I think I'm beginning to understand the Minimized Window Caption issues, since I've spent the day troubleshooting them on several skins of mine trying to get the buttons to look right.
It appears that the Caption Height is fixed at the same dimension as the regular Window Titlebar Caption Height.
It also appears that the buttons are stretched vertically if they are not sufficiently tall and horizontally if they are not sufficiently wide. It looks like buttons can get "squeezed" horizontally as well. Unfortunately, I haven't been able to divine a relationship between the Caption Height & the button size that would allow me to predict the needed dimensions.
I typically use 16x16px buttons, using magic pink to make them "smaller" if necessary. Through trial and error, I found that padding a button with sufficient additional rows of magic pink top & bottom will enable an undistorted display of the buttons. Similarly, adding sufficient columns of magic pink to the sides of a button will avoid horizontal distortion. Unfortunately, the only way I've found to determine what is "sufficient" has been to revise the graphics one (set of 2) pixel row or column adjustment at a time, then save & reload the skin to see the effect. It is needlessly tedious & time-consuming, but there doesn't appear to be a rule of thumb - certainly, using the buttons defined for the regular Window Titlebar results in the distortion problem your screenshot shows.
The black corners are probably specific to PhotoShop & the way it skins (or doesn't) - many people have reported problems with ToolWindows in particular.
Cheers,
Daiwa
