layout manager

The so-called GUI interface, in the final analysis, is the superposition of a bunch of components.We create a window, put buttons on it, put icons on it, and it becomes an interface.The location of the components is especially important when it comes to placement.We have to specify where to put the component so that the window can be rendered the way we want.This involves the mechanism of component positioning.

Qt provides two component positioning mechanisms: absolute positioning and layout positioning

Absolute positioning is one of the most primitive positioning methods: give the coordinates and length and width values ​​of this component.
This way, Qt knows where to put the component and how to size it.But one problem with this is that if the user changes the size of the window, such as by clicking the maximize button or dragging the edge of the window with the mouse, absolutely positioned components will not respond.This is also natural, since you're not telling Qt whether and how the component should update itself when the window changes.Or, there is an easier way: prohibit the user from resizing the window.But this is not always the long-term solution.
Layout positioning: As long as components are placed in a layout, the layout is managed by a dedicated layout manager.When resizing or positioning is required, Qt uses the corresponding layout manager to adjust.

Layout positioning perfectly solves the defects of using absolute positioning.

The following three layouts provided by Qt are the most commonly used:
QHBoxLayout: Layout from left to right in the horizontal direction;
QVBoxLayout:Layout from top to bottom in the vertical direction;
QGridLayout: Layout in a grid, similar to HTML table.

1. System-provided layout controls

These 4 are the layouts provided by the systemControls, but not very flexible to use.

2. Use widgets for layout

The second layout method is to use the widget in the control to do the layout, in the Containers

The controls in the widget can perform horizontal, vertical, grid layout and other operations, which are more flexible.
While re-layout, we need to flexibly use the characteristics of spring to make our layout more beautiful. The following is a login window. Using widgets, we can build the following login interface: