Simplest-quickstart_1.md

After installing delphivcl library using pip, let's enter the Python REPL to understand a few essential things. Python has a pre-defined dir() function that lists available names in the local scope. So, before importing anything, let's check the available names using the dir() function;

>>> dir()
['__annotations__', '__builtins__', '__doc__', '__loader__', '__name__', '__package__', '__spec__']

Now let's import the installed delphivcl module to validate its installation and check for the output of the dir() function:

>>> import delphivcl
>>> dir()
['__annotations__', '__builtins__', '__doc__', '__loader__', '__name__', '__package__', '__spec__', 'delphivcl']

In the above output list, we have delphivcl as part of the available names in the local scope. In this case, if we need to use any classes or functions avialable in the delphivcl module, we should use a dot (.) operator after it. Now let's import everything using * from the delphivcl library and check for the available classes, functions, objects, constants, etc.

>>> from delphivcl import *
>>> dir()
>>> dir()[0:45]
['Abort', 'Action', 'ActionList', 'ActivityIndicator', 'Application', 'BasicAction', 'Bevel', 'BitBtn', 'Bitmap',
'BoundLabel', 'Button', 'Canvas', 'CheckBox', 'Collection', 'ColorBox', 'ComboBox', 'Component', 'ContainedAction',
'ContainedActionList', 'Control', 'ControlBar', 'CreateComponent', 'CustomAction', 'CustomActionList',
'CustomActivityIndicator', 'CustomControl', 'CustomDrawGrid', 'CustomEdit', 'CustomForm', 'CustomGrid',
'CustomMemo', 'CustomStyleServices', 'CustomTabControl', 'CustomToggleSwitch', 'DateTimePicker',
'DelphiDefaultContainer', 'DelphiDefaultIterator', 'DelphiMethod', 'DrawGrid', 'Edit', 'FileOpenDialog', 'Form',
'FreeConsole', 'Graphic', 'GroupBox']

To avoid an enormous list of names, we checked for the first 46 elements only using dir()[0:45]. Let's check for a few available classes, functions, and objects.

>>> CreateComponent
<built-in function CreateComponent>
>>> Button
<class 'Button'>
>>> Form
<class 'Form'>
>>> Application
<Delphi object of type TApplication at 2033DFE9C30>

We need to create an instance/object for other classes like Button and Form. But, Application is an instance/object by itself and is ready to be used with dot(.) operator. There are so many classes and functions but only one object called Application is readily available as part of our import. The Application object/instance is the source of all GUI applications that we create.

Let's now create a simple GUI application. The code for it is;

from delphivcl import *

Application.Initialize()
Application.Title = "Hello Delphi VCL"
app = Form(Application)
app.SetProps(Caption = "Welcome")
app.Show()
FreeConsole()
Application.Run()
app.Destroy()

Using the above code, we just create an empty GUI app. Please save the above code and run it to see the following output:

Let's explore and understand the functionality of the code;

from delphivcl import *

Application.Initialize()
Application.Title = "Hello Delphi VCL"

At first, we import everything from delphivcl. Then, we initialized the application and set a title for it. Later, we create the GUI Application window using the following code;

app = Form(Application)
app.SetProps(Caption = "Welcome")

We can to refer all the classes as part of the import as components. The Form is a special component and is different from all other components that create the GUI window and contain all other components. We instantiated the Form with Application as a parameter in the above code and assigned it to the app object. All the components, including Form, has a method setProps() to set their properties. Here we've set the name that appears on the title bar of the Form/GUI window using the Caption property.

Let's look at the following few lines of the code;

app.Show()
FreeConsole()
Application.Run()
app.Destroy()

As we created the application and set its properties, we shall show it on the screen using the app.show() code snippet. GUI applications run in interaction with the command window (console). To make the GUI perform better without lags, we use FreeConsole() to give primary control to the GUI interface. Application.Run() starts the GUI interaction loop between the GUI and the user of the GUI application. When we close the GUI application, app.Destroy() takes care of not crashing it.