output: default scale to 1

[martinetd]

This prevents us from telling application our scale is 0, when it has no
reason to be.

[ddevault]

Thanks!

[acrisci]

This makes a gtk window actually show up in my VT briefly but then it crashes, so let's start looking into that. 👍

[martinetd]

I also crash with drm, yeah (with nyorain's patch also applied)

==25079==ERROR: AddressSanitizer: SEGV on unknown address 0x7f540a000086 (pc 0x7f54f514950c bp 0x7f54f534d778 sp 0x7ffc8e1c3e80 T0)
==25079==The signal is caused by a READ memory access.
    #0 0x7f54f514950b  (/lib64/libwayland-server.so.0+0xc50b)
    #1 0x7f54f5144553 in wl_resource_instance_of (/lib64/libwayland-server.so.0+0x7553)
    #2 0x7f54f514627b in wl_shm_buffer_get (/lib64/libwayland-server.so.0+0x927b)
    #3 0x7f54f53a310f in wlr_surface_flush_damage ../types/wlr_surface.c:255
    #4 0x4029dc in output_frame_handle_surface ../examples/compositor/main.c:54
    #5 0x402f99 in handle_output_frame ../examples/compositor/main.c:82
    #6 0x4074b2 in output_frame_notify ../examples/shared.c:424
    #7 0x7f54f5374126 in wl_signal_emit /usr/include/wayland-server-core.h:388
    #8 0x7f54f537b8c5 in page_flip_handler ../backend/drm/drm.c:826
    #9 0x7f54f321454d in drmHandleEvent (/lib64/libdrm.so.2+0xb54d)
    #10 0x7f54f537ba54 in wlr_drm_event ../backend/drm/drm.c:836
    #11 0x7f54f5146c51 in wl_event_loop_dispatch (/lib64/libwayland-server.so.0+0x9c51)
    #12 0x7f54f5145499 in wl_display_run (/lib64/libwayland-server.so.0+0x8499)
    #13 0x40808d in compositor_run ../examples/shared.c:535
    #14 0x403ee0 in main ../examples/compositor/main.c:174
    #15 0x7f54f4b4c4d9 in __libc_start_main (/lib64/libc.so.6+0x204d9)
    #16 0x402659 in _start (/home/shared/wayland/wlroots/build/examples/compositor+0x402659)

Happy to either look at it or let you, I still haven't understood #102 so I have other things to work on :p