Was talking to a colleague about XAML and how it is both a presentation and object description language and therefore quite unique and novel among IT technology.
Is this true that XAML is unique and novel?
Does XAML have any counterparts or predecessors in the Java world or elsewhere? I believe someone told me that Java Server Faces was similar to WPF, so what is the equivalent of XAML there?
I know MXML in Flex is similar but as far as I can remember there are some major structural differences, from what I remember MXML doesn't really describe objects but is more of a pure presentation XML.
This is a case of a general technology having such an overwhelming common specific usage that becomes synonmous with the specific usage. For example, discussions of Javascript often assume the browser context and the manipulation of a HTML DOM without anyone having to expressly say so.
Strictly speaking XAML is not like XUL or SVG apart from being XML. XUL, SVG have a defined syntax for declaring User interface or graphical elements, raw XAML does not.
XAML can, for example, also be used to describe Workflows in Workflow foundation.
XAML is actually an approach to reading XML in order to describe types and properties of those types. For example, a property of a type may be described either using an attribute or an Element as long as its name can be interpreted correctly. XAML also includes an extension to the basic XML syntax where { } in an attribute can act as a short hand for a complex element.
I've not come across this sort of thing before. All other XML based technologies come with a specific purpose, XAML is the first usage of XML I've seen that is deviod of any specific nomenclature but just a means of mapping XML to types.
****XAML, XUL, and XHTML Overlap****
The greatest overlap between XAML and other standards lies in its support for concepts drawn from HTML/XHTML. The similarities between XAML and HTML are numerous. Overlap with HTML is not limited to XAML, of course. The other well-known XML GUI dialect—Mozilla's XUL—also overlaps with XHTML. Finally, both XAML and XUL overlap in places that XHTML doesn't even include. XHTML and XUL can be combined in one document (at least in Mozilla browsers). Such a combination is a rough analog for non-Web uses of XAML. In fact, Mozilla's XUL alone is a rough analog for some uses of XAML.
but taken together, they really constitute nothing more than support for most of the basic HTML content and form widgets that are already routine in ordinary Web applications. XUL overlaps XHTML less that XAML does because XUL attempts to separate itself from XHTML. It's not trying to be a drop-in replacement, as XAML is.
One thing I do like about XAML compared with HTML is the increased freedom from the publishing-derived features of HTML. XAML frees you from h1 tags, code tags and a host of other miscellaneous niche tags used infrequently in HTML. For practical purposes, these tags act as little more than style information in modern HTML documents.
HTML is also a poor GUI for applications, despite the popularity of the Web. Both XAML and XUL go a long way towards rectifying that problem. You could re-write your Web applications in XAML and they'd look better than the HTML originals, if only XAML had better CSS support.
Read the comparisons to other presentation technologies with a grain of salt - Xaml is a method of constructing and composing .NET objects. That's in stark contrast to other systems that were designed as a way to build user interfaces. The nice thing about Xaml is that it's independent of the technology stack that its used for - it's a purpose-agnostic declaritive language more like C# than XHTML. In that way, it's unique.
Cocoa from Apple, or event earlier NeXtStep had something similar long before XAML.
The GUI is created with an interface builder, which makes so called nib (Nextstep Interface Builder) files, which contains the layout, bindings, actions, outlets and serialized object instances. In the former time these nib files were stored in a binary file format, but nowadays it is also xml (xib).
So XAML is not the first not unique at all.
Besides XAML, you have XUL which is used by Mozilla. SVG on the other hand, is one recommended by W3C.
Mozilla created their UI description language XUL originally to be able to easily customize the UI of all of their products.
Nowadays it's a package which can be included in other applications and also has an extended functionality.
Although XUL mainly focuses on UI representation it also contains other structures as Events and Scripts and Data sources. Nevertheless as far as I know XAML integrates these concepts much tightlier into their .NET (and attached) frameworks. But I'm not sure if this is enough to call it unique and novel.
XAML is an object graph construction language in the dialect of XML (not the greatest choice). Every XAML element is an object instantiation and the corresponding attributes are property assignments on said instance. Since XML is a string based language, property values need to be converted from their string type into whatever type the property expects. This is done using descendants of TypeConverter that the XAML processor locates and utilizes automatically. XAML and WPF come with a default set of TypeConverters corresponding to their provided types and you can provide your own.
