cursor: fix crash with weird input files
If a cursor file contains multiple images for the same size, this typically indicates an animation. The compositor weston uses wl_cursor_frame_and_duration to figure out at which time a specific image should be shown.
The total delay is the sum of all image delays. But if all images have a delay of 0, the total delay is 0 as well. The code does not check for this special condition and triggers a floating point exception by eventually performing a modulo operation with 0.
This, of course, could also happen if the sum of all image delays triggers an unsigned int overflow. But since a comment in the code already indicates that it does not try to "fix" handling of weird files, I would argue that it's "okay" if that happens. At least the program won't crash.
Proof of Concept:
install -D ~/.icons/poc/cursors base64 -d > ~/.icons/poc/cursors/left_ptr << EOF WGN1chAAAAAAAAEAAgAAAAIA/f8BAAAAKAAAAAIA/f8BAAAAKAAAACQAAAACAP3/AQAAAAEAAAAB AAAAAQAAAAEAAAABAAAAAAAAAAAAAAA= EOF cat > /tmp/weston.ini << EOF [shell] cursor-theme=poc EOF weston -c /tmp/weston.ini
Signed-off-by: Tobias Stoeckmann firstname.lastname@example.org