Draw scrollable chart

compyler

Hello,

I want to draw a stock chart (boxes along a time axis) with Qt. These charts have data for a long time period (i.e. year 2000 until now), but most of the time I only want to show a certain small period from the whole graph (for example only data for November 2013).

I am very new to Qt I have a hard time figuring out how to start. I want to make it as efficient as possible without flickering. I guess its a smart idea to only draw the part of the chart that the user currently sees?

Initially I thought I derive from QWidget, override paintEvent() and draw the whole graph. Then I put this widget into a QScrollArea. But first how does the QScrollArea know what part of the widget it has to show? Second I don't like the idea of drawing the whole graph. I need some "culling" that tells me: Only draw this time span of the graph.

Can anyone help me and tell how I could implement drawing such a scrollable graph? Thanks!

sierdzio

There are numerous chart drawing libraries for Qt:

Uwe's "Qwt":http://qwt.sourceforge.net/
Digia's "Qt Commercial Charts":http://qt.digia.com/Product/Qt-Core-Features--Functions/Charts/
"QCustomPlot":http://inqlude.org/libraries/qcustomplot.html
and "many":http://stackoverflow.com/questions/3537251/chart-library-for-qt others

Or you can base your implementation on "Qt tutorials":http://qt-project.org/doc/qt-4.8/itemviews-chart.html. That will make your task much harder, though.

SteveG

Tomasz, You seem to have extensive knowledge about various Qt libraries. Are there any web pages or sites that contains a "comprehensive" list of Qt libraries, frameworks, examples, tutorials or other resources? Thanks.

sierdzio

There are a few, yes. Google is your friend. Most known are:

"inqlude":http://inqlude.org/
"Qt Project Add-Ons":http://qt-project.org/wiki/Category:Add-ons
"Qt Apps":http://qt-apps.org/

SteveG

Thanks so much. I was aware of some of these and have looked in github, gitorious, sourceforge and others. I've also relied heavily on Google. However, it would be useful to have a repository that listed name, description, link, status, etc. in one place that the Qt community could constantly update.

sierdzio

inqlude is aspiring to do just that: but it's a new site, so it still needs to grow, build up it's database, etc. Their stuff is openly available on github and they are accepting lots of contributions on a daily basis.