A rough overview of the definition process is as follows:
<classG-in-namespace-A
xmlns="namespace-A"
xmlns:alias-B="namespace-B"
xmlns:alias-C="clr-namespace:namespace-C;assembly=assembly-of-namespace-C"
propertyG1="simple text value stipulation"
propertyG2="{alias-C:classH-in-namespace-C propertyC1=valueC1,..}"
>
<classG-in-namespace-A.propertyG2>
<alias-B:class-I-in-namespace-B propertyB1=valueB1,...>
class-I-in-namespace-B's content property value assignment
</alias-B:class-I-in-namespace-B>
</classG-in-namespace-A.propertyG2>
classG-in-namespace-A's content property value assignment
</classG-in-namespace-A>
There are utility types provided by XAML and WPF beyond TypeConverters that facilitate property assignments. In particular, there are the following:
ResourceDictionary,
ObjectDataProvider,
RelativeSource,
StaticResource,
DynamicResource,
...and more as shown in Microsoft Docs
Well, XAML is basically advanced markup for .NET, therefore I think you can draw a lot of parallels from XAML to XHTML - Both being presentation techniques.
There's a lot of differences as well ofc (XHTML being interpreted by a browser to produce graphics, while XAML is being compiled into MSIL and relying on the CLR to do the graphics :) )
Related
I am building a wpf user control to provide navigation facilities for database records.
The control is provided with a set of default images (as illustrated above) which the end user can change is they so wish. In addition the end user can choose to dispense with images altogether. In the event that they select that option (for either one or all of the buttons that comprise the control) I have provided some default fallback text.
This text can also be overwritten by the end user if they so wish, but the default text at least provides them with some basic text that essentially conveys what the button does and saves them having to add text every time they use the control (default tooltip text is also provided).
Now if you happen to speak English, or your intended target audience is English this should work, but it doesn't really cater as is for languages other than English. This I would now like to change.
What reading I've done on the subject of multi-lingual resources and wpf seems to assume that one is talking about the overall application rather than a standalone user control that might be used in different language environments.
I had a talk with a creator of controls who said that making this multilingual would probably involve building several copies of the control for each intended language.
In the light of this I have two questions. Was the gentleman I spoke to correct, should I in fact build multiple copies of this for each language, of is there a way to have multi-language resources within the same copy of the user control?
If the latter is possible what is the correct way to go about achieving this. We will be dealing in total with default texts for eleven buttons (which I will need to be able to refer to in code within the control incidentally) and default texts for thirteen tooltips (which again will need to be able to be referred to within the code of the control).
Take a look on WPF localization extension.
Here's a pretty good documentation for it: link.
You can define your controls' localizable properties, which store their localized values in the satellite resource assemblies.
In your xaml code, define the localized properties with xaml extensions syntax:
<Button Content="{lex:Loc Test}" />
Then, create resource files for each culture your application will support and give them the same name as the main assembly plus the general or specific culture code (e.g. en-US, de, de-AT, ...) before the .resx ending yielding: AssemblyName.CultureCode.resx.
Now, populate the resource files with your localized properties key/value pairs and build the project.
You're done!
it seems there are a number of approaches on how to implement multiple languages in a WPF application. But I would like some more information about what method I should be using with the following requirements:
It's a PRISM application, so a number of independent modules (assemblies) working together. I would like that each assembly has its own translations of UI elements.
I need a simple approach, no tools needed to generate stuff
Should still be able to use blend to design the UI
Optionally be able to switch language without restarting the application (not a dealbreaker)
Can someone advice me on how to achieve this?
Thanks!
A common approach is to bind the text property of your textblocks / labels etc.. to some property on a statically defined localization resource:
<Label Content="{Binding Source={x:Static loc:LanguageContext.Instance},
Path=Dictionary, Mode=OneWay,
Converter={StaticResource languageConverter},
ConverterParameter=TextId}" />
i.e. LanguageContext.Instance exposes a dictionary via a property Dictionary, the Converter uses the given ConverterParameter to look up the text identified via TextId.
This is a cumbersome approach, and will not fulfil all your requirements.
A better method is to defined your own markup extension to perform this sort of logic. There are a couple of solutions I have seen on the web, this high rated codeproject article:
http://www.codeproject.com/KB/WPF/realtime_multilingual.aspx
And a similar solution here that provides Blend, on-the-fly language changes, so is probably a good choice for you:
http://blogs.microsoft.co.il/blogs/tomershamam/archive/2007/10/30/wpf-localization-on-the-fly-language-selection.aspx
With the above example you define an attached property which identifies the key of the translated item, and use the Translate markup extension to identify the properties which are translated.
