Talk:View Menu: Zoom

James 9Aug17: This point below is no longer true. If the selection fits on screen at the current zoom, Audacity will attempt to show it centered.

• Bill 09Aug2017: I disagree. Your recent commit changed Zoom Normal, did it not? But not Zoom In nor Zoom Out? They still do what the advice div below says, and I think that is correct behaviour. It has nothing to do with the selection fitting on the screen, but with the cursor or selection being scrolled out of view. I'm testing with commit 95560a which is after your fix for Zoom Normal. Import or create some audio. Click near zero. Scroll so the cursor is off screen. Zoom In - the cursor does not scroll into the track display area.
• Bill 10Aug2017: Correcting my previous note, above, and testing with the latest commit as well as 2.1.3.
  • With virgin install, generate 30 seconds tone. Select from 5 to 15 seconds. Zoom in once - 10 sec mark moves to center of display. Zoom in again - 10 sec mark remains at center and selection is now bigger than the display. Scroll left as far as possible - display should show 0 to about 7.5 sec (so the 3.75 sec mark is about in the center of the display) and part of selection is visible. Zoom in - the display scrolls but the time at center of display is not maintained, and the center of the selection is not centered on the display. I can live with this, since it seems ambiguous what the user wants when zooming in this situation: zoom in on the time at center of screen or zoom in on the selection. We do neither.
  • Do Zoom to Fit and click at about 20 seconds. Zoom in twice then scroll so the editing cursor is off the screen. Zoom in - the time at center of screen is maintained, so the first sentence of the below advice is still correct.
  • I've tried several experiments to determine the "rules" for zooming with a selection entirely visible or partially visible on the screen, where time at center of track is or is not in the selection, and in situations where the next zoom in would make the selection fit or not fit on the screen. It is all too complicated and not worth documenting. Zoom does what zoom does.
  • Here's what I have observed (turn "Enable scrolling left of zero" on so the "edge" cases don't interfere with what the commands are trying to do):
    • If the editing cursor is visible but not centered in the display, Zoom In will attempt to move the editing cursor to the center of the display
    • If the editing cursor is visible but not centered in the display, Zoom Out will not attempt to move the editing cursor to the center of the display but instead appears to attempt to keep the same time visible at the center of the display
    • If the editing cursor is not visible, both Zoom In and Zoom Out will attempt to keep the same time at the center of the display
    • If there is a selection and the center of the selection is visible in the display, Zoom In will attempt to center the selection in the display
    • If there is a selection and the center of the selection is visible in the display, Zoom Out will attempt to keep the same time at the center of the display
    • If there is a selection and the center of the selection is not visible in the display, Zoom In will scroll by some apparently arbitrary amount, but does not appear to attempt to keep the same time at the center of the display possibly because doing so would cause the selection to move entirely off the display
    • If there is a selection and the center of the selection is not visible in the display, Zoom Out will attempt to keep the same time at the center of the display
  • So, like I said, too complicated and not worth documenting. Users will figure it out.
  • At least zooming in always attempts to move the cursor to the center of the screen when the cursor is visible, which is what I want it to do and what I assume most (if not all) users expect it to do.
  • As well, if the cursor is not visible on the screen then zooming in or out attempts to keep the same time at the center of the display, which I also think is the right thing to do.
  • I got into this because Paul thought it important to document the fact that when "Enable scrolling left of zero" was on that the Zoom commands could behave a little differently. In attempting to respond to his concerns it appears I have created a monster. I will meditate on this and come up with a simpler version.

If the editing cursor or selection is not visible then the zoom in and zoom out commands will not move the editing cursor or selection to the center of the track display, but will instead zoom in or out keeping the same time (as seen on the Time Line) at the center of the window. As above, if the editing cursor is near the start or end of the track and "Enable scrolling left of zero" is off then the command may not be able to keep the same time in the center of the track display.

Possibly we want this point instead?

• Bill 09Aug2017: Well, that's what Zoom In has always done, right? It keeps the center of the selection in the center of the track display.
  It is easy to create a situation where the selection is too big to fit on the screen and Zoom In will move the time at the center of the screen. Create or import some audio. Select a portion (near the middle of the track) and zoom in until the selection is bigger than the track display. Scroll so only a portion of the selection is visible. Note the time at the center of the display. Zoom In - the time at the center of the display changes to the time of the center of the selection. So it looks to me like the first sentence of the advice below is not correct.
• Bill 10Aug2017: See corrected and expanded descriptions above.

If the selection when zoomed is too large to fit on screen, instead of centering the selection, Audacity will zoom in or out keeping the same time (as seen on the Time Line) at the center of the window. As above, if the editing cursor is near the start or end of the track and "Enable scrolling left of zero" is off then the command may not be able to keep the same time in the center of the track display.