What's the difference between the following two?
Background="{x:Null}"
and
Background="Transparent"
Transparent will create a brush that is initialized to a transparent color, null will set the property to null, this means that the destination property has not an brush attached.
In WPF it's often important to set a brush to an element. If you for example want to track mouse downs in an element, you must set a background. If you don't want to set a solid color (make it opaque), you can use a transparent brush. This can be done with the string value "Transparent".
The difference lies in the manner, how the property will be set. If you assign null for a brush-property, the property will be set really to null. If you set the string "Transparent", the default value-converter that converts string to brushes converts this to the Brushes.Transparent brush.
Short version: {x:Null} sets the destination property to null. "Transparent" sets the destination property to a transparent brush.
Both are setting the local value of the Background property. The former sets it to null and the latter sets it to Brushes.Transparent.
There are a couple of important points to be aware of:
Setting the value to null is not the same as not setting it at all. Since dependency properties obtain their effective value from multiple sources, setting a local value (even if it's null) can take precedence over values potentially sourced from elsewhere, such as a style or animation.
Another option for controlling hit test visibility is the IsHitTestVisible property. This property allows you to control hit test visibility regardless of the brush with which the UIElement is rendered.
{x:Null} will not be clickable, Transparent will.
Also see this.
Elements with Transparent background receive mouse click events when clicking on background, elements with Null do not.
The Transparent brush
Will cause the background's alpha channel to be set to 0 which is 100% transparent
The {x:Null} value
Will cause the background to be set to the default control colour by WPF which is usually White on some properties like DataGrid.RowBackground and Transparent on most of the other properties.
It's a good habit to specify a brush colour since setting a brush to
Null may result in undesired default colours.
Related
In the designer, the boundaries of the fields are drawn.
When I click the program, the borders are not drawn.
How to make that when you run the program, the borders of the fields were drawn?
Searching the DevExpress support site is always the best first option.
I found this on there. As it states not all skins support this and the default skin I was using "DevExpress Style" didn't. Changing skin to "Darkroom" did.
To display layout borders, set the LayoutControl.OptionsView.DrawItemBorders Property to true and the LayoutControl.OptionsView.ItemBorderColor Property to a necessary color. Note that in specific skins, borders for layout items are not supported, so you need to either set the AllowItemSkinning option in supported skins to true or change LookAndFeel.Style to another style; e.g., LookAndFeelStyle.Flat. If you do not want to affect the look and feel of embedded controls, set the LayoutControl.OptionsView.ShareLookAndFeelWithChildren Property to false.
Anyway, I'm having a little difficulty with tab control. When I drag a new tab control onto a form, it appears white, rather than the grey (system colour) I was expecting.
When I look at the properties, its colour is set to web-transparent. Ok, so it should be transparent then (it isn't letting anything behind it show through). Setting the tab control back colour manually back to the system grey kind of works, but the tabs at the top still show as white. I'm assuming I could somehow change their colour as well, but I'm quickly getting into the realms of changing so many values from default, I'm clearly missing something type territory. I've googled every varient of "transparent tab control draws white" as I can, and although I found something to do with windows profiles, this seemed mostly confined to access 2003 using the vb you got access to in access.
I'm looking for any explanation as to:
what I need to do to correctly use transparency with tab controls
what I'm mis-understanding as the purpose of transparency in tab controls
how to easily change all the colours of the appropriate parts of the tab control to not be transparent.
I'm looking at windows forms for an MCTS, so please don't give a "you should use X instead" type answer.
No, getting white is certainly normal. TabControl and TabPage are rendered with theme colors when visual styles are enabled. So that makes the tab page white on machines with the standard Windows theme.
Yes, the default BackColor of Transparent is very unusual. You most certainly will never get actual transparency with that, unless you count seeing the background of the TabControl as transparency. The logic is pretty convoluted, rather than trying to explain it I'll just paste the MSDN explanation:
The default value of the BackColor property is the value of the Control.DefaultBackColor property unless the UseVisualStyleBackColor and Application.RenderWithVisualStyles property values are both true and the Appearance property of the parent TabControl has a value of Normal, in which case the default value of the BackColor property is Transparent. Child controls that you place on the TabPage inherit the BackColor value by default, so this behavior causes the background of the child controls to render with the current visual style.
Changing the value of the BackColor property automatically sets the UseVisualStyleBackColor property to false. If you want the TabPage background to render using visual styles but you want the child controls to inherit a BackColor value that you specify, set the UseVisualStyleBackColor property after you set the BackColor property.
Is default value of TextBlock's Foreground one of the SystemColors? If so, which one is it?
This is rather theme-dependent, if there is no override from the applying theme the DP-system uses the default value of the respective DependencyProperty, which is Brushes.Black.
There are however many possibly overrides, in the Aero theme inheritance changes the value in some cases. While the TextBlock style does not set the Foreground directly (which would be a stronger override), the Foreground of Windows is set to {DynamicResource {x:Static SystemColors.WindowTextBrushKey}} so if the TextBlock is in a Window the brush associated with that key will be applied unless the inheritance is overridden by another value of even higher precedence.
Foreground="{ThemeResource DefaultTextForegroundThemeBrush}"
Textblock's foreground hex value is #FF000000
I want to make the background of a PictureBox control transparent. In the PictureBox (rectangular shape), I placed an icon (circular in shape). I want to make the icon transparent so that the other portion underneath the icon is visible.
I have tried setting the PictureBox.BackColor property to "Transparent", but it doesn't work. I also tried to set it during runtime with the Color.FromArgb method, but it doesn't work either.
Is there any solution to this problem?
Setting pictureBox.BackColor = Color.Transparent; definitely should work.
Also verify if you are setting alpha channel of color when using Color.FromArgb(0, 0, 0, 0); (this is a first parameter, zero means transparent color)
And, of course, make sure your icons have transparent background.
If using WinForms then Setting the background color to transparent won't work as transparency handling is not a cascading system - you can only (in most cases) set transparency (or rather the opacity) of a control overall using the Opacity property, however this will alter the alpha channel of the entire control display giving your images a see-througness.
One solution might be to set the background color of the PictureBox to be that of the control beneath it (the color of the form, for example). But this may not suffice in your situation.
hi you must set the icon on the other portion underneath the icon by using this
icon_pictureBox_name.Controls.Add(other_portion_picturBox_name);
and after that you can set the PictureBox.BackColor property to "Transparent" and it will work ;)
I have a small UserControl and it needs to know the Background Brush of the control on which it's being rendered.
However, if I look in the Background property of the UserControl it comes back null.
If I call GetValue(UserControl.BackgroundProperty) it also returns null even though up the Visual tree it is definitely being set.
Seems like I must be missing something pretty obvious as it's can't be that hard to figure out the background colour of a control.
It seems to me that your UserControl does not have a background color defined - null means transparent, which is why the parent control's background is visible at all.
It is still the background color of the parent control - the fact that your control does not have its own background color does not mean that it takes the color from the parent control. The "background" of your control will simply show whatever is behind your control.
The background property is not inherited from the parent, you have to set it yourself.