NOTE: it is not just text which is being translated here, often you have to change colors / graphics etc ...
Meanwhile I found an open source project that works really well: http://wpflocalizeextension.codeplex.com. It's just adding a reference to the dll, adding the resources with translations, and using it in XAML. It worked in 5 minutes. I can add multiple resources to individual modules; and it works fine in visual studio designer and blend. And, locale can be changed on the fly. Meets my requirements :)
I'm currently evaluating QtQuick (Qt User Interface Creation Kit) which will be released as part of Qt 4.7. QML is the JavaScript-based declarative language behind QtQuick.
It seems to be a very powerful concept, but I'm wondering if anybody that's made extensive use of other, more mature declarative-UI languages like XAML in WPF or Silverlight can give any insight into the real-world benefits that can be gained from this style of programming. Various advantages are often cited:
Speed of development
Forces separation between presentation and logic
Better integration between coders and designers
UI changes don't require re-compilation
Also, are there any downsides? A few potential areas of concern spring to mind:
Execution speed
Memory usage
Added complexity
Are there any other considerations that should be taken into account?
(Updated)
The misconception with XAML is that it's not compiled. It is indeed compiled down to BAML a binary pre-tokenized XAML. Apparently there was a IL compiled version of XAML too called CAML. The OP pointed me to this good article explaining what XAML/BAML and CAML are.
Anyway, to the question why to use it:
XAML is simply a Serialization Format for C# objects that it is particularly well suited to describe hierarchical object structures, like found in WPF GUIs.
What WPF helps you do is write less boring C# code like this:
var grid = new Grid();
grid.Content.add(new TextBlock() {Text = "Hello"});
grid.Content.add(new TextBlock() {Text = "World"});
and just express it in a more readable way like this:
<Grid>
<TextBlock Text="Hello">
<TextBlock Text="World">
</Grid>
Since WPF object nesting (putting stuff inside other objects) can get very deep, WPF makes it much easier to read than the resulting C# code.
As for separation of concerns: XAML helps here too since it does only allow you to express objects and their relationships/properties, rather than logic. That forces you to separate logic from UI layout. The MVVM Pattern is very well suited for this task and allows for eay testability and interchangeable Views.
Added complexity in XAML can be also easily dismissed because the same code in C# gets easily more complex than the XAML markup.
I can't give you any insight into QTQuick though. Sorry
QtQuick is extensible via C++ plugins, actually what the Qt guys recomment is that you do the UI, Animations, Transitions etc in QtQuick/QML while all of your business logic is in C++/Qt. So this way you get the best of both worlds, you can debug your C++ code like you usually do, while at the same time making UIs becomes effortless and extremely easy.
Also another important think about QtQuick/XAML is that they are hardware accelerated, so for example you can get pretty good fps without any effort. So they are not slow at all for what they set out to accomplish.
It saves time, soo much time. I did a UI with code in 3 days, did the same in QML in 2 hours.
The point of declarative coding, i.e. WPF or QTQuick is to provide a separation between the developer and presumably the artist that is implementing the visual aspects of your application. With regards to WPF, I find that debugging gets to be a bit harder. As we speak, I am compiling the latest QT to look at QTQuick. (It takes a long time and I have time to look at stackoverflow :-) ) So, I don't have an opinion on that yet.
QML/XAML are:
Great for MVVM pattern
Hardware accelerated (QML with using OpenGL for Windows, MAC, Linux and Phone OSes... XAML with using DirectX for Windows and its phone version)
Closer to artists
You can create a GREAT and NICE UI using XAML/QML
Easier UI implementation
Nice animation is possible
In XAML, usually you can create a Silverlight version of your application just with a little changes
In XAML there is some great features such as Template, Trigger (DataTrigger, Trigger, EventTrigger), Binding (in any side and also both side together), Resource, Commands, DependencyProperty and Notifiable Properties.
But please note in XAML: (I am a XAML programmer, therefore i have not points for QML)
XAML debugging is not possible
For any change in XAML, all program must be recompile
Be more careful for performance. For example if you use much many RoutedCommands in XAML, your application will be unusable!
