| |
| |
On 3/16/24 23:43 Rob McDonald wrote:
On Saturday, March 16, 2024 at 2:29:28 PM UTC-7
Albrecht-S wrote:
The earlier/obsolete FindFLTK (1.1) module allowed to select
which
libraries you need by setting some variables. In modern CMake
you would
select "components" but this is not implemented in our FLTK
build.
OK, in old (module based) FindFLTK.cmake, the above seemed
to work.
That's because none of these libs *implied* linking any other lib.
You had to know which one you need(ed) to link, or FLTK had to list
all dependencies in this variable. The new, modern
CMake approach is that every single lib "knows" its own dependencies
(aka linkage requirements) and provides you (i.e. your build
procedure) with all required include directories and other compiler
flags etc. etc. - that's what "modern CMake" does.
Thanks much for the explanation -- it seems obvious (and I
nearly went down that path). I feel stupid for not knowing
this.
No problem ...
Do you see this on macOS, or on which OS?
I'm diagnosing this on MacOS, but it may happen on other
platforms too.
I believe that only the macOS linker issues a warning about this.
Generally this should be harmless anyway.
Modern CMake adds linkage requirements to each library and
it should - IMHO - avoid duplicating libs. However, if you add
libs more
than once, then I assume that CMake does it in the linker
commandline as
well. That said,
- you should *never* add fltk::z, fltk::png, or fltk::jpeg
explicitly
because they will be linked indirectly by fltk::images.
Where is this documented?
Good question. Thanks for asking. If this is not clearly documented
I need to improve the docs. [see below]
I had assumed that fltk::images contained some common
image-related code and that the other three just contained
format specific code. I did not expect that the linker
targets would be cumulative like this (to create the
possibility of this mistake).
I understand "cumulative" but I'm not sure what you mean. Let me
rephrase this: The term used in CMake is that each library *target*
contains its own linkage requirements. Hence fltk::images has the
linkage requirements that it needs fltk::fltk, fltk:jpeg and
fltk::png. fltk::png requires fltk::z, fltk::fltk requires X11
and/or Wayland libs, libcairo, libfontconfig, ... All this adds libs
recursively to the linkage requirements that result in
the linker commandline generated by CMake.
Also -- how can I be sure that it is safe to leave these
out?
You can be sure that every library target brings its own linkage
requirements with it. So the only question is: which library do you
really use, i.e. whose library's functions do you call directly?
I probably can (I don't explicitly use any of the FLTK
image code), but how can I be sure?
Simple answer: trial and error. Try the minimal list and build your
project. If it works you're done, otherwise the linker will spit out
undefined symbols that give you a clue which other library you need.
More detailed answers: for instance, if you call
fl_register_images() you request functions of the image library
fltk::images. If you use any of the Fl::xxx_Image classes (except
Fl_RGB_Image and maybe a few others) you need fltk::images, etc.
Is setting the operating system icon enough to require
this? Custom widget decorations? I know I don't use FLTK to
open and display images, but there might be some unintended
use.
As said above, if you don't know what you need, just try without
fltk::images and you'll see.
-
if you need one or more of fltk::forms, fltk::images, or
fltk::gl then
add them to your target_link_libraries() but not fltk::fltk
because it
will be included implicitly. Using all three of these libs
should be
harmless.
Again, where is this documented? Is fltk::forms only
needed for old Forms compatibility?
Basically yes, but if you happen to use e.g. Fl_Timer (an old Forms
compatibility widget) you need fltk::forms which is not that obvious
but also not very likely (the docs discourage its usage). There may
be more unexpected things that are in the forms library but usually
you won't use such code in "normal" FLTK applications. Again, the
linker will tell you.
OK, I've gone searching more and have found this stuff
documented in section 3.1 of README.CMake.txt
OK, I see. I thought I documented it but wasn't 100% sure. This
looks pretty complete, are there any more questions?
It is super interesting that fltk::forms, fltk::images, and
fltk::gl will all implicitly add fltk::fltk -- such that
adding all three is harmless and adding any of them makes
fltk::fltk unnecessary. However, there are the other
prohibitions against multiple adds...
Note that multiple adds should never be harmful. A warning (as from
the macOS linker) can indicate something but you can certainly live
with it (I would try to eliminate the warning though, same as what I
see you doing).
From reading all this, I think I should be able to get away
with just
fltk::gl
And nothing else...
Yep, if you are using OpenGL (Fl_Gl_Window). If you need more the
linker will tell you.
BTW, the 'old' FindFLTK.cmake Module approach would
implicitly 'Find(OpenGL)' (unless it was explicitly skipped)
and would add the resulting OpenGL libraries to the FLTK
libraries.
This does not appear to be what fltk::gl does at all --
which is fine, but I guess this is just another implied
difference between the old and Modern way.
Hmm, I'm not sure I understand you. If you link your program with
fltk::gl this *should* imply all required OpenGL libs to satisfy the
linker. If this is not happening then this is a bug in FLTK's CMake
support. I'll check this ... tomorrow.
Or, if I misunderstood you, please clarify what you mean. Do you
need to link OpenGL system libs in your project's CMake files
explicitly?
... this does not tell me that fltk::images includes all
of fltk::jpeg and fltk::png -- and other implied rules like
that.
Simply put, there's only one rule: every CMake
library target contains all of its linkage requirements
(recursively) - and again, if this is not the case then
it's a bug, please let me know.
Thanks for testing and feedback, I appreciate your constructive help
very much.
Albrecht
--
You received this message because you are subscribed to the Google Groups "fltk.general" group.
To unsubscribe from this group and stop receiving emails from it, send an email to fltkgeneral+unsubscribe@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/fltkgeneral/10068035-c2bc-4360-b2aa-5e3e57161611%40aljus.de.
[ Direct Link to Message ] | |
|
| |
