Example: Gaphor services

In this example we’re doing something a little less trivial. In Gaphor, services are defined as entry points. Each service is a class, and takes parameters with names that match other services. This allows services to depend on other services.

It looks something like this:

# entry point name: my_service
class MyService:
    ...

# entry point name: my_other_service
class MyOtherService:
    def __init__(self, my_service):
        ...

Let’s first load the entry points.

from gaphor.entrypoint import load_entry_points

entry_points = load_entry_points("gaphor.services")

entry_points

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/home/docs/checkouts/readthedocs.org/user_builds/gaphor/envs/latest/lib/python3.11/site-packages/gaphor/diagram/text.py:6: PyGIWarning: Pango was imported without specifying a version first. Use gi.require_version('Pango', '1.0') before import to ensure that the right version gets loaded.
  from gi.repository import Pango, PangoCairo
/home/docs/checkouts/readthedocs.org/user_builds/gaphor/envs/latest/lib/python3.11/site-packages/gaphor/diagram/text.py:6: PyGIWarning: PangoCairo was imported without specifying a version first. Use gi.require_version('PangoCairo', '1.0') before import to ensure that the right version gets loaded.
  from gi.repository import Pango, PangoCairo

{'auto_layout': gaphor.plugins.autolayout.pydot.AutoLayoutService,
 'component_registry': gaphor.services.componentregistry.ComponentRegistry,
 'consolewindow': gaphor.plugins.console.consolewindow.ConsoleWindow,
 'copy': gaphor.ui.copyservice.CopyService,
 'diagram_export': gaphor.plugins.diagramexport.DiagramExport,
 'diagrams': gaphor.ui.diagrams.Diagrams,
 'element_dispatcher': gaphor.core.modeling.elementdispatcher.ElementDispatcher,
 'element_factory': gaphor.core.modeling.elementfactory.ElementFactory,
 'elementeditor': gaphor.ui.elementeditor.ElementEditor,
 'event_manager': gaphor.core.eventmanager.EventManager,
 'export_menu': gaphor.ui.menufragment.MenuFragment,
 'file_manager': gaphor.ui.filemanager.FileManager,
 'main_window': gaphor.ui.mainwindow.MainWindow,
 'model_browser': gaphor.ui.modelbrowser.ModelBrowser,
 'modeling_language': gaphor.services.modelinglanguage.ModelingLanguageService,
 'properties': gaphor.services.properties.Properties,
 'recent_files': gaphor.ui.recentfiles.RecentFiles,
 'sanitizer': gaphor.UML.sanitizerservice.SanitizerService,
 'toolbox': gaphor.ui.toolbox.Toolbox,
 'tools_menu': gaphor.ui.menufragment.MenuFragment,
 'undo_manager': gaphor.services.undomanager.UndoManager,
 'xmi_export': gaphor.plugins.xmiexport.XMIExport}

Now let’s create a component in our model for every service.

from gaphor import UML
from gaphor.core.modeling import ElementFactory

element_factory = ElementFactory()

def create_component(name):
    c = element_factory.create(UML.Component)
    c.name = name
    return c

components = {name: create_component(name) for name in entry_points}
components

{'auto_layout': <gaphor.UML.uml.Component element e85419ec-c913-11ed-90e0-0242ac110002>,
 'component_registry': <gaphor.UML.uml.Component element e8541d66-c913-11ed-90e0-0242ac110002>,
 'consolewindow': <gaphor.UML.uml.Component element e8541eec-c913-11ed-90e0-0242ac110002>,
 'copy': <gaphor.UML.uml.Component element e854205e-c913-11ed-90e0-0242ac110002>,
 'diagram_export': <gaphor.UML.uml.Component element e854219e-c913-11ed-90e0-0242ac110002>,
 'diagrams': <gaphor.UML.uml.Component element e85422c0-c913-11ed-90e0-0242ac110002>,
 'element_dispatcher': <gaphor.UML.uml.Component element e85423e2-c913-11ed-90e0-0242ac110002>,
 'element_factory': <gaphor.UML.uml.Component element e8542536-c913-11ed-90e0-0242ac110002>,
 'elementeditor': <gaphor.UML.uml.Component element e8542694-c913-11ed-90e0-0242ac110002>,
 'event_manager': <gaphor.UML.uml.Component element e85427ac-c913-11ed-90e0-0242ac110002>,
 'export_menu': <gaphor.UML.uml.Component element e85428a6-c913-11ed-90e0-0242ac110002>,
 'file_manager': <gaphor.UML.uml.Component element e85429a0-c913-11ed-90e0-0242ac110002>,
 'main_window': <gaphor.UML.uml.Component element e8542a90-c913-11ed-90e0-0242ac110002>,
 'model_browser': <gaphor.UML.uml.Component element e8542b8a-c913-11ed-90e0-0242ac110002>,
 'modeling_language': <gaphor.UML.uml.Component element e8542c7a-c913-11ed-90e0-0242ac110002>,
 'properties': <gaphor.UML.uml.Component element e8542d60-c913-11ed-90e0-0242ac110002>,
 'recent_files': <gaphor.UML.uml.Component element e8542e46-c913-11ed-90e0-0242ac110002>,
 'sanitizer': <gaphor.UML.uml.Component element e8542f36-c913-11ed-90e0-0242ac110002>,
 'toolbox': <gaphor.UML.uml.Component element e854301c-c913-11ed-90e0-0242ac110002>,
 'tools_menu': <gaphor.UML.uml.Component element e854310c-c913-11ed-90e0-0242ac110002>,
 'undo_manager': <gaphor.UML.uml.Component element e8543224-c913-11ed-90e0-0242ac110002>,
 'xmi_export': <gaphor.UML.uml.Component element e854330a-c913-11ed-90e0-0242ac110002>}

With all components mapped, we can create dependencies between those components, based on the constructor parameter names.

import inspect

for name, cls in entry_points.items():
    for param_name in inspect.signature(cls).parameters:
        if param_name not in components:
            continue

        dep = element_factory.create(UML.Usage)
        dep.client = components[name]
        dep.supplier = components[param_name]

With all elements in the model, we can create a diagram. Let’s drop the components and dependencies on the diagram and let auto-layout do its magic.

To make the dependency look good, we have to add a style sheet. If you create a new diagram via the GUI, this element is automatically added.

from gaphor.core.modeling import Diagram, StyleSheet
from gaphor.diagram.drop import drop

element_factory.create(StyleSheet)
diagram = element_factory.create(Diagram)

for element in element_factory.lselect():
    drop(element, diagram, x=0, y=0)

Last step is to layout and draw the diagram.

from gaphor.extensions.ipython import auto_layout, draw

auto_layout(diagram)

draw(diagram, format="svg")

That’s all. As you can see from the diagram, a lot of services rely on EventManager.