In XAML, some feature not works as expected. There is unfortunately some tricks. (It should be clear... should works as expected... isn't it? )
Be careful for some similar namespaces like BitmapEffect and Effect. There is different features and costs. (e.g. BitmapEffect has some effects with software render and Effect has some effect with hardware render)
In real world, artists could not use WPF as Flash (at least with good performance).
Some features works on special places. For example DataTrigger works just in Style tag not in Resource section.
There is some weaknesses in XAML. Some examples: there is not any sequential animation... you cannot do any calculation in XAML (you must write a converter in C# even for a liiiittle work! JavaSript is a great replacement in QML)... some attributes are duplicate. e.g. x:Name and Name... Controlling View from ViewModel is not clear. e.g. closing View from ViewModel (you need some CodeBehind)
Tooooooo much run-time errors. If you use some tags in bad place it will notice you for syntax error, but many of errors occurs just in the run-time. e.g. if i target Background property (instead of Background.Color) for ColorAnimation, it will compile successfully, but in running animation... BUMP... runtime error!!! in such case on Expression Blend, application will crash!!!
I have a RichTextBox and need to serialize its content to my database purely for storage purposes. It would appear that I have a choice between serializing as XAML or as RTF, and am wondering if there are any advantages to serializing to XAML over RTF, which I would consider as more "standard".
In particular, am I losing any capability by serializing to RTF instead of XAML? I understand XAML supports custom classes inside the FlowDocument, but I'm not currently using any custom classes (though the potential for extensibility might be enough reason to use XAML).
Update: I ended up going with RTF because of its support for text-encoded embedded images. XAML doesn't seem to include image data in its encoding, and XamlPackage encodes to binary, so RTF just works better for me. So far I haven't noticed any lack in capability.
If all your users are doing is typing in the RichTextBox and doing character formatting, RTF is as good as XAML. However there are many FlowDocument capabilities you may expose in your UI that are not convertible to RTF.
Here are some examples of FlowDocument (and RichTextBox) features that are not expressable in RTF or are implemented differently:
A Block can have an arbitrary BorderBrush, including gradient brushes with stops, VisualBrush
A Section has the HasTrailingParagraphBreakOnPaste property
Floater / ClearFloaters is implemented differently
Hyphenation can be enabled/disabled per block, not just per paragraph
WPF Styles and ResourceDictionaries can be included in the Resources property
Arbitrary WPF UI such as bound CheckBoxes, etc, can be embedded inside the RichTextBox and can be cut-and-pasted from other windows.
For example, suppose you want to allow users to drag or cut/paste in a "current date/time" field into your RichTextBox that would always show the current date and time. This could be done by adding a second read-only RichTextBox that has the InlineUIContainer and the already-bound control. This even works when cutting and pasting from other applications and does not require custom controls.
Another consideration is that the code to convert between FlowDocument and RTF is relatively complex so it may have lower performance than going with XAML. Of course loose XAML doesn't include images and such - for that you need to use XamlPackage. I store my XamlPackage in the database as a byte[], but you can also choose to Base64 encode it for storage as a string.
The bottom line is that it really depends on whether you want the user to be able to use features not available in RTF. Even if your application doesn't include tools to generate FlowDocuments that use these features, it is possible to cut-and-paste them from other applications.
Be aware that in Wpf RichTextBox's method called TextRange.Save has a bug whereby it loses any end of line terminator. Microsoft will not fix.
https://connect.microsoft.com/WPF/feedback/ViewFeedback.aspx?FeedbackID=478640&wa=wsignin1.0#tabs
Although Hungarian notation is considered bad practice nowadays, it is still quite common to encode the type in the name of user interface elements, either by using a prefix (lblTitle, txtFirstName, ...) or a suffix (TitleLabel, FirstNameTextBox, ...).
In my company, we also do this, since it makes code written by co-workers (or by yourself a long time ago) easier to read (in my experience). The argument usually raised against doing this -- you have to change the name of the variable if the type changes -- is not very strong, since changing the type of a UI element usually requires rewriting all parts of the code were it is referenced anyway.
So, I'm thinking about keeping this practice when starting with WPF development (hmmm... should we use the txt prefix for TextBlocks or TextBoxes?). Is there any big disadvantage that I have missed? This is your chance to say "Don't do this, because ...".
