Is there a Mac app for viewing all the characters of a font?
Font book doesn't seem have this feature.
I use character maps heavily and decides to make one which you access from anywhere using a web interface and requires no installation.
I guess you're on Lion - right ?
Because in Snow-Leopard you could get that by showing the "character viewer" from the inputs menu or launching directly
/System/Library/Input Methods/CharacterPalette.app as described here and choosing "Glyph" view.
Check out the new smilies (now part of the Unicode standard ;) in the DejaVu font
But if you still got access to a Snow-Leopard installation you can copy the CharacterPalette.app from
/System/Library/Input Methods/CharacterPalette.app and it will run on Lion, I would not recommend replacing the Lion version, but rather keeping the Snow-Leopard CharacterPalette as separate app - why did Apple have to make it worse in the first place ?!
As you can drag & drop glyphs from the Snow-Leopard Character Palette but not from the new Lion Font Book...
This idea was inspired by Is it possible to use the character map as a standalone app?
Alternatively in System Preferences -> International in the Input Menu tab there is an option to place a Character Palette on the menu bar that can (among other things) show you all the glyphs in a particular font, what the glyph is called and allow you to insert the character into a document or text field.
Unfortunately the Snow Leopard
/System/Library/Input Methods/CharacterPalette.app no longer works in newer versions of macOS. For example, on High Sierra (10.13) it crashes immediately.
It may be that our only option are apps like PopChar X at this point.
I don't even think I'm happy with PopChar as it doesn't seem to have as strong of a numeric tabular display and so forth and so it will be necessary to keep exploring this path for various options that may exist for native options.