Sumatra PDF is a PDF, ePub, MOBI, CHM, XPS, DjVu, CBZ, CBR reader for Windows

Fluid Smooth Zooming (With <=10% Steps)

I’ve seen this feature work mostly in UWP Apps like Xodo or Microsoft Edge, but never in a win32 app except Microsoft’s own Office suite, Word 2016 does this with 10% steps, which feels really fluid.


So according to these issues, and @kjk

I don’t know what “smooth scrolling and zooming” means in this context.

Zooming will always happen in steps because it’s very expensive operation.

Scrolling already happens in small increments (assuming contiguous layout), which should be true for mouse, touchpad and any other device that generates scroll events.

the reason for this not being implemented is perhaps the performance issue?

I am uncertain why this was not replied to at the time
However for those landing here see the comments to the question below

Hi everybody,

SPDF is great—it’s immensely (no pun intended) better than the bloated, invasive monstrosity Acrobat Reader has become.

The only thing I wish it had was “smooth zoom”—the ability to hold Ctrl, move the mouse wheel, and zoom in and out in fine degrees, rather than in such big steps.

I often use SPDF to view sheet music with many small notes, so I try to zoom in to make the music as big and legible as possible. With SPDF, this requires me to open the “Custom Zoom” box over and over, making repeated guesses, till I find that document’s best zoom level. (Unfortunately their margins vary widely, too; otherwise “Fit Width” would probably be sufficient.)

I realize some people prefer the “convenience” of discrete zoom steps. But couldn’t we have smooth zoom as an option? Or maybe you could give it a different shortcut, such as Alt + mouse wheel, rather than Ctrl+ ? Thanks for considering it! – A.

Several issues in the past with zooming have been addressed in different ways but the core way that SumatraPDF responds quickly is to zoom in fixed steps, otherwise it needs to redraw the page at 99% 100% 101% get the idea%…
However in Settings Advanced Options you can set a small value such as 1, 2 or 3 (NOT 101)

  zoom step size in percents relative to the current zoom level. if zero or negative, the values from
  ZoomLevels are used instead
  ZoomIncrement = 0

OR keep that at 0 and add your own steps to the list

sequence of zoom levels when zooming in/out; all values must lie between 8.33 and 6400
ZoomLevels = 8.33 12.5 18 25 33.33 50 66.67 75 100 125 150 200 300 400 600 800 1000 1200 1600 2000 2400 3200 4800 6400

You can alter the above steps as you wish, so if using a certain size of sheet music could have one startup range of settings that suits say Trad Landscape and another range of settings for Classical Portrait or even the other way round :slight_smile:
To do that you need separate startup shortcuts with -appdata c:\MySettings\Trad etc. Prepare as many sub folders as you think you need and on first run each FOLDER will get its own SumatraPDF-settings.txt that you can then alter to suit for that shortcut. Thus you could use those shortcuts for drag and drop or double click. With the original short cut for default everyday usage.

An easy alternative is to mix desired ranges in your one current settings file as above but using smaller steps where needed e.g. 8.33 … 75 90 95 100 105 110 125 etc … 6400

Thanks for your thoughtful, detailed reply.

In Settings > Advanced Settings, I’ve changed this line:

ZoomIncrement = 3

Now, holding Ctrl and moving my mouse wheel zooms in/out in 3% increments, which I find perfect. :grinning: And it was so simple.

Thanks again for your help, and for all your hard work on this great software.