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qt:icons [2011/05/12 09:26] – [Code implementation] mithatqt:icons [2011/05/13 17:01] (current) – [Creating a Qt Resource for the theme] mithat
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 ====== Icons and Actions ====== ====== Icons and Actions ======
  
-This report discusses different ways of binding icons to actions in Qt desktop applications and provides motivation for exploring approaches to robust icon implementations. The following was written against Qt 4.7.1 and Qt Creator 2.1.0 and assumes the reader has some familiarity with Qt/C++ development.+This report discusses different ways of binding icons to actions in Qt desktop applications and provides motivation for developing approaches to robust icon implementations. The following was written against Qt 4.7.1 and Qt Creator 2.1.0 and assumes the reader has some familiarity with Qt/C++ development.
  
 In Qt, there are (at least) five different approaches to binding icons((http://doc.trolltech.com/4.7/qicon.html)) to actions((http://doc.trolltech.com/4.7/qaction.html)), each offering different pros and cons with respect to development time, system integration, and icon rendering quality. The different approaches are described below. For purposes of demonstration in the following discussions, I will assume we have a main window with three actions: ''action_Open'' that opens a file, ''action_Convert'' that converts the open file and saves it, and ''action_Quit'' that exits the application. In Qt, there are (at least) five different approaches to binding icons((http://doc.trolltech.com/4.7/qicon.html)) to actions((http://doc.trolltech.com/4.7/qaction.html)), each offering different pros and cons with respect to development time, system integration, and icon rendering quality. The different approaches are described below. For purposes of demonstration in the following discussions, I will assume we have a main window with three actions: ''action_Open'' that opens a file, ''action_Convert'' that converts the open file and saves it, and ''action_Quit'' that exits the application.
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 ===== Using Qt Resources in Qt Designer ===== ===== Using Qt Resources in Qt Designer =====
  
-The path-of-least-resistance for binding icons to actions when developing Qt applications with Qt Designer((Throughout, I use Qt Designer to refer both to the standalone application as well as its built-in support for the the version embedded into Qt Creator)) is to use Qt Resources((http://doc.qt.nokia.com/4.7/resources.html)). The support for ''*.qrc'' resource files built into Qt Designer makes adding icon resources and binding them to actions very easy and provides immediate visual feedback((http://wiki.forum.nokia.com/index.php/How_to_use_Resource_Editor_with_Qt_Creator)).+The path-of-least-resistance for binding icons to actions when developing Qt applications with Qt Designer((Throughout, I use Qt Designer to refer both to the standalone application as well as its built-in support for the the version embedded into Qt Creator)) is to use Qt Resources((http://doc.qt.nokia.com/4.7/resources.html)). The support for ''*.qrc'' resource files built into Qt Designer makes adding icon resources and binding them to actions very easy and additionally provides immediate visual feedback((http://wiki.forum.nokia.com/index.php/How_to_use_Resource_Editor_with_Qt_Creator)).
  
-While this approach has the above stated benefits, it's not optimal for a couple reasons. First, it lacks the ability to specify multiple icon sizes. In a typical application, icons bound to actions will need to be rendered at different sizes. For example, toolbar icons may be rendered at 24x24 pixels while menu item icons will be rendered at 16x16. As far as I can tell, Qt Designer (and possibly all of Qt) does not let you set icons for menu items and toolbar items independently. Rather, Qt will automatically shrink (but not grow) icons to fit the desired space as needed((http://doc.qt.nokia.com/4.7/widgets-icons.html)).+While this approach has the above stated benefits, it's not optimal for a couple reasons. First, it lacks the ability to specify multiple icon sizes. In a typical application, icons bound to actions will need to be rendered at different sizes. For example, toolbar icons may be rendered at 24x24 pixels while menu item icons will be rendered at 16x16. As far as I can tell, Qt Designer (and possibly all of Qt) does not let you set icons for menu items and toolbar items independently. Rather, this approach relies on Qt's ability to automatically shrink (but not grow) icons to fit the desired space as needed((http://doc.qt.nokia.com/4.7/widgets-icons.html)).
  
