
*** Bug 251726 has been marked as a duplicate of this bug. ***
> *** Bug 251726 has been marked as a duplicate of this bug. *** I created the dupe, sorry. The summary should include "increase text size" (or decrease), as it is the name of the offending command. By the way, I don't understand why this bug has not been corrected since 3 years, it is SOOOOOO annoying yet seems trivial to correct. Maybe I should quit whining and start learning Mozilla development :-) I have seen the lengthy discussion about what to implement (top of viewport, center of viewport, percentage).... who cares? Any solution would be better than the status quo.
Please don't just say "Me, too." As it turns out, this problem appears simple on the surface, but is not as simple underneath. This bug is ultimately dependent on bug 103279. That is where a lot of the action is going to be.
Summary: Page is not rescrolled after text zoom (font size changed) (page position) → Page is not rescrolled after text zoom (font size changed) (page position) (increase text size)
I suggest it should work like this: When using keys to zoom text, the first line stays fixed. When using ctrl-mousewheel and the mouse is over the client area, the line under the mouse pointer is fixed.
*** Bug 254702 has been marked as a duplicate of this bug. ***
*** Bug 272919 has been marked as a duplicate of this bug. ***
*** Bug 274383 has been marked as a duplicate of this bug. ***
*** Bug 280460 has been marked as a duplicate of this bug. ***
This bug can be seriously annoying for Chatzilla users. Normally, each channel gets its own tab, and the focus in that tab is kept at the bottom - the scrollbar button stays stuck to the bottom until one purposely moves it elsewhere. Now if in the browser I need to temporarily change my default font size smaller for some reason, there is no negative impact on CZ. However, when I change the default size back up to normal, most (or all, depending on how much content is in particular channels) of the CZ channel windows have scrolled up off the bottom, and I have to move each back manually before I see any new channel activity - the channel tailing is stopped until I scroll back to the bottom.
The chatzilla issue is somewhat different than normal page viewing. With chatzilla you want the bottom of the page anchored, which is definitely what you don't want for normal browsing.
Does that mean CZ needs its own bug?
*** Bug 208756 has been marked as a duplicate of this bug. ***
*** Bug 304823 has been marked as a duplicate of this bug. ***
Helo Anybody know about work progress with this issue? Now I have FF 1.5b on MSWin and this bug still exist...
*** Bug 309922 has been marked as a duplicate of this bug. ***
*** Bug 312801 has been marked as a duplicate of this bug. ***
Almost five years old!
try it here: http://www.badboy.com.au/
*** Bug 321266 has been marked as a duplicate of this bug. ***
roc, could you review this patch? I think that the zoomed scroll position is able to calculate using the rate of the scroll position and the content size. This approach improves this problem since the position is in near although it shifts from an original position. Calculated scroll position is a center of the scrollbar in order to make a gap small, if scrollbars do not touch to the left/right side or top/bottom side. If scrollbars touch to left/right side or top/bottom side, scrollbars keep on the side.
Attachment #207624 - Flags: review?(roc)
Hi, First off, I would like to thank Hideo Saito for the work submitted as part of the last post, there has now been five years of discussion so I am very pleased that this is being addressed. I do think that the algorithm could be improved a little however. To give the user intuitive zoom semantics, the zooming should be based on current cursor position. This is consistent with graphics applications and games. I am not familiar with the mozilla codebase, but the general approach is as follows: Store state before zoom is executed: get current position of cursor within view calculate ratio of that position in the current view, - for example, it may be line 100 units from a total view of 400 units or 0.25 calculate absolute position in document from cursor position for example, 500 units into a document of 1000 units (for sake of reference, this would mean that the view was displaying the view from 400-799 in the document) Calculate new position after zoom: calculate new position by starting with absolute position, and calculate new start and end boundary based on the relative position of the cursor - for example, suppose zoomed view is now 200 units, then new relative position would be 0.25 * 200 = 50 (truncated if need be) calculate start of new view by subtracting new offset from original absolution position - in the example above, this would be 500 - 50 = 450, so the new view would span 450 - 649 (given a new view size of 200 units) The final zoom would result in the change from a view spanning 400-799 to 450-649, and would zoom around the point that is 0.25 into the view. -c
(In reply to comment #48) > To give the > user intuitive zoom semantics, the zooming should be based on current cursor > position. This is consistent with graphics applications and games. When reading a long web page with page-down, the cursor tracks the bottom of the viewport, even though the user didn't explicitly put it there, or even read that far. (This is a difference from graphics apps and games.) Keeping the *top-left corner* of the current view fixed would make it more clearly visible how the view changed and help people stay oriented.
As a response to comment 50, the fact that the cursor is at the bottom right of the view appears to be more of an implementation detail since it has no visible impact on the user experience (from testing on this bug report). I also feel that while it may be simpler to make it zoom from the top of the page (despite the cursor / focus being at the bottom of the viewport) it is less intuitive, has less precedent, and is not as flexible. It removes the user from the decision making process and negates the point of fixing this bug in the first place. If the final result is that the user will have to rescroll the text after zooming to get to the point of interest that was scrolled off the bottom of the page since the top was fixed, then we won't have solved much. The one work around for the user to scroll the relevant text to the top of the page and then zoom, which is just as inconvenient. It should also be noted that since the user will often be moving the cursor and zooming with the mouse (a single input device), they will associate cursor position and zoom behavior quite quickly. At the very least I think it would be prudent to do usability testing since this application gets such widespread usage. regards, -c
Comment on attachment 207624 [details] [diff] [review] patch bzbarsky, could you review this patch or can I get your advice? My approach is that the rate of the scroll position against the content size is not chanded. The zooming is done suitably for my test. Should the zooming be based on current cursor position like as comment #48?
