Luckycleveland

• PyQt Tutorial

• Boost Signal Slot Vs Qts
• Qt Signal Slot Parameter
• Qt Signal Slot Example
• Qt Signal Slot Connect

In this Pyside2 GUI iam going to show you QPushButton Creation, also iam going to talk about Signal And Slots in Qt For Python. What is Signal And Slots? How Qt Signals and Slots Work - Part 3 - Queued and Inter Thread Connections This blog is part of a series of blogs explaining the internals of signals and slots. Activate to prepare a Qt::QueuedConnection slot call. The code showed here has been slightly simplified and commented: static void queuedactivate(QObject.sender. Boost has a lot of stuff that is missing in Qt (and vice versa) boost libraries we mainly use here are: shared pointer, property tree (i like it), foreach, filesystem, multi-index, optional, serialization, thread boost test framework is not bad - we use it for non Qt applications and libraries. Boost has a lot of great stuff.

• PyQt Useful Resources

• Selected Reading

Unlike a console mode application, which is executed in a sequential manner, a GUI based application is event driven. Functions or methods are executed in response to user’s actions like clicking on a button, selecting an item from a collection or a mouse click etc., called events.

Widgets used to build the GUI interface act as the source of such events. Each PyQt widget, which is derived from QObject class, is designed to emit ‘signal’ in response to one or more events. The signal on its own does not perform any action. Instead, it is ‘connected’ to a ‘slot’. The slot can be any callable Python function.

In PyQt, connection between a signal and a slot can be achieved in different ways. Following are most commonly used techniques −

A more convenient way to call a slot_function, when a signal is emitted by a widget is as follows −

Suppose if a function is to be called when a button is clicked. Here, the clicked signal is to be connected to a callable function. It can be achieved in any of the following two techniques −

or

Example

In the following example, two QPushButton objects (b1 and b2) are added in QDialog window. We want to call functions b1_clicked() and b2_clicked() on clicking b1 and b2 respectively.

When b1 is clicked, the clicked() signal is connected to b1_clicked() function

When b2 is clicked, the clicked() signal is connected to b2_clicked() function

Example

The above code produces the following output −

Output

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Boost Signal Slot Vs Qts

Qt Signal Slot Parameter

Comments

Qt Signal Slot Example

Compiling a rqt_gui_cpp plugin which (transitively) depends on boost signals (e.g. via tf package) fails to compile due to macro name clashes of Qt's 'signals', 'slots', 'emit' macros as described here: http://wiki.ros.org/qt_ros/Tutorials/Mixing%20Qt%20and%20Boost%20Signals For such a plugin to compile the QT_NO_KEYWORDS flag can be set in its cmake file: ADD_DEFINITIONS(-DQT_NO_KEYWORDS) But this breaks the current code of qt_gui_core at: https://github.com/ros-visualization/qt_gui_core/blob/fuerte-devel/qt_gui_cpp/include/qt_gui_cpp/plugin_bridge.h#L63 And also a few other files in the rqt package are affected: https://github.com/ros-visualization/rqt/search?l=cpp&q=signals+OR+slots+OR+emit&type=Code&utf8=%E2%9C%93 Changing the keywords as follows would resolve this issue: signals -> Q_SIGNALS slots -> Q_SLOTS emit -> Q_EMIT foreach -> Q_FOREACH The use of the QT_NO_KEYWORDS flag should also be mentioned in the rqt cpp plugin tutorial.

Qt Signal Slot Connect