# wx Basics

## Concept

wxPython is a Wrapper around the wxWidgets GUI library, which is written in C++.

You may want to visit these pages for more information:
  - The wxPython home page: https://wxpython.org/
  - The wxPython API documentation: https://docs.wxpython.org/
  - An overview including a Hello World application example: https://wxpython.org/pages/overview/
  - A more comprehensive Getting Started guide: https://wiki.wxpython.org/Getting%20Started
  - The wxWidgets home page: https://www.wxwidgets.org/

The wxGlade documentation is intended to be readable without previous wx knowledge. It will teach you how to create windows, handle events and how to integrate with your ‘business logic’ code. Sooner or later you will have to look into the wx documentation, though.

If you are new to wx/Python, make sure that you work through this documentation at least up to and including section “Create and Use Source Code”.

Also please note that the wxPython demo is probably most important resource for exploring the available controls! The demo has examples and example code for most widgets, including the more complicated and powerful ones like the grid control.

If you don’t have the demo, have a look here: https://extras.wxpython.org/wxPython4/extras/
Go to the subdirectory matching your wxPython version and download the demo archive.
Then unpack the archive and run `demo.py`.

## Sizers (Layout Managers)

With wxWidgets / wxPython and similar toolkits, usually controls are not placed at pixel positions on their windows, but the layout of a window is managed by sizers.
  - There are horizontal box sizers, vertical box sizers and grid sizers.
  - The box sizers may have a label and a box around them. In that case they’re called static box sizers.
  - There are also variants of the box sizers, called wrap sizers. These will wrap around if there’s not enough space for it’s children.
  - Each sizer and contained sizer items can be fixed size or grow to fill the available space, e.g. when the window is resized.
  - Typically in a main window or frame the sizer makes the contents fill the available space, while dialogs will be sized to the minimum required space.

### Sizer Examples

Vertical BoxSizer

- This sizer stacks the controls it manages one above the other.
- This example shows three buttons arranged in this way.

Horizontal BoxSizer

- This sizer arranges its controls alongside of one another.
- This example shows three button arranged in this way.

Allowing controls to grow and/or expand

- Controls in a horizontal sizer can “grow” horizontally, or “expand” vertically in response to changes in window size.
- In this three button example, using a horizontal BoxSizer:

> - The middle button has been allowed to grow horizontally.
> - The third button has been allowed to expand vertically.

Alignment of controls

- The alignment of controls within a sizer can also be specified.
  This example also uses a horizontal BoxSizer to specify that:

> - The first button is “top” aligned.
> - The middle button is “bottom” aligned.
> - The third button has been given a border that provides some space around it on all sides.

StaticBoxSizer

- This sizer puts a border around its edges and provides a label to describe its contents.
- In this example, a horizontal StaticBoxSizer has been used to contain the three buttons (which have the same properties set as those in the previous example).
- StaticBoxSizers can be either horizontal or vertical, just like their “non-static” equivalents.

GridSizer

- GridSizers arrange their contained controls in a grid made up of equally sized rows and columns.
- In this example, the grid has been set to two rows and two columns.
- Each cell in the example contains a button, which has been centred in the cell.

Expanding, growing and aligning in a grid cell

In this example:
  - The first button has been aligned LEFT.
  - The second button has been aligned BOTTOM.
  - The third button has been allowed to expand.
  - The fourth button has been aligned RIGHT and CENTER.

FlexGridSizer

- The FlexGridSizer allows a little more flexibility over cell sizes by allowing individual rows and columns to grow and/or expand.
- In this example, the first column has been allowed to grow horizontally and the second one allowed to grow vertically.
  Note that this becomes obvious when the window is resized by the user.

GridBagSizer

- This example uses a 3x3 grid and five buttons.
- It shows how a GridBagSizer can allow controls to span multiple columns and/or rows.
- All the buttons have their EXPAND property set so that they fill all the space in the cell(s).

WrapSizer

- This sizer is similar to a BoxSizer, but allows to overflow to multiple rows/columns.
- The example shows the same sizer with three buttons with two different widths of the containing frame.

In wxGlade you can easily change the sizer type:

### Example application: Calculator window

This window is managed by one vertical box sizer with six slots for the five rows, plus a horizontal line and five horizontal box sizers for the horizontally arranged controls they contain (i.e. label plus text control, label plus radio box or button plus button):

The Design and Preview windows look like this, but without the colored frames for the horizontal and vertical sizers:
Each blue frame is a horizontal sizer with two slots each. The (invisible) borders between slots are indicated by dashed lines.
The inputs for Value 1 and 2 are set to grow horizontally; the Result output is growing horizontally and EXPANDing vertically.

In the Tree window, you can see the hierarchical structure:
Note that horizontal and vertical sizers are
visualized with different icons: .

Later we’ll have a look at alternative structures which allow better alignment of the fields.

Note

- For your own projects, always use the simplest available sizers. Usually you will need mainly box sizers and maybe one or two FlexGridSizers.
- Use nested sizers to match the hierarchical / logical structure of your project. This will make it easy to re-arrange things to find the best user interface.
- Never ever try to use a Grid(Bag)Sizer as main sizer of a window trying to resemble pixel placement or Tkinter’s grid geometry manager. This is a mess to create and maintain. Actually, a GridBagSizer is rarely needed.