Make the magnifying glass a proper tool instead of a momentary mode. This would allow more extensive and efficient close-up examination workflows.
With a sticky zoom tool you could:
  • Safely navigate zoomed images without accidentally creating sketches
  • hover-zoom - zoom in in an area around a hovering cursor. For example you could just move the cursor along a composited edge and see a magnified area around the cursor location, emulating a real loupe or magnifying glass
  • double-click to cycle through zoom levels or maybe zoom in by some percentage, requiring the alt-key to zoom out by some percentage on double-click
  • drag draws rectangle, release zooms to fit that rectangle in the frame
  • alt- drag zooms around cursor like existing z key behavior
  • space bar allows grabber hand for panning, like the existing functionality
  • holding a hotkey momentarily switches to the most recently used brush for sketching
  • hotkey toggle between current zoom and pan settings and fit frame
  • X key stores current zoom/pan and toggles to another zoom/pan, corresponding to the current X key behavior toggling between color settings
Other users: Feel free to comment on whichever of these you like or don't like, or add further suggestions.