EDIT: I know that with databinding the need to name UI elements decreases. Nevertheless, it's necessary sometimes, e.g. when developing custom controls...
Personally, I find that WPF changes the rules when it comes to this. Often, you can get away with little or no code behind, so having the prefixes to distinguish names makes things more confusing instead of less confusing.
In Windows Forms, every control was referenced by name in code. With a large UI, the semi-hungarian notation was useful - it was easier to distinguish what you were working with.
In WPF, though, it's a rare control that needs a name. When you do have to access a control via code, it's often best to use attached properties or behaviors to do so, in which case you're never dealing with more than a single control. If you're working in the UserControl or Window code-behind, I'd just use "Title" and "Name" instead of "txtTitle", especially since now you'll probably only be dealing with a few, limited controls, instead of all of them.
Even custom controls shouldn't need names, in most cases. You'll want templated names following convention (ie: PART_Name), but not actual x:Name elements for your UIs...
In my experience - In WPF when you change the type of a control, you normally do not have to rewrite any code unless you did something wrong. In fact, most of the time you do not reference the controls in code. Yes, you end up doing it, but the majority of references to a UI element in WPF is by other elements in the same XAML.
And personally, I find "lblTitle, lblCompany, txtFirstName" harder to read than "Title". I don't have .intWidth and .intHeight (goodbye lpzstrName!). Why have .lblFirstName? I can understand TitleField or TitleInput or whatever a lot more as it's descriptive of the what, not the how.
For me, wishing to have that type of separation normally means my UI code is trying to do too much - of course it's dealing with a UI element, it's in the window code! If I'm not dealing with code around a UI element, why in the world would I be coding it here?
Even from a Winforms perspective I dislike semi-hungarian.
The biggest disadvantage in my opinion, and I've written a LOT of ui code is that hungarian makes bugs harder to spot. The compiler will generally pick it up if you try to change the checked property on a textbox, but it won't pick up something like:
lblSomeThing.Visible = someControlsVisible;
txtWhatThing.Visible = someControlsVisible;
pbSomeThing.Visible = someControlsVisible;
I find it MUCH easier to debug:
someThingLabel.Visible = someControlsVisible;
whatThingTextBox.Visible = someControlsVisible;
someThingPictureBox.Visible = someControlsVisible;
I also think it's far better to group an addCommentsButton with an addCommentsTextBox than to group a btnAddComments with a btnCloseWindow. When are you ever going to use the last two together?
As far as finding the control I want, I agree with Philip Rieck. I often want to deal with all the controls that relate to a particular logical concept (like title, or add comments). I pretty much never want to find just any or all text boxes that happens to be on this control.
It's possibly irrelevant in WPF, but I think hungarian should be avoided at all times.
I like using a convention (just a good idea in general), but for UI stuff I like it to have the type of the control at the front, followed by the descriptive name -- LabelSummary, TextSummary, CheckboxIsValid, etc.
It sounds minor, but the main reason for putting the type first is that they'll appear together in the Intellisense list -- all the labels together, checkboxes, and so on.
Agree with the other answers that it's mainly personal preference, and most important is just to be consistent.
On the need for naming at all, given the prevalence of data binding... one thing you might want to consider is if your UI is ever subjected to automated testing. Something like QTP finds the visual elements in an application by Name, and so an automation engineer writing test scripts will greatly appreciate when things like tabs, buttons etc. (any interactive control) are all well named.
In WPF you practically never need (or even want) to name your controls. So if you're using WPF best practices it won't matter what you would name your controls if you had a reason to name them.
On those rare occasions where you actually do want to give a control a name (for example for an ElementName= or TargetName= reference), I prefer to pick a name describing based on the purpose for the name, for example:
<Border x:Name="hilightArea" ...>
...
<DataTrigger>
...
<Setter TargetName="hilightArea" ...
I prefix any user-interface name with two underscores, as in __ so it is sorted before other properties when debugging. When I need to use IntelliSense to find a control, I just type __ and a list of controls displays. This continues the naming convention of prefixing a single underscore to module level variables, as in int _id;.
You can use the official Microsoft website for Visual Basic 6 control naming conventions, and perhaps combine it with the recommended C# naming conventions. It's very specific, is widely used by developers in C# as well for control names, and can still be used in a WPF or Windows Forms context.
Visual Basic 6 control naming conventions: Object Naming Conventions
C# recommended naming conventions in general: General Naming Conventions