This implements simple window shadows around most windows, including
tooltips. Because this method uses a bitmap for the shadow bits,
it is limited to rectangular window frames. For non-rectangular
window frames we'll need to implement a more sophisticated algorithm.
This only renders the window frame once until the size of the window
changes, or some other event requires re-rendering. It is rendered
to a temporary bitmap, and then the top and bottom part is stored
in one bitmap as well as the left and right part. This also adds
an opacity setting, allowing it to be rendered with a different
opacity.
This makes it easier to enhance window themes and allows using
arbitrary bitmaps with e.g. alpha channels for e.g. shadows.
Bitmap::load_from_file("foo.png", 2) will now look for "foo-2x.png" and
try load that as a bitmap with scale factor 2 if it exists. If it
doesn't, it falls back to the 1x bitmap as normal.
Only places that know that they'll draw the bitmap to a 2x painter
should pass "2" for the second argument.
Use this new API in WindowServer for loading window buttons and
cursors.
As a testing aid, ctrl-shift-super-i can force HighDPI icons off in
HighDPI mode. Toggling between low-res and high-res icons makes it easy
to see if the high-res version of an icon looks right: It should look
like the low-res version, just less jaggy.
We'll likely have to grow a better API for loading scaled resources, but
for now this suffices.
Things to check:
- `chres 640 480` followed by `chres 640 480 2` followed by
`chres 640 480`
- window buttons in window context menu (in task bar and on title bar)
still have low-res icons
- ctrl-shift-super-i in high-res mode toggles sharpness of window
buttons and of arrow cursorf
- arrow cursor hotspot is still where you'd expect
