[Ctk-developers] How to wrap a Qt App into an hosted app confirming to DICOM Supplement 118 / Working Group 23

[Sascha Zelzer]

Hi Michael,

Welcome to the CTK mailing list.

DICOM Application Hosting support in CTK is still work in progress, so 
please be aware that not everything will work yet. Especially the data 
exchange interface needs more work. Nevertheless, I hope my comments 
below will get you started to experiment with your own Qt based DICOM 
App. Comments, bug reports, patches etc. are also always welcome!

Best,
Sascha

On 05/13/2011 03:56 AM, Caylus, Michael (SCR US) wrote:
> Hello,
> I am new to the CTK SDK and would like to wrap my Qt application into 
> an hosted app. I have seen such an example by turning on in the CMake 
> configuration:  ctkExampleHost and ctkExampleHosted App.  I came up 
> with the following questions after playing with it:
>
>    1. In order to make this wrap-up for my app; I was considering to
>       edit the org_commontk_dah_exampleapp plug-in which relies on the
>       org_commontk_dah_app and org_commontk_dah_core plug-in and keep
>       the ctkExampleHostedApp. Is this approach the right way to
>       proceed? This implies splitting my app into the hostedApp and a
>       CTK plugin; with most of the work to be done on the plug-in
>       level I guess. I have seen some doc explaining how to embed the
>       CTK plugin framework in my app too. Can I achieve the same
>       result with this approach and how?
>
As you have already seen, it is possible to use the plugin framework 
from inside your own application and this is also the preferred way 
(instead of modifying the existing CTK plug-ins directly). In the case 
of a DICOM App, I can think of two different approaches, depending on 
your requirements:

1.) Your app is a "pure" DICOM App, i.e. you do not need run it outside 
the context of a "Hosting Application"

This is the easier approach. You would create your own plug-in, 
equivalent to org.commontk.dah.exampleapp, which contains all your app 
code (logic, widgets, etc.). Additionally, you create your own 
ctkExampleHostedApp executable, which is essentially the same code as in 
the CTK repository (just adapt paths and plug-in names).

The 
http://www.commontk.org/index.php/Documentation/CTK_Plugin_Framework:_Setting_up_a_project?action=purge 
tutorial explains how to create a CTK-based project.

2.) You want to use your app both "stand-alone" and as a "hosted app"

This involves a little bit more knowledge about the plugin framework, 
but should also be easy to achieve. What the org.commontk.dah.exampleapp 
plug-in actually does, is to register a class containing the DICOM 
"application logic" as a service within the plugin-framework. You could 
either create this class (similar as the ctkExampleDicomAppLocig class) 
inside your current project (not in a separate plug-in) and register an 
instance by using the plugin framework context, or create a small 
plug-in containing this class and taking care of the registration 
itself. Then start the plugin framework from inside your executable, if 
you recognize the host and app url command line parameters (otherwise, 
create a QMainWindow yourself).

Depending on how fancy you would like to get concerning the minimization 
of dependencies of your app in stand-alone mode to the CTK libraries, 
you could think of a more complex set-up containing two small wrapper 
executables, one for "app mode" starting the CTK plugin framework and 
one for "stand-alone mode", both linked to a library containing your 
application gui and logic...

>    1. I couldn’t find to which QMainWindow is the button attached to
>       in the ctkExampleDicomAppLogic::do_something()function.It
>       doesn’t look like thectkExampleDicomAppLogic is heritating from
>       a widgetalso. Which object is responsible of the creation of the
>       mainwindow?
>

The org.commontk.dah.exampleapp plugin does not create a QMainWindow. It 
just create a button an shows it (moved and resized to respect the 
prescribed screen area from the host). In Qt, widgets become top-level 
windows if they don't have a parent widget and are "shown".

>    1. Is there any doc that explains how to create a CTK plug-in and
>       App from scratch. It would be probably better in my case to
>       create a new plugin instead of editing an existing one.
>

There is no doc about creating a plug-in yet, but you can easily create 
one by using the ctkPluginGenerator executable (you may have to enable 
it in CMake). It might have some rough edges though...

A CTK "app" is actually nothing special. Any executable can do, which 
links to the CTK libraries. The tutorial linked above explains how to 
use the plugin framework in an arbitrary executable.


>    1. How can I add additional includes directories through a
>       CMakeLists in the CTK framework.  I couldn’t find a way to
>       define additional directories in the CMakeList of a plug-in (no
>       include_directories). Is that define somewhere else?
>

Inside CTK itself, include directories are set-up auto-magically through 
our custom CMake dependency system. If you need to use external 
libraries in your own CTK plug-in (contained in your own project), just 
use standard CMake INCLUDE_DIRECTORIES (before calling the 
ctkMacroBuildPlugin macro) and LINK_LIBRARIES(${PROJECT_NAME} ...) 
(after the ctkMacroBuildPlugin call) commands.

Happy coding,

Sascha
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