Attachment #207624 - Flags: review?(roc) → review?(bzbarsky)
I don't think cursor position is relevant here. We need to provide a view that allows the user to maintain their orientation within the page; keeping the top-left corner fixed will provide this. Content will always flow in and out of the right and bottom of the window, so it will be easy to know where you are and locate something that flows out of view on zoom. As an aside, I tried figuring out how cursor position would affect things by turning caret browsing on (F7), but its easy for the caret to be off-screen, and we definitely do not want to zoom there. Caret browsing provides the most explicit cursor I know of, and it isn't what we want at all. Let's get this reviewed and checked in so that page zoom can FINALLY be useable on long pages!
Well, top-left corner is not correct solution. Zooming should always be made based on the middle-center position, e.g. absolute center of viewing port. That's how zooming works everywhere - starting from Acrobat Reader, through Word, up to Photoshop. Changing this will certainly confuse user and is not recommended.
Keeping 0,0 unchanged on zoom is the only way that makes sense and won't disorient me.
(In reply to comment #50) > It removes the user from the decision making process That's just it. A user scrolling down a long page isn't involved in a decision to put the focus to the lower corner. I spent a little time looking at Acrobat right now, which seems to zoom from the center (although only approximately; i.e., you don't neccessarily get to where you started if you zoom in and out repeatedly.) It was okay once I figured out what was going on. I think I still might prefer top-left, but user-testing would of course be ideal. (Perhaps simply timing people to find their place again on a text-heavy page after a zoom-in/out.) PS. If it'll still be a long time before this is fixed, perhaps it's worth considering "smooth"-zooming?
I added following changes in order to limit the effect of scaling scroll position only to the zooming text. ClearStyleDataAndReflow(); + mPrevTextZoom = mTextZoom; }
Attachment #207899 - Flags: review?(bzbarsky)
I really think that if we're going to mess with this we should fix it in the context of bug 43114, not on its own. In any case, I will not be able to get to this review for a long time (probably several weeks at least).
So to make it clear, I would recommend finding a different reviewer.
Comment on attachment 207899 [details] [diff] [review] patch David, could you review this patch? If this patch is unuseful and this problem should not be fixed now, I also need to wait for that time to come.
Attachment #207899 - Flags: review?(bzbarsky) → review?(dbaron)
Doing this using only math is likely to make things worse in almost as many cases as it improves (especially since the things near the top of the viewport, which are often what the user is focusing on, would now be likely to move offscreen instead of moving lower within the viewport). I'd prefer an approach more like the one described in bug 16806 comment 39, something that's currently covered by bug 43114.
Comment on attachment 207899 [details] [diff] [review] patch My inclination (and I think Boris's is the same) is that we don't want to take this approach, both because: * we don't want something specific to just text zoom * this is the wrong algorithm for fixing the problem
Attachment #207899 - Flags: review?(dbaron) → review-
Same problem exists for full page zoom.
There's a variant of this bug related to opening links in a new tab. If the link points to an anchor in the new page, then when you select that tab it initially displays the correct location of the anchor in the default font size, but then it immediately resizes the font to match the one you've set in the link source page (this is a relatively new feature I _really_ like). But when it auto-resizes you loose the anchor off the top or bottom of the page. Will this variant be fixed by the fix for this problem, or should I submit a different problem report?
It was reported: https://bugzilla.mozilla.org/show_bug.cgi?id=474770
(In reply to comment #21) > BTW, for whoever fixes this: I suggest that the center of the viewport will > remain fixed, that is to say if the middle character in the line closest to the > middle of the viewport is the X%'th character on the page, this should remain > the case (give or take 1 line) after the font resize as well. This is the way that Adobe Acrobat does it. It makes the most sense when zooming up, because you really do not know which portion of the page that the user is viewing will be pushed out of the viewport. Take the center as your anchor and, on average, the user will not need to reposition the page very much to bring the desired bit back into view.
For what it's worth... The vote count for this bug report stands at 30. Additionally, 21 bug reports were filed that have been marked as duplicates of this one. If those were counted as votes, the total would be 51. That's a lot of Me Too's. However, we cannot all be developers; even those of us who have a little coding experience (like me) may not be able to work at this level of complexity. Yes, I get it that this issue is complicated by other scrolling-related problems. But it is an issue that negates much of the usability of the zoom feature. Can fixing it not be given priority over adding nifty new features, such as adding the activity indicator to the list of customizable toolbar elements? By the way, someone posted a workaround to one of the Mozilla wishlist newsgroups: turn on caret browsing (F7), place the cursor on a line of text in your current area of focus, adjust the zoom, depress the left or right arrow key-- the page will scroll to bring the cursor back into the viewport (usually at the top or bottom of it), turn off caret browsing. It's not great, but is usable, and better than the current situation.
I found this very interesting link in the last comment of the discussion on bug 43114: http://blogs.msdn.com/ie/archive/2009/05/18/making-the-web-bigger-part-1-improvements-to-zoom.aspx I haven't tried IE8 yet; if the M$ development team managed to solve the problem in anything near the style they claim, they have at least as much bragging right as they show in their article.
I tried IE8, works properly
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