Walking zigzag in a Custom buffer

Walking zigzag in a Custom buffer

[Lennart Borgman]

This is probably not very important now but it points to a problem that 
one day may become important. If you do M-x customize-option RET 
minibuffer-prompt-properties RET and move around up and down in the 
buffer you will notice that Emacs seems to be mistaken about the width 
of the buttons when doing this.

If one looks at "Property:" and "Value:" they seem to be aligned 
horizontally ok. However placing point at one of those words and moving 
up and down between them shows that something else in Emacs seems to 
make a different computation of the button width than was used when 
displaying the buffer.

This makes me think there is a potential bug.

-----
Beside this I also find the behaviour when walking up and down with the 
arrow keys between the fields after these prompt strange. Try putting 
the point at the end of the text in both fields and use the up and down 
arrows to switch between them. I do not always come back to the same 
position in the other line. Instead the point is moved to the beginning 
of the field.

Re: Walking zigzag in a Custom buffer

[Jason Rumney]

Lennart Borgman <lennart.borgman.073@student.lu.se> writes:

> If one looks at "Property:" and "Value:" they seem to be aligned
> horizontally ok. However placing point at one of those words and
> moving up and down between them shows that something else in Emacs
> seems to make a different computation of the button width than was
> used when displaying the buffer.
>
> This makes me think there is a potential bug.

This is due to the fact that Emacs uses characters, not pixels as its
unit of horizontal position. The decoration on the buttons causes them
to be wider than the equivalent fixed-width text without such
decoration. You can see this by going to the beginning of the line
containing "Value", and moving foward 3 characters. I think the
alignment of the colons is more by careful hand placement than a
difference in computation of button width.

Re: Walking zigzag in a Custom buffer

[Lennart Borgman]

Jason Rumney wrote:

>Lennart Borgman <lennart.borgman.073@student.lu.se> writes:
>
>  
>
>>If one looks at "Property:" and "Value:" they seem to be aligned
>>horizontally ok. However placing point at one of those words and
>>moving up and down between them shows that something else in Emacs
>>seems to make a different computation of the button width than was
>>used when displaying the buffer.
>>
>>This makes me think there is a potential bug.
>>    
>>
>
>This is due to the fact that Emacs uses characters, not pixels as its
>unit of horizontal position. The decoration on the buttons causes them
>to be wider than the equivalent fixed-width text without such
>decoration. You can see this by going to the beginning of the line
>containing "Value", and moving foward 3 characters. I think the
>alignment of the colons is more by careful hand placement than a
>difference in computation of button width.
>  
>
Thanks, I guess you are right. I did not think about that possibility. 
Looks to me like one button decoration is a half character wide there. 
Seems to be the easiest way to solve it.