Problem getting Cimgui to work

[Thomas]

Hi guys!

I need some help or advice about Cimgui (a C-API for Imgui) 
because I have no idea how to get it working.

First, I'm new to D (only a few weeks) and still learning. I have 
a small C++/C# background, but wanted to try something new. So D 
got into my focus.
I am working on Manjaro Linux btw.

Since 2 weeks I am working on a small project of mine to test the 
SDL2 functions with derelict. Until now everything worked just 
fine and I got my first window in SDL.
For this I have installed all SDL library and development files 
with the package manager of Manjaro Linux. Even GLFW.

To fill the SDL window with some widgets I have decided to try 
Imgui via Cimgui.
My first approach was to use the derelict-imgui version 0.9.4 
over DUB.
import derelict.imgui.imgui; has been accepted yet, but 
DerelictImgui.load(); not

While compiling I got the following error message:

derelict.util.exception.SharedLibLoadException at ../../.dub/packages/derelict-util-3.0.0-beta.2/derelict-util/source/derelict/util/sharedlib.d(158): Failed to load one or more shared libraries:
	cimgui.so - cimgui.so: cannot open shared object file: No such 
file or directory

so Cimgui was missing..

Ok, so in a second attempt I downloaded Cimgui as a ZIP and also 
the Imgui files from the homepage into the appropriate directory 
and unzipped them. First, the compiling via make doesn't wanted 
to compile:


cimgui.cpp: In Funktion »void 
ImGuiTextBuffer_append(ImGuiTextBuffer*, const char*, ...)«:
cimgui.cpp:1716:13: Fehler: »struct ImGuiTextBuffer« hat kein 
Element namens »appendv«; meinten Sie »appendf«?
      buffer->appendv(fmt, args);


Translated from german -> "there is no element appendv in 
ImGuiTextBuffer"

So I changed the code myself on that position by replacing 
"appendv" with "appendf"
That worked fine. But next problem was this:


/usr/bin/ld: ../imgui/imgui.o: relocation R_X86_64_PC32 against 
symbol `_ZN6ImVec2C1Eff' can not be used when making a shared 
object; recompile with -fPIC
/usr/bin/ld: final link failed: Bad value


After some research I found out it meant that the imgui files had 
not been compiled with -fPIC to be used as a shared library. So I 
deleted all .o files in the imgui directory and recompiled
imgui.cpp
imgui_draw.cpp and
imgui_demo.cpp
each with "g++ -c -fPIC -pie"
So I copied the new compiled .o files to the cimgui project and 
recompiled it again.
This time it worked without problems :-)

The new shared library file cimgui.so moved to my project 
directory and exported LD_LIBRARY_PATH so it could be found by 
the compiler.
This time the compiler cried this error:


derelict.util.exception.SymbolLoadException at ../../.dub/packages/derelict-util-3.0.0-beta.2/derelict-util/source/derelict/util/sharedlib.d(181): Failed to load symbol igPushIdPtr from shared library cimgui.so
----------------
??:? void* 
derelict.util.sharedlib.SharedLib.loadSymbol(immutable(char)[], 
bool) [0xcfec77a6]
??:? void* 
derelict.util.loader.SharedLibLoader.loadSymbol(immutable(char)[], bool) [0xcfec5cce]
??:? void derelict.util.loader.SharedLibLoader.bindFunc(void**, 
immutable(char)[], bool) [0xcfec5978]
??:? void derelict.imgui.imgui.DerelictImguiLoader.loadSymbols() 
[0xcfebe7a5]
??:? void 
derelict.util.loader.SharedLibLoader.load(immutable(char)[][]) 
[0xcfec5b4e]
??:? void 
derelict.util.loader.SharedLibLoader.load(immutable(char)[]) 
[0xcfec5ac8]
??:? void derelict.util.loader.SharedLibLoader.load() [0xcfec59ab]
??:? _Dmain [0xcfeae0af]
Program exited with code 1


After some research again I found a workaround on the Derelict 
Util homepage:



import derelict.util.exception : ShouldThrow;

ShouldThrow myMissingSymbCB( string symbolName )
{
		if ( symbolName == "igSetNextWindowPosCenter" ||
		     symbolName == "igAlignFirstTextHeightToWidgets" ||
		     symbolName == "igPushIdStr" ||
		     symbolName == "igPushIdStrRange" )
		{
			return ShouldThrow.No;
		}
		else
		{
			return ShouldThrow.Yes;
		}
}

int main()
{
     DerelictImgui.missingSymbolCallback = &myMissingSymbCB;
     DerelictImgui.load();
}


But with each attempt to compile my project with "dub" by adding 
the next symbol name into the list above a new symbol fails to 
load. Again and again.

Since 1 week I tried several ways to get the libray to work. 
Unfortunately without success.

Because I couldn't find any relevant information on the internet 
about this problem I hope to get a solution here. Maybe someone 
(an Cimgui expert here?) can give me a step by step instruction 
how to compile the library properly ?

Thank you!