Why is the mouse cursor slightly tilted and not straight?
Is this a legacy thing or does a tilted cursor serves a purpose? I can tell that, the angle provides a totally vertical left edge which helps when highlighting text but what else apart from that?
EDIT: When cursor is swapped by the little hand cursor when hovered over buttons, the angle seems to be smaller. Why the difference?
I have seen straight cursor in some old DOS GUI apps and have also tried it in Windows and Linux - straight cursor just looks and feels nasty like handling a spoon straightly perpendicular to your face when eating (feeding yourself) or positioning your elbow to the center of your body when giving a handshake... Also can cause some Freudian associations when thought about :-)
Also, consider that some text (for cultural reasons or others) are written vertically, having a straight mouse would hide the next letter after the one you point at. Making it go towards the right side and down makes it very practical in many situations.
The historical reasons are given by some great answers here. However, I would like to add that a tilted pointer hides as less information as possible. Of course not in all cases, but generally, data is aligned vertically or horizontally. Therefore, the diagonally aligned cursor is not in the way.
It was straight by default. I added an underscore at both ends and it turned italics. Weird...
This is the historical reason:
(Concept drawing taken from document: VLSI-81-1_The_Optical_Mouse.pdf)
When the XEROX PARC machine was built, the cursor changed into a tilted arrow. It was found that, given the low resolution of the screens in those days, drawing a straight line (left edge of arrow) and a line at a 45 degree angle (right edge of arrow) was easier to do and more recognizable than the straight cursor.
So pixel layout is the real reason :) To make it vertical and still look smooth the cursor would have to be twice as wide. Also that most def. is 45º, just think about the image... it's a grid.. one line goes down down down down, the other line goes down right down right down right. It must be 45º
@AlbertRenshaw: ...at least if you assume square pixels--but that wasn't a given in those days (e.g., it wasn't normally true of an EGA or Hercules card at their maximum resolution).
@JerryCoffin Ah! Well I was just basing it off of the image above which does have squares, but you are right, even today a lot of pixels are rectangular.