Rather than use an inline wrapper and rely on the compiler optimizer to
redirect gr_set_current_canvas(nullptr) to gr_set_default_canvas,
rewrite all relevant calls directly in the source.
git grep -l 'gr_set_current_canvas' | xargs sed -i -e 's:gr_set_current_canvas(\s*NULL\|nullptr\s*);:gr_set_default_canvas();:'
For switch cases where existing comments or code flow logic obviously
intended to fall through, add a gcc-7 /*-fallthrough*/ comment to
silence warnings about this. Some cases which are less obvious are not
converted, so the code does not yet compile clean with
-Wimplicit-fallthrough.
Reported-by: parkerlreed <https://github.com/dxx-rebirth/dxx-rebirth/issues/338>
Macro LINE_SPACING previously used global grd_curcanv implicitly.
Change it to take a canvas argument. Change all callers to pass
grd_curcanv, so that usage is explicit.
Replace delete dcx::window kludge with a better solution: instead of requiring every handler to delete the window, add a window_event_result::deleted, which gets returned if the window was deleted by the handler, so window_close knows not to attempt to delete it again.
Allow dcx::window struct to be subclassed step 3. This step adds the window destructor and both requires and implements the window to be deleted by the event handler/client in all cases.
ASan reports a 2K read from a small string literal.
Also, fix silly double copy in con_add_buffer_line and delete too-short
memset in con_add_buffer_line.