The idea of "Hot Corners" has been gaining in popularity for some time now. The first time I recall seeing it in a major distribution was when Gnome 3 was released, and of course the other major example of its use today is in Windows 8.
The concept is pretty simple — do something at one of the corners of the screen, and some action will result. What is interesting in this case is the flexibility of the implementation in the Cinnamon desktop.
The Hot Corners configuration screen is found in the System Settings group, and can be reached either by right-clicking on the bottom panel and choosing All Settings, or in the Preferences section of the Mint Menu.
Each corner of the screen may have an action associated with it; by default, though, none of them are active, so a lot of users don't even know that this capability exists in Cinnamon. I guess that is better than having them active by default, and the user is left to wonder what the heck is going on the first time they hit a corner and something new and unexpected pops up. In the control screen, if a hot corner is active the shaded area is green; if it is not active, it is pink.
The action associated with the corners can be individually configured so that you only have to move the mouse to the corner to initiate the action, or you actually have to click an icon in the corner to initiate the action — or neither of these, in which case the corner is not "Hot".
There are four possible actions which can be assigned to any corner:
Show (and Select) workspaces
Show (and Select) windows
Show the desktop
Run a command (you get to specify what command)
These are not exclusive; you can assign the same action to more than one corner. So one possibility I have seen in use is to have both top corners display/select Workspaces, and both bottom corners display/select Windows. Of course, in the extreme case you could assign a different action to each corner.
Okay, that's the theory but what about the reality? What I really wanted to talk about in this post is some things I have found in my own use of this feature.
I always use auto-hide on the bottom panel, so it gets out of the way when I don't need it. This has some interaction with the bottom hot corners — moving the mouse to the bottom of the screen should bring up the hidden panel, but if moving the mouse to one of the corners of the bottom of the screen should do something else, well, which one of those things "wins"?
First, if you select "Icon visible" to enable click for hot corners, the icon(s) actually overlay the panel. That may look a bit confusing, but it actually still works ok, the area just around the icon becomes the Hot Corner click surface, and going there with the mouse does not bring up the panel.
If you select "Hover Enabled", the very tip of the corner becomes the Hot Corner activation point and does not bring up the panel. You can see this by moving the cursor to the edge of the screen and then sliding it down to the corner, the hidden panel doesn't come up. But if you switch from Hover to Click enabled and do the same thing, the panel comes up when you get to the bottom of the screen.
That's all pretty cool, and from a programmer's standpoint I find it impressive that the Mint developers were able to implement all of this in such a logical way. From a user's standpoint, though, I doubt if I would use Hot Corners together with hiding the panel.
It has also been interesting to see how this works with multiple displays. Hot Corners only exist on the "Primary" display — that makes sense, it was the most obvious of the three options I could think of (the others were identical hot corners on every corner of every display, or only on the "outermost" four corners of however you have the multiple displays arranged).
This can make it a bit challenging or surprising if you have "Hover" enabled on whichever two corners border between the two displays. For most people, until now "Hover" has meant "slam the mouse over to the corner", but when you have multiple displays, doing that on the border where the second display sits will just send the cursor flying off to the other display, usually without triggering whatever the hot corner is supposed to do.
Here is a screen shot of the dual-display setup on my desktop system:
Wow. Okay, that clearly needs some explanation. First, I don't normally use that wallpaper — I think it would make me nauseous pretty quickly if I did. I am only using it here because it has a bit more contrast with the white Hot Corner icons. Second, the laptop display is 1280x800, and the external monitor is 1920x1080, thus the difference in size (and the black area) that you see in this combined screenshot. Third, if you squint really hard at this picture, you can just about make out the icons in the four corners of the laptop screen. If I switch to having the external monitor as the Primary, those four icons move over to it.
So in the specific case of this screen layout, with the laptop screen as primary and the external display to the right of it, getting the two Hot Corners at the right side of the laptop display to trigger can be a bit more difficult because it is easy to overshoot them.
What about the actual functions triggered by Hot Corners, when used with multiple displays? When you hit the "Show all Workspaces" function, everything is shown on the Primary screen:
Oh, and by the way you can hit the "+" at the right edge of the screen to add a new workspace.
When you hit the "Show all Windows" function, the windows are shown on their respective displays:
That pretty much makes sense too. You can select any window here and the display will return to normal with that window active. But if you just want to get out of this function, without selecting a window (ie, you got here because you hit a corner by mistake), you have to hit the corner again or hit the Esc key, because just clicking the background doesn't do it.
The "Show Desktop" function works exactly the same way as the equivalent button on the Cinnamon task bar (and many others) — it minimises all open windows. If you hit it again, it restores the open windows — and the state of the windows is kept, so it only restores those that were open originally, it doesn't pop open every window.
Finally, the "Run a Command" function does exactly that. The trick here is that if you want to interact with it, or see the output of it, then you have to run a GUI-compatible program. That means, for example, if you want a shell you can't just run bash, you have to run something like gnome-terminal. You could bind firefox to get quick/easy access to a browser. Things like that.
So that pretty much covers it for Hot Corners. Not terribly complicated, but very useful and wonderfully flexible and configurable. I generally have mine set up with Workspace and Windows on the top corners, Desktop on the bottom left and Run gnome-terminal on the bottom right.
But I've been thinking about something different while writing this. Wouldn't it be extremely cool to combine something like the PCLinuxOS Full Monty distribution with Cinnamon and Hot Corners? Having all those wonderful predefined workspaces, and all those wonderful applications, with such an easy and convenient method for switching and selecting between them? Could be nice...