-Developers using this approach typically provide an icon in a resource that is as large as the application is likely to require, and then let Qt resize it as needed. Thus, for example, you might bind a 48x48 icon to an action and let Qt shrink it to 24x24 for the toolbar and 16x16 for the menu item. While this works, the shrunk icons often appear fuzzy or otherwise suboptimal((As near as I can tell, it's not possible to specify multi-sized icons in Qt Designer. You can supply Windows-style multi-size ''*.ico'' files as Qt Resources and bind those to actions. However, when I tried this on Linux, I got it to show the smallest icon in the set. In other words, Qt doesn't seem to automatically select the best icon size in mult-size ''*.ico'' files for the given situation. This may work on Windows and/or OS X but requires testing.)).+Developers using this approach typically provide an icon in a resource that is as large as the application is likely to require, and then let Qt resize it as needed. Thus, for example, you might bind a 48x48 icon to an action and let Qt shrink it to 24x24 for the toolbar and 16x16 for the menu item. While this works, the shrunk icons often appear fuzzy and/or otherwise suboptimal((As near as I can tell, it's not possible to specify multi-sized icons in Qt Designer. You can supply Windows-style multi-size ''*.ico'' files as Qt Resources and bind those to actions. However, when I tried this on Linux, I got it to show the smallest icon in the set. In other words, Qt doesn't seem to automatically select the best icon size in mult-size ''*.ico'' files for the given situation. This may work on Windows and/or OS X but requires testing.)).
  
 FIXME (an image here would help a lot) FIXME (an image here would help a lot)
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 }</code> }</code>
  
-If you have more than a handful of such icons, you will probably want to write a helper function to reduce the repeated data entry.+If you have more than a handful of such icons, you will probably want to write a [[MainWindow-buildIcon|support method]] to reduce the repeated data entry.
  
 ==== Pros ==== ==== Pros ====
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 ===== QStyle's standardIcon() function ===== ===== QStyle's standardIcon() function =====
  
-An alternative to using icon resources is provided by the ''standardIcon()'' function, which is an instance member of the ''QStyle'' abstract base class((http://doc.qt.nokia.com/4.7/qstyle.html#standardIcon)). This function provides access to the subset of standard system icons enumerated in ''StandardPixmap-enum''((http://doc.qt.nokia.com/4.7/qstyle.html#StandardPixmap-enum)).+An alternative to using icon resources is provided by the ''standardIcon()'' method, which is an instance member of the ''QStyle'' abstract base class((http://doc.qt.nokia.com/4.7/qstyle.html#standardIcon)). This method provides access to the subset of standard system icons enumerated in ''StandardPixmap-enum''((http://doc.qt.nokia.com/4.7/qstyle.html#StandardPixmap-enum)).
  
-The enumerated icons should be available on all platforms, so testing for their existence isn't required. The main issue with using ''standardIcon()'' is that on my platform at least (Linux, Ubuntu 10.10) it does not provide multi-sized icons. You'll get icons from the system theme, but they will be resized and fuzzy at times. (I haven't tested the behavior on Windows and OS X, so it might not be the case on those platforms.) Another issue is that many common icons are not part of ''StandardPixmap-enum''.+The main issue with using ''standardIcon()'' is that on my platform at least (Linux, Ubuntu 10.10) it does not provide multi-sized icons. You'll get icons from the system theme, but they will be resized and fuzzy at times. (I haven't tested the behavior on Windows and OS X, so it might not be the case on those platforms.) Another issue is that many common icons are not part of ''StandardPixmap-enum''.
  
 Implementation requires only a bit of straight-forward hand-coding. Implementation requires only a bit of straight-forward hand-coding.
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 On X11 systems, Qt lets you access all the icons that are part of the system icon theme using the static function ''QIcon::fromTheme()''((http://doc.qt.nokia.com/4.7/qicon.html#fromTheme)). Icons so accessed will be selected as needed based on the required rendering size. On X11 systems, Qt lets you access all the icons that are part of the system icon theme using the static function ''QIcon::fromTheme()''((http://doc.qt.nokia.com/4.7/qicon.html#fromTheme)). Icons so accessed will be selected as needed based on the required rendering size.
  
-As was the case with QStyle's standardIcon() function, implementation with QIcon::fromTheme() requires a bit of hand-coding.+As was the case with QStyle'''standardIcon()'' function, implementation with ''QIcon::fromTheme()'' requires a bit of hand-coding.
  
 ==== Code implementation ==== ==== Code implementation ====
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 ==== Caveat ==== ==== Caveat ====
-QIcon's determination of the system icon theme is at the time of this writing not reliable under Linux -- at least not under Openbox; GNOME and Xfce are yet to be tested. A possible workaround is to use as yet undefined ''HeroicMeasures()''™ to suss out the actual icon theme and then set it((http://doc.qt.nokia.com/4.7/qicon.html#setThemeName, http://doc.qt.nokia.com/4.7/qicon.html#themeName)) in the constructor:+QIcon's determination of the system icon theme is at the time of this writing not reliable under Linux -- at least not under Xfce, Openbox, Fluxbox, and IceWM; GNOME seems to work as expected((http://bugreports.qt.nokia.com/browse/QTBUG-19268)). A possible workaround is to use as yet undefined ''HeroicMeasures()''™ to suss out the actual icon theme and then set it((http://doc.qt.nokia.com/4.7/qicon.html#setThemeName, http://doc.qt.nokia.com/4.7/qicon.html#themeName)) in the constructor:
 <code cpp-qt> <code cpp-qt>
 QString iconTheme = My::HeroicMeasures(); QString iconTheme = My::HeroicMeasures();
 QIcon::setThemeName(iconTheme);</code> QIcon::setThemeName(iconTheme);</code>
  
 +Until such ''HeroicMeasures()''™ are worked out or the bug is fixed, this method can't really be recommended.
 ===== Custom theme using  QIcon::fromTheme() ===== ===== Custom theme using  QIcon::fromTheme() =====
  
-The static function ''QIcon::fromTheme()'' used above can also be used with custom, locally defined icon themes that are placed into Qt Resource files((This idea comes from http://tkrotoff.blogspot.com/2010/02/qiconfromtheme-under-windows.html)). To accomplish this we need to do three things: Create a custom icon theme, create a Qt Resource with the theme, and implement the code needed to use the custom theme.+The static function ''QIcon::fromTheme()'' used above can also be used with custom, locally defined icon themes that are placed into Qt Resource files((This idea comes from http://tkrotoff.blogspot.com/2010/02/qiconfromtheme-under-windows.html)). Themes defined this way can be used across all platforms. To accomplish this we need to do three things: Create a custom icon theme, create a Qt Resource with the theme, and implement the code needed to use the custom theme.
  
 To describe the process, I will use an example of a custom theme that provides icons in a variety of sizes for our example application. The icons themselves are taken from the raucously popular, public domain Tango Project((http://tango.freedesktop.org/Tango_Desktop_Project)) using files provided in Ubuntu's 10.10 tango-icon-theme package((http://packages.ubuntu.com/maverick/tango-icon-theme)). Because unlike Bill Bruford I am not good at naming things((Bruford, Bill. "Who Managed the Manager?" In //Bill Bruford: the autobiography : Yes, King Crimson, Earthworks, and more.// London: Jawbone Press, 2009. 60-72. )), I call the custom theme, "TangoMFK". To describe the process, I will use an example of a custom theme that provides icons in a variety of sizes for our example application. The icons themselves are taken from the raucously popular, public domain Tango Project((http://tango.freedesktop.org/Tango_Desktop_Project)) using files provided in Ubuntu's 10.10 tango-icon-theme package((http://packages.ubuntu.com/maverick/tango-icon-theme)). Because unlike Bill Bruford I am not good at naming things((Bruford, Bill. "Who Managed the Manager?" In //Bill Bruford: the autobiography : Yes, King Crimson, Earthworks, and more.// London: Jawbone Press, 2009. 60-72. )), I call the custom theme, "TangoMFK".
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 </RCC></code> </RCC></code>
  
-Once you have created the ''*.qrc'' file with the needed content, you will need to add it to your project. In Qt Creator, right-click the name of the project, select //Add Existing Files...//, and add the ''*.qrc'' file. After doing this, you can use Qt Creator's GUI-based resource manager to verify that all the icons have been correctly included.+Once you have created the ''*.qrc'' file with the required content, you will need to add it to your project. In Qt Creator, right-click the name of the project, select //Add Existing Files...//, and add the ''*.qrc'' file. After doing this, you can use Qt Creator's GUI-based resource manager to verify that all the icons have been correctly included.
  
 Note that in the set of icons I drew from, there were no 48x48 icons. To maintain best compatibility with Windows OSes, you ideally should include 48x48 icons as well((See http://msdn.microsoft.com/en-us/library/ms997636.aspx for a discussion of Windows XP icons and http://msdn.microsoft.com/en-us/library/aa511280.aspx for Windows 7.)). Note that in the set of icons I drew from, there were no 48x48 icons. To maintain best compatibility with Windows OSes, you ideally should include 48x48 icons as well((See http://msdn.microsoft.com/en-us/library/ms997636.aspx for a discussion of Windows XP icons and http://msdn.microsoft.com/en-us/library/aa511280.aspx for Windows 7.)).
  
-The pros and cons associated with this approach are essentially identical to [[#Explicitly build and bind icons at runtime]] above, but there is one important difference: you cannot combine this approach with [[#Custom theme using  QIcon::fromTheme()]] because the setting of icon themes is dynamic: the last theme name you set is the theme with which all icons will be rendered. +The pros and cons associated with this approach are essentially identical to [[#Explicitly build and bind icons at runtime]] above. There is, however, one important difference: you cannot combine this approach with the [[#Custom theme using  QIcon::fromTheme()]] approach because the setting of icon themes is [[MainWindow-setActionIcon|dynamic]]: the last theme name you set is the theme with which all icons will be rendered. 
  
 ==== Code implementation ==== ==== Code implementation ====
qt/icons.1305192360.txt.gz · Last modified: 2011/05/12 09:26 by mithat

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