Somehow got very distracted from Qt. And then the other day had to come back =) Spent a long time remembering how I used to implement delays, or sleep in Qt (yes, yes, yes, it's bad, etc., but sometimes you really need it, especially if you need to turn in a lab to make others stop bothering you.)

Example of a trivial implementation:

Previously, we learned to use the QwtPlotSpectrocurve component (here). Qwt provides an alternative component that is more convenient for visualizing analytical functions. In this note, we will learn how to use QwtPlotSpectrogram.

An application written in cross-platform Qt. (Except for tricky third-party libraries, but that's the exception). However, to run the application on different platforms, you often still need to properly configure the Qt project. (The project is configured in the .pro file).

The Qt framework allows automatic optimization of the program's interface for any monitor resolution or window size change. This can be done using Qt layouts.

Using QwtPlotSpectroCurve (first familiarize yourself with QwtPlotCurve here) you can display information that requires representation in three dimensions; create pseudo 3D graphs on a two-dimensional plane. The third dimension will be conveyed through color gradients - these graphs are called spectrograms. Unlike the QwtPlotSpectrogram component, you control each point on the curve, rather than intervals. The QwtPlotSpectroCurve component is less functional but more logical for graph plotting.

For using the timer in Qt, the class QTimer is intended. First, you need to set the time after which it will trigger. You also need to define a slot that will handle the signal emitted when the timer overflows. Thus, a mandatory condition for using QTimer is the ability to use signals and slots, which means that the class that uses the timer must be a descendant of QObject. Let's create a simple clock as an example.

For easier perception of information, for reading charts, you can enable the grid. This is done using the QwtPlotGrid class. Everything is as usual: the object needs to be created, configured, and attached to the qwtplot.

It so happened that there is no ready-made component for drawing bubbles in QwtPlot - like, for example, in TChart from Borland (Delphi). But it's no problem. All this can be done manually, and it's not very difficult.

Building histograms in QT is done using Qwt. The logic of building them is similar to building graphs. (First, I suggest reading this.) Let's consider a simple example of building a histogram using QwtPlotHistogram.

Unfortunately, in QT there is no convenient component TChart (from Borland, for Delphi/Builder). But there is a good alternative - Qwt. There should be no problems with adding graphs and histograms, but sometimes (depending on the task) there may be difficulties with bubbles. But not now. Let's start with regular graphs.