From last blog, I’ve demostrated the usage of Ubuntu *-dbg packages. However, not all *-dbg packages seem to work as libssl0.9.8-dbg. For instance, libcurl3-dbg and libqt4-dbg packages do not work. I’m afraid some debug info are missing in these two packages. I’m not sure.

I googled a lot, but was not able to find a solution. So I decided to build the debug version of the two library myself. Here are steps for libcurl:

After all, the compiled binary is located in /home/gonwan/testgdb/curl-7.19.7/lib/.libs/. Note, this is a hidden folder.

Here comes our test code:

Build commands:

I use /usr/lib/ instead of lcurl, since lcurl will link the binary to /usr/lib/ But I currently cannot afford it :(. Last, start our GDB:

It prints the backtrace now, though I’m not so accustomed to console debugging. I add the LD_LIBRARY_PATH environment to let our test program find our homemade version of In fact, we can run ldd like following lines. You see the re-direction?

Later, I successfully made it possible to debug Qt source code in IDE. I chose QtCreator, since it has both windows and linux version, and it’s easy to install and configure. I also built my homemade version of Qt:

I only built the most common modules, excluding webkit, script, xmlpatterns, phonon, multimedia and declarative modules. It took only 25 minutes to finish (An entire build under windows may take 3 – 4 hours.). After all, start your QtCreator, create a Qt console project with the source below:

Build the project in debug mode. And now, here’s the magic: Go to Project tab –> Run Settings –> Run Environment, append our homemade Qt library path to LD_LIBRARY_PATH. In my example, it’s /home/gonwan/testgdb/qt4-x11-4.6.2/lib. Ok, you’re almost done! Go back to the Edit tab, set a breakpoint at line 4 (or line 3 as you like), press F5 to start debugging the project. Then continue pressing F11, you will find GDB has stepped into Qt source code! Let me take a screenshot:


In order to load our homemade *.so, we can also run “make install”.

开门见山, 我就直接罗列了, 主要是naming convention, style convention 的话, 私以为自己还不错, 就不参考了.

0. General:
a) 命名要有意义.
b) 命名要一致. 比如不要先用prev, 然后用previous.
c) 命名尽量不要缩写. 超过2 个字母, 第一个字母大写其余小写; 只有2 个字母的则全部大写.

1. Class:
a) 类名: 单词首字母大写, 以Q 为首字母.
b) 成员变量: 除了第一个单词, 其余首字母大写.
c) 成员函数: 同上.
d) 静态成员: 同上.
e) 接口: Qt 似乎除了plugin 相关, 不太用接口(纯抽象类). 一般以QXxxInterface, QXxxPlugin 来命名.

2. 结构:
a) 命名跟类一样, 没有特别的convention.
b) 公有的结构以Q 为首字母. 如果是嵌套的, 似乎没有规律.

3. 枚举:
a) 命名跟类一样, 没有特别的convention.
b) 与类相关的枚举可以定义在类中, 这样可以用类名作为前缀.
c) 公有枚举放到公共的名字空间中. 类, 结构, 接口不放到这个名字空间.
d) 命名体现枚举值的相关性. 比如Qt::CaseInsensitive, Qt::CaseSensitive.
e) 尽量用枚举作为Flag 使用. Qt 中有QFlag, QFlags 两个类作为辅助.

5. 函数:
a) 全局函数: qXxxXxx. 比如qFill, qBinaryFind.

6. 宏:
a) 全部大写, 下划线分隔.
b) static const 的全局变量同上.

7. PS:
a) 编辑器的文本编码最好设成ascii, 这样就保证不会出现中文之类了.
b) 函数的参数, Qt 推荐使用指针, 而不是引用, 因为能显式说明参数会被修改.
c) 头文件include 的顺序, 越是specilized 的放在前面, 越是general 的越放在后面.

Qt 的coding convention 跟Java 的非常像. 私以为加上匈牙利命名法会更好一些. 其实又参考了wxWidgets 的部分代码, 由于它不用命名空间, 所以枚举的命名有些小不一样.

Designing Qt-Style C++ APIs
Qt – CodingConventions
Qt – CodingStyle

今天开始, 所有的技术文尽量全部用e 文! @@

I don’t really know the exact difference between “transparency” and “translucency”. But the flowing pictures of my running application may show you.

Pic-1 shows a normal dialog with gradient background filled. Pic-2 add opacity ability to the whole dialog(transparent). While Pic-3 only add opacity to the dialog’s background(per-pixel, translucency).

If you’re using windows sdk, there’s an API called “SetLayeredWindowAttributes” to realize the function in Pic-2. You can also call it with a transparency color key to make all pixels of this color to be transparent. But, how to realize the function in Pic-3? My dialog’s background is in gradient color. As mentioned here(in Chinese): To realize it, you must use an API called “UpdateLayeredWindow”. And it’s quite troublesome.

There are also GUI libraries to fill this requirements: 1) WPF, 2) Qt. My application is written in Qt. How do WPF and Qt implement this feature? By drawing all controls themselves. They do not use native windows controls. So if you do it yourself, what a big project !

Using Qt, I call QWidget::setWindowOpacity() to set whole transparency of a window(Pic-2). Qt 4.5 is just released. There’s a new translucency attribute in QWidget class. I use it to realize per-pixel alpha blending(Pic-3). Here’s Sample code:

The demo project can be found here. Note:
a) Make sure you have Qt 4.5 installed to build the project.
b) The translucent window’s type should be set to Qt::FramelessWindowHint.