Hovering over a launcher icon on the weston panel should display a tooltip.  No tooltip appears and the mouse-over highlight stays lit when the cursor is moved away.  Once this occurs, clicking on the launcher icon or right-clicking on the panel has no effect.  Restarting weston seems to be the only way to get launcher buttons working again.

Using linux-3.19.0-rc7
mesa-10.4.4
cairo-1.12.18
wayland git-52d971c9
weston git-82d19aab

Tooltips worked okay in weston-1.4.0, but not in 1.50 and later.  Attempted to bisect, but build errors prevented narrowing down to an exact commit.  Probably occured in: [7f4386e90a64a1a478730ca9f7f30b998d8ac36b] westoy: Use subsurfaces for tooltips instead of transient windows

-----------------------------------
# only skipped commits left to test
# possible first bad commit: [088ba5e4754cd1e92039357445e544f359bde6a5] Makefile.am: Fix protocol source files usage
# possible first bad commit: [5e647ca1468d50d00d44178d4c5f776523b36605] xwayland: Fix typo in open flags for Xorg log file
# possible first bad commit: [6fd73cd3c08d99e1894d21fb38f559dcbc5ac4db] build: Add -Wsign-compare to GCC flags
# possible first bad commit: [1e47a93f8577027240564693e43bc27e0447531b] Revert "stacking: Remove transient window support"
# possible first bad commit: [53686048ccb9836c1e36d32d36e788d49239a634] window: Add wrappers for xdg_surface_set_transient_for
# possible first bad commit: [0790e3978a771328b276cf5ee73fcf31a41fa051] westoy: Port the toy toolkit over to xdg-shell
# possible first bad commit: [c0f17aba5e007821bf08e58b5033e7e545f6ab10] westoy: Remove MAXIMIZED and FULLSCREEN as separate window types
# possible first bad commit: [76ec0826bc390010b347da28985e68f5252f2f95] westoy: Remove fullscreen methods
# possible first bad commit: [7f4386e90a64a1a478730ca9f7f30b998d8ac36b] westoy: Use subsurfaces for tooltips instead of transient windows
# possible first bad commit: [e22952bb13cf7e7d16b9d8a36c6e9c82307436eb] westoy: Schedule a full resize when we add a subsurface
# possible first bad commit: [b0d604ff5b079b2d182af539c12a7991ccf19e18] stacking: Remove transient window support
# possible first bad commit: [faf27a9a3b24014c5c47574e5f67986327387556] weston: Send xdg_surface_send_focused_[un]set when focusing surfaces
# possible first bad commit: [f84327aef2f7b68ef4ae882991b4331ee9f3d164] input: Remove exported function weston_pointer_verify()
# possible first bad commit: [adaa20c017a549593e2a735a2d8a73edc9c17b6d] desktop-shell: initialize children link
# possible first bad commit: [38b58eba74ef7d9e8460b455f1e1cbea12d87bae] desktop-shell: maximize the surface with the kbd focus
# possible first bad commit: [32b793cb7fc4b17eb3a7af182f7adbf853e76e2d] compositor: Clarify XDG_RUNTIME_DIR misconfiguration message
# possible first bad commit: [4d363cfcf6025db2277005845957e0b0e956ebd0] input: Fix weston_seat_init_keyboard() error path
# possible first bad commit: [23900f70e57277805db652316b76d18b2d59281c] input: Empty the current input region when configuring pointer surfaces
# possible first bad commit: [cd31275f28b0a04d2ec5426dc81e875197b47e52] build: Stop using xmllint to validate protocol files
# possible first bad commit: [0822942be2d76e01a749f630952545fd0663bbbe] build: Drop wayland-scanner.mk
# possible first bad commit: [0aa19e9457ce3258a4df74876e542f0b6fbbf2ba] build: Only regenerate src/git-version.h when .git/logs/HEAD changes
# possible first bad commit: [0987f81ee9d3ae5a2ec183bfb9c3ba3dd3bbb4a7] build: Move shared/Makefile.am into toplevel Makefile.am
# possible first bad commit: [e73eccdb66782104fe9b0b05e534313d4e49d420] build: Move clients/Makefile.am into toplevel Makefile.am
# possible first bad commit: [1e80afa36c652302149aedc0b0ef4af964b8bfd5] build: Move tests/Makefile.am into toplevel Makefile.am
# possible first bad commit: [b7e3ef460f57f40ed1816ddcb45141dafb90bafd] build: Move src/Makefile.am into toplevel Makefile.am
# possible first bad commit: [68c5c109052610e5873e2160129d21a0ad94482d] build: Move man/Makefile.am into toplevel Makefile.am
# possible first bad commit: [f9bc6f63fbd4c1541f733465984ddff0dfd24e9f] build: Move protocol/Makefile.am into toplevel Makefile.am
# possible first bad commit: [058bd326208e638fbdf0dc5b868f7880cb84cec6] build: Move xwayland/Makefile.am into toplevel Makefile.am
# possible first bad commit: [bc00dbe4f5c044efef3359b3418bf0417c3669b2] build: Move desktop-shell/Makefile.am into toplevel Makefile.am
------------------------------

I'm using the following patch to disable tooltips in the launcher as a workaround.

--- clients/desktop-shell.c     2015-01-08 17:06:00.000000000 -0800
+++ clients/desktop-shell.c.new 2015-02-10 02:37:27.994904169 -0800
@@ -253,8 +253,6 @@
 {
        struct panel_launcher *launcher = data;
 
-       widget_set_tooltip(widget, basename((char *)launcher->path), x, y);
-
        return CURSOR_LEFT_PTR;
 }
 
@@ -306,7 +304,6 @@
        struct panel_launcher *launcher = data;
 
        launcher->focused = 0;
-       widget_destroy_tooltip(widget);
        widget_schedule_redraw(widget);
 }