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  Save QWidget as image

Qt library is an excellent GUI library for C++ programmers developed by Nokia and now is an open source project. Often, we may use QPainter to draw strings, lines or images on a QWidget. We can override the QWidget's paintEvent() method when we want to use QPianter object to draw something on a QWidget. If we want to save the items drawn on QWidget as image for later reference, what can we do? We can save a QWidget as an image. Here is the code for achieving this: QPixmap pixmap(this->size())...

   Qt,C++,QWidget,Image     2012-08-19 12:01:18

  Why is Golang's Compilation Speed So Fast?

Overview When I started learning the Go language, I already had experience with three statically typed languages—C/C++ and Java—and two dynamically typed languages—PHP and JavaScript. Because of this background, when I compiled a demo file of several hundred lines for the first time in Go, I was genuinely impressed by its compilation speed. At that moment, I thought to myself, "Go claims to have the execution speed of statically typed languages and the compilation speed of dyna...

   GOLANG,COMPILATION,GO     2024-10-07 22:02:23

  How to let Google index AJAX contents?

There are lots of websites containing only one page now with the popularity of AJAX. The website will load different contents according to different inputs from users. This approach provides good user experience and it also helps save bandwidth, the drawback is that AJAX contents are not easy to be indexed by search engines. For example, if you have a website: http://example.com Users can see different contents with the appended # structure in the URL: http://example.com#1 http://example.com#2 h...

   AJAX,Search engine,Google,History     2013-07-16 00:47:14

  Use downcase! with caution in Ruby

Ruby provides ! to change state of some object in place. Hence if you see some functions have ! appended, it means the state of the caller of the function is expected to be changed. This is a very interesting Ruby feature. But sometimes one should be cautious when using this kind of functions because you would get unexpected behavior if using improperly. Let's take an example of String#downcase!. According to the documentation. Downcases the contents of str, returning nil if...

   RUBY,EXCLAMATION MARK,DOWNCASE     2017-02-10 06:34:44

  Resolve stylesheet_link_tag fails to work in Ruby on Rails

When developing Ruby On Rails application, developers sometimes will see an unexpected behavior where the application cannot be loaded due to "TypeError: Object doesn't support this property or method" when invoking stylesheet_link_tag. The symptom looks like  And the Rails log will show something similar to below The error occurs because there is some problem finding the correct assets which are located in app/assets. To resolve the issue, you can following below steps. Add gem 'coffee-...

   RUBY ON RAILS,STYLESHEET_LINK_TAG,JAVASCRIPT_INCLUDE_TAG,TYPEERROR     2016-10-14 03:59:11

  noConflict mechanism in jQuery

Many JavaScript frameworks like to use $ as function or variable name, jQuery is one of them. In jQuery, $ is just a reference to window.jQuery, so even if $ is deleted, window.jQuery will still be available to ensure the whole library can work normally. jQuery API design takes fully consideration of multiple frameworks conflicts, we can use jQuery.noConflict function to easily handle control. jQuery.noConflict accepts one optional boolean parameter[1] to determine whether to hand jQuery object ...

   jQuery,noConflict,$     2013-03-14 19:40:36

  Problem and Solution for Installing wxPython on Ubuntu 20.04

When we try to install wxPython lib on Ubuntu system to do software GUI development, most of time we may meet some installation and lib dependency problems. For the latest Ubuntu version, the problems still happen. Below are some common problems which happened frequently and their solution: --------------------------------------------------------------------------------------------------------------- Problem [1]: Install wxPython on Ubuntu 20.04 fail because of dependency package Gtk is not in...

   PYTHON,WXPYTHON,UBUNTU 20.04     2020-09-09 05:32:35

  Which one has a worse reputation, JavaScript or PHP?

There has a been a lot of criticism of PHP over being a badly designed programming language. JavaScript seems quite a similar language with loose-typing and flexible array declarations/memory management, but is widely adopted by industry leaders such as Google. Google even has a JavaScript style guide. Many people think that PHP has a worse reputation than JavaScript. Carlos Ribeiro gave his analysis on a high level which doesn't touch the language syntax. Attributing JavaScript success to it be...

   JavaScript,PHP,reputation,comparison     2014-05-03 06:26:10

  Eight C++ programming mistakes the compiler won’t catch

C++ is a complex language, full of subtle traps for the unwary. There is an almost infinite number of ways to screw things up. Fortunately, modern compilers are pretty good at detecting a large number of these cases and notifying the programmer via compile errors or warnings. Ultimately, any error that is compiler-detectable becomes a non-issue if properly handled, as it will be caught and fixed before the program leaves development. At worst, a compiler-detectable error results in los...

   C++,Compiler,Error detection     2012-04-08 09:55:20

  File upload once again

File upload is one of the oldest operation of web design. After 20 years, it's still has no big change, difficult to handle, lack of interaction and poor user experience. Web developers have thought many methods to improve the experience of uploading file in web apps, they developed various plugins based on different JavaScript libraries. However, because of the difference among different web browsers, there is no common interface which makes these plugins work properly or easily on all web brow...

   Web design, File upload, Asynchronous,HTML5     2012-09-02 11:52:21

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